How good is the LA-7's Engine?

[Angus]

This thread is perhaps a tad more complicated than it needs to be.
Karnak  found out that the Mossie's endurance is a lot less than it was in real life. We will have to accept Real life figures as true, and there is no way to calculate ones way out of there. In WW2 the mossie was running missions as far as Berlin you know, while the Spitfire mission wouldn't even go deep into France!

Now regarding fuel burn rate pr/hp/time of course engines can be compared, but then the weight and aerodynamic factors such as frontal area, wingloading, or in other words, Drag, start playing with the equation, and as you can see on the comparison between the F6F and the F4U-1 these do quite a bit!
Anyway, if you guys prove your points nicely like Karnak did, I am sure those little things will be corrected by HTC in the future:D

[crowbaby]

alt-tabbed, got bored of reading a book.

About this SFC stuff people keep bringing up (F4UDOA and joeblogs) and i keep trying to shoot down. Look at the SEFC above.
At take off power, the R2800 in the F4u produces 2000hp for a fuel flow of 290 gallons ph.
At max cruise, 570hp for 42 gallons per hour.
This is without even bringing alt into the equation.

There just is no magic formula for fuel consumption over time equals output (hp).

[crowbaby]

And here are the results of the tests on the F4u-1. These are not 100% accurate because i kept getting distracted, but they're pretty close. Some of them don't take long anyway, feel fry to try yourself...

Max Cruise
10,000ft alt - 2150rpm - 34"Man
i got 150IAS/285TAS and 59mins from 1/4 tank = 90 gallons.
chart says 83gph, my result is 91.5gph - 10% over

Normal Rated
7,000ft alt - 2550rpm - 44"Man
i got 275IAS/300TAS and 24:30 from 1/4 tank
chart says 220gph, my result is 220.4gph - spot on.

Military
16,000ft alt - 2700rpm - 53"Man
i got 305IAS/380TAS and 23mins from 1/4 tank
chart says 275gph, my result is 234gph -  14% under

Military
2,000ft alt - 2700rpm - 52.5"Man
i forgot to record speed:) 22:00mins from 1/4 tank
chart says 290gph, my result is 245gph - 15.5% under.

This doesn't surprise me. The F4u-1 Specific Engine Flight Chart as used by pilots in WW2 says 290gph if you fly at full military power, which people seem to be doing in the MA (full rpm and Manifold pressure, no WEP). The F4u-1 carries 361 gallons. This would equate to 74 minutes of flight, or 37 minutes with fuel multiplier set to 2. Snefens chart, which people are so upset by, shows 43 minutes endurance. This is 16.2% better than the plane performed historically.

If i were you i'd back sheepishly away from those drums you wanted to bang.

As for the F6f-5 - we know that with the same engine and more fuel than the F4u, it had a significantly lower range historically. I don't see any point pursuing this further.

The Mosquito, however, does definitely seem to be off. to Karnak for finding and testing that.

again, i'm prepared to eat my words if someone can prove my logic, or my math, wrong.

edit for P-38 and P-47D-11
Snefens chart suggests 332gph for the P-38, it should consume 334gph.FOIC here
Snefens chart suggests 242gph for the P-47D-11. As it consumes 205gph at a max continuous of 36" and 2550rpm, this figure seems reasonable to me for Military Power. FOIC here
Snefens chart suggests 152gph for the P-51D, it should consume 180gph.
FOIC here

[niklas]

Originally posted by crowbaby

Has anybody compared the weights of these aircraft? F6f-5 'combat' weight 12,740lbs. La7 weight ranges from 2,638kg empty to 3,400kg absolute maximum. That's 5,800 to 7,500lbs!

This could be why the ASH-82 is listed for 1,330hp cruising at alt (probably optimistic), where the R2800 in the F6f-5 makes 1,625. Hardly comparable.

Pls explain me why weight should influence engine ouput...

Originally posted by crowbaby

Snefens endurance chart shows 28mins for both La5 and La7, 30mins for F6f. To me this chart is pretty meaningless, as efficiency varies hugely across speed ranges

Pls explain me why speed should influence the engine consumption when those engines run with constant RPM. We donīt talk about range, we talk about endurance. We donīt even talk about aircraft or prop efficiency, we talk about results that could also be measured on ground in the caves of a testing institute.

Originally posted by crowbaby

Which would equate to 276 litres per hour, or 73 us Gals.

