Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: F4UDOA on October 29, 2002, 09:52:29 PM
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Read this senario and keep in mind that the F6F was the Navy's long range strike fighter and the La7 was a short range interceptor.
Lets just say for example I up in an F6F and I am one sector away from the enemy field I am targeting. So I load 75% fuel for my journey.
25% for travel to the target
25% for combat
25% for return to base.
Half way there I run into a La7 who has taken off with 75% fuel also. Hypothetically we have both burned 25% percent fuel and have 50% in the tank at the time of battle. The La7 is a monster in the MA although the Hellcat is certainly no pushover. But is this really a fair fight? I don't mean historically or even performance. I mean that these two A/C where purpose built for different missions. The F6F often flew several hours before encountering nme opposition and the La7 was a interceptor that often saw action right over it's own airfield.
So what am I complaining about??
This.
The Hellcat has almost the same exact fuel duration as the La7 in the MA. According to the posted chart the F6F has 30minutes of flight time at full throttle mil power and the La7 has 28 minutes.
Internal fuel loads
La7 122 gallons
F6F 250 gallons
Why do they have the same fuel duration?
The Fuel burn Mil power of a R2800 is approximately 280 GPH in mil power. I have no clue what the GPH fuel burn is in a La7 but I'm going to say that it probable doesn't have the duration of the F6F.
Why is that so important?
Because the F6F should never have to take off with he same fuel load to achieve the same duration as the La7, Spit, 190, yak. In fact either should the P-51, F4U, P47 and others. So if the F6F only needs 25% fuel to make the same journey then it's performance is far closer the La7 in climb and maneuverabilty and the matchup is far more realistic and competitive.
Here is a list of current MA durations. IMHO the F6F, F4U, P-38 and P-47 are the greatest handicapped. The Spit, LA7, F4F and others benifit greatly.
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Is it me maybe I am missing somthing hear, but was not the F6F's longer range a result of it's abaility to cary a large amount of fuel in DT's, while the La-7 did not. Also would it not be the fuel consumption in the La 7 is simply less compared to the Hellcat, The Hellcat is a bigger plane.
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At the risk of sounding like a total "Luftwaffle" I must say that the 190's, especially the late 190's had rather good endurance, with multiple internal tanks and beer can. The P47 on the other hand was short legged, that's why they needed to have the P51 designed. The P51 is prolly the allied fighter with the longest range whith those huge DT's ... dunno about the F4U, it was a huge plane. Maybe it could out distance the P51 with beer cans?
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With DT's nothing (single engine fighter wise) could go as far as the Mustang. Only thing that was close was the early model A6M ZERO. But to do this the aircraft had to be trimmed just right with prop and fuel mixtues cut so lean the plane would barely fly. (Good discription of this procedure in the book by Saburo Sakai - SAMURAI!). The Pony could do it at normal cruise.
While the early model Juggs were short legged - later D, M & N models with twin & sometimes 3 DT's could go nearly as far as the Mustang.
The Corsair has pretty good range with the DT's but nothing like the Mustang. That's why the AAF put them on Iwo Jima to escort the B-29's to Japan and back.
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That chart is for military power. It is not representative of the maximum range of each plane and nor is it running each engine under equal conditions.
At military power, the R-2800 in the F6F should use about 250 GPH (about 280 with WEP but WEP not shown on that chart), which would run the F6F out of gas in about an hour....times 2 fuel use due to the MA fuel multiplier and you have 30 minutes, matching that chart exactly. OTOH, at cruise power the F6F should be able to stay up for around 3 hours (90 minutes in the MA) That is TRIPLE the range for the same amount of fuel! Can the F6F do this in AH?
I have no idea how much fuel LA7's engine uses. Multiplying it out suggests that at military power the LA7 uses around 140 GPH in AH. Military power in the LA7 is I believe 41 inches MAP.
It is quite possible that the LA7 might simply get better fuel economy at military power than the likes of the F6F (remember that military power in the F6F is a much higher MAP rating which affects fuel use). What could determine this is whether the LA7 gains as much range from using cruise power settings as the F6F does. In theory, the F6F should gain far more additional range from using reduced power settings than the LA7. I believe cruise power for the LA7 is 30 inches MAP at 2000 RPM.
Anyone care to test it?
Perhaps the wise AH F6F pilot would be wise to cruise around at 34 inches MAP and hence require less fuel. Of course, then there's the issue of the fuel multiplier penalizing slower-climbing airplanes, but that's not a new issue and beyond the purpose of this thread.
J_A_B
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As a separate note (which is why this is a separate post), the F4U-1D should outrange the P-51D in AH. The AH P-51D only has the small 75-gallon droptanks available (fine for MA purposes), not the 108-gallon tanks more commonly used in the ETO and a far cry from the 165-gallon tanks used towards the end of the war in the Pacific.
J_A_B
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Originally posted by Andijg
With DT's nothing (single engine fighter wise) could go as far as the Mustang. [...]
Ta152?
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Ta 152 on internal beats P51, but not so sure with DTs.
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NO DROP TANKS!!
Where in the post did I mention DT's??
What I am looking for is Mil power fuel consumption for the La7, 109, spit and 190.
Internal fuel consumption only.
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http://www.hitechcreations.com/forums/showthread.php?s=&threadid=68371
Some fuel capasity/consuption data (near the bottom).
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It should be a Thermo equation. If you know what the Military power was for the La-7 then you can calculate the fuel required to make that much power. I'm sure Funkedup could whip this out in a matter of seconds. ;)
Spritle
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I don't know the first thing about aerospace, mechanics or all the technical stuff of flight, but to me these types of topics can prove very interesting. I just want to pop in with a comment after seeing someone bring up the F4U-1D which has always struck me as having very short legs in the MA when I was always under the assumption it wasn't too shappy in that department.
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I repeat myself--the increase in fuel use from cruise to military power isn't the same for every engine.
I repeat myself again--test these planes at cruise settings if you want to see if their fuel consumption is actually right.
J_A_B
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JAB,
Cruise settings do not mean anything. All power settings in AH are mil power full throttle.
I don't think testing cruise power helps you determine mil power fuel consumption.
Is this what your trying to say??
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No, what I'm trying to say is each engine doesn't use the same amount of fuel proportionately at military power. Planes like the F6F use proportionately more fuel than the LA7 at higher power settings (because they run at a higher MAP). In other words, using military power costs the F6F more range.
At cruise settings the F6F should far outrange the LA7.
Why do you need to test fuel consumption at military power? If that chart is right, then you can just multiply it all out! The F6F at least matches what it should use and the LA7 seems to use about 135-140 GPH at military power.
In other words, what I'm saying is if the F6F/F4U pilots choose to fly around at military power all the time, then they're shooting themselves in the probverbial foot and wasting lots of fuel.
J_A_B
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J_A_B,
You don't get something for nothing. I don't know what kind of HP the La-7 engine has, but I believe this statement would hold true.
Assuming equivalant efficiency if both engines produce approximately the same HP at WEP they will both use approximately the same amount of fuel regardless of the differences in MAP.
It's a mass flow rate equation I believe. You put fuel and air in and get power and heat out. Both sides of the equation HAVE to equal.
I believe 1 gallon of gas is 125,000 Btu. 4 stroke engines have pretty crappy efficiency ~20+/-%. Higher compression ratio engines TEND to have better efficiency.
F4UDOA,
What you might be missing is this. The La-7 often didn't have far to travel to the fight in real life as you stated. In the MA this isn't true, but if the La-7 can utilize a lower power setting to get to the fight (due to less drag) then he will have burned less fuel. But in regards to this:
The Hellcat has almost the same exact fuel duration as the La7 in the MA. According to the posted chart the F6F has 30minutes of flight time at full throttle mil power and the La7 has 28 minutes.
Internal fuel loads
La7 122 gallons
F6F 250 gallons
That doesn't seem right. Assuming that full throttle mil power means that both engines are making their full rated HP for that altitude I would say that the fuel burn rates would be some how proportional to their HP outputs.
Spritle
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JAB
Regarding the F6F-5 and fuel consumption rates at Mil and cruise settings.
Arena fuel burn at 1.5
12,000ft with 2x 1k eggs, rockets and 100% internal fuel, from a worst of 38 minutes and 160 miles, using the correct cruise settings you can get the F6F-5 to fly for 125 minutes and cover 360 miles.
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Spritle,
For some reason your the only one who is getting my point.
In fact you hit the nail on the head.
How does an engine in the La7 develope 1850HP and only burn a fraction of the fuel of an engine that generates 2000HP?
JAB,
I don't know that the fuel burn in cruise is proportional to fuel burn in military. If it was I would do that. In fact it is not the same from the F6F to the F4U with an identical engine. The F4U has a more economical cruise by about 10GPH.
And even if the La7 had a fuel burn of approx. 140GPH and the F6F has a fuel burn of 280 GPH then the La7 is much more efficient than the Pratt&Whitney R2800. Last time I checked the Russians had to capture a B-29 to copy a Pratt&Whitney.
F6F
2000HP Mil.
280 GPH
7.14 HP per Gallon of fuel per hour
La-7
1850
140 GPH???
13.21 HP per Gallon of fuel per hour
Meaning the La7 would be almost TWICE as efficient as the F6F!! Actually the number is 1.85 times more efficient.
Wow, I had no idea the Soviets were so advanced in 1944
:rolleyes:
Seriously I doubt this is true.
In fact if both engines were equally as efficient in producing HP then you could take the 30 minute fuel duration number for the F6F and multiply it by 1.85 to even the playing field then the F6F flight time at mil power would be
55.22Minutes in the MA on full internal fuel at mil power!!
Meaning that the long range F6F would only have to fly with half of the internal fuel percentage (albeit still more volume than the La-7) to accomplish the same mission as the short range La-7. IE La-7 100% fuel 122 Gallons to the F6F 50% fuel 125 Gallons.
Hmm, sounds like reality to me:D
Cav,
I am comparing apples to apples. Mil power to Mil power. The F6F should have twice the range of the La-7 no DT's on either in cruise or mil power all things being equal.
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Yes F4UDOA i understand thats why my post was aimed at JAB just as information he had asked about.
Some of the difference could easily be explained by engine efficiency however what your describing is pushing it a bit.
I have no idea of the specifics of these 2 engines but for example compression ratios, combustion chamber shape, spark plug positioning and even the amount per cylinder, metal the bores and cylinder heads are manufactured from can all have significant effects on an engines efficiency. Also what fuel grade where they using in each plane ?
Spritle your post does not really hold water as you are making some huge assumptions that the efficiency of the engines is the same, if it was and they produced the same HP (which they dont) then yes i would agree.
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"Arena fuel burn at 1.5 "
I thought it was 2.0 in the MA.
Anyway......
F4UDOA, your mistake is in the assumption that these engines are equal, or anywhere close to it. In truth, the R-2800 develops FAR more power than the M-82FN. 2200 max in the F6F compared to 1850 max for the LA7, a 350 HP difference. NOTE: 1850 represents WEP for the LA7, NOT MIL power!
The R-2800 runs at 300 more RPM and 11'' more MAP with WEP. At military power, the disparity is even greater--a full 13'' MAP and the same 300 RPM difference between the R-2800 and the M-82FN.
What makes you think that these engines would be anywhere close in fuel consumption at military power? They're running at different power settings and developing different amounts of power--there is absolutely no reason NOT to expect the R-2800 to use a lot more fuel at MIL power. More MAP, more RPM means more power, and more fuel consumption. Heck, the R-2800 at MIL power is running more MAP and RPM than the M-82FN does with WEP!
