P-38 fuel endurance question

[leitwolf]

All historical text I've read credit the twin engined devil with a long range - especially over the P-47. Having flown the 47 quite a bit last tour I decided to check out the 38 and to me it seemingly doesn't have that advantage in AH.
Of course, the MA isn't a historical environment because we all keep flying at max power and that might hurt the allisons more than any other engine but even if i reduce man it doesn't look like the 38 will be in the air for an hour - on its own power that is.
Has any of the experienced 38 drivers here tips on fuel management? What's an efficient cruise setting? They flew six-hour missions in RL and i'm dry after 40minutes (even if you factor in the fuel burn multiplier it's too short)  

[Karnak]

The P-38 didn't have particularly long legs on internal fuel, but with drop tanks it's range was better than the P-51s.

Are you testing it with droptanks or without?

[F4UDOA]

Leitwolf,

Your not crazy.

I have done a mountain of testing in this area. It seems the fuel multiplier is probably correct in it's effect on the P-38 however it is some of the other A/C in AH that have an unusual ability to fly at max power well beyond the normal.

Without rehashing the whole bloody thing I'll make it short and sweet.

Airplanes like the La-7 specifically run in AH their engines at max power all the time. The also run at their max efficiency at all times. Typically and A/C runs at max efficiency only at max cruise however here they run that way at mil power. The key factor in all of this is something called the engines SFC. This is a ratio of the amount of fuel used to create 1 HP. Most WW2 fighter had a SFC of somewhere around .40 at max cruise.

How this affects you is that you carry 300 plus gallons in your P-38 and he carries roughly 100 gallons to achieve the same range and duration. So basically your flying around with a tanker truck tied to your arse while he is running on fumes. And you wonder why they are UFO's.

[MiloMorai]

The P-38L carried 410 gal of fuel internally while the P-51 carried 184 gal in the wings plus 85 gal in the fuselage (269 gal). That is 205 gal/engine for the P-38 .

[Karnak]

IIRC, Allisons drink more than Merlins too.

[gwshaw]

The V-1710/B-33 combo in the P-38 was roughly 33% more fuel efficient than the V-1650-3/7 in the P-51B.

Comparison:

P-51D V-1650-7
520 hp @ 2000 rpm, 27 in  Hg & 16,500 ft - .60 lbs/hp/hr

V-1710-111/113 P-38L
525 hp @ 1600 rpm 31 in Hg & 15,000 ft - .46 lbs/hp/hr

The allison had a higher compression ratio - 6.65:1 vs 6.0:1 for the Merlin, and was using waste heat in the exhaust to provide compression.

The merlin would be even worse at higher altitudes after shifting into high gear, while the allison would stay pretty constant.

The Pony's range was due to its slick airframe and high cruise speed, not any range superiority of the merlin.

Greg Shaw

[Guppy]

Originally posted by Karnak
IIRC, Allisons drink more than Merlins too.

After reviewing the P-38 and P-51 range charts, it seems to me that the P-38J/L's Allison and the P-51D's Merlin are roughly equivalent as far as fuel consumption goes.

The P-38's Allisons have a noticeable edge in fuel economy at low-power cruise settings (35" and under), but there's a big difference when the MP rises over 40" and the P-51 can stay in auto-lean, whereas the P-38 has to go to auto-rich and its fuel consumption shoots up. At combat power the two are basically equal (the V-1650-7 at 61" and the V-1710 at 60" are both rated at 180 GPH).

Economical cruise for the P-38 is 46 GPH at sea level and 77 GPH at 30,000 ft, whereas the P-51's is 42 GPH at 5,000 ft (probably about 37 GPH @ SL) and 62 GPH at 30,000 ft. However, the P-51 cruises about 25% faster than the P-38 at those settings. That seems to yield about equal range on full tanks (1,400 - 1,500 mi.) with no reserve or climb allowance. As previously mentioned, if the cruise speed is pushed up to the point where the P-38 has to use auto-rich, the P-51 takes the advantage on range.

Basically, it seems to come down to the P-51 having a faster (and thus tactically advantageous) cruise speed, and the P-38 having more endurance (good for a loitering interceptor, or for staying over a downed buddy on overwater missions).

