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

[nuuumannn]

Can't give you a number but here are some P-40Cs still in front line service defending the Panama Canal in 1943:

Cool photo, and a solitary Cessna Bobcat too...

 

[special ed]

This has reminded me of three gentlemen who came to a Civil Air Patrol senior meeting sometime in the 1970s to show a 16mm B&W movie of P-40 long noses of the AVG in the 23rd used for ground attack. They carried rocket tubes bundled in three under each wing and were live fire training. I had never seen bundles of three tubes on the old p-40s the way I had on much newer fighters.

 

[P-39 Expert]

Without knowing the criteria or method of figuring out either the practical range or the theoretical range we are simply speculating.

As I have said, AHT is a very good source but that table has a number of errors and inconstancies.

One might define practical range as the range that has some combination of probability of hitting plus the potential to do a certain amount of damage. It may have something to do with the amount of rounds fired to get a certain amount of damage.
Max theoretical range may be the range at which a golden BB hit will still do something? but a hit from a 37mm doesn't need to be golden BB, it just needs to hit.

Without having any idea of the criteria used it is impossible to critique.


I would also note that both the practical range and theoretical range will change with altitude. Higher altitudes with thinner air mean less drag, shorter times of flight and more impact energy.

Germans figured the MG 131 had an effective range of 400 meters against bombers but a max range of 700 meters at 3000 meters altitude and a max range of 1000 meters at 6000 meters altitude. The 15mm MG 151 is listed as having a 600 meter effective range, max range of 800 meters at 3000 m altitude and 1,100 meters amx range at 6000 meters altitude.

However this is complicated by the fact that the 13mm MG 131 was a pretty crappy long range gun/cartridge. At sea level it lost 55% of it's velocity by the time it had gone 600 meters and the time of flight was 1.22 seconds. The much higher velocity MG 151 lost 39% of it's velocity and and a time of flight of just 0.816 seconds to the same distance.
For a real head scratcher the AP round out of the MG 17 was rated as having an effective range of just 200 meters. But it lost57% of it's initial velocity in 600 meters but since it started faster than the MG 131 it's time of flight to 600 meters was 1.159 seconds, not really much better than the MG 131 but since it is going to arrive at pretty much the same time and have about the same drop why does it have such a short effective range? Granted it won't do as much damage but it's chances of hitting would seem to be as good.

BTW the .50 cal loses less velocity and has shorter times of flight to given distances than the 20mm Hispano which really calls into question the numbers in the AHT chart.

Good information. You made a comment in a previous post about the projectile weight of the 30cal round. Were the actual rounds used lighter?

AHT also listed the 37mm as firing 90rounds per minute, when it actually fired 150. Big increase in weight of fire per second.

Quoted from the AHT Armament section: "The .30cal MG fell by the wayside as the war progressed...limitations in range and hitting power of this weapon were very evident...With half again the range and two and one half times the hitting power (based on delivered projectile weight per second) the advantages of the .50cal over the .30cal could not be ignored." That's all I know about the subject. Thanks for the information.

 

[pbehn]

Umm, yes it did. Bf 109s carried out fighter sweeps from higher altitudes while escorting bomber formations. RAF fighters had difficulty intercepting them, but the German tactic was to dive down upon the attacking RAF aircraft then climb back to height. Dog fights, which is what usually broke out once the Bf 109s dived among the RAF fighters tended to descend with altitude, but yes, altitudes of over 30,000 ft were flown by the Bf 109s. And wot Pbehn said.

There was also a phenomenon that developed earlier in the battle. The RAF vectored an interception to a raid, and it was bounced. So squadrons started adding a few thousand to the vector height, and sometimes missed the interception completely, the LW sent squadrons higher looking to come out of the sun, so Park sent flights on patrol even higher looking to do the same.

 

[P-39 Expert]

In an active war zone? Or just in the AAF.
Those based in the PI were mostly wiped out on December 8.
The 23rd FG, the successor to the AVG, took over the aircraft of the AVG, predominantly H-81s, on July 4, 1942, and continued to fly them in combat during the later half of 1942
Other units in the US and the Canal Zone continued to operate them for defensive or training purposes, but did not see combat.
But you bring up an excellent point. By the end of 1941, the USAAF and USN were equipping with fighters that were armed with 4-6 wing mounted .50 caliber MGs. Fighters with nose mounted, synchronized MGs were considered obsolete. The P-39, still armed with synchronized MGs and wing mounted .30 caliber guns was therefore obsolete before it entered combat. Why didn't Bell put .50 cals in the wings? There wasn't room. In the Q they slung a single .50 under each wing. Still wasn't good enough

Agree with you about the .30s on the P-40. Of the hundred thousand fighters built in the US for WW2 only a handful of P-40B/C (and the P-39) actually used the .30s in combat. And .30s were used on the Mustang I but that plane was used by the British. The AAF/USN fought the war with .50s and 20mm cannon and a few 37mm cannon.