At best cruise settings, I'd expect these engines to be a lot closer in fuel use--the R-2800 has a cruise setting of 34'' 2150 RPM, and the M-82FN cruises at 30'' 2000 RPM. Even then the R-2800 would be making more power and using somewhat more fuel, but it'd be a lot closer.
In truth, these engines are very similar--at low to medium power settings. The big difference is the R-2800 can develop MORE power than the M-82FN because it is rated for higher power settings. The R-2800 is simply a better engine. I'd bet that if you ran the R-2800 at the same settings as the M-82FN, it'd get roughly equal fuel use in AH.
The LA7 is 7000 lbs, compared to around 12000 lbs for a loaded F6F....THAT is why the F6F needs so much power to haul itself around.
What you have to remember is "military power" is not some magical benchmark for fuel economy comparison. It just represents the max power settings the engine was rated to run at for any length of time. All else being equal, an engine rated for more power will use more fuel. It's that simple. If you want to actually compare their fuel consumption, compare them at equal RPM's and MAP, and even then it's not totally equal because of differences in compression ratio, engine valve design, etc.
Am I saying AH is definately right? No. I AM saying you're trying to over-simplify this issue and trying to comapre things which shouldn't really be compared.
J_A_B
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214thCavalier,
Actually my post holds a huge amount of water. Otto cycle 4 stroke gas engines ALL have crappy efficiency PERIOD! Diesels are much more efficient. While ALL of the factors that you listed DO play a part in the overall efficiency of an engine they are NOT going to amount to a 100% difference! Did you hear that?
Are you actually suggesting that the Russians in 1944 somehow developed an engine that was TWICE as efficient as any of its contemporaries?!?!?!? NOT!
Now for the next lesson. It is NOT easy to increase the efficiency of an engine. Even today’s completely computer controlled, computer designed, advanced materials and manufacturing engines are NOT even 10% more efficient than those aircraft engines. Do you know why? For a hint re-read my post.
There is NO way that an engine that produces 1750 HP is only going to consume half the fuel of an engine producing 2000 HP if both engines are under full load.
Spritle
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JAB,
I know I am over simplifying, and I expect the R2800 to burn more fuel in a larger A/C.
However I am doing it to make a point.
1. I did not find WEP rating and mil rating on the La-7. Do you know what the Mil power number is for the La-7?
2. I am comparing GPH to generate 1 HP. I was coming up with 1.85 for the La-7 compared to the F6F. This ratio is very high.
How can an aircraft that produces 1850HP and runs at Mil power with a fuel tank of 122 gallons can have the same duration as an A/C that has twice the internal fuel and produces 2250HP?
The La-7 produces 82% of the HP(1850HP) of the F6F(2250HP) but only uses 49% of the fuel in the same amount of time? Does this sound right? It doesn't to me.
One last thing. The P-51D with the Merlin V-1650-7 used 180 GPH at mil power. And It was 12 cylinders and produced 1490HP and it was liquid cooled. By comparison it is a gas guzzler compared to Honda civic of the air(La-7).
BTW. If you have gallon per hour numbers on the Spit IX, FW190A or 109G I would luv to do the same comparison. Frankly I'm surprised nobody has come up with these.
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"I did not find WEP rating and mil rating on the La-7. Do you know what the Mil power number is for the La-7? "
I know the RPM and MAP values, but I do not have actual power figures MIL power for the LA7's M-82FN engine. At WEP the LA7 reaches 1850 HP. Of note is the fact that WEP on the LA7 adds more MAP than WEP on the F6F, so the LA7 likely has more power loss from WEP to MIL than the F6F does. This large drop in power is supported by the plane's massive drop in performance in MIL compared to WEP.
I estimate the LA7 makes around 1500HP on MIL power, perhaps slightly less. That is merely an estimate though and certainly not "fact". I also estimate that WEP on the LA7 would increase fuel usage to around 200 GPH, although this guess is too much of a "ballpark figure" to be of any real use.
While this would mean the M-82FN is still more efficient at MIL power than the R-2800, this is not unexpected since the R-2800 is developing a lot more power--as you increase power you will lose more and more efficiency.
Basically, MIL power in the LA7 is equal to a high cruise setting in the F6F, in terms of both fuel usage AND power output.
J_A_B
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JAB,
Like I said. I don't have the numbersfor La-7 fuel consumption.
But even if the Mil power La-7 HP rating is 1500HP that is still equal in output to the Merlin 12 cylinder at 60"+MAP at mil power sucking down 180GPH.
Speaking of which. The Spit IX uses a similar engine to the Mustang with a fuel capacity of 137 gallons. That should give it a fuel duration of .76 hours at mil power.
Compared to the F6F which has a 250 gallon tank and a 280GPH for a duration of .89 Hours.
So you might expect the F6F to have an advantage?
Well In AH the F6F has 30minutes of flight time and the Spit IX has 35minutes. I just don't think this is right.
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Where are you getting your fuel consumption numbers? They are different than what I can find.
You quote 280 GPH for the F6F at MIL power.
The info I can find all says around 250 GPH at MIL, and about 280-290 GPH at WEP.
You quote 180 GPH for the Merlin, presumably a Mustang Merlin.
The info I find generally says about 150 GPH in MIL, and 200-210 in WEP.
Generally your consumption figures are higher than mine. It seems almost as if you're quoting WEP numbers instead of MIL numbers.
Of note, if YOUR F6F MIL comsumption figure is correct, then the F6F actually has TOO MUCH range in AH at MIL power. Think about that for a minute.
I will re-check every source I can find, and I suggest you do the same.
J_A_B
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Why do people insist on comparing apples and oranges all the time?
Engine output is a function of Torque, RPM, fuel mixture, compression ratio, engine efficiency etc etc
Just because an engine produces less horsepower does not mean it is necessarily less fuel hungry.
From what J_A_B posted the F6F fuel consumption figures look fine. Until someone posts some figures for the La-7, this argument is pure speculation.
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JAB MA is 2.0 those fuel tests were done for a Scenario which used a 1.5 fuel modifier.
Some of the difference could easily be explained by engine efficiency however what your describing is pushing it a bit.
Spritle you Tard you seem to have the impression i am saying the LA7 is twice as efficient as the F6F, I suggest you go and read my post again then POINT out to me where i say that.
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Blue Mako,
Your making my point for me and it's not apples and oranges.
I am comparing two radial engine fighters with comprable HP in the F6F and La-7. Then I am comparing the P-51D Mustang and Spit IX.
Frankly I'm surprised more people don't recognize this as a problem.
Why does a short range fighter like a Spit have greater range than the F6F?? Does this make sense? And it makes the F6F fight at a hugh disadvantage by carrying way to much fuel into combat reducing performance greatly. Same for the P-51, F4U, P-38 and P-47 or any other long range fighter.
JAB,
My numbers for the P-51, P-47, F4U, F6F all come from the pilots manuals. In fact the P-47, F6F and F4U numbers for consumption are all practically identical.
I have hard copies of these but you can see (almost see) most of the numbers here.
Zeno's (http://www.zenoswarbirdvideos.com/) They don't have the F6F but here are two R2800's
Here is the P-47
(http://www.zenoswarbirdvideos.com/Images/P-47/47SEFC.gif)
Here is the F4U
(http://www.zenoswarbirdvideos.com/Images/F4U/F4USEC.GIF)
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BTW JAB,
Your point about WEP on the La7 is really moot.
The fuel consumption number that are always used are never sea level numbers.
The La-7 has no measurable WEP affect above very low altitudes.
And here is the P-51 fuel consumption
In low blower mil power the number is 180GPH
High blower is 140GPH. Who in AH flys at High Blower Alts?? This applies to Mustangs and especially Spits.
(http://www.zenoswarbirdvideos.com/Images/P-51/51FOIC.gif)
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I know I am over simplifying, and I expect the R2800 to burn more fuel in a larger A/C.
Any aircraft engine burns about the same amount of fuel for a given power setting/altitude regardless of the plane it is bolted to.
ra
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214thCavalier,
You TARD. Did you read my post?
Are you actually suggesting that the Russians in 1944 somehow developed an engine that was TWICE as efficient as any of its contemporaries?!?!?!? NOT!
It's a rhetorical question dolt.
In fact the difference in efficiency between those engines would probably be in favor of the R-2800 based on numerous factors. Like time of development, materials, production techniques, pure R&D,...etc.
ra hit the nail right on the head. This discussion has NOTHING to do with airframes. I don't care if these engines are mounted on blimps or Hellcats, or La-7's the discussion is about fuel consumption under full load. Drag is NOT part of the equation.
The fact of the matter is that both of these engines would be within a few percentage points of one another in efficiency which does NOT account for the difference in fuel consumption under full load.
Spritle
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Easy with the name calling kids. Lets keep it civil.
Anyway,
The F6F carried 250 gallons of fuel weight 1500LBS
The La-7 carried 122 Gallons of fuel weight 732LBS.
Which means that since both A/C in AH have the same endurance then all things being equal the F6F has to fight with a 768LB weight tied to it reducing climb acceleration and turning ability.
This is even worse for the P-47D-25/30, P-38, P-51, F4U-1 and Mossie since they carried even more fuel than the F6F. The more you carry the worse the penalty is compared to La-7, Spit, 109 and 190's.
This should not be.
Currently the Hurricaine has longer range than the F4U, F6F, P-38 and is equal to the P-47. Funny I don't remeber the Hurri being a long range escort fighter??
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"JAB MA is 2.0 those fuel tests were done for a Scenario which used a 1.5 fuel modifier. "
It says right on top of that chart that it's for a 2.0 setting. I doubt the guy who made it labeled it wrong.
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"Why does a short range fighter like a Spit have greater range than the F6F?? "
It doesn't, unless the guy in the F6F makes a point of wasting as much fuel as he possibly can. If both the Spit and F6F pilots actually TRY to maximize range, the F6F will outrange the Spitfire.
I notice that in the F4U chart you posted, it shows a number of 275-290 GPH for MIL power, but only 245 GPH for WEP. That strikes me as being sort of odd. If by some fluke that chart has those numbers backwards, everything would make a lot more sense. Unless, amazingly, the fuel use of the F6F/F4U dropped by 45 GPH despite the engine developing 250 more HP.
You should take note of this--if the F6F did indeed run at 290 GPH at MIL, then it should use all its internal fuel in only 54 minutes, or 27 minutes with the MA fuel modifier. This would mean the F6F in AH actually has TOO MUCH range at MIL power, not "too little"!
Since the F6F in AH runs out of fuel exactly when I would expect it to, I believe HTC uses numbers equal to what I can find (which are about the same as that F4U chart except for the apparent reversal of MIL and WEP fuel usage).
LA7 fuel use at low altitude is very important with regards to AH, both because people fly around a lot at low levels in AH and because that's the only level where the engine reaches max rated power.
I am still trying to find more info on the V-1650-7. Remember that the Merlin in the Spitfire we have in AH should use less gas because it operated at lower power settings. The P-51D in AH certainly runs at about 150 GPH at MIL at normal arena altitudes. The chart posted there is a Korean War-era chart.
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"The fact of the matter is that both of these engines would be within a few percentage points of one another in efficiency which does NOT account for the difference in fuel consumption under full load. "
You seem to think the LA7's engine and F6F's engine develop equal amounts of power. They don't. It's not even close. At MIL power the F6F is probably developing 500 or more extra HP than the LA7, which would account for a large drop off in efficiency.
