Ad: This forum contains affiliate links to products on Amazon and eBay. More information in Terms and rules
One wonders if the Russians pulled the wing .30 cal guns to improve climb OR to improve roll response. The P-39D was not a particularly good roller, at least until the IAS was near 340mph. And it wasn't that the P-39 got "better" it was that most of the other aircraft got worse quicker and the gap was much reduced.
IMO, without adding some rear ballast, YES!
Step away for a couple hours and miss all kinds of interesting stuff! I did a little research on tail heavy 1900 crashes and couldn't find one by United Express. The two shining examples I found were Ryan Air in Homer AK, and US Air Express in Charlotte NC, both classic out-of-CG-aft loss of control situations. In an earlier thread I detailed my own experience with a badly out of limits aft Be1900, which I won't reiterate here. Suffice it to say, the 1900 had an exceptionally wide CG range, but due to it's long cabin and relatively narrow chord, was often flown at or very near both forward and aft CG limits at various times, giving crews plenty of experience over the entire CG range. Our adventure happened very shortly after the Homer AK crash, so when we got into the air and realized we had a real squirrel on our hands, we made a point of flying real gingerly and quickly but smoothly correcting every bob and weave.Tail heavy, on the other hand, make it difficult to recover from a stall (See United 1900 Crash). Also tail heavy can cause very light control surfaces making It easier to over stress the aircraft.
Step away for a couple hours and miss all kinds of interesting stuff! I did a little research on tail heavy 1900 crashes and couldn't find one by United Express. The two shining examples I found were Ryan Air in Homer AK, and US Air Express in Charlotte NC, both classic out-of-CG-aft loss of control situations. In an earlier thread I detailed my own experience with a badly out of limits aft Be1900, which I won't reiterate here. Suffice it to say, the 1900 had an exceptionally wide CG range, but due to it's long cabin and relatively narrow chord, was often flown at or very near both forward and aft CG limits at various times, giving crews plenty of experience over the entire CG range. Our adventure happened very shortly after the Homer AK crash, so when we got into the air and realized we had a real squirrel on our hands, we made a point of flying real gingerly and quickly but smoothly correcting every bob and weave.
It was my leg to fly, and I've got to hand it to my captain, he let me fly it, but kept a close watch on my progress. He pulled out my W&B and checked my figures again and confirmed we were near the aft limit, but not over it, then said it wasn't unusual to act a bit squirrelly at the aft limit. More than squirrelly, it wanted to go everywhere but straight and level. More like herding it than driving it, and very tiring. When we got to BTV we agreed we should land fast with only one notch of flaps, since full flaps had been the undoing of the Ryan aircraft. At the gates a couple hefty baggage smashers hopped up into the aft compartment to throw down the bags, and the old girl promptly sat down on her tail.
Turns out we were hauling 400 pounds of undocumented Piedmont Comat hiding under the passenger baggage. If the Ryan crew and passengers hadn't paid with their lives for the lesson, it could have been us.
And yet with two big guys in the cockpit, with their overnight bags in nose baggage, full fuel and no pax, she was at the forward CG limit.The 1900 as you know very well was notoriously tail heavy. If we did not use a tail stand when doing maintenance on them, they would tip right over.
The engine bay was 90.25" long in both the P-39 and P-63. The aux. stage did not extend past the aft end of the engine bay, there was a bulkhead there.There are none so blind as those that will not see.
Ask yourself these questions
Why did they move the oil tank aft and cut a far larger hole in the rear fuselage front bulkhead on the P-63? That much bigger hole requires heavier material and significant additional structure to replace the original bulkhead and that means that bulkhead is heavier and that in turn means the aft CG is made very slightly worse.
Why was it necessary that they create this large volume of space behind the engine, in the rear fuselage, that can only be accessed through the engine bay in the forward fuselage. Apart from inspection panels there is no other access unless you remove the oil tank. That makes this totally dead space unless it is filled with something that extends aft from the forward fuselage engine bay.
Was it to fix the aft CG problem? No because it will actually make the aft CG problem worse.
Was it to install the coolant tank? Obviously not as that was moved to behind the pilot.
Was it to look pretty? Obviously not.
Was it because it seemed like a good idea at the time? Obviously not.
Was it to install helium to fix the aft CG problem? Obviously not.
Was it to fill with horse feathers? Obviously not.
So what does that leave? To extend the engine bay in order to make room for the ASB.
That's because the ASB was in the engine bay, the oil tank was not, and they were separated by a bulkhead. Engine bay was the same length as on the P-39, 90.25".This manual page shows how little spare room there was between the ASB and oil tank on the P-63.
View attachment 597432
America's Hundred Thousand lists the weight of the IFF radio on the P-39D-2 as 130lbs, and on the P-400 as 110lbs.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?
That's because the ASB was in the engine bay, the oil tank was not, and they were separated by a bulkhead. Engine bay was the same length as on the P-39, 90.25".
America's Hundred Thousand lists the weight of the IFF radio on the P-39D-2 as 130lbs, and on the P-400 as 110lbs.
The engine bay was 90.25" long in both the P-39 and P-63. The aux. stage did not extend past the aft end of the engine bay, there was a bulkhead there.
America's Hundred Thousand lists the weight of the IFF radio on the P-39D-2 as 130lbs, and on the P-400 as 110lbs.
Here is a picture of a P-39 engine bay, looking rearwards
View attachment 597503P-39 engine bay by Errol Cavit, on Flickr
Actually my bad, no ballast!Adding rear ballast after removing forward ballast?
How many times do I need to say this: Bell stated that the nose armor was not needed for ballast on the P-39M. Quoted from Vees for Victory, which most of us recognize as the best reference for the Allison V-1710.
How does that work in your CG calculations?