We talk about l/Ps/h,  not l/h

Originally posted by crowbaby

-We don't know that any of these HP figures are accurate.
-We have no historical data to compare to Snefens tests because its an arcade-y way to fly the planes.
-We really can't assume any equivalence of engine performance. If engine performance was as simple as fuel in equals HP out across a range of power outputs. If engines were that staightforward, then people wouldn't write head-breaking reports like these:

A) Not true, we know very well the correct engine outputs
B) Not true, because flight endurances were measured systematically, and for flight endureance you just need a clock. Again, we donīt talk about range. All what it needs is a pilot that takes the aircraft in the air and cruises around for a given TIME with constant power setting. If you think this would be to complex for a test pilot, ok believe it, i for myself think that such a test was probably the simpliest, most boring test for a test pilot.
C) American radial engines were probably the best radials in the world, due to the concurrence pressure of Wright and P&W some very fine engines were available. Nearly all other foreign radial engine manufactors (russians, germans) copied or were influenced by the american engines.

Check the link to the rtf file from tilt in the other thread once more, and compare those numbers to AH. This is all you need to do.

niklas

[crowbaby]

Nope. i'm sick of jumping through hoops. Did anyone even read the test results, do the sums based on Snefens chart?

I've tested AH against the best historical data and the fuel consumption seems o.k. across a wide range of settings. The P-51 and F4u seem to do better than historical figures dictate, but then in reality they only flew at these setting for 5-15 minutes, whereas in AH people want to use them constantly. Who knows how HTC have decided to address this? The Mosquito, however, seems to be way out. This may be a simple mistake.

Other than Karnak's test of the Mossie, all i've seen is bald headed conjecture, faulty logic and whines. I'm sorry, but that's how it looks to me.
 
Pls explain me why speed should influence the engine consumption when those engines run with constant RPM. We donīt talk about range, we talk about endurance. We donīt even talk about aircraft or prop efficiency, we talk about results that could also be measured on ground in the caves of a testing institute.

You're suggesting that increasing speed won't decrease range? that altitude is irrelevant? These arguments still seem to come back to this notion of an 'SFC'. Engine fuel consumption for power output is radically different for different engines. It will also change differently for each engine depending on rpm, Manifold pressure, altitude, fuel injection, superchargeing and temperature. The richer your mixture, or the higher your manifold pressure - the more inefficient the engine is likely to be. Where do you think the energy comes from when an engine overheats?
Look at the charts, the hp for gph listed for the F4u changes its ratio hugely. Show how an SFC makes sense of this chart!
Why do you want to stick your head in the caves when we can flight test the planes and see that they match historical data?

As modeled, the endurance numbers in AH imply the American engines (about which we know the most) are half as efficient as shown in the historical data.
i refer you to my previous post. Snefens chart, at full AH power (2700rpm and 54"Man at sea level) shows 43 minutes endurance for the F4u-1. Double this to allow for the fuel multiplier and we get 86 minutes. With 361 gallons in the tank this is 251gph. The F4u-1 historical data says it should consume 290gph at these settings. please answer this.

as for,
About the only test that remains to be tried is for a good heavy iron pilot to fly one of these plane to an intermediate altitude (where there is less drag), say 15k, and fly at the lowest power setting that will maintain altitude and look at the watch until the engine quits. If you really want to be rigorous, do this for 1/4, 1/2, 3/4, and full internal fuel.
i've done this, but by the book, and i'm happy that the results match the historical documents. Tell me where my tests are wrong or do your own.

[maxtor]

Originally posted by LLv34_Snefens
"Snefens endurance chart shows 28mins for both La5 and La7, 30mins for F6f. To me this chart is pretty meaningless, as efficiency varies hugely across speed ranges.

First, those charts are not meant to compare to any historic values, they are simply there to let the player know how much fuel he have on 100% power. Second, the AH engine model is rather simplistic. I choose to list the endurance for 100% power, because that's simply what the majority of players use all the time with the occasionally WEP, but there is no difference in the consumption. I just tested it again to be sure:

La7, SL, 100% power, Max speed: 56 min
La7, SL, WEP power, Max speed: 56 min
La7, SL, 100% power, 175mph: 56 min
La7, 30K, 100% power, Max speed: 56 min

Fast/slow, WEP On/off, high/low. At the moment it makes no difference in AH.

__________________
Ylil. Snefens
Lentolaivue 34
My AH homepage

I'm not sure if this factors into your findings or not, but

Originally posted by hitech
If wig = Ground Effect, then yes. Yes planes gain mpg effiecentcy with alt.