J_A_B
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Just as kind of an aside that harks back to various strat changes...
These issues would really stand out if we loaded fuel in gallons rather than percentage as I and many others have suggested.
(In case you've missed some of the past strat bits, the idea would be to limit the amount of fuel loadable to volume rather than percentage as a strat effect. By way of example, this is because a Yak that is limited to 25% of it's full fuel load is paying a far greater penalty than a P51 at 25%.)
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"Currently the Hurricaine has longer range than the F4U, F6F, P-38 and is equal to the P-47. Funny I don't remeber the Hurri being a long range escort fighter??"
The Hurri does NOT have a longer range. Stop flying around at full throttle all the time and maybe you'll notice that.
At MIL power the Hurri 1 gets LESS than half the power of the F6F/F4U/P-47. It also uses FAR less fuel because of this. WHY, WHY does it surprise you that at MIL power the Hurri 1 stays airborne longer than the F6F????? Do you REALLY think the F6F/P-47/F4U should use the same amount of fuel at 2000HP as the Hurri 1 does at 900 HP???
If you want range, USE CRUISE POWER instead of wasting huge amounts of fuel. Why do you think REAL F6F/P-47/P-38/P-51 pilots flew around at 35'' or so MAP, because they liked going slow? No, because flying at high power reduced range too much.
AH might not be perfect. It probably has some small errors. But it isn't as badly off as you're trying to make it out to be.
J_A_B
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J_A_B,
500HP less is NOT half of the R-2800 HP. The La-7 engine uses HALF the fuel at WEP compared to the R-2800. THAT ISN'T RIGHT! Is that so difficult to understand?
Also remember the discussion is about fuel burn rate at full load/full engine output. It is NOT about cruise settings.
Assuming the La-7 engine made 1500HP and the R-2800 made 2000HP then the fuel burn rate of the La-7 should be about 75% of the R-2800 +/- a few percent under full load. The fact of the matter is that it is HALF of the R-2800. That means that if the R-2800 had a 25% efficiency (note: 25% is GOOD for 4 stroke gasoline engines) then the La-7 engine was 50% efficient. Hah! You obviously don't have a clue. Modern gasoline engines don't even approach 50% efficiency. And modern engines have the benefit of computer designed intake and exhaust ports, computer designed combustion chambers, exotic materials, modern quality controls, exotic lubricating oils, etc. The list goes on. But this majical 1940's technology La-7 engine somehow is more efficient!? Think man, think!
Spritle
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Hi Jab,
>I notice that in the F4U chart you posted, it shows a number of 275-290 GPH for MIL power, but only 245 GPH for WEP. That strikes me as being sort of odd.
Indeed! :-)
Could it be that WEP is based on water injection? Since at military power the engine is run at a very rich mixture for cooling, I'd expect water to substitute a considerable amount of the extra fuel. Water actually cools better than fuel, so total liquid consumption might still be lower at WEP than at MIL.
Well, that's a quick guess :-)
Regards,
Henning (HoHun)
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That might explain it Henning, but the chart doesn't mention anything about water injection--the engine listed should have a W in it if it used water injection (like the F6F-5's using the R-2800-10W). Still, something is up.
F4UDOA--
Are you saying you want the F6F's endurance at MIL power decreased further in AH?
Spritle--
So you think fuel consumption will be totally linear as you increase power? Take a look at those charts up there, for example the F4U chart. Notice how, from cruise to MIL power, the engine uses triple (or more) fuel for less than double the power?
It's not always linear, there are other factors in play. You know that.
How can you claim that AH must be wrong when we don't even have all the facts? Do you know what mixture the LA7 uses at its 41'' MAP power setting? For that matter, do you know how much power the LA7 develops at 41'' (remember that 1500 HP at 41'' was my GUESS!!!)? Do you have good HP/GPH info for the M-82FN engine? You claim I don't know what I'm talking about, yet you're willing to condem AH when you don't even have all the facts. I hope you never serve on a jury!
Oh, BTW, you're even wrong in your own post. We weren't talking about WEP in the first place, the LA7 does in fact use more than half the fuel of the F6F at WEP (actually it uses better than 2/3 of the fuel).
J_A_B
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J_A_B,
You guessed wrong. Here are some specs for the ASh-82FNV engine that is used in the La-7.
Displacement 41.2 liters = 2514 cubic inches.
Rated HP = 1850.
Based on that the R-2800 makes .803 hp/in^3
and the ASh-82FNV only makes .735 hp/in^3
http://www.aviation.ru/La/
http://www.btinternet.com/~fulltilt/Engine.html
So now you are saying that the La-7 engine producing 1850 HP uses half the fuel of the R-2800 producing 2250? Remember the difference in displacement is lass than 300 cubic inches.
Did you actually look at the plot of the fuel flow rate vs. horsepower? I made a plot of this and besides the rather odd data point of 290 gph for 2000HP it looks pretty damn linear to me. It certainly isn't an exponential increase.
So what say yea?
Spritle
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"So now you are saying that the La-7 engine producing 1850 HP at WEP uses half the fuel of the R-2800 producing 2250?"
No I never said that, and I have no idea where you got that from. And why do you keep talking about WEP, you're the only person in thid thread who keeps on discussing WEP.
J_A_B
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Oh BTW, on the one website you posted, it lists two figures for LA7 fuel use at sea level--310 litres/hour and 274 litres/hour
At 5400 feet fuel use is listed at 355 litres/hour.
It takes 3.78 Litres to = 1 US gallon.
274 = 72.5 GPH, 310 = 82 GPH, 355 = 94 GPH
It looks like those fuel consumption figures are for some cruise setting, NOT MIL power and certainly not for WEP. It lists MAP as being 1200mm, but that is equal to the LA7's WEP and there is NO WAY it gets 82 GPH at WEP.
Are you a native English speaker Spritle?
That website gives the very useful information that this engine is umtimately derived from the Wright Cyclone. This might be useful info.
J_A_B
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JAB,
HoHun beat me to the punch on the less fuel consumption with WEP. Indeed the engine runs a leaner mixture and stays cooler as well as saves more fuel.
As far as you satement about "Stop running around wasting fuel", that is rediculous. Your not getting the point at all.
ALL OF THE A/C ARE RUNNING AROUND WASTING FUEL!!
I'm posting accurate pages on the fuel consumption and you keep telling me that the La-7 which produces 1500HP at Mil power(That number is your guess) which is 75% of the 2000HP the R2800 puts out but only uses 50% of the fuel to do it in the same amount of time. Meaning that the ASh-82FNV is 25% more efficient. Not!!
That is the whole arguement in one sentence and the La-7 engine is NOT 25% more efficient than the R2800 causing many AH A/C to carry far more fuel than neccesary to accomplish the same mission.
BTW. Spritle seems to know what he is talking about you may want to read his post.
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"That is the whole arguement in one sentence and the La-7 engine is NOT 25% more efficient than the R2800 causing many AH A/C to carry far more fuel than neccesary to accomplish the same mission. "
The only problem is we don't KNOW what the LA7 does on MIL power. I'm not saying AH is right or wrong with regards to the LA7, I'm saying WE DON'T KNOW. If someone would be so kind as to locate good data on the engine settings of the LA7 at MIL power (41''), then we would have something useful to look at.
For all we know MIL power in the LA7 might be the same thing as a lean-mixture high cruise setting in the F6F. That's sure as heck what it looks like.
You are so convinced that AH must be wrong that you're ignoring the fact that much of what we're discussing is based on guesswork and assumptions. It's good for discussion, but NOTHING in this thread *proves* anything.
*IF* the LA7 indeed produces 1500HP at MIL power (we don't know), and *IF* it's running on a rich mixture like the F6F is at MIL (we don't know), THEN I would expect it to use a similar amount of gas to develop X amount of power.
I *suspect* that at MIL the LA7 is running on a leaner mixture than the F6F because the F6F needs additional cooling at the higher power output. Run the F6F in a high cruise configuration at ~1500 HP at low alt like the LA7 and I bet that R-2800 would be just as efficient or dang close. On your chart up above, at 1675 HP at low alt the F6F gets 220 GPH and it's still on auto-rich....reduce this by another 200 HP and use auto-lean and I don't think it'd be far from 140 GPH.
It's equally possible that AH might be wrong. It's *possible*, but we haven't PROVED anything, either way.
J_A_B
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Your right JAB,
Nothing is proven becuase we don't know the numbers for Mil power consumption for the La-7. I also have serios doubts about weather a 14 cylinder engine even today could put out 1500HP in a high cruise mode. No one else could do it with anything close to the same size displacement and the Russians didn't have the quality of castings for engines that the Americans, British or Germans had at the time.
In anycase you can expand that arguement to the Spit and 109's. They all seem to out distance all of the longer ranges birds. Compare the Spit and the Mossie. Same engines, the Mossie has four times the fuel and two engines.
Why on earth does the Spit IX have the same endurance as the Mossie?? The Mossie should not have to take 500 plus gallons of fuel to fly the same distance as the Spit with 130 gallons of fuel.
Somethings rotten in Denmark!!
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Lol JAB i am happy to see i am not the only one having problems with Spritle putting words in my mouth :)
Btw the fuel consumption i posted earlier was as i said tested for a scenario which ran a 1.5 burn rate it was not reffering to the chart posted above i posted it only to show how much fuel consumption could be affected.
From that site Spritle linked and if they are accurate ?
As this one is limited to 10 minutes its reasonable to assume its Wep and at sea level.
Engine speed 2500 rpm
Manifold pressure 1200 mm mercury = 47 inch map.
Fuel consumption 310 l/hr
Duration 10 minutes maximum per flight
This one drops 100 rpm and 200mm mercury, so probably Mil setting and as stated at sea level.
Engine speed 2400 rpm
Manifold pressure 1000 mm mercury = 39 inch map.
Fuel consumption 274 - 310 l/hr
@ 1,650 m ( 5,400ft) (1st stage boost)
Engine speed 2400 rpm
Manifold pressure 1000 mm mercury = 39 inch map.
Fuel consumption 310 - 355 l/hr
Ok found this one as well from http://www.ctrl-c.liu.se/misc/ram/eng_ash-82.html
Refers to engine ratings of 1460HP / 1850) HP i assume Mil and Wep settings?
Worth noting this site refers to Fuel consumption as g/hp/h now could that in fact be grams per HP per hour and not litres per hour ? ?
Now if it is Grams per HP per Hour then plucking some figures out of the air:-
For the Ground max rating (call it sea level) we have 1430 Hp quoted and a consumption of 315 to 340 now if its grams and using the max figure thats 0.340 KG fuel per HP per hour multiply by 1430 Hp and we get 486 KG of fuel per hour, multiply by 2.2 to convert to lbs and we get 1069 lbs of fuel.
Using a specific gravity for the fuel of 0.6 thats 6 lbs per US gallon we can work out that it uses 178 US gallons per hour.
(Using both figures the range works out at 165 to 178 US gallons per hour)
That is 136 to 147 Imperial gallons per hour pretty damn close to the figure JAB worked out earlier quoted here.
I have no idea how much fuel LA7's engine uses. Multiplying it out suggests that at military power the LA7 uses around 140 GPH in AH. Military power in the LA7 is I believe 41 inches MAP.
So F4UDOA and Spritel does that make it easier to swallow ?
Nearest Cyclone i found power wise is this one but no fuel consumption data as a rough comparison found yet.
