XP-39 II - The Groundhog Day Thread

Hello P-39 Expert

P-39 Expert said:

Matthews also lists a Dr. W. F. Atwater, U.S.Army Ordnance Museum, Aberdeen Proving Ground, Md.

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Does this mean that you are sticking with your claim that the typical muzzle velocity of the 37 mm M4 cannon as installed in the P-39 was achieving 2600 - 3000 fps?

P-39 Expert said:

The 37mm gun didn't have to be used in conjunction with the .50s. It had a separate firing button on the stick and could be used independently.

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This sounds like you are accepting that the 37 mm cannon and .50 cal MG did not work well together.
Be careful. This is not in agreement with what you appear to be stating above.

P-39 Expert said:

The P-40 also has a big fat fuel tank right behind the pilot.

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The Airacobra also has a fairly large area in the wings occupied by fuel tanks that are no better protected.

P-39 Expert said:

Absolutely. The ideas you are repeating have been around since the war ended. What I am trying to show you is information that has surfaced more recently from wwiiaircraftperformance.org, recently ('90s) released information from the Russians, and other more current sources. Keep believing the older information if it makes you comfortable, but the P-39 was quite a different airplane than we all have been led to believe.

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I have also read through a fair number of those reports from ww2aircraftperformance.
What they tend to indicate is that for specific examples, often the performance may be a touch higher than one might have expected. I am not discounting that information. I am just noting that the numbers from those test reports do not seem to be supported by actual combat reports. The other question to ask is whether the results of the test report are representative of the type or just of a particularly good example.
There are also test reports from the same time period that do seem to be much more in line with performance in the field.

Also, many of your CLAIMS of performance increases are based on ESTIMATES of the results of stripping off of "unnecessary" weight in equipment that the operators determined was necessary.

You also might want to note that many of the issues that have been brought up have been about handling problems, CoG issues, overheating problems and other issues which have not received mention in reports at ww2aircraftperformance. So far, your response to CoG issues seems to be to declare them to be incorrect. Interesting!

- Ivan.

XBe02Drvr said:

Actually ATP licensed. Never got to fly a "D", as they were just coming out when our company was driven out of business. Pilots who've flown both said they liked the "C" better. Better performance and lighter on the controls.

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I've never flown a C. Only bled the hydraulic brake system on one before. I've done a test flight on a D (As a mechanic), done dozens of ground run and taxi tests, and completed two complete phases on two D's.

XBe02Drvr said:

"Don't let it fly you! Five degrees bank into the working engine. HOLD YOUR HEADING! DON'T let it creep around toward the dead engine! Right leg getting a little tired? Trim it out! Zero or positive rate? Gear up. HOLD HEADING! Got VYse yet? Alright, now EASE those flaps up. HOLD HEADING, HOLD VYse! Positive rate? Yes? Now identify: 'dead foot, dead engine'. Say it out loud, 'left engine'. Confirm: ease LEFT throttle back; any change? No? LEFT throttle, IDLE; LEFT prop, FEATHER; LEFT mixture, IDLE CUTOFF. Now HOLD HEADING AND VYse, and execute engine shutdown checklist." As the treetops whiz by the wingtips.
A light piston twin is a pretty marginal flying machine on one engine. If you can't be in a clean VYse climb before you reach the departure end, you'd be better off to put it back down after a takeoff engine failure and get on the brakes. Better to go off the end rightside up at 1/3 to 1/2 flying speed than into the treetops beyond the overrun inverted at full flying speed. This decision needs to be made and rehearsed based on local conditions before you push the throttles up for takeoff. "THIS is the time I will lose an engine at Vr, and this is what I'm going to do." Shortens your "deer in the headlights" freeze time when it actually happens.

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Wes,

I went through 800ALLATPS for my ATP back in 96. I did two flights in a Seminole with an "IP", then did the check with a retired USAF guy as the designated FAA Examiner. I was completely shocked at the performance of the Seminole engine out. It was slightly better than "the good engine gets you to the crash site". But not much.