Disagree with you that the synchronized .50s made the P-39 obsolete. Over a hundred thousand German and Russian fighters used synchronized guns. And the nose cannon and synchronized .50s were sufficient armament in WW2. Just my opinion.

 

[P-39 Expert]

from the Operation and Flight Instructions for the YP-39 and P-39C pursuit airplanes, dated Feb 15th 1941. Page 6.

"d. heating and ventilating equipment. - A Stewart-Warner Cabin heater is provided. A ventilator is installed in the left side of the cabin enclosure. A shutter, installed in the ventilator, is operated by a control located at the pilot's left. "

This is pretty basic and does not say the Stewart-Warner is a combustion (fuel) heater. But why designate it by brand name unless it was well known? If it was a car type heater core and duct why use the Brand name of a combustion heater company?
Stewart-Warner built combustion heaters for A-20s and other aircraft and also built ground heaters for warming up engines prior to starting.

"The Design Analysis of the Bell Airacobra" (Aviation Magazine) details the structural systems and weights for the P-39D. It shows the normal cabin ventilation system of warm air ducted into the cabin (and nose gun bay) from the coolant radiator exhaust just like the subsequent P-39s. There were only 13 YPs and 20 P-39Cs manufactured before series production began with the D. I didn't realize the D-1 and D-2 used the Stewart-Warner cabin heater. They were the Bell model 14 like the P-400 and were often listed as "export" models. Production was relatively small with only 336 D-1 and 158 D-2 models built. The D/F model was the Bell model 15 with the normal ducted heat system as were the subsequent model 26 for the K/L/M/N/Q. Of the 9500+ P-39s built only 527 (13+20+336+158) had the gas heater and those models were completed by summer of '42.

Thanks for the information on the YP, C, D-1 and D-2. Your information is always appreciated.

 

[pbehn]

So the British didnt specify the cabin heater, I am glad we cleared that up at least.

 

[Shortround6]

Disagree with you that the synchronized .50s made the P-39 obsolete. Over a hundred thousand German and Russian fighters used synchronized guns. And the nose cannon and synchronized .50s were sufficient armament in WW2.

We have been over this before. The American Browning did not take to synchronization well. It lost a lot of rate of fire.
The US .50 was powerful but it was heavy, The German guns had a good rate of fire, even when synchronized, they were light.
The Russians used a 7.62 gun to start and rapidly went to the 12.7mm. Their 12.7mm was both light and had a high rate of fire.

Gun................................weight...........................rate of fire
MG 17............................12.6kg..........................1000-1100rpm S
MG 131..........................17 kg.............................about 800rpm S
ShKAS (7.62).................7.1kg...........................1800 rpm unsyc
Berezin (12.7)................25kg.............................800rpm S
US .30 cal........................10kg ...........................1200rpm unsyc
US .50 cal........................29kg.............................as low as 450rpm when synchronized, later ones may have been somewhat faster. perhaps 600rpm?

Russians are a poor example as they deliberately cut armament to avoid sacrificing performance due to the low power of the M-105 engine.
Even the LA-5 and LA-7 had weight issues. When the 25kg B-20 20mm gun was introduced the LA fighters went to 3 guns instead of two 42kg ShVAK cannon.
The MG 131 was deliberately designed to fit (mostly) into the space of the MG 17 and was the lowest power (individual cartridge) heavy machine gun used in WW II.

The Russians also show how different reasons can affect armament selection. They changed from the ShKAS to the Berezin not only to get the larger more powerful 12.7mm round but because the high rate of fire and light ShKAS required a lot of skilled work to manufacture/assemble and the larger Berezin was actually cheaper/easier to make.

Synchronized .50 cal Brownings may not have been "obsolete" but they didn't offer as much hitting power for their weight (bang for buck?) as some other set ups.