SPECIFICATIONS
Model: R-2600-13 (Wright Cyclone Model C14B)
Type: Static Radial, Air Cooled, Double Row
Number of Cylinders: 14
Bore: 6.125 in.
Stroke: 6.312 in.
Piston Displacement: 2603 cu.in.
Compression Ratio: 6.90:1
Blower Gear Ratio: 7.06:1 and 10.06:1
Blower Diameter: 11.00 in.
Rated RPM of Crankshaft: 2400
Rated BHP/RPM at 6700 ft: 1500/2400
Rated BHP/RPM at 13,000 ft: 1350/2400
Take-Off BHP/RPM: 1700/2600
Rotation of Crankshaft (from anti-propeller end): Clockwise
Rotation of Propeller (from anti-propeller end): Clockwise
Propeller Reduction Gear Ration (crankshaft to propeller): 16:9
Average Weight of Engine: 1978.50 lbs.
Overall Length of Engine: 63.10 in.
Overall Diameter of Engine: 54.26 in.
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Don't get me wrong F4UDOA, I'm not trying to be an "AH cheerleader". Far from it. I AM playing "devil's advocate" though because we need real proof, rather than conjecture. "Feeling" something is wrong isn't good enough unfortunately. We need something concrete.
The Mosquito has been brought up before. It is also "wierd". Good onfo on the Mossie should be a lot easier to find than info for the LA7. This is a much better direction for this thread!
But if you REALLY want to see something wierd, think about this:
The Hurricane IIc has 22 minutes endurance at MIL power with 121 gallons of fuel. The LA7 has 28 minutes endurance with 122 gallons.
The Hurri 1 has something like 1300 HP MAX, probably less than 1200 on MIL power, yet it has about 22% LESS endurance than the LA7 for the same amount of fuel.
Now THAT is odd.
The more I think about it, it seems as if the AH LA7 is running around on a very lean mixture until it engages WEP. Maybe possible in theory, but it definately seems wierd, wouldn't the dang thing overheat and prematurely detonate?
Now this is total conjecture on my part, but could that have been possible to do without overheating during the very cold Russian winters?
J_A_B
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Heya Cav,
The fuel consumption numbers on that site are a little suspicious. 310 L/Hr = 63 Gallons per hour at mil power at sea level producing roughly 1500HP. That is just this side of impossible.
That would give the La-7 a fuel duration at Mil power of roughly 2 hours, 45 minutes better than the P-51D with all internal tanks full.
If that was true the perpetual motion machine would be just around the corner.
The good news is that it is so close to the Wright Cyclone. That engine I can definitely find numbers for. And I can assure you the f4F didn't have better range than the F6F.
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F4UDOA go and re read my post again, you replied while i was editing and adding more info i was working on.
If you read it you will see i make it 178 US gallons per hour at 1430 HP (I am assuming thats Mil) at sea level.
I kept it as US gallons to make the comparison easier for those who may confuse US gallons while the rest of the world used Imperial gallons.
And why does everyone assume JAB and I are batting for the LA7 ?
We have been trying to keep an open mind and help figure it out without stomping our feet and saying that cannot be !
Now if any smart bellybutton wants to pick holes in that please feel free, I am open to polite corrective actions, well unless your Blond, long legged, big busted and female then abuse me all you want :)
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"And why does everyone assume JAB and I are batting for the LA7 ?
We have been trying to keep an open mind and help figure it out without stomping our feet and saying that cannot be ! "
AMEN!
We're trying to see whether it could be correct or not, and if it IS wrong, then WHY it's wrong--or why it's correct if it happens to be. Look at it from every possible angle.
If you just say "it's wrong" with no support nothing will be changed. If you can say "it's wrong by X amount for THIS reason and here's my proof", then you'll see changes.
J_A_B
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So JAB have you read my post a few up where i worked out 178 US gallons and 147 Imperial at sea level Mil power ?
If so any thoughts on possible errors?
So far to me coming at it from completely different angles with your extrapolating it from AH figures and my working it from grams used per HP per hour it seems AH could well be in the right ball park.
F4UDOA the next time i reply to one of your threads do me a favour and tell me to sod off !
That way i might get to actually play the game instead of wasting an entire night chasing info :)
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Let's for a minute assume the F4U chart posted by F4UDOA is exactly correct. It shows 290 GPH at MIL power (low levels) for the R-2800.
Lets also, for a minute, assume your estimate is also correct--178 GPH.
Now, in AH the F6F runs at 250 GPH and the LA7 runs at about 140 GPH--BOTH are low by about 40 GPH.
Of course, that's a lot of assumptions, but maybe that gives us something to go with.
It's also possible that the F6F might be spot-on and the LA7 might just be running at some crazy lean mixture
J_A_B
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JAB the F6F is on US GALLONS.
Fuel rates for the LA7 are 165 to 178 US gallons.
BUT if you use imperial gallons for the LA7 it works out at 136 to 147 smack in the range AH uses.
Also the F4U chart using the Imperial gallons column is 240 Imp gallons per hour.
Now is that a coincidence or what ? cos they match pretty damn close to AH if you use imperial gallons.
Next thing is to confirm whether the LA7's capacity is in fact in US or Imperial gallons, after all we must compare apples to apples and oranges to oranges :)
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Okay that is a hypothesis--perhaps the LA is sucking down 140 US gallons when it should be using 140 IMP gallons.
Can it be proven right or wrong?
If indeed AH is wrong, then the LA7 would have an endurance of roughly 20 minutes in the MA--this is much more in line with what would be expected from its power output and fuel load.
Unfortunately, I have no good data on the LA7's engine. I can't prove that hypothesis OR disprove it. I hope someone with good data will chime in.
-----------------------------
About the F6F, it flies 30 minutes (60 without the MA multiplier) on 250 gallons of gas, or 250 GPH. I'm not really concerned with the F6F though because I can locate stuff that shows 250 to be correct for the F6F's engine (and apparently HTC can too) and even if it's wrong (which is debatable) it'd only make a tiny difference in AH anyway....it's just not signifigant.
J_A_B
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The earlier figures that were giving ridiculously low consumption figures were from Tilt's page (AH player) and he has a lot of info on the LA7 at,
http://www.btinternet.com/~fulltilt/Lavochkin.html
However i cannot believe the fuel figures he has posted are correct, there has to be an error in that data.
But damn him he does not give the fuel capacity everything else but that ! :)
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Tilt's fuel consumption data isn't unbelievable. A lot of websites and general sources list "best" fuel comsumption, right next to "best" power, giving the false impression that the engine would use much less fuel at full power than it actually did.
Those fuel comsumption figures are totally believable if you're talking about cruise settings. It's sort of like how an airplane will often be listed for a "best speed", giving people the false impression that the plane would reach said speed at any altitude (even here in AH we get the occasional person asking why various planes are so much slower than what their books say).
J_A_B
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Cav and JAB
,
That could be exactly what the problem is in regard to the La-7 fuel consumption. The 178(US) Gallon would really put it more in line with the expected efficiency levels of other engines.
The strange thing is that if you look at that fuel burn chart again the numbers are all over the place. You would expect certain A/C to be better and some to be worse.
1. The P-40 and P-38 have almost identical endurance. Really?
2. The Hurri 1 has 119 Gallons and the Hurri IIC has 121 gallons but the Hurri I has TWICE the range???
3. The Spit IX has the same range as the Mossie??
4. The F4F/FM-2 have longer range than the F6F and F4U?
5. The NIK2 has a longer range than any American Naval counter part despite having a 2,000HP engine and a 190 gallon tank
6. The F4U-4 has less range than the F4U-1D. Despite having a slightly smaller tank it was rated with a longer combat range.
Just a few Knits to pick.
BTW. Cav. I can't tell you to bugger off. I need you to clear my 6!!
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F4UDOA the figure i worked that 178 US gallons with was 1430 HP now if we take that as approx 75% of the F6F-5's power and add 25% to the fuel consumption rates for the LA7 we get a figure of 237 Gals per hour IF it could produce 2000HP, which of course the LA7 cannot but its damn close to the F6F-5 figure.
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Cav,
Actually I was thinking the opposite of what you are.
I'm thinking that HTC is calculating the range of the La-7 based on Imperial gallons instead of US. I say this because it would be hard to do it the other way without adding weight to the La-7.
And it still doesn't explain the rest of the anomolies.
I think it's about time for Hitech to burst in and call me a whiner or say it's all a figment of my imagination.
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Range and Endurance are not the same thing. Range will depend on how fast the plane is flying.
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Uh.. why you throwing all these numbers around?
Just find what was the max flying time for an La7 in WW2 and the max flying time for the F6F or any other fighter and compare them to AH
But I do agree, the La7 and hurri/spits have quite a flight time when you compare them with the long range fighters of their day.
P-47 had almost 2 times the range, the spitfire could barely fly over the french coast while the Jug got near Aachen GERMANY. In AH the Spit and the Jug have almost the same flight time.
And thats what F4UDOA is saying I believe.
For game purposes I can see the furball trash will need their turny cannon planes last quite a while so they can fly to the nearest furball and have their fuel last longer than their ammunition... just like the high alt realism fanatics want their long range zoomMboom rides last a LOT longer in the air so they get a chance to SPEND all their ammo before their fuel runs out.
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Yes Whels I appreciate that but F4UDOA's point was why does the LA7 and F6F have nearly the same flight time at Mil power in AH when the F6F carries twice as much fuel ?
There is no question that the F6F will be airborne a lot longer if you use Cruise power settings and altitudes.
Oio if you look for max flight times of which i have seen nothing mentioned for either plane, all i see is max range and combat radius figures, neither of these represent flight time at Mil power settings.
F4UDOA's concern was that the LA7 was using some magical economy engine, throwing all them figures around shows thats not the case and its fuel consumption generally falls into line with the F6F.
So whats the fuel capacity in US or Imperial gallons ? that could make a large difference IF its incorrect.
IF the LA7 is modelled with Imperial gallons and it should be US gallons then drop the fuel capacity by 0.83 and the flight time.
However i suspect its more likely the capacity was in Imperial gallons.
Understand i am not pushing to alter the LA7's duration just trying to answer F4UDOA's question, but if it is incorrect then by all means lets get it right.
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because its beautifle.
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Ok. I must come in and throw my fit.:eek: I had to run home away from my first contacts of the flight today two separate times. Now I was in my trusty F4U-C loaded with 100% fuel and 2 1k bombs. Both flights I flew about 15 min to the target which was about 1.5 sectors away. I dropped my eggs and looked for a fight. Now i'll add that I was climbing untill I got to about 17k-20k then I level off. Ok at about the 20 min mark I find a enemy dot. I go to engage and since he/her is low I play it safe and avoid the mindless HO's for 2 passes from this spit. I then look down for some odd reason and say OH Chit, I am like vapors. This was no more than 25 min of flight.
So I have two questions to ask.
1) Since MA is a 2.0 fuel consumption, does this mean that at full power (no WEP) the F4U-C could only fly for 50 min?
2) J.A.B. keeps ramling on about conserving fuel by flying at cruise alt and settings. Where do I find these? I have tried lowerin manifold pressure, tried lower RPM, tried lower both, tried flying high, tried lots of stuff and the only thing I can get to change the rate my fuel disappeares is to turn off the engine and glide for awhile.
Does anyone get a niticable difference in fuel consuption by flying like a slow target? I mean I don't see any difference, and that if there is one it doesn't seem large enough to justify the risk of flying slow in a Hog.
