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The P-39 oil tank is completely behind the bulkhead. It's base sat in the same type of cradle as the P-63, behind the bulkhead.
- The aux. stage blower was installed in the XP-39E.
- The engine compartment was not enlarged to accommodate the aux. stage, it was the same length as the other P-39s and the P-63
- as evidenced by the drawings in my post #236.
The E model was longer because the tail section was longer, not the engine section as reported by other sources.
Not if the fuel is on the center of gravity as it should be.
Not if the fuel is on the center of gravity as it should be.
Or ammunition, or oil, or signal flares, or oxygen, or bombs...you can't put every consumable item "on the center of gravity". This is getting ludicrous.
Ding, ding, ding. Someone gets it!
I stand corrected, the oil tank did protrude slightly into the engine bay.Yes it fits in a cradle similar to the P-63 but the tank is mounted at an angle and protrudes thru the bolted bulkhead at stn 228.5 as shown in the first diagram in post 293.
Seeing that you will not believe someone who has worked on these aircraft maybe you will believe the Bell Aircraft Company, though I am beginning to doubt even they can convince you.
View attachment 597411
As shown in post 293 the P-63 oil tank is mounted vertically some six to eight inches behind the bulkhead and the bulkhead has a far larger cutout.
View attachment 597414
1. Yes, one out of three is correct
2. Yes and no.
Yes, the engine bay in the forward fuselage was not extended
No because the rear fuselage bulkhead was changed to allow the total engine bay to extend into the rear fuselage, unlike on all other P-39s, like on the P-63, and the angled oil tank was moved rearwards and positioned vertically, and the coolant tank relocated, to provide the space required to install the ASB.
The only way to fit the ASB in the P-39E was to extend the rear fuselage so that the ASB can extend through it like on the P-63 as shown above.
3. Station and skin panel drawings do not show any internals so are totally irrelevant to this discussion.
Yes and no. See above. The rear fuselage was longer in part because the engine bay was extended into the rear fuselage and the oil tank was moved aft and mounted vertically, and coolant tank relocated, to provide room for the ASB.
And then there are the structural modifications that must be made to move something.I get the feeling that some people believe W&B and CG is a simple task, when there really is a science to it. You cannot simply take weight away from somewhere, and add some weight here. When I was on 2nd shift working as an A&P I had to work with QC quite a bit doing them after modifications had been performed. I always enjoyed it.
And then there are the structural modifications that must be made to move something.
At 9g a 150lb radio "weighs" 1350lb so the structure where it is being moved to needs to reflect that.
Further there is the structure that originally held the radio. Can all or part of it safely be removed? If it is left in will it produce other problems like too much rigidity in the area which will cause cracking nearby? This is not an insignificant issue as shown on the Lockheed L-188 which was too strong in one area. This resulted in the wings separating from the aircraft in flight and killed a lot of passengers and crew before the LEAP mods which changed the engine mounts to reduce a specific vibration, caused by whirl mode, and removed a lot of structure in the wing to fuselage joint area.
Right there you're wrong - the C/G will move (as shown) depending on weight, arm and momentI also understand that the CG is also a fixed point on the plane
AbsolutelyI also understand, as should you, that the manufacturer was able to maintain the CG within acceptable limits when items of different weights were substituted or removed.
Of course different equipment will change weights and C/G limits but are you trying to say that Bell would pick out a "heavier" propeller or cannon of the same make/ model to adjust for weight and balance requirements on a specific production model? And again you're making the statement " According to you all the Russian P-39s should not have been able to fly." All I'm saying is "Show me the math" to prove your point! I actually think removing 120 lbs from the tail would have made the plane fly better, but that's just an opinion - I'd have to do the mathSuch as larger (heavier) propellers or different (lighter) cannons were substituted in the nose, or different radios were substituted or removed from the tail. Balance was maintained by the manufacturer through all these different equipment changes. Bell stated that the P-39M did not need the nose armor as ballast. And the Russians removed the IFF radio that weighed 120lbs from the tail cone of the plane yet did not remove anything from the nose to maintain balance. According to you all the Russian P-39s should not have been able to fly.
No - we're actually trying to get you to prove your point based on the data shown.All of you are making much more of this than actually happened.
Agree, providing the aircraft stays between 23 - 31% MAC (which is a little over 6 inches) during all flight regimes in it's factory condition.The P-39 was by all accounts easy to operate, safer than most and capable of performing all combat maneuvers. It had good stalling characteristics, acceptable spin characteristics (which could only happen after a stall) and would not tumble when ballasted properly. Most all other fighter planes had some unfortunate characteristics. Such is the nature of high performance airplanes.
I don't think he's caught on yet that CG is not a fixed location. Most of my flying students were reluctant to wrap their heads around that idea, even after reading the W&B chapter in the student pilot manual.
Look - it's evident you never weighed a real aircraft. This has nothing to do with fuel being on the center of gravity!Not if the fuel is on the center of gravity as it should be.
Yes the Russians removed the IFF radio that weighed about 120lbs from the tail section and didn't remove the 100lb nose armor. According to some folks on here the plane should have immediately fallen out of the sky.
Why would the IFF radio be important to the AAF and not the Russians? I don't know.
Question - what IFF set are talking about here? The only Allied electronic IFF bare units used (before the very end of the war) topped out at around 36 lbs plus a few pounds for wiring and such (most of the installation weights I have seen were around 40 lbs total). Where does the 120-130 lbs value come from?
Thank you for all the comments about what I understand and don't understand. I understand mean aerodynamic chord and CG being within certain limits of distance from the wing leading edge.
I also understand that the CG is also a fixed point on the plane
Not if the fuel is on the center of gravity as it should be.