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I think they removed fuel cells from the wings and supplied them as kits. Quote "500 of P-39Ns were built, with all but the first 160 featuring elimination of three internal fuel cells to reduce weight. The P-39N could of course carry an external tank to compensate for the smaller internal fuel load, and service units that wanted the full internal fuel load back could install a field upgrade kit to restore the deleted fuel cells. "I also think he is mixing and confusing information from the P-39N manual and the P-39Q manual. Both manuals show internal fuel capacity of 87 gallons in the weight and balance charts. I see no reference of 120 gallons.
He is correct about the IAS/ TAS conversion table only found in the P-39Q manual. With no instruction to convert in the earlier manuals, I think there was the source of some confusion (as you pointed out earlier).
Bottom line, I think with some of the numbers shown, the P-39 had a dismal high altitude intercept radius.
I think they removed fuel cells from the wings and supplied them as kits. Quote "500 of P-39Ns were built, with all but the first 160 featuring elimination of three internal fuel cells to reduce weight. The P-39N could of course carry an external tank to compensate for the smaller internal fuel load, and service units that wanted the full internal fuel load back could install a field upgrade kit to restore the deleted fuel cells. "
From The Bell P-39 Airacobra & P-63 Kingcobra.
Lieutenant Colonel of the Guards Alexander I. Pokryshin, a Soviet ace with 59 kills to his credit, scored 48 of these in a P-39. He was awarded the Distinguished Flying Cross by President Roosevelt. There are eight other P-39 pilots with at least 20 kills. Among top Airacobra aces were Grigorii A Rechkalov (44 kills) , Nikolai D Gulayev (36 kills), Ivan I Babak, Aleksandr F Klubov, Andrei I Trud, and the brothers Boris B Glinka and Dmitrii B Glinka
The internal tanks were removed to reduce weight, so the best combination of range and high altitude performance is chosen for the benefit of the discussion. Use the external tank then drop it to go through the 25,000ft speed trap.Good info, but it seems our friend played with the example that was going to give the greatest range. The external tank installation is indicated clearly in the W&B report
I'm so confused!!
Which aircraft are we comparing now? The reason I ask is that the latest thread (now sub-thread) started with P-39 v P-40, then switched to the P-39 v F4U, then P-39 v ?, and now P-39 v P51.
No doubt in my mind but to convince "experts" sometimes you have to painfully jump through hoops!Questions:
1. Is there really any question (in anyone's mind) that the P-39 (any variant) can be grossly outranged by the F4U-x, P-38x, P-51x? Except maybe on a Point Local intercept, where internal fuel and DTs would not be used for range (ie WUTO, ~max climb to intercept altitude (whatever is suitable for the aircraft), combat, return to Home base/nearby base and land on fumes if necessary)??
No question in my mind!2. Is there any question that the main limitation to a P-39 long range mission is the internal fuel load (87 or 120 USgal)? Just as it is for any of the other aircraft (ie If the profile is internal for WUTO and initial climb, switch to DT for climb to operational altitude, DT for cruise outbound, drop DTs at/near point of contact, internal for combat, internal for cruise home, internal for some amount of reserve at/near home)??
I used the example straight out of the posted P-39N flight manual with 87 gallons of fuel shown per the weight and balance report. It was pointed out that some aircraft had additional wing fuel tanks installed but those weren't used in my examples although our expert friend keep plugging in this and performance data from the P-39Q3. Which variant of the P-39 are we using for the comparison? If I understand correctly, P-39 Expert is using a variant of the P-39N with either 87 or 120 USgal internal fuel (depending on mission profile), armed with 1x37mm or 20mm and 2x.50 cal, lightened and rebalanced through a change in armament, reduced armour, with a reposition/removal of some equipment. The idea being that the P-39 could have been significantly more capable in modified form. (I am leaving out the possibility of the engine change to the -93 model due to the current discussion being focused on the range and altitude issues of the standard variants.) It should not be difficult to specify the operational weights, and agree on ~speeds, ROC, fuel burn, etc.
Hope this helps, any additional information you can add would be appreciated but probably not convincing to some!Answers please.