Not to mention that it takes 10 min or so just to get to 20k in Hog when loaded with bombs, so I ask again, What is the cruise alt and speed, manafold pressure/rpm supposed to be so I can try it out.
Help me, I hate running out of fuel just as I find the silly dweeby Bish/Knight at 20k. I suppose I could just fly at 5k for them:rolleyes:
Booky
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"Since MA is a 2.0 fuel consumption, does this mean that at full power (no WEP) the F4U-C could only fly for 50 min? "
Yes, that is correct. The R-2800 consumed a HUGE amount of fuel at high power settings, hundreds of gallons per hour. You can TRIPLE your range if you use cruise settings in the F4U, which leads us to:
"J.A.B. keeps ramling on about conserving fuel by flying at cruise alt and settings. Where do I find these? "
For the F4U-1C and -1D, a good cruise setting would be 34'' MAP at 2200 RPM (it is debatable as to whether the RPM will affect fuel use in AH but MAP definately does). Again, this will greatly multiply your range.
Remember that different planes will benefit different amounts from using lower power settings. Planes like the F6F and F4U, which consume massive quantities of fuel at MIL power, will benefit most from using lower cruise settings. Other planes which don't suck up as much gas, like the Spitfires or P-40's or such, won't benefit as much although it'll still help.
Still hoping somebody can come up with definative evidence to either confirm or deny the LA7's fuel use/fuel load.
J_A_B
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Hi Jab,
>Still hoping somebody can come up with definative evidence to either confirm or deny the LA7's fuel use/fuel load.
From a German evaluation report of the La-5FN with Ash-82FNV engine:
Fuel (460 L): 345 kg
"The low endurance of about 40 min at rated power, which decreases further when high blower is used, deserves mention."
This is equivalent to about 137 USGPH . Rated power was 1000 mm Hg, 2400 rpm.
(The La-5FN's and La-7's Ash-82 engine featured a fuel injection, which generally tended to give slightly better fuel economy than with carburetted engines.)
Regards,
Henning (HoHun)
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Hmm Henning...
The rated power you listed is basically the same as AH MIL power, 41'' hg. Interesting!
460 litres = 122 US gallons.
40 minutes = 2/3 of an hour.
122 = 2/3 of 180, so I would think it was using 180 US GPH.
How did you get 137 US gal/hour? What am I missing?
J_A_B
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Hi Jab,
>How did you get 137 US gal/hour? What am I missing?
You're right, it should be 182 USGPH. I must have mis-typed some numbers on the pocket calculator.
>The rated power you listed is basically the same as AH MIL power, 41'' hg. Interesting!
Hm, 1000 mm seems to be jut 39.4 in. Emergency power was given as 1180 mm or 46.4 in. But remember that this was for a La-5FN, so the engine settings might not be equivalent to those used for the La-7.
Regards,
Henning (HoHun)
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Does anyone get a niticable difference in fuel consuption by flying like a slow target?
Yes , throttle back to a slower in flight speed and you will go farther on the same amount of fuel . I don't think the prop setting makes much differance in AH unless the engine is turned off .
Many times in P51's I throttle back at alt to move between sectors , it does work .
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Ok Fuel conservation tip,
Find the recommended cruise setting for your ride and use it, it definitely matches AH.
Lowering rpm definitely helps fuel as does playing with map.
Good to see the Gph seems to be working out at 180 US g/p/h whichever way we come at it from.
So burning 180 US gph with a 122 US gallon tank giving 40 minutes flight time, the MA's 2.0 fuel modifier should mean approx 20 mins flying only.
The current settings allow for 56 minutes at a 1 fuel modifier when it appears it should be 40.
That LA7 sure was a short range beast.
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Thanks guys, when I get home in the morning I'll try it out. Going to run my Hog at the suggested 34" and 2200RPM, then at 34" and max rpm to see if the difference in consumption from RPM is worth the speed/endurance/times messin with it.
Does anyone else have a different manafold pressure I should try? I am kinda etchy about this since I feel my speed is going to be way hampered at these lower settings :eek: And my Hog is already slow enough considering what im up against.
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Booky you get speed or range, unfortunately not both.
As an example the F6F cruise speed is about 167 i believe, painfully slow but it makes the fuel last a lot longer.
F4U's cruise speed will not be much different.
You save more fuel by climbing on wep to cruise alt then reducing rpm and map than you do climbing on Mil or a reduced throttle.
Reason as far as i can see is going wep you get up quicker then spend longer in the cruise phase actually saving fuel.
May sound daft but a wep climbout really is more efficient.
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I belive this discussion will never be resolved. My reasoning is because the AH planes are *not* historically correct. Not that I intend to convince anyone of this. Afterall, if the sky looks green to you, then its green. How's that logic for ya?
The inaccuracy bothered me for a while, but I got better. Oh sure I can look up data at several sources, but what's the point? The planes are modeled as they are modeled. Perhaps that's to give an advantage to those who fly them or take the time to record their performance for comparison. Myself, I prefer the latter category.
(as an aside, the F4U-4 was a waste of someones time to model, I am fond of the plane but will never fly the current model in AH)
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Heya Gents,
That 180 GPH figure sounds exactly as I suspected!! This would reduce endurance in the LA7 dramtically in the MA.
The most important part of this equation is it causes A/C like the P-47, Mossie, F6F and F4U to fly with way to much fuel to compete with smaller A/C.
For instance
1 gallon of fuel weights approximately 6lbs.
F6F-5
250 Gallons fuel
1,500LBS
30 minutes endurance in the MA currently mil power
Wing loading= 37.37
Power loading Mil power= 6.24
LA-7
122 gallons fuel
732LBS
28 minutes indurance in the MA currently mil power
Wing loading =38.87
Power loading mil power Assuming 1500HP for mil power= 4.87
If the LA-7's fuel consumption was corrected to 180GPH then it's endurance would be 20 minutes in the MA at 100% fuel!!!!
(Sorry for repeating you Cav)
20 minutes is .66 of the F6F flight time and fuel.
.66 of the F6F's fuel is 990LBS
Changing performance to
Wingloading= 35.82
Power loading mil power= 5.98
This is a more competitive matchup for the Hellcat wouldn't you say??
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Originally posted by 214thCavalier
The earlier figures that were giving ridiculously low consumption figures were from Tilt's page (AH player) and he has a lot of info on the LA7 at,
But damn him he does not give the fuel capacity everything else but that ! :)
Sorry only just picked this thread up..... fuel consumption at various alts and engine conditions at
http://www.btinternet.com/~fulltilt/Engine.html
This is from the actual La7 pilots manual........
I am at work and will dig up some stuff on range trails I have this evening .... you must bear in mind that range time/distance was normally recorded as a factor of cruising speed...........
I seem to remember two figures of 35 and 45 minutes depending upon boost.but will confirm
as a generalisation I would agree that the range of an La 7 would be significantly less than most bloooo planes. Infact most VVS fighter fields moved with the fronts and AC rarely took off with any thing less than 100% fuel............ even IL2's based them selves further behind the lines than Yaks and La's......... Interestingly the the Yak 9D & T had quite significant ranges in comparison to the Yak 3, 9U and La's
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Following is a translation of test data on La7 range and fuel consumption..............if you wish I can put up the original Russian as well. Sorry if some of the formatting is lost
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Edited out due to poor format and linked to this file instead
Some La7 test data (http://www.tilt.clara.net/pics/AKT_LA7.rtf)
Link is fixed
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Your link isn't working.
Would like to see what ya got.
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good data Tilt.
2400 rpm isn´t even WEP, and flight time is already below 40minutes.
Oh well those big radial engines were thursty
niklas
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FWIW, when AH was first released the planes with small fuel capacity, like the 109 and the La-5, had very short endurance. You needed to grab full fuel and a drop tank in the 109, even then the endurance was very short. Somewhere along the line an adjustment was made, and internal fuel capacity became less of a limiting factor. It could be that the fuel multiplier penalizes planes with large fuel tanks more than it does planes with small fuel tanks. That would explain why the Mossie has such crap range, for example.
I think F4UDOA is on to something here, but it might not be a bug. It may be the way HTC decided to handle endurance differences without making the small planes unappealling because of their limited flying time.
ra
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CC Niklas,
I think this closes the case.
Fuel consumption is even higher than I thought.
35 minutes flight duration in Mil power for the LA7 at sea level.
That is nearly half of the fligth time of the F6F. That means that all other A/C in AH are flying at a burn multiplier of 2:1 and the La-7 is almost 1 to 1.
Feels good to be right for a change.
Anyone have Spit and 109 numbers for Mil power?
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F4UDOA,
Feels good to be right for a change.
Sure does.
Spritle
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Originally posted by ra
FWIW, when AH was first released the planes with small fuel capacity, like the 109 and the La-5, had very short endurance.
In fact the La5FN had a combat endurance (2400 rpm) of 40 minutes............... giving it some 120 km greater range than the La7 under normal test conditions.
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Hi Tilt,
>In fact the La5FN had a combat endurance (2400 rpm) of 40 minutes............... giving it some 120 km greater range than the La7 under normal test conditions.
Surprising! What were the reasons for that?
Regards,
Henning (HoHun)
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RA,
I missed your post when you put it up.
But I think your absolutely right about HTC deciding to handle the fuel consumption issue by just leveling the field. What they have done in effect by doing that is create a fleet of small superplanes.
When people complain about their performance the response is something like these.
1. The La-7 is a low altitude fighter and your fighting at it's best height.
2. The Spitfire was the best dogfighter of it's time.
or my favorite.
3. The NIK2 really was the best PAC fighter. The Japanese just didn't have any pilots.
When the real answer is.
We decided to make you fly your F6F towing a Volkswagon to level the playing field against the shorter range fighters.
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I think the damaged fuel effect should be in gallons not percentage. Why penalize the guys with smaller tanks?
Change it from
no droptank
75%
50%
25%
to
Full
300gallons
200 gallons
100 gallons
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Great thread you guys. Cant believe it didnt turn into the crap we are all used to. I hope pyro and hitech pay attention to this. You may want to put your data together very well and post it in a new thread that is not 2 pages long, with a very catchy title....
This could really improve game play if they accept this.
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Originally posted by HoHun
Hi Tilt,
>In fact the La5FN had a combat endurance (2400 rpm) of 40 minutes............... giving it some 120 km greater range than the La7 under normal test conditions.
Surprising! What were the reasons for that?
Regards,
Henning (HoHun)
Early La5 fns were fitted with only 3 of the 5 tanks fitted in the original La 5 this infact reduced range to circa 500Km..... with the advent of the metal sparred La5FN they introduced 4 tank set ups (2 x 168 L & 2 x 148 L) totalling 632 L . Air intake clutter at the wing roots and attempts to lighten the fuel load forced the La 7 back to 3 tanks ( 460/470 L).
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We are so ready for engine management to be added to the playpen I mean main arena. Imagine how funny it would be when you see quakers popping engines left and right because the keep there throttles pegged.
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Useful info there Tilt thanks for posting it.
Btw do you know the actual power rating at Mil ?
Tilt your info here http://www.btinternet.com/~fulltilt/Engine.html
take the sea level one for example at 2400 and 1000 Mercury gives a fuel consumption of 310 L/Hr.
Assuming thats meant to be Litres per hour that equates to approx 82 US Gallons an hour.
Cant be true at the quoted engine settings, from the rest of the data you have now posted here thats roughly twice as efficient as it actually is, mebbe you got a typo in there or it was not in Litres.
