Sal good to see you back… Nice chart which I see seems to confirm my climb data from where we left off; wish you had posted this then…
Jabberwocky I have a lot of respect for you; however, in this issue I do not agree with you… Full War Emergency Power could be used for a max duration of 5 minutes the initial sea level climb rate at 'full combat weight' (Sal, another point from back in the day, by coincidence...) is 4,000 ft. p/m (@ 60"Hg)… but that is not maintained… requires pushing the aircraft to beyond it's 'safe operating limits'
Magister, wmaxt in the past has pointed out that the Allison was cleared for higher operating pressures in the '38 L; as high as 66"Hg. It's not that I don't believe this wasn't done in combat, in an act of desperation, or anticipation, but here is why I agree with you; I understand that a '38 may achieve these numbers once. When you are done achieving this at the very least your engines will be a write off, if not… At 60 Hg you had 5 min. running time, so you make it to twenty thousand feet. Now what? Unless you're on 'holiday' or suicide watch, or a test/sim pilot, you must cut back power… avoid 'combat', or testing procedures for a time; so you better have gotten far enough away.
FlyboyJ, not fair... My p-38 manual states 54"HG as well. …But on page 27 in one version, up to 60"Hg can be used for 'war emergency' climbs. Now pbfoot yourself used the tact that the charts I posted (to display that a 2G turn in one aircraft, as opposed to another, although implemented at the same 'bank angle' due to the same 'loading' represented two different turn rates) in the P-51D vs. FW 190D thread (
http://www.ww2aircraft.net/forum/viewtopic.php?t=3703&postdays=0&postorder=asc&start=140 ) was used for 'formation, or instrument flying' pbfoot especially asked why I was using them as they had nothing to do with combat. Are you not doing this here FlyboyJ? The 54"HG is the max setting, or 'combat' setting, it is not WEP, which could be used for a 5 minutes climb, right?.
wmaxt 1st told me of the website linked below, and I believe he references data found there in his post. On his behalf I invite you all to visit it to see some great stuff on Spits, P-47s, P-38s other aircraft.
http://www.spitfireperformance.com/p-38/p-38-67869.html
Excerpts…
Flight Test Engineering Branch
Memo Report No. Eng-47-1706-A
4 February 1944
FLIGHT TESTS
OF A P-38J AIRPLANE
Flight tests have been conducted at Wright Field on the P-38J Airplane, AAF, No. 42-67869, at the request of the Fighter Branch, Experimental Engineering Division. These tests were made on this airplane primarily to obtain comparative performance data with similar tests on a P-47D-10, a P-39Q-5 and a P-51B airplane. The performance should be that of a typical production model as it was selected at random from airplanes which had been delivered from the factory. From 2 December 1943 to 21 January 1944 approximately 30 hours were flown on this airplane by Capt. G. E. Lundquist, Capt F. C. Bretcher, and Capt J. W. Williams.
High speed and climb performance have been completed on this airplane at a take-off weight of 16,597 lb. This loading corresponds to the average P-38 combat weight with full oil, 300 gallons of fuel and specified armament and ammunition.
The principal results are as follows:
Max speed at critical altitude, 25,800'
(60.0" Hg. Man. Pr. 3000 rpm) = 421.5 mph
Max speed at sea level
(60.0" Hg. Man. Pr. 3000 rpm) = 345.0 mph
Rate of climb at sea level
(60.0" Hg. Man. Pr. 3000 rpm) = 4000'/min.
Rate of climb at critical altitude, 23,400 ft.
(60.0" Hg. Man. Pr. 3000 rpm) = 2900'/min.
Time to climb to critical altitude, 23,400 ft.
(60.0" Hg. Man. Pr. 3000 rpm) = 6.49 min.
Service Ceiling = 40,000'
The airplane was equipped with wing racks, otherwise the configuration was normal with all flights at a gross weight at take-off of 16,597 pounds with the c.g at 24.75 m.a.c., gear down; and 28.5% m.a.c. , gear up. Gross weight included 300 gallons of fuel, 26 gallons of oil, 457 lbs. of ballast for ammunition, 100 pounds of ballast in the nose to locate the center of gravity within the allowable range, and automatic observer, complete radio equipment and antenna, and 200 pounds for the pilot. All items affecting the drag of the airplane may be seen in the photographs which are included at the end of the report.
Alt.Ft.----- Rate ofClimb Ft/Min. -----Time to Climb-Min.-----Intake Man. Pr.
