REPUBLIC AVIATION PERFORMANCE DATA - P-47 "M" and

[DAVIDICUS]

It has arrived!

I have purchased Republic Aviation Corporation's dimensional, specification and performance data concerning the P-47 "M" and "N" models from Essco.

www.esscoaircraft.com

I will post some data later on after I get home from work.

[FLYBOYJ]

Great Stuff David, looking forward to seeing it!

[DAVIDICUS]

This P-47N was flown by 1Lt Oscar F. Perdomo, who was America’s last "ace in a day", the last American ace of WW II, and perhaps the last ace of all the WW II belligerents.

Perdomo scored all his victories on 13 Aug 1945, two days before the Japanese surrender, on a long-range mission from Ie Shima, Okinawa to Keijo (Seoul), Korea. This 1,800 mile round-trip mission lasted 8 hours and 18 minutes.

On his tenth and last combat sortie of the war, and his first encounter with enemy aircraft, Perdomo scored his 5 kills in three separate engagements. He first downed 3 Ki-84 "Franks", then a Yokosuke K5Y "Willow" biplane trainer, and finally a fourth "Frank", all in less than 15 minutes.

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OK, here it is.

This is data published by Republic Aviation Corporation.

The publication starts out with a quote from Noah Webster. (Author of the first American Dictionary)

"A Thunderbolt is a destructive flash of lightning - to be accompanied by the fall of a solid body. A Thunderbolt is a dreadful threat."

All performance data is for "Combat Gross Weight" which means a full internal ammunition load and a full internal fuel load. This is different than "Normal Gross Weight" which is the maximum weight in which the aircraft can be maneuvered to its design load factor. The "N" has a massive internal fuel capacity of 570 gallons.

A full internal ammunition and fuel load in an "M" model weighs 2,833lbs.

A full internal ammunition and fuel load in an "N" model weighs 5,332lbs.

The "N" model would thus carry an additional 2,500lbs (2,499lbs) of fuel over and above the "M" model (under circumstances where the ammunition load is the maximum) in "Combat Gross Weight" configuration.

Empty Weight

"M" is 10,442lbs.

"N" is 10,998lbs.

Combat Gross Weight

"M" is 13,275lbs.

"N" is 16,330lbs.

Powerplant

A.C. Designation is R-2800-73

Model is R-2800-TSC2G

Mfg. Spec is A-8088-C

Weight of engine dry is 2,336lbs.

Oil tank capacity is 28 gallons for "M" and 40 gallons for "N"

Propeller is 13' in diameter and weighs 565lbs.

"The following performance data is at WEP and at "Combat Gross Weight" of 13,275lbs for the "M" and 16,330lbs for the "N" except as noted."

Take off over 50ft obstacle (flaps retracted)

"M" is 1,800ft.

"N" is 6,030ft. (Loaded at maximum take off weight of 21,198lbs)

There are no sea level climb figures provided. The altitude markers are 5,000ft, 15,000ft and 28,000ft.

Rate of Climb at 5,000ft

"M" is 3,775ft/min

"N" is 2,950ft/min

Rate of Climb at 15,000ft

"M" is 3,425ft/min

"N" is 2,600ft/min

Rate of Climb at 28,000ft

"M" is 2,375ft/min

"N" is 1,600ft/min


Given the above data, can someone help me to estimate what the maximum climb rate at sea level would be for an "N" model at "Normal Gross Weight" (13,854lbs)? I think it would be helpful to first estimate what the maximum climb rate at sea level would be for the "M" model, as configured above.

Remember that the above data is for "Combat Gross Weight" and not "Normal Gross Weight" (The Combat Gross Weight of the "N" is 16,330lbs while the Normal Gross Weight is 13,854lbs)

The "N" model's Normal Gross Weight is thus 579lbs heavier than the Combat Gross Weight of the "M" model.

We know from the Pilot's Manual for the "N" model that the wing area is 322.2sqft. The data provided by this publication lists the "M" model's wing area as 300sqft.

The "M" model's wing loading as reflected in the data above is 44.25lbs.

The "N" model's wing loading in "Normal Gross Weight" is 43lbs.

[DAVIDICUS]

Given the "M" model's ability to cliimb at 3,775fpm at 5,000ft, it would appear likely that the maximum climb rate at sea level would be in excess of 4,000fpm. (That, of course, would be under a "Combat Gross Weight" loading. Under a "Normal Gross Weight" loading, the climb rate would be significantly higher.)

Given the "N" model's mere 579lb heavier weight in "Normal Gross Weight" configuration and lower wing loading of 43lbs as opposed to the "M" model's 44.25lbs, I would expect the "N" model to have a climb rate within 100fpm or so of the "M" model's figures reflected above.

I believe it is quite possible then that the "N" model, in "Normal Gross Weight" configuration, could attain a 4,000fpm rate of climb at sea level.

Any thoughts?

