In 1942: top 3 Allied fighters

[tomo pauk]

Thanks for the effort to extract and write down the numbers, Jeff
A few nit picks - the V-1710 F3 in Mustang I have had supercharger gearing of 8.8:1, and that was indeed changed to 9.6:1 on the (non-turbo) engines from second half of 1942. The result was the better altitude power - instead of 1150 HP at 12000 ft, it offered 1125 HP at 14500 ft. Some power charts show the rated altitude of 15000 ft, and it was increased further ( with new intake manifold that enabled removal of backfire screens) to 15500 ft (all for 1125 HP). Looks only the P-39Q got these engines?
The shortcoming was the decrease of power at low altitudes, instead of 1500-1600 hp between 4500-2500 ft, it was now 1410 at 9500 ft (and a bit less towards the SL).
The engines with 8.77:1 S/C gear ratios were the 'old', sharp nosed V-1710, like the C15 used on early P-40s (until -C).

The Mustang I has over the P-38G: roll rate, it is a smaller aircraft, there are no blind spots/angles, better speed under ~5.5 km, less expensive complicate to build operate. The P-38 'has' the climb rate at all altitudes, range/radius (has drop tank facility), firepower, speed above 5.5 km, can also lug bombs.

 

[CORSNING]

You are quite welcome Tomo, it was my pleasure.

You are right about the P-38 load carrying capability. It could accommodate up to 2 x 1000 lbs. bombs.

Mustang Ia is an easier aircraft for a new pilot to master (single engine). This, in the grand scheme of things, is a very important consideration when two aircraft are close in performance.

Both aircraft's roll rates are very poor when compared to the Yak-9 or Fw-190A in 1942. The Mustang does eclipse the Fw's rate of roll at about 375 mph and up though.

 

[Vincenzo]

the speed of roll rates are ias?

 

[CORSNING]

No. They are almost always T.A.S. unless noted differently.

 

[CORSNING]

I just remembere another advantage the P-38G-1 had over the Mk.Ia, Acceleration.

 

[Vincenzo]

i thinked that was the reverse were ias unless note different

 

[tomo pauk]

Tend to agree with Vincenzo - it is IAS in most of roll rates' graphs, not TAS.

Back to the comparison of the P-38G s. Mustang I. The A.C No. 42-12687 have had 2 HMG less than what would be otherwise carried in combat. It also carried 180 gals of fuel, vs. 300 that would be carried in combat. Both things influence speed and RoC.
For the P-51 in question - it was an equivalent of Mustang Ia, ie. has 4 cannons - no MGs. We don't know when the war emergency power was allowed on the Mustang I/Ia (my guess is that it was used in 1942), that gives substantial increase of speed and RoC at lower altitudes. For example, British have clocked the AP.222 doing 392 mph at 7900 ft, with 'usual' F3R engine run on 56 in Hg. Also not on max fuel - 168 US gals Unfortunately, testing for climb rates was still done on lower power setting, 2600 rpm and up to 36.8 in Hg, on British tests.

 

[CORSNING]

Vincenzo and Tomo,

I did some checking and you both are absolutely right. I.A.S. is used on the NACA chart.

Jeff

 

[Vincenzo]

1st a add the fulmar was operational in '42 (and fleetairarmarchive is offline
i try to put actual result of fighters in my list and a few adds (fighters vs fighters)
Buffalo very bad (for all just talking of allies side '42)
CW-21 few data but very bad
Hawk not so bad
Lancer very few battle not bad
I-16 very bad probably
other soviet types i've not dada probably bad
Wildcat enough good
P-39 bad
P-40 bad excluding AVG that get good, excluding vs Bf 110 get good, and vs old italian fighters.
Mustang i have no data
Typhoon i have no data
Whirlwind i've no data
Hurricane bad to very bad
Fulmar very bad or exceptionally bad
P-38 i've no data for 42 alone but in the operation in NA in 42-43 they get bad v/s 109, also in the pacific the valutation was not more that near enough

 

[drgondog]

I haven't looked at the roll charts but can see no reason to state IAS as the velocity parameter.

400mph IAS on the deck not so very bad correlation but 400mph IAS at 30,000 feet represents an unattainable airspeed for all those fighters

 

[CORSNING]

Hi Bill,
The altitude is 10,000 ft. http://www.wwiiaircraftperformance.org/naca868-rollchart.jpg http://www.wwiiaircraftperformance.org/p-38/p-38e-rolling-velocities.jpg

I almost forgot: I completely agree with your statement about 400 IAS at 30,000 ft. That is why I originally stated TAS for the roll charts. See there?, I told you my memory was no where near as good as yours.

Jeff

 

[CORSNING]

I was very tempted to post the P-38G-10 figures from the graph on www.wwiiaircraftperformance because it has the same engines as the P-38G-1. Then I noticed the power output recorded, 1,425 hp. I am 90% sure that the Allison engines in all the -Gs were rated 1,325 hp. I am also 90% sure that was at around 48"Hg boost. What I do not know is what the USAAF and or Allison Mfg. sanctioned for those particular engines in Late 1942.?