0---------- 4000------------------------ 0-------------------------60"Hg----------
5000-------3960------------------------1.25---------------------60"Hg----------
10000------3820------------------------2.54---------------------60"Hg----------
15000------3550------------------------3.89---------------------60"Hg----------
20000------3190------------------------5.37---------------------60"Hg----------
*23400------2900-----------------------6.49---------------------60"Hg---------
*Critical altitude in climb for 26400 limiting turbo speed and 60.0" Hg. manifold pressure.
Conclusions
It is concluded that the performance reported is representative of the P-38J airplane, as the subject airplane was flown at combat weight and was also selected at random from P-38J airplanes delivered from the factory.
Recommendations
It is recommended that this method of selection of airplanes for flight test be adopted, and that hereafter all airplanes be test flown at the specified combat weight.
My own conclusions between these two, '47 vs. '38… Outstanding aircraft, the both of them... By WW2s end they were too expensive to purchase as the performance level offered did not better or maybe I should say, meaningfully better, the performance of an aircraft that cost less, the '51. The USAAF was at war's end able to purchase P-80s for less than a '38, and about the same price of a '47... I just skated the issue… I'd be flying the '47. Although out classed by the '38 in most performance categories, the '47 does it for me for the following reasons… mostly 'personal' opinions, therefore hard to argue…
It's better looking, especially in razor back form; I would take one PW 2800 over 2 Allison 1710s (although I do believe the Allison to be a fine 'under praised' power-plant); I would be an aircraft whose performance most closely matches my 'style' (in my sim) of combat flying, I do not dogfight much, I use tactic speed, zoom boom. The '38 is also a Z B fighter, but compressibility issues impede me, as I zoom in my '38, I'm close to Vmax before entering into a dive, good thing they had installed dive breaks. The extra turn performance potential of the '38, in most instances, is an invitation to disaster, they both should not be 'dog fighting', exceed the human body's ability to cope with G forces. The '47 however will change direction more easily since it rolls better at turn fighting speeds (during WW2 centered at about 250 MPH). The overall performance of the '47 is much more linear, it's less tricky, picky, finicky, it is less likely that I (you) might fly the plane apart. The firepower issue between the two would also be a classic debate. The '38 is able to open fire at greater distances due to the nose mounted weapons… the 47 having more guns, wing mounted guns with firepower and bullet density at or near the point of convergence of those guns far in excess of the formidable firepower of the '38. For me, a bias that is formed from a 2D screen, as opposed to 3D reality, I'm more successful with the wing guns than with centered guns. I can much more easily establish in my mind the view of a successful firing solution as a point rather than a stream as the stream offers me 'too many choices', I tend to fire too soon, exposing my position. I do better close, exploiting the aid of a 'convergence' firing pattern in close since there is no radar lock (defeated in most of my CFS-2 installs) or homing missiles…
In my tables the '38 out flies the '47D by enough to outweigh the '47Ds firepower advantage. My tables ranked the '38 as 3rd overall and the '47D as 5th overall out of 21. However, the 47N's extra capacity of 500 rpg, as opposed to the D's 425 rpg was enough to bring the N to 2nd overall position. In my tables I used WEP climb to represent the best climb rate, but did not include any 'time to height' figures, as I believe in 'combat' this is not a important issue, unless intercepting bombers or V1s. Here I briefly would defend my position by saying radar of the day was able to provide in most instances, enough warning, as should have your patrol aircraft, to meet your adversary at the 'correct' height. If sustained max climb was a way to press an edge while in combat, or provided a means of escape I believe more focus on this 'maneuver' would have been given. Unlike Twitch, I believe sustained climb is not a meaningful way to determine much. If a sustained climb was used in a turn fight as a means to press an advantage, or escape, it would be a gentile climb used in conjunction with a high (relative) rate of horizontal speed. After all, If your aircraft has a 1,000 FPM edge in climb rates, I'm on your tail say just outside my 'firing' distance, and we both are traveling at about 200 to 250 mph, as you climb, you will slow down horizontally at a much higher rate than you gain height over me, after all you can only out climb me by about 35 mph, at best. Not only will I be in firing range if you choose this means of escape, rather quickly, but you would be giving me at least 15 seconds to kill you, unless you turn, or dive.
Yet again, the pilot, and or luck, as on race day, will be the determining factor, not the aircraft spec.