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Any Russian speakers amongst us?
(http://www.tilt.clara.net/pics/page123.gif)
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Just a note about plane's uberness.
Actually more than 75% of players never think about returning to base. So, their rides will fight with less than half the normal fuel load. And more than half of these players are flying already uber planes like La7s or Spits.
Basically, you will keep seeing incredible turns, acceleration, climbs, etc whatever the fuel consumption rate of the plane.
If you fight vs a spit or La7 loaded with 75% of fuel you will see incredible moves and E retention, but if you fight a spit or La7 loaded with 25% of fuel you are actually fighting an ufo.
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Tilt,
That's a menu from a Russian steakhouse.
ra
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Hi Tilt,
>Early La5 fns were fitted with only 3 of the 5 tanks fitted in the original La 5
Ah, finally something to classify Lerche's Lavochkin :-) So if it had 460 L only, it must have been one of those!
>Air intake clutter at the wing roots and attempts to lighten the fuel load forced the La 7 back to 3 tanks ( 460/470 L).
Did you read Prokryshkin's "Sky of War"? In the final stages of the war, his squadron flew Lavochkins, and they had some difficulty to keep up with the moving frontline. They finally used a length of Autobahn as their base, though it was tough to keep the tanks from rolling down the landing strip all the time :-)
Regards,
Henning (HoHun)
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Originally posted by MANDOBLE
If you fight vs a spit or La7 loaded with 75% of fuel you will see incredible moves and E retention, but if you fight a spit or La7 loaded with 25% of fuel you are actually fighting an ufo.
don't you just hate it when they put a crimp on your historical vulching streaks in your dorka?
:mad:
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No serial La-5FN had 5 Fuel tanks.
Even The La-5F fuelload was already reduced by 50k / ~70l. While the La-5 had 390kg fuel, the La-5F and all further models had 345 kg.
What i read is that studies from "Zaks" permitted to eliminate the outer fuel tanks with 3 new tanks concentrated in the center section, but total fuel capacity remained the same, so "only" 3 tanks is not quite correct. This was introduced with the 82FN engine.
And it stayed this way.
Maybe they build a long range La5FN but the usual serial FN had 460l maximum
Otherwise takeoff weight would have been way over 3400kg. Even the La-5FN with 460L had a takeoff weight of 3300kg (or 3350 in german sources). But you won´t be able to show me a takeoff weight of over 3400kg.
niklas
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Mandoble,
I hope you see this post because I just want to make my point clear. I am not whining about the performance of the La-7 or Spit (And I have more of a reason to suspect the Spit of being a bit to fuel efficient as I did the LA-7).
What I am whining about is how the A/C with large fuel loads are affected.
If you want an example take an F4U-1, F6F or P-47 and put 75% fuel in it. Fly it offline and note the stalls, climb and turn radius. Then put 25% in the tank and try it. It is a huge difference because these A/C carry huge amounts of fuel. The difference is not nearly as pronounced in the La-7 and Spit because they cary so little fuel it really doesn't affect their wing loading as significantly. But in the case of the F6F, F4U-1 and P-47 the wing loading from 100% to 25% can range for instance in the F4U-1 from 40.87 with 100% to 25% fuel wingloading of 35.7. That is the differance between a P-51D and a NIK2. And the fact that any of these A/C with 50% fuel are carrying more fuel than the La-7 has in it's capicity.
So not only will these flying fuel tanks be able to carry less fuel but they will be able to fly longer with less fuel relative to the smaller A/C. So my performance gap won't be nearly so large for so long.
What the guy in the La-7 chooses to do is not at all my concern.
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Originally posted by niklas
No serial La-5FN had 5 Fuel tanks.
Even The La-5F fuelload was already reduced by 50k / ~70l. While the La-5 had 390kg fuel, the La-5F and all further models had 345 kg.
What i read is that studies from "Zaks" permitted to eliminate the outer fuel tanks with 3 new tanks concentrated in the center section, but total fuel capacity remained the same, so "only" 3 tanks is not quite correct. This was introduced with the 82FN engine.
And it stayed this way.
Maybe they build a long range La5FN but the usual serial FN had 460l maximum
Otherwise takeoff weight would have been way over 3400kg. Even the La-5FN with 460L had a takeoff weight of 3300kg (or 3350 in german sources). But you won´t be able to show me a takeoff weight of over 3400kg.
niklas
I agree no La5F or La5FN ever had 5 tanks (proper) ..and would also accept that the 5 tank set up was a Lagg3 set up the La5 still had the 65 litre tanks in the outer wing which were deleted in the La5f. There could be some confusion here because the first la5's were made with LaGG wings which would have the outer tanks........latterly as the wings were made for the La5 (rather than those left in prioduction) with slats etc the outer tank might well have been removed.
With the advent of the metal spared wing in the last few La5F and and a large proportion of the La5FN they were able and did increase the fuel load to four tanks. Being one in each inner wing containing 148 l each and two central tanks of 168 litres each.
The La5FN metal sparred wing saved about 179Kg over its wooden counter part however many La5FN's were produced with wooden sparred wings again due to wings being produced far in advance of other production needs. The weight trade off between spar and tank would explain the full weight below3400kg,,,,,,,,,,,,,,you will see data on full weight vary from 3250 kg to 3375 kg across various texts.
I refered to 5 tanks proper above because actually there was a 5th tank which I consider to be part of the fuel system.............it was small (i dont know its actual capacity) and housed just to the rear of the engine.
reading further it seems a reasonable deduction that is was one of the 168 L central tanks that was removed in the La7.............this to make way for the air duct work from the inner wing area and the hydraulic/oil system now re piped under the pilots cockpit.
If you have any reference stuff to the contrary I would be obliged if you could provide it.
Ho Hun
I wish wish wish I could get an English translation of Prokryshkin's memoirs............... his squad did not like the La7 having formulated tactics heavily defined by the Air Cobra.........as some one who flew most types of VVS AC in combat.............. I would dearly like to read his comparative views.
I have often thought that the Rechlin la5FN was a early wooden sparred one...........but then you go and spoil it by stating it had a FN"V" engine which is definately a 44 classification for front line La's.
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They save the weight mainly with the elimination of the outer fuel tanks, and not with the metal spars. And this was realized already for the first -5FN.
Actually i have meanwhie the impression that the differences in takeoff weight depends on whether they calculated the pilot weight in or not.
Stalin demanded a higher range, and Zaks proposed a higher fuelload, but problems with the COG didn´t allow it.
What source do you use?
niklas
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Hi Tilt,
>I have often thought that the Rechlin la5FN was a early wooden sparred one...........but then you go and spoil it by stating it had a FN"V" engine which is definately a 44 classification for front line La's.
Is the fuel tank size of any help? I couldn't follow the details of your discussion with Niklas :-) Maybe it was an aircraft that underwent an engine change? The weight without fuel/oil/ammunition/pilot was 2773 kg, take-off weight 3347 kg.
>I wish wish wish I could get an English translation of Prokryshkin's memoirs...............
To find a used German copy of GDR origin would be easy via Amazon and the associated ZShops - I could pick from 18 examples, I think. I'm not even sure the book actually was translated to English, though.
>his squad did not like the La7 having formulated tactics heavily defined by the Air Cobra.........
They didn't? Suprising - nothing in his book suggests that (if I remember correctly).
>I would dearly like to read his comparative views.
Pokryshkin criticized the MiG series aircraft at first sight for its lack of cannon armament, and later as too heavy compared to the Luftwaffe fighters. I think the latter criticism gave him a lot of trouble as he was thrown out of the Communist Party for that, which he considered highly unfair, but he was rehabilitated relatively quickly. (The Airacobra received similar criticism for being overweight, if I remember correctly.)
After given the order to pick a fighter type to re-equip his unit with, Pokryshkin went to Moscow. After a coupel of test flights, his opinion of the Jakovlev fighter was that with a single cannon, it was lacking in firepower, and he prepared a diplomatic formulation of that opinion for his discussion with Jakovlev.
Jakovlev however, who was a great Stalin supporter, apparently considered Pokryshkin suspect due to the black spot on his party records (my personal guess), and left the visiting Pokryshkin without reply.
On the same evening, though, Lavochkin rang at Pokryshkin's door. Lavochkin was very enthusiastic and showed great interest in Pokryshkin's experiences and ideas as well as in the fate of pilots he had met earlier, and invited Pokryshkin to the factory, asking him for his opinions on the latest Lavochkin design.
Pokryshkin's central question on the new La-7 was "Cannon or machine guns?" The answer he received from an armourer at Lavochkin's factory: "Machine guns - what for? The fascists are pouring cannon shells at you, and you want to respond with bullets? That's of no use. Am I right?" Of course, Pokryshkin agreed :-)
So Pokryshkin decided on Lavochkins - though the La-7 wasn't ready yet and they first were equipped with La-5s.
Regards,
Henning (HoHun)
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Originally posted by HoHun
Hi Tilt,
So Pokryshkin decided on Lavochkins - though the La-7 wasn't ready yet and they first were equipped with La-5s.
Regards,
Henning (HoHun)
Interesting ..................... he was then in command of 9GIAD?
Hans Seidl has him converting directly to the La7............
Niklas
Gordon & kazimov, as well as Hans Heiri Stapfer............
The claimed weight saving (for the metal spar) is pretty clearly nothing to do with the saving of the outer tank which had been eliminated over a year before hand.
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F4UDOA, your point is crystal clear and valid. My point is that range is not a valuable factor when you dont plan to return, and this is actually a common denominator in the MA.
I've done a lot of tests with SpitIX, Typh and D9 offline and in DA with 100% and 25% fuel, and basically, all the planes performance is affected in the same way by the fuel load difference. Yes, there is a notable difference between a 100% loaded spit and a 25% one.
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My point is that range is not a valuable factor when you dont plan to return, and this is actually a common denominator in the MA.
Sure there is. It means the LA7 has less time chasing me around and/or it means the LA7 has to put more fuel in its tanks if it wants to fight for any appreciable amount of time and thus be subject to weight penalties such as most other aircraft.
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Hi Tilt,
>Interesting ..................... he was then in command of 9GIAD?
>Hans Seidl has him converting directly to the La7............
He was promoted to lieutenant colonel while he was in Moscow to decide on an aircraft. He returned to his regiment (which he lead at that time), and found a telegram by Lavochkin there stating that they could take delivery of their fighters, which turned out to be La-5s. On re-reading, I'd say they only received two aircraft, which they flew to Moscow where they did the administrative work for the delivery of the La-7, and then returned to the regiment with these La-5s. Pokryshkin was made commander of his air division (9th "Maruipol" Guard Division) on that day.
Apparently, the La-7 was only collected at the Moscow factor after 18 August 1944, where Pokryshkin still was at the front, and a 6-day leave from the front to Nowosibirsk following that date.
In October, the division - which had been pulled out of combat for the conversion - hadn't converted fully yet, and they remained in re-eqiupment and training status until they were ordered back to the front on 8 January 1945, entering combat on 12 January.
Regards,
Henning (HoHun)
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Originally posted by HoHun
Hi Tilt,
In October, the division - which had been pulled out of combat for the conversion - hadn't converted fully yet, and they remained in re-eqiupment and training status until they were ordered back to the front on 8 January 1945, entering combat on 12 January.
Regards,
Henning (HoHun)
that bit I knew.........the irony was that once proven by 63 GIAP annd 176 IAP 9GIAP would have been the 3rd but in fact due to delays and accidents they were delayed into action beyond several other units............