I figured out during the second sortie with the "IP" that he was just there building time, and was very light on the IP ability. Basically self taught with a safety observer along. So we are flying towards the end of the second flight when he casually says to me, lets make this one a full stop. I know full well that I'm doing my check ride after this flight unless I want to buy a "third" sortie. Ugh. They want you to buy a third sortie, and the kid doesn't care about anything but logging the shortest flight possible as he gets some sort of kick back on every 1/10th under a preset amount. So after he makes his comment I say nope, lets do two more patterns and I will make the call then. He looks at me a bit flustered, and then mutters okay. I was pissed to say the least, and briefed all the guys in my wing on how things worked so they would be prepared.

I show up for the check ride and the examiner is on the phone. He motions for me to take a seat and starts the oral while he is on the phone. First question is what are the engine oil limits. I look at him like an RCA dog, and he laughs and says it's a color. I respond "in the green". He laughs again and continues the oral, all the while having a great convo with someone else. Then we step, he follows me through the walk around, then before we crawl in I hand him the weather and NOTAMS while briefing him. He looks at me like I have three heads, and replies "I've been doing this for ten years and you are the first guy who ever checked the WX & NOTAMS". I'm thinking to myself WTFO (what were the other guys thinking as the WX / NOTAMS are the basics), but hey he seems happy so maybe that will carry over to the rest of the sortie. I taxi out and get permission from tower to take off. So I do what every fighter guy does, which is switch to departure before starting the takeoff roll. He didn't notice and there was some frequency change hair pulling going on shortly after take off. Fighter guys do this as we take off via interval take offs, and the first guy will be 4-5 miles airborne before #4 gets his gear up (and you want everyone on the same freq - if you abort you have to switch back to tower to notify them). We go flying about the Pensacola local area, shoot an approach then I notice him reach down between the seats to shut off the fuel to one of the engines. Sure enough it sputters and dies, and I go through the relight / restart procedure and get it running. Except now it's running rough as hell. So for the next 30 minutes I finish the profile and he farts with the engine the entire time. I figure if he is busy with that he isn't paying total attention to me so all the better.

We finally land and he tells me i pass. He then fills out my new license and when he is done I ask him for an honest debrief. He looks at me again like I'm a three headed snake, then laughs and says you fly great, but suck on the radios. I laughed and agreed.

Cheers,
Biff

windhund116 said:

Are computer game/flight simulators pretty good at giving the user some 3D awareness? What are the best ones for PC and PlayStation?

Thanks!

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Flight sim games CAN be useful at gaining practice with aircraft procedures, provided the source data for the procedures is verifiably accurate, and the program is patched to show the actual cockpit configuration in question. I've practiced on my FSX computer with airline pilot friends who were waiting for their training date at the schoolhouse for an upgrade or an equipment transition, but only under certain conditions. They've got to have the actual current AFM, checklists, procedures, and flight maneuver profiles for the version they'll be flying, and I have to be able to find and download patches for the aircraft version and cockpit configuration they'll be flying. For procedures practice, they always need another cockpit crew member, something I'm happy to do.
Situational awareness? The computer sim helps that in some ways due to enhanced system and procedural awareness, which is useful in an airline scenario, but in terms of overall flying ability, it's no substitute for the real thing, be it a full function simulator or an actual airplane.

FLYBOYJ said:

This has been beat to death on this forum. PC sims can provide some basic perspectives and some good "numbers" (I use one to help me when I was earning my instrument rating, but understand in the end, they are toys.

So to answer your question; Are computer game/flight simulators pretty good at giving the user some 3D awareness?

"Include the toxic cockpit fumes, the extreme heat or cold, sitting on a lumpy seat while restrained with belts that almost cut through your soaking wet flight suit and have a 300 pound woman sit on you every time you pull Gs - oh while breathing smelly oxygen through a face mask that smells like a prophylactic."

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The good quality ones can be good for learning procedural stuff, like for instrument flying like you pointed out, but thats about it.

I asked my instructor if I should invest in one for my private license. He forbid it. Told me to fly my couch every evening.

FLYBOYJ said:

"Include the toxic cockpit fumes, the extreme heat or cold, sitting on a lumpy seat while restrained with belts that almost cut through your soaking wet flight suit and have a 300 pound woman sit on you every time you pull Gs - oh while breathing smelly oxygen through a face mask that smells like a prophylactic."

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Ahh...sheer ecstacy!

FLYBOYJ said:

"Include the toxic cockpit fumes, the extreme heat or cold, sitting on a lumpy seat while restrained with belts that almost cut through your soaking wet flight suit and have a 300 pound woman sit on you every time you pull Gs - oh while breathing smelly oxygen through a face mask that smells like a prophylactic."

