Groundhog Thread Part Deux - P-39 Fantasy and Fetish - The Never Ending Story (Mods take no responsibility for head against wall injuries sustained)

[tyrodtom]

Hey guys,

At the risk of fanning flames, P-39 Expert is correct as to the length of the engine compartment being the same in both the P-400/P-39 and the P-63.

_________________P-400_______ P-63
Aft Station_______228.50"_____ 231.50"
Fwd Station____ -138.25"_____-141.25"
Length___________90.25"__=___ 90.25"

You're right. My apologies P-39 expert.
I thought the engine compartment ended at frame 182 15/64 on the P-39, and frame 189.062 on the P-63, but it extends all the way to end of the triangular plate.

On the radios, if you look at a lot of WW2 era fighter cutaways and detail views you'll notice some builders even went so far as to mount the entire radio on bungee cords, and about as far from the engine as possible.
The transmitter has to be isolated from static sources as much as possible, or that's what you'll be transmitting, static.
With the old tube type radios, the transmitter was the had more tubes than the receiver, was more fragile, and heavier.

 

[GregP]

I know it for some of the warbirds, but the information is not generally public. For instance, I have seen weight and balance for 20+ warbirds, but was usually asked not to pass the information along to anyone. I haven't except for the odd single variable here and there. You can find SOME weight and balances online, but not many for a currently-flying warbird.

Most are lighter than military stock, no surprise, but a few are a LOT lighter. Some are decently close to stock weight, but all are somewhat lighter. There is a lot of extraneous military equipment not needed for a modern warbird. For instance, some P-51s have the stock-appearing radios in them, but they are just shells. The birds really have modern radios that are a LOT lighter than a WWII unit. Modern batteries are lighter, armor plate is removed, drop mechanisms are removed, etc.

Generally, the % MAC is very close to stock, and WWII military fighters were designed so most loads would not generally put them anywhere close to out of CG for any reason.

I'll bet Der Adler and a few other moderators can verify that most operators don't make weight and balances public.

 

[Shortround6]

G

Hey guys,

At the risk of fanning flames, P-39 Expert is correct as to the length of the engine compartment being the same in both the P-400/P-39 and the P-63.

_________________P-400_______ P-63
Aft Station_______228.50"_____ 231.50"
Fwd Station____ -138.25"_____-141.25"
Length___________90.25"__=___ 90.25"

Great, now how wide and tall was the engine compartment in the last 15-30 inches?

You may have the length (what was occupying the space/volume the 2nd stage takes up?) but do you have the room needed to fit the 2nd stage in the narrowing tail cone?

 

[Schweik]

I feel like if they made that groundhog a bit lighter it could fly higher than the hawk.

 

[Schweik]

Apparently they don't take the guns out of all of them, down in NZ they have a couple of them which are shooting (blanks, I assume) at air shows

 

[special ed]

The RP-63 "Pinball" was not Radio Controlled. It was a piloted target with added armor to keep the frangible bullets from damaging airframe and pilot.

 

[FLYBOYJ]

You're right. My apologies P-39 expert.
I thought the engine compartment ended at frame 182 15/64 on the P-39, and frame 189.062 on the P-63, but it extends all the way to end of the triangular plate.

On the radios, if you look at a lot of WW2 era fighter cutaways and detail views you'll notice some builders even went so far as to mount the entire radio on bungee cords, and about as far from the engine as possible.
The transmitter has to be isolated from static sources as much as possible, or that's what you'll be transmitting, static.
With the old tube type radios, the transmitter was the had more tubes than the receiver, was more fragile, and heavier.

100% - I also believe on the later units, the IFF were part of the transmitter.

 

[ThomasP]

I can not guarantee the data, but I have read that the engine section dimensions and structure were the same for the P-39x, P-39E, and P-63 - with only minor detail mods made for strengthening and ease of manufacture of the P-63. There were also a couple of added-modified access panels, along with modified upper sections for the changed air intake and rear of the canopy. The P-63 tail section was different from the aft station of the engine compartment on back.

 

[Schweik]

Hi thomas P,

I have flown in a P-40N and have spoken with people who operate P-40s of various sorts, including P-40E and M models. None of them have any trouble climbing at 2,500+ fpm at normal weights. Then again, none are being operated at very heavy weights, either. Most are operating just a small bit less than normal weight and none are at max weight, even with a belly tank. You should not be surprised by that since none have actual guns in them except for one very realistic P-40M restoration. And, none of them are limited to 1,000 HP. Most P-40s in combat in the Pacific didn't use only 43" - 43.5" of MAP. Most used 48" - 60" and the AVG used to use 70" - 75" if they needed to do so. Low MAP flight was the norm for training, not for front-line units. I'd think they would take off at normal power and cruise to battle at normal cruise power but, if it came to combat, my bet is they pushed the throttle forward and used what power it could make, without worrying overly much about MAP book maximums.

I don't have nearly as much first hand experience as Greg, but I have spoken to several P-40 pilots, originally when I was a kid as my father was a journalist for Life magazine with a special interest in war veterans in general and WW2 fighter pilots in particular. I was a little quiet kid he had trained to sit still and shut up (often with the help of a model airplane) but I listend to them talk and occasionally got to ask a few questions of my own after they were done with formal interviews and started drinking. Later in life I've talked to the guys flying the warbirds at airshows, especially the P-40s which I had a special interest in. They do apparently push those engines sometimes, more than I expected, though for regular airshow flying I was told low throttle settings were sufficient, partly because they weren't carrying a full load of fuel.