Milos Vestik writes that some elements of this regiment did go into action in November 44 as part of 303IAD............they fought beside the Normandie Niemen.............. or they would have but very rainy weather grounded them for long periods.......
They next particiapated in the January push of the 3rd byelorussian front.as your text confirms
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This is one of two notes to summarize what I learned from the voluminous data already presented in this thread. This note addresses US aircraft built around the P&W R2800 engine. The second note deals with what we have learned about the La-7, built around the Ash-82FN engine.
Thanks to charts contained in the posts by F4UDOA, it does not take much work to nail down the fuel economy of two versions of the R2800. I’ll focus on just the R2800-8, the workhorse of the F4u-1. I’ll pretend this is also the engine used in the F6f, when in fact that plane used an engine that was a little less powerful. F4UDOA also gave us numbers for the –21 model (used on the P57) which are only a little different, primarily because of the turbo supercharger installed.
I have generated a table and two charts of the resulting data (see below). The table tells it all, but the charts may be easier to follow. The first point to start with is Specific Fuel Consumption (SFC), which is really what the argument about endurance is all about.
The first chart plots SFC in US gallons/horsepower/hour. Note there are really two lines to consider which are driven by the choice of fuel mixture – auto lean or auto rich. SFC at minimum fuel consumption or maximum cruise are very similar and do not very much with altitude. That’s why it pays to fly higher at a modest manifold pressure. On auto rich settings (other than WEP), SFC is about 80 percent higher and it is somewhat more sensitive to altitude. The difference between normal and military power is not very great. SFC for WEP is higher, for the reasons described in our thread – you are substituting water for fuel and adding more air, so you are leaning out the fuel mixture.
How does this translate into endurance (hours in the air)? That is illustrated in the second chart. I have to caution that these numbers are somewhat over estimated because they may assume you are get to the specified altitudes without burning any fuel (below I present an alternative calculation where this is not an issue and I can show nearly the same results). Also I’m am using the wrong engine model for the F6f, but that too does not matter much.
The result is that all settings that use a rich fuel mixture, internal fuel gets you about an hour’s flight time in the F6f and slightly less in the F4u-1. The military setting is a little worse, giving you only about 50 minutes of time. The max cruise setting gives you 3 hours of flying time at virtually any altitude and would be what most of us should expect if we are serious about missions like CAP or long haul escorts. The minimum fuel economy would get you an obscene 4-6 hours of flying time on internal fuel. But we should remember that it may not include the climb and it is much more sensitive to altitude.
From the table we see that fuel consumption varies by nearly 7 times from the most economical to the most rapacious settings. The worst performance on auto lean is more than twice as good as the best setting on auto rich. Maximum cruise is attained using half the engine's rated horsepower and only 30 percent of the fuel consumed at the rated horsepower.
Should we believe the fuel economy numbers?
I would say yes because we can observe nearly the same data from two economists who carefully studied how radial engine performance affected costs in civil aviation before and after the war (Miller and Sawyers, Technical Development of Modern Aviation). Here are their numbers for engines of the same era:
Wright Cyclone (R 1820) 87 octane 0.57
Wright Cyclone (R 2600) 100 octane 0.47
P&W Double Wasp (R 2800) 100/130 octane 0.42
The Cyclone was known for its fuel efficiency in its day. Note the primary gain in specific fuel consumption across these engines is due to the substitution of fuel with more energy. Note also these numbers almost certainly assume a lean fuel mixture, as the authors’ focus almost exclusively on civil aviation where fuel economy is important.
Another implication is that one should not believe a SFC below 0.40 for a 1940s high output radial engine. It’s possible that the really good water cooled engines did better, because their lower cylinder head temperatures allowed them to run on a leaner fuel mixture. Heron's history of aviation fuels (1949) suggests the best SFC obtained from a high output engine was 0.37 on 115 PN avgas on a postwar US engine (the Wright Turbo-Compound Cyclone R3350).
I point this out because some calculations in this thread based on data for the Ash-82FN imply a SFC of 0.30 or lower, which is simply incredible.
A better calculation of endurance for the F6f
Now I turn to the data contained in the Standard Aircraft Characteristics chart (dated 1949) from Hal Andrews, "F6F Hellcat," Naval Aviation News Sept-Oct 1988. A copy can be downloaded from
http://www.history.navy.mil/branches/hist-ac/fighter.htm.
I work right off the chart to minimize the chances of introducing an error. That means I will use the standard fighter load out with full fuel and a drop tank, and assuming a climb to 15,000 feet.
There is separate estimate of range in which the drop tank is dropped prior to combat, but this introduces a lot of uncertainty into the calculations so I ignore it.
Based on the chart, the F6f-5 with a full load of fuel (internal and external), has a “combat range” of 950 nautical miles at an average speed of 178 knots an hour. 950 knots/178 knots/hr = 5.3 hours of flying time
We can also work out the best fuel consumption using the SAC. Assuming the tanks are empty at landing (there should at least be 20 gallons in the reserve), we have 400 gallons/5.3 hrs = 75 gallons/hr, a number in between the estimates for minimum fuel consumption and maximum cruise in F4UFOA’s charts. Note that on internal fuel only (250 gallons), we are getting an estimate of endurance of 3 hours and 20 minutes, just a little better than what is shown in the previous chart.
One other thing to note from this source - In the description of the Fighter combat Radius formula, we see the climb-out calls for 60 percent normal sea-level power. The chart is good enough to tell us that at 6,200 ft, normal power is 1,710 HP. Given the plane is at low blower there is practically no drop-off in performance of the R2800 at such a low altitude so we can assume this as a good approximation of normal sea-level power. Sixty percent of this amount is 1026 HP, just about half the maximum output of this engine. That is pretty much what we observe for economical cruise settings in F4UDOA’s charts.
I mention this because it is a plausible way to approximate horsepower at a cruise setting when you don’t have the information and you’d like to estimate specific fuel consumption. For example, with the La-7, we have numbers on the engine’s rated and emergency horsepower but not at a cruising power setting. That’s one reason why the thread took so long to converge.
-Blogs
p.s. I don't seem to know how to post more than one attachment at a time so I'll drop them in a sequence of posts
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This from F4UDOA's data
-Blogs
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Again thanks to the information in F4UDOA's post.
-Blogs
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Endurance of the La-7 and its engine
In my preceding post I used the data presented by people smarter than I (and better librarians too) to present hard numbers on the endurance of the US heavy iron navy fighters. This was an easy exercise because of all the information made available.
Now I turn to the La-7 and its Ash-82FN engine, where we have a lot of information, but not all we need. We also saw some inconsistent information. I hope to convince you that the technique I used for the plentiful American data can tells us something about the Russian data.
The bottom line is that the La-7’s engine seems about as efficient as its American counterparts, possibly exceptional at very high output settings. That said, no matter what power settings you consider, An F6f or an F4u-1 running on internal fuel only should always fly for twice as much time, or more, as an La-7. It turns out that, possibly entirely by coincidence, most of the complicated issues we argued about in this thread simply can’t change the general conclusion. I wonder if that would be true if we looked at other light planes with small fuel tanks…
Some background on the La-7 and its engine
The 1944 edition of the LA-7 weighs in at 7164 lbs (3250 kg) gross. It has a maximum speed of 408 statute MPH (658 KMH), Operating range is 413 statute miles 665 km). See Gordon and Khazanov Soviet Combat Aircraft of the Second World War.
The Ash-82FN is a 2514 CU (41.2 liter) radial engine, just a little smaller than Wright’s 14-cylinder version of the cyclone. Its cylinders are derived from the cyclone, but with a shorter stroke. The engine could generate 1850 HP when run flat out on 100 octane fuel. Its rated power was about 1460 HP. Note that front line units typically had fuel of 90-95 octane fuel.
By the time the La-7 is being produced the engine benefits from direct injection and over-boosting (i.e. more than 1 atmosphere of pressure in the cylinders) at high and low super charger speeds.
Tilt’s November 4 post includes a trove of flight test information and other data for the La-7 as of the last 9 months of the war. It is from a translation of a Russian report on tests of several production models.
From that post we know for certain the fuel tanks is 460 liters or 122 US gallons. There’s a great deal of information on the combat maneuverability of the plane, which we usually never see. I hope someone has verified that the AH flight model tracks this pretty well.
Endurance for the La-7 compared to USN Heavy Iron
Tilt’s report spells it out so no calculations, other than converting to American measurements is necessary (see the attached table). Running the plane at what HTC calls military power (2400 RPM at 40 inches HG) provides a brief 32 minute ride at 16,500 feet, 35 minutes at 3,300 feet. Plug whatever fuel multiplier you want into this and its clear the La-7 has very short legs.
Compare the F6f with full internal fuel load running at a comparable engine setting (2550 RPM, 44 inches HG, 7k alt) and you have an estimated endurance of 68 minutes (see my previous post). Just shy of running these planes to the firewall, the F6f flies about twice as long as the La-7. The La-7 is burning 164-6 gallons an hour while the F6f is burning 34 percent more (220 gallons an hour).
Let’s compare the planes at a cruise setting. On full internal fuel, the La-7’s maximum range is 413 miles and maximum flying time is 1 hour 45 minutes at 3,300 feet. At the most economical settings tested, it burns 52-5 gallons and hour.
My analysis of the SAC data (see my previous post) shows the F6f can fly 3 hours and twenty minutes, burning about 75 gallons an hour, reaching a peak altitude of 15k. So the F6f can cruise for twice as long while burning about 42 percent more fuel an hour.
In other words, power settings do not affect the relative endurance of the F6f and the La-7. In either case, the F6f on internal fuel only should last twice as long as the La-7.
Note that my result is very conservative. I could have used the minimum fuel consumption numbers from F4U1DOA’s charts. In that case, the F6f is burning essentially the same amount of fuel per hour as the La-7 and it fly’s 5 hours or more on internal fuel. I don’t use those numbers because I don’t think there are very many pilots in Aces that would be comfortable holding these planes in the air with only 500 HP and a steady hand.
Specific Fuel Consumption of the Ash-82FN engine
One of the problems we had in the thread is that we did not have good information on the fuel economy of this engine. Thanks to Tilt’s treasure of data we now know all we need about the plane’s endurance, and a lot more about its performance as a fighter. Before we saw that data, we were trying to match up data on horsepower, fuel capacity, and endurance from disparate sources.
This is what AH tells us about the Shvetsov M-82FN:
Emergency Power- 48" @ 2400 RPM (5 minutes) [probably should be 2500 RPM]
Military Power- 41" @ 2400 RPM
Normal Power- 36" @ 2200 RPM
Max Cruise- 30" @ 2000 RPM
We can use these numbers to infer power settings in some of our other data. For example, its likely that near sea level the first setting is consistent with the 1850 HP number we’ve seen and the second setting is probably consistent with the engine’s rated horsepower of 1460, although Tilt has some numbers suggesting rated horsepower was 1650.
For example, at one point we had a calculation that at the engine’s rated horsepower (1460 HP at 2400 RPM and 40 inches HG) fuel consumption was 310-55 liters and hour. Could this be right? What is the implied Specific Fuel Consumption? 355 liters is 94 gallons and weighs 563 lbs (I am rounding). That implies and SFC of 0.39.
That is not an impossible number for a really good radial engine running on a lean fuel mixture. But there is no way this engine will generate its rated power in auto lean if no American radial can. For the very good P&W R2800, SFC is 0.8 at normal power and 0.9 to 1.0 at the engines rated power. Both settings require an auto rich fuel mixture.
