Author Topic: Why the La7 is so Uber(important) (Read 2324 times)

F4UDOA · « **on:** October 29, 2002, 09:52:29 PM »

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.

brady · « **Reply #1 on:** October 29, 2002, 10:30:11 PM »

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.

GScholz · « **Reply #2 on:** October 30, 2002, 12:55:44 AM »

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?

Jester · « **Reply #3 on:** October 30, 2002, 01:16:19 AM »

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.

J_A_B · « **Reply #4 on:** October 30, 2002, 01:56:12 AM »

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

J_A_B · « **Reply #5 on:** October 30, 2002, 02:02:25 AM »

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

moot · « **Reply #6 on:** October 30, 2002, 04:19:46 AM »

Quote

Originally posted by Andijg
With DT's nothing (single engine fighter wise) could go as far as the Mustang. [...]

Ta152?

Hristo · « **Reply #7 on:** October 30, 2002, 05:41:36 AM »

Ta 152 on internal beats P51, but not so sure with DTs.

F4UDOA · « **Reply #8 on:** October 30, 2002, 08:21:46 AM »

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.

GScholz · « **Reply #9 on:** October 30, 2002, 10:22:45 AM »

http://www.hitechcreations.com/forums/showthread.php?s=&threadid=68371

Some fuel capasity/consuption data (near the bottom).

Spritle · « **Reply #10 on:** October 30, 2002, 10:43:30 AM »

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

Puke · « **Reply #11 on:** October 30, 2002, 12:55:08 PM »

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.

J_A_B · « **Reply #12 on:** October 30, 2002, 01:08:15 PM »

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

F4UDOA · « **Reply #13 on:** October 30, 2002, 01:24:48 PM »

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??

J_A_B · « **Reply #14 on:** October 30, 2002, 01:50:20 PM »

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