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

[FLYBOYJ]

As to the weight of the radio equipment in the aft compartment, and possible movement of it to correct CG:

View attachment 624357

This is great but there is also an installation that goes behind the pilot;

Looks like this is the SCR-535A IFF

 

[FLYBOYJ]

And it may look something like this;

 

[P-39 Expert]

I believe a catch box was installed to maintain the shell casings from the cannon

The spent shells from both the cannon and two 50calMGs were collected in the nose on all production models, no shell casings were ejected overboard from the nose. Measures were taken to alleviate any CG issues on the P-39N but that was not one of them.

 

[P-39 Expert]

"The P-39C may have been ordered in August 1939 but the first production delivery was in January 1941 and it suffered substantial weight gain during production like the P-400. The weight specified on the contract was substantially lower, more like the original P-400 weight."

And why the weight gain?

You are the one claiming the British started specifying all manor of extraneous stuff to get the weight up and the Performance down AFTER The BoB in order to get out of a cash contract.

YP-39, was first flown on September 13, 1940, same day the USAAC ordered the P-39Ds. One source says "Empty and normal loaded weights rose to 5042 pounds and 7000 pounds, respectively. "

Bell simply could not deliver a working (or read viable) combat aircraft at the weights specified in the contract. Yet you want to blame the British.

" Okay, in detail (AHT) the P-39D weighed 5523lbs empty and grossed 7690lbs. The P-400 weighed 5550lbs empty and grossed 7700lbs even. You can look for the 10lb difference if you like."

If that is what you consider "detail" it is no wonder these threads have dragged out so long.

I will try to be plainer.

Please list all of the items that the British specified that ran the weight up over and above the weights for the YP-39 or P-39C.
Items that the USAAC did not specify for either the P-39C or the P-39D so that we can see exactly how the British were trying to get out of the contract.

Don't bother just copying the gross weights. I am looking the the specific item or items of equipment that ran the weight up that weren't needed for a successful combat fighter of the time.

You made the claim the British ran the weight up unnecessarily. Show us how.

Let me be as plain as I can be. The British specified the 30cal wing guns (about 400lbs with 4000 rounds of ammunition) and excessive armor plate (almost 300lbs when 125 would have been plenty). That's almost 600lbs of unnecessary/redundant weight among other items. Remove that and the P-39 had very competitive performance.

If you want specifics, just open up your copy of AHT and turn to the P-39 chapter. Item by item weights are all right there.

 

[P-39 Expert]

It was a standard production fit from Nov 43 and conversion kits were produced so aircraft could be modified in the field. There was as you would expect a transition period, and just by looking at photographs, its rare to find a photo of the old 'car door' version after March/April 44. I have a couple of photo's of squadrons in flight dated March 44 in my book on the 2TAF and both versions are in both photo's
I wouldn't be surprised if there wasn't a push to get it as a standard equipment for the invasion, but cannot guarantee that.

So the better performance had to wait until 1944? I'm talking about 1942 and 1943.

 

[BiffF15]

And here we go again.

 

[rochie]

The P-39 should be made a political topic on this forum.
Then we might be spared this endless back and fourth!

 

[wuzak]

Let me be as plain as I can be. The British specified the 30cal wing guns (about 400lbs with 4000 rounds of ammunition) and excessive armor plate (almost 300lbs when 125 would have been plenty). That's almost 600lbs of unnecessary/redundant weight among other items. Remove that and the P-39 had very competitive performance.

What extra armor was added by the British compared to the contemporary P-39?