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And some types were noisey as hell, too.

This day and age, we have nice David Clark or Flightcomm headsets, but back then, the speakers were bakelite with hard rubber or leather on the rim and crushed your ears - while doing squat for cancelling out the engine noise.

BiffF15 said:

We finally land and he tells me i pass. He then fills out my new license and when he is done I ask him for an honest debrief. He looks at me again like I'm a three headed snake, then laughs and says you fly great, but suck on the radios. I laughed and agreed.

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On my first CFI attempt, at Miami (Opa Locka) GADO, the FAA Inspector gave me a thorough oral, then put me through my paces in the air, then as we were getting out of the plane, was summoned into the office, just after he'd said "Nice flight". Five minutes later he came out of the office and handed me a DISAPPROVAL OF APPLICATION notice and said: "You fly well, but your teaching needs work. See you again some day".
"Can you at least brief me on where my teaching was inadequate?" (I had worked long and hard on the teaching part with my instructor, who was very good at it, and got a glowing recommendation)
"No, you need to figure that out for yourself. Go reread your Flight Instructor Handbook and Principles of Instruction, you'll get it eventually. See you then. Safe flight home!" This after he'd complimented me on the lesson plans and lecture in the oral.
When I got back to the flying club, my instructor said he figured that would happen. He said the FAR 141 FAA approved flight school downtown had sent three poorly prepared CFI candidates in a row to the Miami GADO, and they'd all failed, resulting in "corrective action" being taken against the school (read the riot act), and the Feds couldn't afford to have one of their approved schools shown up by an FAR 91 club operation. "You'll do better next time."

I would note that the americans used a rather confusing set of 37mm guns and ammo in the P-39 through P-63 series.

The P-39s used the M4 cannon that fired the 37mm X 145mm cartridge.


this had about 2000fps velocity.

Many of the P-63s got the M10 cannon which used the same ammo, fired just a bit faster and used an actual belt instead of magazine and held more ammo. Used the same ammo as the M4 cannon.

however there was also an M9 cannon which was flown in one (?) P-63D-1 which used the same ammo (or at least cartridge case) as the 37mm AT gun and the 37mm AA gun.
37mm x 223mm ammo

this is the 2600-3000fps ammo. This automatic cannon was used on some very late war PT boats much like the earlier M4 cannon.

Now what adds to the confusion is that M4 cannon it it's early days was known as the T9 cannon.
The T9 and the M9 had nothing to do with each other except the 37mm diameter of the shells and barrels.

Some old authors claim the M9 was used in the P-39 and P-38 (?) but it never happened. It does thoroughly muddy up the waters concerning the velocity of the shells fired by the P-39 though.

Source for most of this is "Flying Guns World War II" by Anthony Williams and Dr Emmanuel Gustin.

Page 195 of Birch Mathews book has a sidebar that says, in part,
" The following data pertains to the M9 cannon, but these characteristics are representative of all Kingcobra 37mm weapons" and goes on to give barrel lengths, weights and velocities that are correct for the M9 cannon. Just before the above quote it is stated that only one P-63D used the M9 cannon.
BTW the weight for the M9 cannon was 405lbs without magazine.

You can't have it both ways, you either have the high velocity heavy cannon or you have the low velocity but lighter weight M4/M10 cannon.
You don't have a light 37mm gun with high velocity.

Shortround6 said:

You don't have a light 37mm gun with high velocity.

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I don't have my featherweight .30-06 any more, either. The fun went out of it when shoulder pain became permanent.

wuzak said:

How many single engine fighters in WW2 had feathering props?

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IIRC, the RR Merlin II was the first version of the Merlin with the ability to take a Rotol or de Ha.villand variable pitch prop with feathering capability, though the feathering props were put on RAF bombers before they were put on Spitfires and Hurricanes with the Merlin III. The VDM prop on the Bf109E-3 was also capable of fully-feathering. With regard to the Allison in the P-39 (and P-38, P-40 and P-51A), I know at least the Aeroproducts prop on the P-39Q (V01710-89) had full feathering, and I think the Curtis Electric on the P-38J (V-1710-89/91) has full-feathering, though I'm not sure if that was the same Aeroproducts and Curtis props as fitted to the earlier P-39s. But I suspect even the XP-39 had feathering capability seeing as Curtis had props with full feathering as early at least as 1937 (see here)

XBe02Drvr said:

I don't have my featherweight .30-06 any more, either. The fun went out of it when shoulder pain became permanent.