P.S.: I was just using my memory for this post, so who knows.? Jeff

 

[Neil Stirling]

Hi Corsning, P38 performance article here The P-38 Lightning

Neil.

 

[CORSNING]

Hi Neil,
Thank you for posting that. I have read that article several times but your post made me slow down and absorb a bit of it.

All,
I have all the numbers handy for the P-38G-10 from that graph, but then we all need to remember that all the early Allison engines were overboosted (according to Allison) in the field. You can bet that the figures I posted for the Mustang Ia were exceeded also.
I think I am just going to take a stand on the difference in performance figures that I have posted for the two aircraft in question. If I raise the figures on one, I have to raise the figures on the other.

Thanks again Neil. You are one of the best.
Jeff

 

[kool kitty89]

P-38 prior to the J model had issues with the intercoolers functioning effectively, leading to high manifold temps and more limited boosting. (though in practice, it might have been felt worth the risk to overboost in spite of high carb temps)

With the un-turbocharged V-1710s, Allison allowed up to 60" Hg boost for the 8.8 geared superchargers (P-40E and earlier and P-39 prior to M model) though some squadrons reported use of 66" (1770 HP at 2000 ft) and 70" without apparent problems. The 9.6 supercharger ratio used on the P-51A, P-40M, N and P-39M, N, and Q was more strictly limited to 57" HG due to the higher carb temps.

See Overboosting here:
Perils P40 Archive Data

 

[CORSNING]

E-GEH-16

Look under the last heading titled "Performance of the Mustang I and IA", paragraph No.36.:
"...The British have operated at full throttle at sea level (72"Hg) for as much as 20 min. at a time without hurting the engines. According to them, the Allison is averaging 1500 hours between bearing failures as compared to 500 to 600 hours for the Merlin."

In this report and on the Allison Division letter you will notice that the use of 70"Hg and above is stated at sea level. High boosting can only be done at the very low levels (in 1942-1943 combat zones).

 

[kool kitty89]

Nice info, Corsning.

I'd forgotten to mention it before, but it appears that Allison's more cautious restrictions on boost were due more to lack of testing than actual limits to the engine, at least in the case of the 8.8 blower. (not sure if the 57" limit on the 9.6 blower was overly conservative as well -or other possible factors like use of 100/150 fuel). The P-38 J/L later got cleared for 75" boost WEP for 2000 HP output too.

On a separate note, I believe the very early long-nosed V-1710s (like the -33 of the P-40B/C) had issues with reduction gear failures if pushed beyond rated power for extended periods. (I remember some mention of this in regards to the AVG's experience)


Overboosting Mustang Is is an interesting topic in general, though. They'd seem like good V-1 chasers (especially if stripped down to interceptor configuration) and better than the merlin engined models at this due to the lower weight and high low-alt power output. (P-51A would have too if that 57" boost limit could be broken)

Also makes me wonder how well turbo-less P-38s would have fared at low-level. (especially given early models were better suited at low level anyway due to cockpit heating and compressibility issues ... and the MTO campaign taking place at lower altitudes)

Edit: or for that matter, how significant overboosting was for the P-39. I don't recall reading anything on that topic.

 

[tomo pauk]

The P-51A will have significantly less power down low than the Merlin P-51, especially if the V-1650-7 is on board. 200 HP deficit vs. V-1650-3, 300 HP vs. -7, all for WER on 100/130 grade fuel.
P-39N was capable for some 385 mph on WER, with wing guns. The P-39Q, with WER power setting, was capable for around 400 mph when gun pods were not installed. Engine of the P-39Q have had another 1000 ft greater FTH than the engine on P-39N, due to removal of backfire screens (that was possible once the redesigned cylinder air intake was installed).

Also makes me wonder how well turbo-less P-38s would have fared at low-level. (especially given early models were better suited at low level anyway due to cockpit heating and compressibility issues ... and the MTO campaign taking place at lower altitudes)

I'm all for it. Pack fuel where the intercoollers were (as in late P-38s), 4-6 additional wing racks and there is an useful fighter-bomber.

 

[CORSNING]

Kool Kitty89,
Thank you. Where did you get your information about the P-38J/L Allison engines being cleared for 75"Hg? I have put together a quick reference operational timeline for the Lockheed P-38 and would like to add this information if applicable.

Jeff.

 

[CORSNING]

Just a note in support of anyone who was thinking that the Yak-9 might be a good choice here. In August 1944 Yak-9DDs were dispatched to Bari, Italy. British, US and Russian pilots had an opportunity to examine each others aircraft. The other Allied planes involved in this area were Spitfire V, Spitfire VIII, Hurricane, P-38, P-40, P-47D P-51Bs. The Yak-9DD did not have the speed to dictate the terms of battle at medium and high altitudes but in these mock combats the Yak-9DD bested all. Keep in mind the Yak-9DD was the long range version an was the heaviest and least maneuverable of all the first and second generation Yak-9s.

One British pilot stated, "Their fighters are wooden, simple jobs and seem to be lightly armed; but, they have lots of armor protection, are very agile, and we could not outmaneuver them in the air..."