When I was a little kid I didn't know enough to ask about things like manifold pressure, but one consistent story I remember hearing from guys from the 49th FG and the 23rd FG (former AVG) was that once they had figured out how to push the planes they were able to outrun the Japanese fighters and they would run for their lives, gather their wits, and sometimes come back for another shot. One guy was telling my Dad how he was so shit scared in an air battle he swore to himself he'd never get into an airplane again, but once he pulled away and realized he had gotten free and clear, the panic passed, and he started getting angry and went back looking for targets.

Many units seem to have gone through a shakeout process where they learned they could push the engines a bit harder than the manual said. But Shortround pointed out to me a while back, and I believe he is correct - the heavy MAP overboosting was only doable at pretty low altitudes, and not everybody did it. It certainly put the engine at risk. What is true however is that the manual increased the standard boost levels, just like with so many RAF fighters and others around the world - and P-40s were being used with higher boost, both the Allison and the Merlin-engined ones. This isn't always accounted for in the shorthand on these planes (for example that a P-40K had up to 1550 hp at low altitude according to the WEP setting in the manual).

Allison specifically made changes to strengthen the crank case and crank shafts among other things, to make the engines better able to handle the higher boost, but it's also worth pointing out, as it says in the famous Allison memo on the subject, once the the higher-geared Allison engines came out with the P-40M, the very heavy overboosting was likely to be dangerous and was more likely to blow the engine.

I believe most of this should apply to both P-39s and P-40s obviously, and also P-51A (et al), though I don't know as much detail about the combat history of the P-39.

 

[Schweik]

The RP-63 "Pinball" was not Radio Controlled. It was a piloted target with added armor to keep the frangible bullets from damaging airframe and pilot.

That must have been such a depressing, not to say scary job I would think...

 

[buffnut453]

That must have been such a depressing, not to say scary job I would think...

Concur...not sure I'd be willing to fly an aircraft where my entire survival was dependent on the armourers working on a different airframe. "Ooops! Sorry sir. Forgot what I was doing and put regular bullets in the belt instead of frangible. Ever so sorry, sir!"

 

[SaparotRob]

To go up in a P-39 and the mission is to be shot at.
Who did that guy piss off?

 

[GrauGeist]

To go up in a P-39 and the mission is to be shot at.
Who did that guy piss off?

To be honest, it would be far better to have rookies plugging away at you rather than angry Japanese or Germans...

 

[Schweik]

I was wondering the same thing. I bet there are some amusing stories behind the people who were forced to do this. Hell of a use for a formidable aircraft like a kingcobra too. I wonder if it was some kind of anti-commie thing? I was at an airshow where they had a kingcobra flying and the guy on the loudspeaker went on ad nauseum about the various mundane training duties they used it for, but never once mentioned the Soviets actually using it in combat.

Found a pretty good article about the 'pinball', with a few brief pilot commentaries

Just Shoot Me | Military Aviation | Air & Space Magazine

 

[P-39 Expert]

Only about 300 P-63s were converted to armored targets. No P-39s that I know of.

 

[P-39 Expert]

Went back and looked at this - there is a RADIO behind the pilot on some models. There is ALSO one in the tail on ALL models!!!! Receiver/ Transmitter. This is not an optional installation, two units, two locations, "on some models."

From the manual you posted!


View attachment 623679

I can tell you flat out, the transmitter was not moved behind the pilot nor can it be!!!!

Same set up on the P-63.

So, the transmitter was left in the tail - I wonder why???

My whole point is that radios COULD be mounted behind the pilot, which they often were. This is just one way that CG could have been adjusted after removing the nose armor. I'm sure Bell had other ways of adjusting CG. The Soviets removed the IFF radios in the tail (and wing guns) as unnecessary and kept the nose armor and it didn't seem to affect their flying qualities.

Would be fun if Greg P could add the IFF radio in the tail cone to his P-39 CG chart.

 

[Peter Gunn]

I do recall last year in another thread where P-39 Expert pointed out (and I believed) that the engine compartment WAS large enough to hold the 2 stage supercharger. As SR6 points out, is the tail cone wide/tall enough to take it? Well, if it fit in the P-63 I don't think it's much of a stretch to say the P-39 could handle it, I'm sure Bell engineers (they did give us the supersonic X-1 after all) were capable of making it work.

Now if the 2 stage engine is installed, being longer and by extension then, more weight aft, how's the CG looking then? Making it fit is one thing, W & B issues would seem to me to be worse than ever but I'm no engineer.

I've always loved the P-39 for it's looks (it is literally my second favorite WWII a/c after the Mustang) and it is frustrating to think it could have been much better than it was but them's the breaks I guess.

 

[FLYBOYJ]

My whole point is that radios COULD be mounted behind the pilot, which they often were. This is just one way that CG could have been adjusted after removing the nose armor. I'm sure Bell had other ways of adjusting CG. The Soviets removed the IFF radios in the tail (and wing guns) as unnecessary and kept the nose armor and it didn't seem to affect their flying qualities.

Would be fun if Greg P could add the IFF radio in the tail cone to his P-39 CG chart.

You are correct about "a" radio mounted behind the pilot BUT the transmitter CANNOT be moved, so in the bigger picture you're still in the same boat by removing any nose armor. And again, I believe the later transmitter units had the IFF (SCR-535A) incorporated in the installation.

 

[SaparotRob]

Aside from my "humorous" answer, I believe those target 'Cobras were piloted by WASP pilots. Those guys were really under appreciated and certainly deserved more from Uncle Sam.

 

[Clayton Magnet]

Apparently they don't take the guns out of all of them, down in NZ they have a couple of them which are shooting (blanks, I assume) at air shows

Does anyone know if those are actual M2's? I may be wrong, but I suspect those are some sort of pyrotechnics in the wings, simulating gunfire. Even with blank firing adaptors, they probably aren't allowed to fire them off that close to crowds.