HiTech

I noted he says mpg and not time.

[F4UDOA]

Crowbaby,

Please use the the F4U-1D for comparison. It carried 237 gallons of fuel and for the prupose of arguement it compares more easily with the F6F-5.

This is why you are wrong or mistaken in either your math or logic.

Math the F4U-1D uses 290 gallons per hour of fuel at full mil power with a 237 gallons tank. 237 is 81.7% of 290.  That gives it a durantion (forget about range) of 81.7% of an hour or 49minutes. I'm not sure were you got 43minutes.

Mistaken-The table of range and flight duration for La-7 No 38103254 with
G full=3265kg, full tank fuel supply - 460 l.

Mode Mode values Level flight
up to dry tanks:
Range, km duration,
h-min

Max. H=1000m(1st sup.sp.),n=2400, Ps=1020mm Me.pl. 355 0-35
speed 3000 1 2400 990 355 0-33
5000 2 2400 1020 355 0-32
7000 2 2400 870 405 0-38


The duration here from the VVS test data clearly shows a duration of either 33 or 35 minutes at low alt.

Logic- the SFC for the La-7 of .46 is for max cruise power setting. A comparable SFC for the F4U-1D is also at max cruise and shows an SFC of of .465 and a GPH of 83 or a duration of 2.85 hours for the F4U-1.

Here is the La-7 at max cruise and economical cruise.

Near   H=5000m(2nd sup.sp.),n=1810, IAS=388 km/h        580        1-10
fast range                          TAS=500 km/h

Optim. H=1000m(1st sup.sp.),n=1500, IAS=360 km/h        665        1-45
mode     3000  1              1500      345             625        1-34
         5000  2              1600      340             590        1-20
         7000  2              1600      300             665        1-32

This shows a fast cruise duration of 1 hour 10 minutes and a optimum cruise duration of 1.45 minutes. This is not even comparable to the F4U, F6F or P-47 all using the same engine. In fact it's not even in the ballpark. It is less than half.

Here is what I have calculated based on a duration of 35 minutes at mil power for the La-7

122 gallons burned in 35minutes= 193 gallons burned for 60minutes.

193 GPH for the La-7 at mil power = 1158lbs of fuel per hour giving it a SFC of .70!!! that is still a rediculously low number for what it should be and that only gives it 35 minutes of flight time.

The Comparable SFC for the F4U is .87 with a far superior engine.

Even with the SFC of .70 the F4U and F6F should still have a significant advantage in duration and I still doubt the La-7 was anyware near that good.

Joe Blog please check my numbers. .70 sounds rediculous at mil power.

[crowbaby]

Crowbaby,

Please use the the F4U-1D for comparison. It carried 237 gallons of fuel and for the prupose of arguement it compares more easily with the F6F-5.

No. I have a chart for the F4u-1. I used it. It worked.

As regards the VVs La7 data, it clearly says this:

1. For range and flight duration calculations the following fuel consumptions
are taken into account:

a) for engine work on the ground (warming-up and engine test, taxiing to and
from the start) 35 l per 15 min;

b) for climb to: 1000m - 15 l; 3000 m - 55 l; 7000 m - 80 l;
c) for circle flight before landing - 45 l.

The 35 minutes is not for a full tank, it is real flight duration after warm up, etc. That is why I compared to the fuel consumption data only. Which I found to be reasonably accurate in three separate tests. I have pointed this out previously.

[F4UDOA]

Here is what I have calculated based on a duration of 35 minutes at mil power for the La-7

122 gallons burned in 35minutes= 193 gallons burned for 60minutes.

193 GPH for the La-7 at mil power = 1158lbs of fuel per hour giving it a SFC of .70!!! that is still a rediculously low number for what it should be and that only gives it 35 minutes of flight time.

The Comparable SFC for the F4U is .87 with a far superior engine.

Even with the SFC of .70 the F4U and F6F should still have a significant advantage in duration and I still doubt the La-7 was anyware near that good.

Joe Blog please check my numbers. .70 sounds rediculous at mil power.


__________________

[F4UDOA]

CrowBaby,

Warm up is done at idle with barely any fuel consumption.

Read my calculation above.

SFC varies with power setting.

At full mil power the La-7 should have the fuel duration of an Estes Rocket.

[joeblogs]

For high output US radials on 100/130 PN avgas the SFC at military power (no WEP) ranges from 0.9 to above 1.  At normal rated power SFC is about 0.8 to 0.9 depending on altitude in the flight test data I have seen.

