Originally posted by Treize69
Yes, the F had no maneuver setting on the flaps. All P-38 flaps were the Fowler type. The F was also the first Lightning to be able to carry drop tanks (of 165 gallons) or bombs under the center wing sections. Engines were of the 1,225hp Allison V-1710-49/53 type.
G had the maneuvering flaps, an improved engine control system, and was upgraded to carry 300 gallon drop tanks. Engines are the V-1710-51/55 type,rated at 1,325hp.
H had 1,425hp V-17170-89/91 engines, the same as in our P-38J. Unfortunately the leading edge intercoolers were inadequate for an engine that powerful, and power was limited to 1,240hp. The redesign of the intercooler/oil cooler assembly led to the P-38J. The H was heavier than the G with weaker engines, so it was slightly less maneuverable and only had a combat range of 1,950 miles with 300 gallon drop tanks.
The H also upgraded the cannon from the older M1 to the better AN/M2C model.
All three models had the windscreen armor, the J lost it starting with the J-10 block when a new flat, bullet proof windscreen was standardized.
A couple of points...
Before F models were reaching squadron service, E models were already being retro-fitted for drop tanks. This can be seen in photographs and in reference documents. As early as May of 1942, P-38Es were flying with two 160 gallon drop tanks, having been upgraded right alongside early P-38Fs at Burbank. Virtually all P-38Es were upgraded to F standards. These Lightnings saw combat in the Aleutians.
As to the P-38H, max power rating was 1,600 hp (combat rating), and this power was available without restriction, beyond the standard 5 minute limit. Intercooler limitations were not a factor until altitudes of 25,000 feet and higher. Up high there were MAP restrictions due to the inability of the leading edge intercoolers to sufficiently cool the compressed and heated intake air. This frequently lead to detonation and engine damage. If you examine the Specific Engine Flight Chart for the P-38H you will see that there are no special MAP restrictions until 25,000 feet. If you compare this to the same chart for the P-38J, you can see the differences clearly. P-38Hs were limited to 54 in/hg, whereas the P-38J could pull the full rated 60 inches. Your quoted rating of 1,240 hp was for MIL power at 25,000 feet. Max power available (WEP), subject to the 54 in/hg limit, was 1,465-1,470 hp at 25,000 feet. However, one could get max rated power of 1,600 hp @ 60 inches, with the understanding that the risk of detonation greatly increased every minute you maintained that power. This is why there was a MAP restriction to 54 inches, which by the way, was generally ignored when an emergency required absolute max power. Engines were cheap compared to whole airplanes and their pilots.
Weights: The empty weight of the P-38H was 180 pounds greater than the G model, up to 200 lb when calculated as "basic weight". When one considers that the P-38H had a minimum of 200 more hp (MIL power) and a maximum of 550 more hp (WEP below 25k), you realize that the minor weight increase is insignificant. Actual performance of the H model was superior to the G in every measurable aspect. In terms of climb, the H could reach 25,000 feet four minutes faster than the G. Acceleration improved by a similar margin.
In terms of best speed at best altitude, the H was slower than the J simply due to the J being able to pull 60 inches MAP at 25,000 feet. However, below 22,000 feet speeds were virtually identical, and faster than the G model. Max speed for the H (at 25k), depending on many factors, such as surface finish, panel fit and state of tune, varied between 402 mph for especially well used planes, up to 408 mph for factory fresh. G models typically were capable of 397 to 403 mph depending upon the same factors. J models typically pulled 418 to 423 mph. I am referencing both factory and USAAF speed and climb charts for both types, as well as official Flight Operation Instructions for both. I am also referencing test data from Eglin Field (for the H and J models).
My regards,
Widewing