[FLYBOYJ]

Very cool stuff David and what you say might be correst, but somewhere there has to be a climb performace chart that will give numbers at SL. I think that's where your going to find this out for sure.

[DAVIDICUS]

Other data that may be of interest.


Armor protection around the pilot was as follows for both the "M" and "N" models:

Armor plate - Bottom/Rear - 1/4" from the bottom of the seat up to the shoulders

Armor plate - Rear - 3/8" for head

Armor plate - Front 3/8"

Bulletproof Glass - 1-1/2" set at 39.5 degree angle
__________________________________________

The "N" model had an automatic pilot feature. (I wonder how that operated?)

The "N" model was designed to have "chemical spray tanks" fitted under the wings where bombs or wing tanks would be carried. There was a pilot operated special release mechanism for the spray tanks. (Anyone care to guess what the "chemical spray" would have been? She'd certainly make a pretty lethal crop duster!)

[FLYBOYJ]

Originally Posted by DAVIDICUS

The "N" model had an automatic pilot feature. (I wonder how that operated?)

It was probably Sperry unit, typical of the day. If I remember right you'll see a large panel in the center instrument panel with a turn and bank indicator and a directional gyro (DG) along with several switches. This was "slaved" into another set of gyros (control unit or computer) that gave electrical inputs to servos located at the ailerons, elevators and maybe rudder. You simply dialed a heading on the DG, turned on the autopilot and it followed that heading while keeping the aircraft straight and level.

[DAVIDICUS]

More data of interest:

Standard Armament Installation

Standard armament installations of the P-47 airplane have always been extremely heavy. This feature has been retained in both the P-47N and P-47M airplanes. Eight .50-caliber M-2 machine guns with a normal ammunition load of 267 rounds per gun are installed in the wings. The guns are mounted, four in each wing, and all fire outside of the propeller disc. The guns are fired by means of electrical solenoids which are controlled by a trigger switch on the control stick.

Armament

.50 Cal Machine Guns Normal - 6 (Both "M" and "N" models)

Rounds Per Gun Normal - 267 (Both "M" and "N" models)

.50 Cal Machine Guns Overload - 2 (Both "M" and "N" models)

Rounds Per Gun Overload - 233 (Both "M" and "N" models)

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Thus, it appears that the "M" and "N" models could be outfitted with eight .50's loaded up with 500 rounds per gun.

There is no mention of M3's (The significantly faster firing .50 cal gun).

1) It is possible that the M3's were switched out for existing M2's without a perceived necessity to update this information in official publications (or at least this one) or,

(2) It is possible that the entrance of the M3's on the scene late in the war came after this publication or

(3) It is possible that the P-47N was not in fact the recipient of the M3 after all.

[Soren]

So the 16,300lbs normal loaded figure for the -47N was correct afterall....I thought so

Originally Posted by DAVIDICUS

All performance data is for "Combat Gross Weight" which means a full internal ammunition load and a full internal fuel load.

Which is what we were looking for. (or atleast me)

For example the Spit XIV's Combat gross weight was 8500lbs, and the Bf-109K-4's was 6,940lbs. Both are with full internal fuel load and ammunition.

So to keep it fair, we should be looking at the -47N's combat gross weight aswell.

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Anyway great info DAVID, keep it coming

[DAVIDICUS]

Soren, after I posted the 13,854lb figure which I clearly labeled as "Normal Gross Weight", you stated:

"However what I'm questioning most at the moment, is why should the data from several books about the P-47 be wrong about the -47N's normal loaded weight figure ? Seems strange...

The -47N's normal loaded weight is quoted as being 16,300 pounds by every single one of my sources. That's allot more than 13,850lbs!"

So, we can conclude that you understood that the "Normal Gross Weight" figure I quoted meant the same thing as "normal loaded weight" which is why you were questioning the strangeness of the data. I have no idea what "normal loaded weight" is but to the extent that you believed that these two terms meant the same thing, you were incorrect.

I have data for "Combat Gross Weight" and "Normal Gross Weight" Call me unreasonable but "Normal Gross Weight" sounds a lot more similar to "normal loaded weight" than "Combat Gross Weight" Look, they even contain the same modifying word "Normal".

Since the P-47N can be laoded up to over 21,000lbs, it is indeed possible to load it over 13,854lbs to a 16,300lbs weight level. Call that 16,300lbs level of weight whatever you like. That does not change the fact that such a loading takes it well outside and above the "Normal Gross Weight" level which I accurately quoted.

With regards to your statememt, "Which is what we were looking for. (or atleast me)" all I can say is that I posted the accurate "Normal Gross Weight" figure which you took issue with. Again, I never said that the P-47N or any other variant for that matter, could not be loaded up to 16,300lbs. Obviously loading an additional 2,500lbs of fuel, or anything else for that matter, onto a plane will adversely affect its climb rate.