 

[Shortround6]

From the ""The Design Analysis of the Bell Airacobra" (Aviation Magazine)"
Air is exhausted from the cabin through ducts over the rudder pedal well. These ducts lead to the cannon and .50-cal machine guns. The air supply to the cabin is constant and only temperature may be regulated. Because of this, there is greater air pressure in the cabin than in the gun compartment, thus preventing fumes from the gun compartment entering the cabin.

Hmmmm, a fix for the gun fumes noted in the cockpit by the British after firing the guns?
perhaps having nothing to do with the weight of the gasoline heater?
A number of American light planes (like Cessna's) used gasoline fueled cabin heaters. Granted they used air cooled engines.

 

[Peter Gunn]

Stop putting words in my mouth. I have never said that the P-39 was able to do the Mustang's job. I have said that P-39s could have escorted B-17/24s in Europe, certainly not as far or as well.

Well, you ARE the one that said a P-39 could escort B-17's and B-24's in the ETO, if that isn't the Mustangs job I don't know what is.

Also I've been pondering this "British adding weight to kill the P-39" issue. Didn't the "British" have dealings (aviation wise) with:

A). Lockheed
B). Boeing
C). Douglas
D). North American
E). Grumman
F). Chance-Vought

At what point did they try to "sabotage" the Mustang, or the Hudson or the Wildcat etc? I suppose you could make an argument for the P-38 but I've never seen any real evidence of them singling out Bell for this underhanded treachery.

Unless perhaps Dutch Kindleberger had pictures of one of the BPC screwing a goat or something.

 

[pbehn]

Also I've been pondering this "British adding weight to kill the P-39" issue. Didn't the "British" have dealings (aviation wise) with:

A). Lockheed
B). Boeing
C). Douglas
D). North American
E). Grumman
F). Chance-Vought

At what point did they try to "sabotage" the Mustang, or the Hudson or the Wildcat etc? I suppose you could make an argument for the P-38 but I've never seen any real evidence of them singling out Bell for this underhanded treachery.

There were similar sentiments about the British use of the B-17, by the time the USA started using the B-17 everything the British said had been acted upon or was found out to be true.

 

[33k in the air]

AHT also listed the 37mm as firing 90rounds per minute, when it actually fired 150. Big increase in weight of fire per second.

With only 30 rounds carried, I don't think the firing rate is going to make much of a difference.

It might be all right for going after bombers, but scoring hits on faster, smaller, and sharply maneuvering fighters is another matter entirely.

 

[DerAdlerIstGelandet]

And, in return, you either ignore responses and refuse to answer questions, or you ignore evidence that contradicts your general statements....or you continue to restate opinions that have been debunked.

Here's two penn'orth of free advice for you:

1. Stop making general comments that aren't backed up by facts. For example, you said that no fighters got up to 30,000ft during the BoB. That's patently untrue and no amount of dissembling (e.g. making (again) unsupported claims about the number of sorties at that altitude) will change the fact that your statement was just plain wrong.

2. Stop viewing every engagement on this forum as an argument that you have to win. This thread would be much more productive if you would demonstrate a willingness to learn new facts rather than clinging to old opinions. You criticize others for not accepting your arguments and yet any view contrary to yours is met with the responses listed above. Rather than simply dismissing the contributions of others, maybe occasionally you might try a different tack...for example, perhaps thanking them for making you aware of something that you didn't know.

Your knowledge about the P-39 is impressive and I've learned a lot from your posts. In particular, some variants did have better performance than I'd previously accepted. But (and it's a BIG BUT) those better-performing variants arrived after other designs were already in service with at least as good if not better performance.

 

[P-39 Expert]

From the ""The Design Analysis of the Bell Airacobra" (Aviation Magazine)"
Air is exhausted from the cabin through ducts over the rudder pedal well. These ducts lead to the cannon and .50-cal machine guns. The air supply to the cabin is constant and only temperature may be regulated. Because of this, there is greater air pressure in the cabin than in the gun compartment, thus preventing fumes from the gun compartment entering the cabin.

Hmmmm, a fix for the gun fumes noted in the cockpit by the British after firing the guns?
perhaps having nothing to do with the weight of the gasoline heater?
A number of American light planes (like Cessna's) used gasoline fueled cabin heaters. Granted they used air cooled engines.

Only the P-400, D-1 and D-2 had the gasoline heater. The rest had the heating system you described.