Regarding the P-47 vs. the P-38; the early P-38s had much less internal fuel (only 300 US gallons, about the same as the early P-47), but the early P-47s had no wing racks and could only carry a 200-gallon belly tank (whereas the P-38s had two 165-gallon wing tanks). Pilot technique was another factor; earlier in the war, it doesn't seem like the training schools were teaching pilots how to obtain maximum range.

[leitwolf]

I'm not comparing the La7 or any other 'short range' fighter with the 38.
The only thing that I can't really understand is:
The P-47D-30 has ~ 45mins and the P-38 ~ 38minutes of flight time on internal fuel in the MA. Adding external fuel tanks helps the 38 to catch up a bit but still doesn't change the fact - the P-47D-30 has more flight time with 72 vs 68 minutes with DTs.
Maybe this is apples and oranges because the D-30 is a late version of the 47 and carries considerably more fuel than a D-11.
But even the 'short legged' D-11 has about the same flight time with internal fuel as our P-38 - it takes 2 additional 2 DTs for a 38 to achieve a longer flight time. This is, of course, MA like full-throttle values but this means that either one of the fuel endurance values of these two planes is off in comparison or the 38 has an extremely efficient cruise setting (which was also my initial question: what *is* the cruise setting ?  )

EDIT: gwshaw and guppy posted after I wrote this - took some time to check the numbers. I'm going to check flight times with considerably lower MP as soon as possible.

Thanks for the input

[Guppy]

Originally posted by leitwolf
This is, of course, MA like full-throttle values but this means that either one of the fuel endurance values of these two planes is off in comparison or the 38 has an extremely efficient cruise setting (which was also my initial question: what *is* the cruise setting ?  )

Maximum-range cruise for a P-38L is listed as follows:

22", 1,600 rpm @ SL (168 TAS)
22", 1,600 rpm @ 3k (173 TAS)
23", 1,600 rpm @ 6k (187 TAS)
24", 1,600 rpm @ 9k (199 TAS)
25", 1,600 rpm @ 12k (212 TAS)
26", 1,600 rpm @ 15k (229 TAS)
27", 1,650 rpm @ 20k (248 TAS)
27", 1,750 rpm @ 25k (267 TAS)
27", 1,900 rpm @ 30k (285 TAS)

[hazed-]

I once saw a P38 fly through a forest and cut down trees with its wings, then it flew around the world 3 times and the moon once..........



common people!! the p38 did indeed fly extra long range raids in the pacific using a method of engine management developed by a famous P38 ace, I cant remember his name but basically he almost doubled the endurance by tweaking the mixture etc.I think he got it to fly over a 1000 miles i think. He used it to launch a surprise attack on a japanese oil refinery or fuel dump.The p38s attacked it and it was almost undefended because the japs thought it was well outside the fighters range. The normal range for a P38 with internal fuels is not so dissimilar to other US aircraft. I think the p38G's range was 425 miles on internals, with externals I think it almost doubled that, the p47b's were stuck at their internal range.The later p38J model increased fuel capacity considerably and pushed its range up to 2,598 miles! with externals (the p47D had a range of 1,800 with externals). The P47B's that first arrived in europe could carry no DT's. Like said here it was drop tanks that made the difference and it was other fighters lack of ability to use them in the early stages of the war that meant the p38 was a prefered long range fighter. Once fighters like the P47D's started to aquire those huge DT's the difference wasnt quite so obvious. The p38 isnt a super plane.It has good and bad points like all the others.Our P38 should be better than the P47s but only by a few hundred miles and with our burn rates it means only a short time longer.

If you take your P47D11 with internals only and match that against the P38 with one external tank you will have 'roughly' what the allies did when long range escorting was a problem.The p38 would obviously be the prefered choice in this way.so yo see it IS good for range but it just doesnt notice so much with our late war planeset.

[gwshaw]

It was Lindbergh that showed the P-38 pilots how to extend their range.

Basically it boiled down to moderate MAP and low rpm, combined with lean carb mixtures and let the turbos do all the work of providing manifold pressure.

The SWPA pilots had been flying nearly the worst possible combination; high rpm, low MAP and auto-rich. They didn't like Lindbergh's recommendations because they made the engines run rough, but after Lindbergh flew some demonstration missions they were convinced.