The Airacobra I was powered by an Allison V-1710-E4 twelve-cylinder V in-line engine rated at 1150 hp for takeoff. Weights were 5462 pounds empty and 7845 pounds normal gross. Maximum speeds were 326 mph at 6000 feet, 343 mph at 10,000 feet, 355 mph at 13, 000 feet, 341 mph at 20,000 feet. Initial climb rate was 2040 feet per minute. With an internal fuel capacity of 100 Imp gal the Airacobra had an endurance of 1 hour 20 minutes at maximum continuous cruising speed at 6000 feet, 1 hour 5 minutes at 12,000 feet, and 1 hour 35 minutes at 20,000 feet. The true airspeeds at these altitudes were 287 mph, 327 mph, and 308 mph, respectively. Under most economical cruise conditions, the endurance increased to 3 hours 20 minutes, the relevant speeds being 183 mph at 6000 feet, 217 mph at 12,000 feet, and 215 mph at 20,000 feet. Under maximum continuous climb conditions, it took 15 minutes to reach 20,000 feet. The operational ceiling was considered to be about 24,000 feet, although there was a marked decrease in performance above 20,000 feet. At the Airacobra's rated altitude of 13,000 feet, it was 18 mph faster than the Spitfire VB. However, the speed fell off rapidly above that height, and the two planes were almost exactly matched at 15,000 feet. At 20,000 feet, the Spitfire VB was 35 mph faster and at 24,000 feet it was 55 mph faster. The ground run of the Airacobra during takeoff was 2250 feet, as compared with 1470 feet for the Hurricane II and 1590 feet for the Spitfire V.

Airacobra I for RAF, P-400

Engine: One 1150 hp Allison V-1710-35 twelve-cylinder liquid cooled engine. Performance: Maximum speed 309 mph at sea level, 335 mph at 5000 feet, 355 mph at 10,000 feet, 368 mph at 12,000 feet, and 360 mph at 15,000 feet. An altitude of 5000 feet could be reached in 1.9 minutes. It took 5.7 minutes to reach an altitude of 15,000 feet and 9.1 minutes to reach 20,000 feet. Service ceiling was 32,100 feet. Maximum range (clean) was 600 miles at 10,000 feet at 231 mph. Range with one 145.7 Imp gal drop tank was 1100 miles at 196 mph. Weights: 5462 pounds empty, 7500 pounds gross, and 8200 pounds maximum takeoff. Dimensions: Wingspan 34 feet 0 inches, length 30 feet 2 inches, height 11 feet 10 inches, and wing area 213 square feet. Armament: One 37-mm cannon in the nose with 30 rounds. Four wing-mounted 0.30-inch machine guns with 1000 rpg, two fuselage-mounted 0.50-inch machine guns with 200 rounds per gun. One 250 lb, 325-lb, or 500-lb bomb could be carried underneath the fuselage.

Bell P-39D Airacobra

Compared to the D the Airacobra I had the same empty weight, it had the 20mm vs the 37mm, both had the cowl 0.5" HMGs, the US 0.30" LMGs were replaced by British 0.303" LMGs.

The gross weight was more for the Airacobra I, but that is to do with fuel, ammo, oil, etc. Not armour plating.

 

[wuzak]

So the better performance had to wait until 1944? I'm talking about 1942 and 1943.

I believe the improvements were introduced in 1943.

Glider was pointing out that the older Typhoons had (mostly?) gone by early 1944.

 

[P-39 Expert]

Tell you what - let's see YOU calculate the maximum P-39 range (any model you want) "with the appropriate takeoff and climb allowance, cruise out at high altitude, 20 minutes of combat and cruise back at high altitude with the appropriate reserve for landing."

Gladly. P-39N with 120gal internal less 16gal res. for T/O&Climb, 24gal for combat at 25000', and 10gal reserve for landing nets 70gal x 344mph cruising speed = 378mi. range.
F4U calculated the AAF way 237gal internal less 45gal for T/O&Climb, 93gal for 20min combat at 25000', and 20gal reserve for landing nets 79gal x 344mph cruising = 292mi range. F4U cruising speed was estimated, not in the pilot's manual.

That's for an AAF interception or escort mission at 25000ft. Both straight from the pilot's manuals. Range includes distance covered in climb but not descent. That R-2800 was a gas hog.