Suppose the 310-55 number was kilograms per hour rather than liters. In that case the resulting SFC is 0.55 lbs/hp/hr, certainly reasonable for a radial engine on auto lean, but still too low for an auto rich setting, which this almost certainly has to be.
I wonder if this range of numbers is really a reference to range in kilometers.
Let’s use Tilt’s flight test data to compute a more plausible SFC for the Ash-82FN. At an altitude of 3,300 feet, 2400 RPM and 40 inches HG, the La-7 is burning 164 gallons an hour. These engine settings and the low altitude suggest we should be generating the engines rated power of 1460 HP. In that case, we have SFC = 0.67, which is remarkably good. If the engine was about as efficient as the P&W R2800, we should expect it to develop only 1,090 HP.
What is the Ash-82FN’s specific fuel consumption at a cruise setting? Using Tilt’s flight test data we see the engine settings are something like 1500 RPM at about 23 inches HG. We know the fuel consumption, but we don’t know the resulting horsepower. Suppose the engine is as efficient as a contemporary Double Wasp can possibly be (0.44). Then the resulting horsepower would be
HP = (Lbs/hr)*(1/SFC) = 331/0.44 = 752.
Suppose we use the trick from my analysis of the cruise settings of the F6f. At the cruise, the engine is generating about 60 percent of normal power, which worked out to be 50 percent of the engine’s rated power. Fifty percent of the Ash-82FN’s rated power is 730 HP. That would make the engine’s specific fuel consumption at a cruise setting something like 331/730 = 0.45, a very respectable but still plausible number.
Other modeling issues
An important question all game designers have to answer is whether they want to model aircraft based on data generated by prototypes or production models. For the US, UK, and Germany there would not be much difference. That is emphatically not the case for Russia, where production aircraft were always 20-40 MPH slower than prototypes and had significant problems with reliability.
Russian engine designers were able to get significant performance gains throughout the war, but for many engines, they did not get service lives up to anything like the American standard. The Ash-82FN engine was not even mass produced until the fall of 1943. At the time their service lives were about 100-150 hours. By the war, the American engines could go about 500 hours and typically longer before an overhaul. Even when the engines were fine, the propellers had flaws and the finish of production aircraft was typically poor.
In the case of the La-7, the same engine in La-5 broke down more often, in part because poor design of the air intake resulted in more dirt in the engine. Engine failures in the La-7 were very common occurrences.
None of these things are captured in games, and that is why many late war Japanese and Russian planes perform better than they typically did in the actual war. What's more, these planes never accounted for a significant share of the front line inventories of those countries.
Is it wrong for a game to ignore such things? Depends on the philosophy of the game. There’s lots of things we might not want a game to model.
-Blogs
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This thanks to the flight test data Tilt posted.
-Blogs
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Jeez!!
Joe Blogs, you make me look like an amateur.
That is some great work. I noticed you copyrighted those charts. I'll save them but I won't repost without your permission.
I emailed the data provided by Tilt to the Q&A forum a few days before HTC killed the thread. Although something tells me HTC is not really concerned with the result or not interested in addressing it. Notice in a 100+ post thread no answers from HT or Pyro.
Your extra data is the Coup De Grace. I have been a little suspicious of the La-7 for a while. It flys so well in every aspect of combat. So what is the advantage? Power to weight obviously like most Euro types seem to be better than there American counter parts. So what was the historic draw back, range. Check the numbers and viola. There is your answer.
The question I have now is this. Did HTC even the playing field for light A/C for gameplay reasons? I ask this because of other AH birds like
1. Spitfire
2. Me109G-10
3. NIK2
4. Yak-9U
All of these uber birds seem to have endurance that far exceeds their historic capability which puts them at a huge advantage of fighting A/C like the P-47, F4U and F6F which have to carry an extra 1,000+LBS of fuel to maintain the same endurance as these short legged birds.
The question of Soviet A/C using prototype data and higher octane fuel I haven't even started to question.
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Get rid of the fuel multiplier. It sucks, and really hinders the planes w/ short ranges. Take a full load of gas in a Jug, (no DT's) and climb to 20k... then enjoy your glide back down cause yer already out of fuel. And don't give me the "if there were no fuel multiplier then alt monkeys would be everywhere" argument. With the enormous use of the p51, and its extremely long range, this should already be a problem. However, as we know, it is not. Giving the planes their true ranges would make for a much better MA.
Stang
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Hi Blogs,
>Here are their numbers for engines of the same era:
>Wright Cyclone (R 1820) 87 octane 0.57
>Wright Cyclone (R 2600) 100 octane 0.47
>P&W Double Wasp (R 2800) 100/130 octane 0.42
A good calibration point for the Ash-82FN would be the specific fuel consumption of the BMW801D (which not only shared the general layout but actually the same injection pump). As a minimum, it consumption was 272 g/kWh according to von Gersdorff et al.
With regard to the engine of interest, a German data sheet for the M-82FNV gives specific fuel consumption at take-off power as 442 g/kWh.
Since these measures (sensibly) are based on fuel mass rather than on volume, my question is now how to convert the imperial measurements to the international system? I'm sure the consumption numbers you quote require certain fuel characteristics, most importantly a precisely defined specific weight.
Regards,
Henning (HoHun)
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Good work Joe blogs................
I think we can all acknowledge that several comparable fuel/range models in AH are unbalanced.............
infact we knew this from the Mossie and Ju88..........further F4uDOA paints a convincing arguement that some AC are limited in combat ability due to carrying more fuel for a lesser range.
If we accept the above I would ask if any work has been done to establish the AH model for reduced manifold and rpm settings................
rpm settings never "seem" to make any considerable effect on range......and manifold settings do not "seem" to have the effect of more than doubling range when set to cruise settings........
It seems to me that an La7 with an "economy cruise range" of 100 minutes is a very viable MA tool.........if true cruise range settings were available...........
given all this we should be careful for what we ask........... this could be a mamoth undertaking by HTC to cure in one sweep of development and any changes would have to be trickle fed during other onging development.
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You are free to post or email the charts and tables.
I copyright simply to ensure that someone down the line can't tell me they had a copyright and I cannot distribute my own work. But as we all know this is simply a presentation of underlying data that is in the public domain.
You guys are the experts, I am not. And I am amazed at the data you find. HoHun please send me links on the BMW 801D, that was next on my agenda. Gordan and Khazanov argue the Ash-82 was superior to that engine in a number of ways and I'd like to test that. Even so, the engine is only superior so long as it runs!
Most of the ideas in my post were already contained in the thread, but I assembled them in a way that seemed the clearest to me. It does turn out we had enough data to answer a few more questions than we thought we could.
A quick way to do all the metric conversions is by using the following web site:
http://www.admiralmetals.com/metric_conv.htm
I simply drop all the data into a spreadsheet and run it through a conversion table. I find it much easier to think in terms of Englsih measurements, but the rest of the world probably does not.
I always convert to US gallons and I assume a gallon of fuel is 6lbs. The critical factor is octane as the higher the octane the more energy per pound of fuel. I do not know if octane affects the specific gravity of the fuel in any significant way.
As for modeling in AH it would be useful to verify if there is a systematic departure between the endurance of light planes with small fuel loads and heavier ones that carry more fuel relative to what we can find in historical data. I think there was some evidence of this in the begining of the thread, but I don't know the power settings of the tests that were run (it may well be that power settings don't matter).
My favorite light weight is the 109f, which has short legs, but are they longer than they should be?
Suppose there is a systematic distortion? What should HTC do about it? My personal preference is towards more historical realism but I have to concede others have different preferences and it is entirely possible that too much faithfulness to the history might result in a less pleasant games (imagine modeling the ubiquitous oil leaks and electrical failures).
-blogs
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Take a full load of gas in a Jug, (no DT's) and climb to 20k... then enjoy your glide back down cause yer already out of fuel.
Not in any Jug I've flown in AH.
ra
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Hi Blogs,
>HoHun please send me links on the BMW 801D, that was next on my agenda. Gordan and Khazanov argue the Ash-82 was superior to that engine in a number of ways and I'd like to test that.
My reference is a book, "Die deutschen Flugmotoren und Strahltriebwerke" by von Gersdorff et al., so I don't have a URL ready, sorry! :-( But it would be interesting to know in which regard the M-82 was considered superior.
>I always convert to US gallons and I assume a gallon of fuel is 6lbs.
Well, that gives a density of 720 g/L, while the German weight data for the La-5FN indicates that their fuel had a density of 770 g/L. My physics book agrees with the 720 g/L for aviation fuel, but quotes 780 g/L for automotive fuel, so it obviously depends a lot on the exact composition of the fuel.
By the way, are you sure you quoted the fuel consumption values correctly? When I convert them to the international system, they're not even close to the values from von Gersdorff. Of course it could be my conversion!
Regards,
Henning (HoHun)
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Thanks for the reference, I'll have to try to locate a copy.
The relative comparison of the BMW801D with the Ash-82 FN comes from Gordon and Khazanov's Soviet Aircraft of the 2nd World War. I think this is a very good book and the performance numbers for the La-7 in that book correspond to Tilt's flight test data. That said, I think the authors do some editorializing here and there when they don't have hard numbers. That's why I want to get numbers on the BMW engine.
I did my work quickly so I could easily have made a mistake somewhere.
From Tilt's data I converted from liters to US gallons using the formula 1 liter = 0.264 liquid gallons (not dry), or conversely
1 gallon = 3.785 liters.
For the La-7 table I converted kilomters to US statute miles using 1 km = 0.621 mile or 1 mile = 1.609 km.
I was worried about getting the MAP correct though as I could not remember if the US measure is in linear or cubic inches. I assumed both the metric and US measures should be linear and converted them accordingly. This gave me numbers that looked spot on to other data presented in the thread.
Your numbers on specific gravity of fuels are very interesting. The difference is about 7 percent, which could matter. It would change and estimate of specific fuel consumption of 0.50 (in gallons per horsepower) to about 0.54, or 0.46 depending on the bias.
I may have some numbers on the weight and volume of fuel in the La-7 and that can be used to check for the assumed specific gravity.
I wonder if adjustments need to be made for specific gravity? There are some (old) papers on aviation fuels I may be able to scare up.
BTW, it should be easy to translate KwH into horsepower, but I haven't looked up the equation.
-Blogs
Originally posted by HoHun
Hi Blogs,
...My reference is a book, "Die deutschen Flugmotoren und Strahltriebwerke" by von Gersdorff et al., so I don't have a URL ready, sorry! :-( But it would be interesting to know in which regard the M-82 was considered superior.
>I always convert to US gallons and I assume a gallon of fuel is 6lbs.
Well, that gives a density of 720 g/L, while the German weight data for the La-5FN indicates that their fuel had a density of 770 g/L. My physics book agrees with the 720 g/L for aviation fuel, but quotes 780 g/L for automotive fuel, so it obviously depends a lot on the exact composition of the fuel.
By the way, are you sure you quoted the fuel consumption values correctly? When I convert them to the international system, they're not even close to the values from von Gersdorff. Of course it could be my conversion!
Regards,
Henning (HoHun)
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I don't know exact numbers but the aviation fuels used by the Russians were indeed heavier (weight/volume) than other fuels used by Finnish airforce.
gripen
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"With DT's nothing (single engine fighter wise) could go as far as the Mustang."
The P-47N had quite a bit further range than the P-51.
Daff