With lower rated fuels the SFC numbers would be significantly higher.

-Blogs

Originally posted by F4UDOA
Crowbaby,

Please use the the F4U-1D for comparison. It carried 237 gallons of fuel and for the prupose of arguement it compares more easily with the F6F-5.

This is why you are wrong or mistaken in either your math or logic.

Math the F4U-1D uses 290 gallons per hour of fuel at full mil power with a 237 gallons tank. 237 is 81.7% of 290.  That gives it a durantion (forget about range) of 81.7% of an hour or 49minutes. I'm not sure were you got 43minutes.

Mistaken-The table of range and flight duration for La-7 No 38103254 with
G full=3265kg, full tank fuel supply - 460 l.

Mode Mode values Level flight
up to dry tanks:
Range, km duration,
h-min

Max. H=1000m(1st sup.sp.),n=2400, Ps=1020mm Me.pl. 355 0-35
speed 3000 1 2400 990 355 0-33
5000 2 2400 1020 355 0-32
7000 2 2400 870 405 0-38


The duration here from the VVS test data clearly shows a duration of either 33 or 35 minutes at low alt.

Logic- the SFC for the La-7 of .46 is for max cruise power setting. A comparable SFC for the F4U-1D is also at max cruise and shows an SFC of of .465 and a GPH of 83 or a duration of 2.85 hours for the F4U-1.

Here is the La-7 at max cruise and economical cruise.



This shows a fast cruise duration of 1 hour 10 minutes and a optimum cruise duration of 1.45 minutes. This is not even comparable to the F4U, F6F or P-47 all using the same engine. In fact it's not even in the ballpark. It is less than half.

Here is what I have calculated based on a duration of 35 minutes at mil power for the La-7

122 gallons burned in 35minutes= 193 gallons burned for 60minutes.

193 GPH for the La-7 at mil power = 1158lbs of fuel per hour giving it a SFC of .70!!! that is still a rediculously low number for what it should be and that only gives it 35 minutes of flight time.

The Comparable SFC for the F4U is .87 with a far superior engine.

Even with the SFC of .70 the F4U and F6F should still have a significant advantage in duration and I still doubt the La-7 was anyware near that good.

Joe Blog please check my numbers. .70 sounds rediculous at mil power.

[crowbaby]

CrowBaby,

Warm up is done at idle with barely any fuel consumption.

try again,
1. For range and flight duration calculations the following fuel consumptions
are taken into account:
a) for engine work on the ground (warming-up and engine test, taxiing to and
from the start) 35 l per 15 min;
b) for climb to: 1000m - 15 l; 3000 m - 55 l; 7000 m - 80 l;
c) for circle flight before landing - 45 l.

that's a possible 95 litres depending on their methods and the translation. Which is why i tested against their listed data for fuel consumption at various altitudes and power settings. Flight testing in AH against historical data works - why do you not want to do this?

[F4UDOA]

CrowBaby,

Thanks.

Thats 95 total Litres = 25US gallons

Like I said that's not much fuel especially in the world of AVGAS.

You realize that just makes the La-7 fuel endurance that much worse?

The SFC of .70 which is already to low is based on 122gallons of fuel at mil power. If you base it on 97 gallons and the fact that it used 95octane fuel then the SFC becomes even more outragous.

I'm not sure this Aircraft should have been able to make it to the end of the runway. It keeps getting worse!

[crowbaby]

I show that you've been making the same wrong assertion over and over and you thank me? This mad scientist stuff is going to your head.

I'm not sure this Aircraft should have been able to make it to the end of the runway. It keeps getting worse!

Well, lots of people seem to think it flew. They took note of its flight characteristics and performance. Years later HTC came along and used those numbers to model a simulator.  

You can now compare the performance of the plane in the simulator with those 50 year old numbers. I did this and saw that HTC did a great job.

If your engine theories, unrelated to real life or the game, disagree, then it might be you who is wrong.......


crowbaby over and out.

[F4UDOA]

These are not my theories.

Bernoulli, Newton and Venturri maybe but definitely not mine.


Test this based on numbers that you showed me.

According to YOU. The La-7 burns 95 litres or 25 gallons warming up and climbing to 1,000Meters. Or exactly 20% of it's fuel.

Jump in your AH La-7 sit at idle then climb to 1,000Meters and see if you have burned 20% of your fuel. If you have then you might have a point but I doubt it.

Drum Roll Please!!!