 

[buffnut453]

Let me be as plain as I can be. The British specified the 30cal wing guns (about 400lbs with 4000 rounds of ammunition) and excessive armor plate (almost 300lbs when 125 would have been plenty). That's almost 600lbs of unnecessary/redundant weight among other items. Remove that and the P-39 had very competitive performance.

If you want specifics, just open up your copy of AHT and turn to the P-39 chapter. Item by item weights are all right there.

So you're saying that the customer was asking for 30cal machine guns which were unnecessary/redundant? Really? I'd have thought the RAF, coming hot out of the Battle of Britain, would have a pretty solid idea of what they wanted in a fighter.

 

[pbehn]

Let me be as plain as I can be. The British specified the 30cal wing guns (about 400lbs with 4000 rounds of ammunition) and excessive armor plate (almost 300lbs when 125 would have been plenty). That's almost 600lbs of unnecessary/redundant weight among other items. Remove that and the P-39 had very competitive performance.

If you want specifics, just open up your copy of AHT and turn to the P-39 chapter. Item by item weights are all right there.

Let me be as clear as I can be, that was less than half of what was fitted to a Typhoon. Operating close to the ground across the channel exposes you to a lot of ground fire.
from wiki on the Typhoon "Because of the vulnerability of the Typhoon's liquid-cooled engine cooling system to ground fire, some 780 pounds (350 kg) of armour was added, lining the sides and bottom of the cockpit and engine compartments, as well as the radiator bath.[67]"

 

[P-39 Expert]

So you're saying that the customer was asking for 30cal machine guns which were unnecessary/redundant? Really? I'd have thought the RAF, coming hot out of the Battle of Britain, would have a pretty solid idea of what they wanted in a fighter.

RAF did have a pretty solid idea for armament: the 20mm cannon, which they went to right after the BoB.

Biggest drawback with the 30calMG was effective range was only 200yds (AHT).

 

[P-39 Expert]

Let me be as clear as I can be, that was less than half of what was fitted to a Typhoon. Operating close to the ground across the channel exposes you to a lot of ground fire.
from wiki on the Typhoon "Because of the vulnerability of the Typhoon's liquid-cooled engine cooling system to ground fire, some 780 pounds (350 kg) of armour was added, lining the sides and bottom of the cockpit and engine compartments, as well as the radiator bath.[67]"

Exactly right, a liquid cooled ground attack fighter will need a LOT of armor protection. How much did a Spitfire V have?

 

[pbehn]

Exactly right, a liquid cooled ground attack fighter will need a LOT of armor protection. How much did a Spitfire V have?

The Spitfire was the high altitude interceptor for the RAF until the end of the war. Thats why it only had 2 cannon.

 

[BiffF15]

The wheels on the bus go round and round, round and round…

 

[pbehn]

So you're saying that the customer was asking for 30cal machine guns which were unnecessary/redundant? Really? I'd have thought the RAF, coming hot out of the Battle of Britain, would have a pretty solid idea of what they wanted in a fighter.

They did, 4 x 20mm cannon. The P-39 was the most lightly armed of any fighter in RAF service except for Gladiators somewhere in Africa.

 

[FLYBOYJ]

The spent shells from both the cannon and two 50calMGs were collected in the nose on all production models, no shell casings were ejected overboard from the nose. Measures were taken to alleviate any CG issues on the P-39N but that was not one of them.

So this shows the criticality of the CG of the aircraft on all production models!

 

[SaparotRob]

1003 posts left to catch up to roadking01's thread.

 

[buffnut453]

RAF did have a pretty solid idea for armament: the 20mm cannon, which they went to right after the BoB.

Biggest drawback with the 30calMG was effective range was only 200yds (AHT).

And yet the cannon-armed Spitfires in the period 1940-1943 continued with 4x.303 machine guns in addition to the 2x20mm cannon. Perhaps the RAF wanted additional 30cals for the P-400 because they knew that one cannon and two machine guns wouldn't be sufficient for combat operations?