Lockheed figures for early models (300 US gallons)

1300 miles on internal fuel
2200 miles with 2 x 165 gallon external
3200 miles with 2 x 330 gallon external

Milo Burcham managed 2907 miles with 2 x 330 gallon externals in August of '42. They estimated that more economical flight profile and dropping the tanks when empty would have made 3200 miles reachable.

That isn't a practical combat range, but correctly piloted 80% of that probably was attainable.

Greg Shaw

[leitwolf]

Well, hazed, I was never talking about 'range' I always said 'flight time' which can be a whole different thing. Nor did I quote some fantasy anecdotes, I simply stated that I am surprised to see what I didn't expect: a 38 is not markedly superiour in flight time compared to the Thunderbolt in Aces High MA.

Nevertheless, a quick test offline reveals that:
With MP (26") and RPM (1600) settings from guppy's list and full internal tanks our 38L is not able to maintain 15k alt in auto-level and is barely able to hold a speed above 100mph IAS. It's far away from being able to achive the 229mph TAS on this list.
Guppy are you sure your cruise settings are for a 38 L or is it a different version?
The AH help page quotes 35" @ 2300 RPM and 63 GPH.
With these settings the Lightning can stay airborne 1.6hours on internal fuel.
With 26" and full rpm we achieve a flight time of roughly 2.8hours (@15k,internal fuel only)
Flying on the deck instead of 15k has no noticeable effect, neither has lowering RPM from max to 1600 when flying at 26" MP.
Maximum flight time at 26" with both DTs and internal tanks is approx. 5,2 hours. The resources I have found credit the 38J and L versions with 12hours flight time (with 1000+gals fuel [using two 300gal DTs]).
Doing some math we end up with: 410gal internal + 2x150gal DT and 5+ hours flight time yield roughly 130GPH. Even if we had those 300gal DTs we would only have ~8 hours in the air.

Am I missing something?

[gwshaw]

26 in Hg & 1600 rpm @ 15,000 ft should give about 440 hp

Compared to the 525 hp, 1600 rpm & 31 in Hg @ 15,000 ft I gave earlier.

26/31 * 525 (both ratings are @ 1600 rpm so you can take it out of the equation)

Plugged that into my model for the P-38L and it came up with 177 mph IAS and 224 mph true at 15k, pretty close to the figure Guppy gave.

Greg Shaw

[hazed-]

leitwolf sorry i was just ribbing you with the anecdote

I do understand what you mean and reading your figures it does look weird in AH.
I was merely pointing out that the engine management that allowed the real P38 to fly for such distances isnt possible in AH.
yes it was Lindbergh, thnx gshaw.

I think leitwolf that this is something that plagues many aircraft in AH. For one thing the ju88 has a very short flight time/range in AH and I was thinking maybe HTC has tweaked several aircraft to fit the game enviroment?

I have been told time and time again that lowering the RPMs helps with fuel consumption but i cant see hardly any difference.Lowering manifold helps but does it reflect the real thing? ive no idea.

I gave up using lower manifold/rpms after finding the benefits dont outweigh the boredom of cruising everywhere.

the only time i run less than full is in ACM's or when flying as a lead in formations. The rest of the time I just ignore it. Maybe theres a few experts out there who can teach us a way to use AH's basic system for good benefits?
where can we find information like best cruise settings for all the various aircraft? maybe ill help do some tests.

again sorry leitwolf I was only kidding about p38

[Guppy]

Originally posted by leitwolf
Nevertheless, a quick test offline reveals that:
With MP (26") and RPM (1600) settings from guppy's list and full internal tanks our 38L is not able to maintain 15k alt in auto-level and is barely able to hold a speed above 100mph IAS. It's far away from being able to achive the 229mph TAS on this list.
Guppy are you sure your cruise settings are for a 38 L or is it a different version?

Those settings are most definitely for a P-38L (with no external load). You should be able to maintain an IAS of 178 mph.

The reference I'm using is the P-38L Flight Operation Instruction Chart, which you can find at:

http://www.zenoswarbirdvideos.com/Images/P-38/38FOIC.gif