Soren, you also said, "So to keep it fair, we should be looking at the -47N's combat gross weight as well." and then threw in the Spitfire and Bf-109 as examples.

Soren, the P-47N is an extremely long range escort fighter (2300+ miles). The Spitfire and Bf-109 are very short range interceptors. We can easily conclude that "So to keep it fair, we shouldn't be comparing them at all."

Even as between the "M" and "N" models, it is unfair to compare the "M" model's climb rate with a fuel and ammunition load of 2,833lbs and the "N" model with an additional 2,500lbs of fuel.

In light of the vastly different roles that a Spitfire IX and P-47N perform, perhaps the way to "keep it fair" would be to compare, say the Spitfire, with whatever fuel weight would give it a range of 450 miles and the P-47N with whatever fuel weight would give it a range of 450 miles.

At any rate, The bottom line here on the information I was looking for all along is that it does appear quite possible that the P-47N, in a "Normal Gross Weight" figure, could achieve a 4,000fpm climb rate at sea level. I have no contention with your pointing out that at a "Combat Gross Weight" with 2,500lbs of extra fuel, it would be severely handicapped.

[Soren]

Stop complicating things DAVID.

The Normal load to me is the "Combat weight", in which your "Combat gross weight" figure applies. Now 'normally' this is called the "normal loaded" weight, unless "combat weight' is addressed there aswell.

I set up the Bf-109K-4 as an example, because these two would meet in battle under these exact conditions; The 109 would be weighing its normal combat gross weight of 6,940lbs while the -47N weighing its normal combat gross weight of 16,300lbs. Thats how it would be, now you can call that unfair all you'd like, but thats how war is.

Originally Posted by DAVIDICUS

Call me unreasonable but "Normal Gross Weight" sounds a lot more similar to "normal loaded weight" than "Combat Gross Weight" Look, they even contain the same modifying word "Normal".

DAVID, the normal loaded weight 'is' the combat gross weight, unless combat gross weight is otherwise addressed.

[FLYBOYJ]

Originally Posted by FLYBOYJ

It was probably Sperry unit, typical of the day. If I remember right you'll see a large panel in the center instrument panel with a turn and bank indicator and a directional gyro (DG) along with several switches. This was "slaved" into another set of gyros (control unit or computer) that gave electrical inputs to servos located at the ailerons, elevators and maybe rudder. You simply dialed a heading on the DG, turned on the autopilot and it followed that heading while keeping the aircraft straight and level.

As I reading the latest discussion I noticed in the "N" manual I downloaded the other day (thanks again David) on p66 there is a description of the auto pilot system and its operation. It looks like it was made by GE and and had electrically controlled hydraulic servos. The operation is described and similar to what I have stated previously (most autopilots are very similar).

[DAVIDICUS]

Flyboy, thank you again for the kind words but the credit for bringing that site to us properly belings to RG_Lunatic. He first posted it a while ago. It's a great site indeed.

Soren, you said, "I set up the Bf-109K-4 as an example, because these two would meet in battle under these exact conditions;"

In the interest of accuracy, the "N" model wouldn't meet any German fighters unless it was operational in the ETO which it was not. Later in the war, German fighters could afford to have ranges of a mere 20% of the P-47N as they were meeting allied threats over their own airspace.

The "N" model was specifically designed to be an extreme long range escort in the PTO where enormous distances had to be traversed while escorting bombers. It would meet Japanese threats over, or close to enemy airspace. In order to meet this challenge, it carried an enormous internal fuel capacity of 570 gallons. (Think of ten and a half 55 gallon drums)

Now, had the "N" model been deployed to the ETO, it would not have carried that kind of enormous fuel load because (1) It would not need to in order to fulfill its mission as an escort for heavy bombers in that theatre of operations because of the far shorter distances involved (Look at the P-51D's range as opposed to the P-47N) and (2) Carrying such a vastly unnecesary and heavy fuel load would have meant that the aircraft's air to air combat abilities would be unnecesarily and heavily burdened, making for a tremendous fireworks show over the skies of Germany as late war high performance Me-109's and Fw-190's ignited those heavy flying tubs of fuel.

And that, Soren, as you said, "is how war is" in the ETO and why it would be erroneous to say that "these two would meet in battle under these exact conditions" and why such an enormous fuel reserve would not be carried. The P-47N did, however, do quite well in the PTO, waxing late war Japanese rice rockets like the Ki-84 Frank which, I might add, boasted a very high rate of climb.

[DAVIDICUS]

Flyboy,

The auto-pilot you described is really interesting. What other combatant aircraft had autopilot features? Did the heavy bombers have these? I would think that formation flying would militate against it.

One other question. In light of the piece I posted about Frank Perdomo's extremely long missions from Le Shima, how does a pilot relieve himself? I know the P-47 cockpit was spacious but I don't think it included a urinal.

[plan_D]

I imagine it would either be A) Urine bags or B) Tubes.