 

[P-39 Expert]

With only 30 rounds carried, I don't think the firing rate is going to make much of a difference.

It might be all right for going after bombers, but scoring hits on faster, smaller, and sharply maneuvering fighters is another matter entirely.

12 seconds of firing time. P-38 had 15 seconds for their 20mm, Spitfire had 12 seconds for theirs.

 

[P-39 Expert]

Well, you ARE the one that said a P-39 could escort B-17's and B-24's in the ETO, if that isn't the Mustangs job I don't know what is.

Also I've been pondering this "British adding weight to kill the P-39" issue. Didn't the "British" have dealings (aviation wise) with:

A). Lockheed
B). Boeing
C). Douglas
D). North American
E). Grumman
F). Chance-Vought

At what point did they try to "sabotage" the Mustang, or the Hudson or the Wildcat etc? I suppose you could make an argument for the P-38 but I've never seen any real evidence of them singling out Bell for this underhanded treachery.

Unless perhaps Dutch Kindleberger had pictures of one of the BPC screwing a goat or something.

They sure did refuse to pay for the P-38 Lightning equipped as they specified it.

 

[33k in the air]

12 seconds of firing time. P-38 had 15 seconds for their 20mm, Spitfire had 12 seconds for theirs.

The P-38 carried 150 rounds for its 20mm cannon.

More rounds carried means more opportunity to actually score a hit.

 

[pbehn]

They sure did refuse to pay for the P-38 Lightning equipped as they specified it.

I think we went through this before, was it one aircraft or four, how many of the planes the USA wouldnt send (because they themselves were now at war) did they refuse to take? This anti British BS of yours is getting personally insulting. Now, again, where did the British specify that Bell take off their wonderful ducted system and add a gasoline heater as you claimed.

 

[P-39 Expert]

We have been over this before. The American Browning did not take to synchronization well. It lost a lot of rate of fire.
The US .50 was powerful but it was heavy, The German guns had a good rate of fire, even when synchronized, they were light.
The Russians used a 7.62 gun to start and rapidly went to the 12.7mm. Their 12.7mm was both light and had a high rate of fire.

Gun................................weight...........................rate of fire
MG 17............................12.6kg..........................1000-1100rpm S
MG 131..........................17 kg.............................about 800rpm S
ShKAS (7.62).................7.1kg...........................1800 rpm unsyc
Berezin (12.7)................25kg.............................800rpm S
US .30 cal........................10kg ...........................1200rpm unsyc
US .50 cal........................29kg.............................as low as 450rpm when synchronized, later ones may have been somewhat faster. perhaps 600rpm?

Russians are a poor example as they deliberately cut armament to avoid sacrificing performance due to the low power of the M-105 engine.
Even the LA-5 and LA-7 had weight issues. When the 25kg B-20 20mm gun was introduced the LA fighters went to 3 guns instead of two 42kg ShVAK cannon.
The MG 131 was deliberately designed to fit (mostly) into the space of the MG 17 and was the lowest power (individual cartridge) heavy machine gun used in WW II.

The Russians also show how different reasons can affect armament selection. They changed from the ShKAS to the Berezin not only to get the larger more powerful 12.7mm round but because the high rate of fire and light ShKAS required a lot of skilled work to manufacture/assemble and the larger Berezin was actually cheaper/easier to make.

Synchronized .50 cal Brownings may not have been "obsolete" but they didn't offer as much hitting power for their weight (bang for buck?) as some other set ups.

Not arguing with you at all. But the twin .50s did have some rate of fire and none of us can seem to find out exactly what it was. Whatever it was it worked out to be some percentage of one .50calMG. By my calculations I have always maintained that the rate of fire was 75% of normal. That means that both MGs put out the equivalent of 1.5 .50s.

The Navy calculated that one 20mm cannon was worth three .50calMGs. 37mm cannon had just about the same weight of fire/sec (AHT). Coupled with the 1.5 equivalent .50calMGs then the P-39 had the equivalent of 4.5 .50calMGs. I think that was adequate as compared to the P-51A/B/C, FM2 Wildcat, and F8F Bearcat that were armed with 4 .50calMGs. Plus the P-39 had the benefit of centerline fire and the exploding shell.

 

[P-39 Expert]

So the British didnt specify the cabin heater, I am glad we cleared that up at least.

Yes they did, see subsequent posts.