Please expand above.I'm so confused!!
Which aircraft are we comparing now? The reason I ask is that the latest thread (now sub-thread) started with P-39 v P-40, then switched to the P-39 v F4U, then P-39 v ?, and now P-39 v P51.
Questions:
1. Is there really any question (in anyone's mind) that the P-39 (any variant) can be grossly outranged by the F4U-x, P-38x, P-51x? Except maybe on a Point Local intercept, where internal fuel and DTs would not be used for range (ie WUTO, ~max climb to intercept altitude (whatever is suitable for the aircraft), combat, return to Home base/nearby base and land on fumes if necessary)?? About the same as F4U-1, see my previous post. Certainly not as good as P-38 and P-51, they held more fuel.
2. Is there any question that the main limitation to a P-39 long range mission is the internal fuel load (87 or 120 USgal)? Just as it is for any of the other aircraft (ie If the profile is internal for WUTO and initial climb, switch to DT for climb to operational altitude, DT for cruise outbound, drop DTs at/near point of contact, internal for combat, internal for cruise home, internal for some amount of reserve at/near home)??
3. Which variant of the P-39 are we using for the comparison? If I understand correctly, P-39 Expert is using a variant of the P-39N with either 87 or 120 USgal internal fuel (depending on mission profile), armed with 1x37mm or 20mm and 2x.50 cal, lightened and rebalanced through a change in armament, reduced armour, with a reposition/removal of some equipment. The idea being that the P-39 could have been significantly more capable in modified form. (I am leaving out the possibility of the engine change to the -93 model due to the current discussion being focused on the range and altitude issues of the standard variants.) It should not be difficult to specify the operational weights, and agree on ~speeds, ROC, fuel burn, etc. There were really only two P-39s, despite the variations that ran all the way up to Q. Main difference was their engines. 1942 P-39D/F/K/L had the -35 or -63 engines with critical altitude of 12000ft. They were limited to low and medium altitude (under 20000ft) because they were too heavy for their engine power. Unnecessary/redundant items (30cal wing guns, one piece or armor plate, IFF radio) could have been removed at front line bases to greatly improve climb/ceiling.
1943 P-39N/Q had uprated -85 engines with higher S/C gear ratio and critical altitude of 15000ft. The N model had a 38,500ft ceiling and an excellent rate of climb at all altitudes at stated weight, nothing needed to be removed. Only real difference in the N and Q was wing guns. Remove the underwing podded 50calMGs from the Q and they were about the same as an N.
Answers please.
P-39 was built for 120gal internal fuel. AAF reduced fuel in some N and Q models, probably at the request of their primary user the Soviets. Kits were available to restore the full 120gal in the field. Any range discussion should use the normal 120gal. Also if the wing guns are removed there is room for more fuel, at least 30gal which would bring internal fuel up to 150gal, same as P-38F/G.
Shortround post #1564: Yes IAS was mislabeled in column I from P-39Q range chart. Correct that to TAS for cruising speeds at max. continuous. 330mph at 25000ft etc.
Shortround post #1590: Your combat reserve of 33gals vs mine of 24gals results in about a 50 mile difference. Not really significant. I'll stick with mine.
Flyboy post #1567: Regarding fuel capacity, every production P-39 was built for 120gal internal fuel. AAF reduced fuel in some N and Q models, probably at the request of their primary user the Soviets. Kits were available to restore the full 120gal in the field. Any range discussion should use the normal 120gal. Also if the wing guns are removed there is room for more fuel, at least 30gal which would bring internal fuel up to 150gal, same as P-38F/G.
Flyboy post #1584: Again, 1942 P-39s were way too heavy (could have been lightened easily). Gen. Kenney had made up his mind about the P-39 and welcomed the P-38s.
They came in about the time the vastly improved P-39N was available, end of 1942. And the AAF had already decided that (based on the 1942 P-39s) the war would be fought primarily with the P-38 and P-47 and the P-39 would be sent to Russia or used for training. Compared to the P-38F/G the P-39N climbed better and was faster under 20000ft. The Russians greatly benefitted from the lend lease P-39N/Q.