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Your not supposed to shoot it (much) just carry it

XBe02Drvr said:

I don't have my featherweight .30-06 any more, either. The fun went out of it when shoulder pain became permanent.

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Since my wreck several years ago, I haven't been able to shoot my .300 Savage, but I still have it, she's a beauty to behold.

Mine are great to shoot but suck to carry, 375 Remington ultra mag 9 pounds 8 ounces 26 inch barrel, 458 Lott 10 pounds 2 ounces, 300 win mag 12 pounds 8 ounces 28 inch barrel, 22-250 ackley improved 17 pounds 4 ounces

pinsog said:

Mine are great to shoot but suck to carry, 375 Remington ultra mag 9 pounds 8 ounces 26 inch barrel, 458 Lott 10 pounds 2 ounces, 300 win mag 12 pounds 8 ounces 28 inch barrel, 22-250 ackley improved 17 pounds 4 ounces

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Hello pinsog,

All those critters weigh just a bit less than a M1927 Thompson Carbine with a 50 round drum. (A bit over 18 pounds.)
That had to be the heaviest pistol I have ever fired. Yes, it CAN be fired with one hand.

- Ivan.

Ivan1GFP said:

Hello pinsog,

All those critters weigh just a bit less than a M1927 Thompson Carbine with a 50 round drum. (A bit over 18 pounds.)
That had to be the heaviest pistol I have ever fired. Yes, it CAN be fired with one hand.

- Ivan.

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Shot a full auto Thompson sub machine gun one time at a range. Very nice weapon. My 22-250 is a long range benchrest varmint gun, the 300 win mag is a longer range benchrest varmint gun. The 375 ultra mag is my deer rifle

XBe02Drvr said:

Mad Dog, what's your information source for these statements? The Curtiss Electric prop we had at mech school was not at all like this.....

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I do recall that the Curtis Electric prop in the P-39K/L had a manual speed/angle control, but the Aeroproducts one did not. No idea about the earlier P-39s that might have been used in training (P-400s, P-39C/D, etc.). If anyone has a flight manual for the early P-39s it should show the propeller controls by the mixture controls to the left side of the instrument panel.
One interesting bit of tech with the Curtis Electric prop (sorry, do not know if this applied to the Aeroproducts prop) was that it had a little heating element to keep the hydraulic fluid and lubricating grease from freezing at altitude. I guess that would be another source of failure if the heating element burned out.

pinsog said:

Shot a full auto Thompson sub machine gun one time at a range. Very nice weapon. My 22-250 is a long range benchrest varmint gun, the 300 win mag is a longer range benchrest varmint gun. The 375 ultra mag is my deer rifle

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That .375 Ultra Mag sounds like a bit of overkill for deer? I only have perhaps two rifles that are suitable for deer in this area though I don't hunt and have never hunted (unless you count insects). Just about everything else is a heavy scoped gun or collectible (to me) or service rifle type. My preference is mostly .308 semi autos these days.
My Wife recently got into bicycling and commented that the plastic valve stem cap on one of my Daughter's bikes had disintegrated.
I told her that those caps were probably almost two decades old so it wasn't surprising. They were salvaged along with metal caps from valve stems that I sometimes found when processing wheel weights for cast bullets. I literally went through hundreds of pounds of wheel weights back then for black powder guns, .45-70 and pistols. Lead doesn't actually go far when you are only getting about 14-15 bullets per pound.

- Ivan.

Ivan1GFP said:

Hello pinsog,

All those critters weigh just a bit less than a M1927 Thompson Carbine with a 50 round drum. (A bit over 18 pounds.)
That had to be the heaviest pistol I have ever fired. Yes, it CAN be fired with one hand.

- Ivan.

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My Stepdad always tasked me with loading the drum for his Thompson.
Yeah, there was a winding key on it, but one slip while sticking a .45 round in and there goes your thumbnail.
I much preferred the stick mags...

Interesting site Oleg Kaminsky in Russian, but Google translate works reasonably.

This particular article Messerschmitts do not want to burn and fall has a lot of Airacobra victory claims in a couple of weeks in June 1944. I was expecting a high level of overclaiming, but still....