There were really only two P-39s, despite the variations that ran all the way up to Q. Main difference was their engines. 1942 P-39D/F/K/L had the -35 or -63 engines with critical altitude of 12000ft. They were limited to low and medium altitude (under 20000ft) because they were too heavy for their engine power. Unnecessary/redundant items (30cal wing guns, one piece or armor plate, IFF radio) could have been removed at front line bases to greatly improve climb/ceiling.
1943 P-39N/Q had uprated -85 engines with higher S/C gear ratio and critical altitude of 15000ft. The N model had a 38,500ft ceiling and an excellent rate of climb at all altitudes at stated weight, nothing needed to be removed. Only real difference in the N and Q was wing guns. Remove the underwing podded 50calMGs from the Q and they were about the same as an N.
"Could have, would have, should have" once again you're cherry picking. I think you know as well as I the AAF units in the SWP (80th FG, 35th FS for example) that were using P-39Ds and P-400s did not operate with 120 gallon fuel tanks. Even with the extra fuel the P-38 F/G, let alone the J easily outranged the P-39. So please, stop trying to throw "what ifs" into what actually happened.Flyboy post #1567: Regarding fuel capacity, every production P-39 was built for 120gal internal fuel. AAF reduced fuel in some N and Q models, probably at the request of their primary user the Soviets. Kits were available to restore the full 120gal in the field. Any range discussion should use the normal 120gal. Also if the wing guns are removed there is room for more fuel, at least 30gal which would bring internal fuel up to 150gal, same as P-38F/G.
Could have, would have, should have."Flyboy post #1584: Again, 1942 P-39s were way too heavy (could have been lightened easily).
Gen. Kenney had made up his mind about the P-39 and welcomed the P-38s. They came in about the time the vastly improved P-39N was available, end of 1942. And the AAF had already decided that (based on the 1942 P-39s) the war would be fought primarily with the P-38 and P-47 and the P-39 would be sent to Russia or used for training. Compared to the P-38F/G the P-39N climbed better and was faster under 20000ft. The Russians greatly benefitted from the lend lease P-39N/Q.
And we still have the questions
a) How much weight is involved adding the extra fuel plus its tanks and plumbing
b) If the N was so good why was it replaced with the Q which had less performance
c) You don't just rip out guns and add fuel
d) what is the performance of the N with the extra weight. My guess is that it will be very similar to the P39Q which was a very similar aircraft, which in turn knocks great holes in your claim for the P39N being such a wonder weapon
Somewhere I had post with the listed performance of not only the P-39N but the P-39M (same plane with different reduction gear and propeller) the P-39Q, (same plane with different wing guns), the P-40 using the Allison with 9.6 supercharger gears and the P-51A using the Allison with 9.60 gears.
The P-39N was way, way better in many categories, suspiciously so. like double digit percentage changes in climb.
Maybe the test aircraft did perform that well, sometimes you get a plane where everything just "clicks" but what happens when you don't?
If somebody made a graph with all the P-39 models in speed and climb from the D through Q all of the planes except the N would be somewhat closely gathered together in a bunch, with the lines for P-39N way out by themselves. There doesn't seem to be enough difference for the N to justify that change in performance.
Somewhere I had post with the listed performance of not only the P-39N but the P-39M (same plane with different reduction gear and propeller) the P-39Q, (same plane with different wing guns), the P-40 using the Allison with 9.6 supercharger gears and the P-51A using the Allison with 9.60 gears.
The P-39N was way, way better in many categories, suspiciously so. like double digit percentage changes in climb.
Maybe the test aircraft did perform that well, sometimes you get a plane where everything just "clicks" but what happens when you don't?
If somebody made a graph with all the P-39 models in speed and climb from the D through Q all of the planes except the N would be somewhat closely gathered together in a bunch, with the lines for P-39N way out by themselves. There doesn't seem to be enough difference for the N to justify that change in performance.
What I can ask him is why the P39Q which was in many ways inferior in performance brought into service in the first place. Plus all the other questions that people have raised without response. The silence is deafening and yet speaks volumes