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

[Soren]

DAVID all else being equal, fighters did not fly out on half full or even 3/4 full internal fuel tanks, that's just not the way it was done. And they certainly didn't fly on half full internal fuel tanks coupled with drop tanks..

So while the -47N might have had an excessive amount internal fuel for 'one' mission, it would still be fully fueled up in case of any emergency.

 

[DAVIDICUS]

I would be inclined to agree with you if were talking about the ETO and the aircraft designed for that theatre of operations like the "M" or "D" model. The hypothetical we are entertaining, however, is that of a P-47N model in the ETO.

Specifically, I do not agree because carrying the maximum fuel load that an "M" or "D" model would carry would not subject the "N" model to any additional fuel related threat or danger not borne by the "M" or "D" models. However, ladening the P-47N with thousands of extra pounds of fuel over and above the maximum fuel load of the "M" and "D" models would expose the P-47N to additional threats not borne by the "M" or "D" models.

At any rate, why don't we just agree to disagree?

 

[FLYBOYJ]

However, ladening the P-47N with thousands of extra pounds of fuel over and above the maximum fuel load of the "M" and "D" models would expose the P-47N to additional threats not borne by the "M" or "D" models.

David, there is never such thing as "extra fuel" unless you're on fire!

Seriously at up to 200 gph, there really isn't such thing!

 

[DAVIDICUS]

Sure there is Flyboy. If you are flying a P-47N to and from a target 350 miles away, why wouldn't you load up on 996 gallons gallons of fuel in the internal and external tanks? (Yes, that's right. That's the maximum internal and external fuel load carried ny the P-47N) It would be for the same reason you wouldn't load up the internal tanks to a 570 gallon capacity. Too much weight.

When you're in a fur ball with late model Me-109's and Fw-190's, the last thing you'd be thankful for is that extra margin of safety of being able to fly to Greece should you not feel like returning to base.

Where does that 200gph figure come from? Is that in the Pilot manual?

 

[FLYBOYJ]

Sure there is Flyboy. If you are flying a P-47N to and from a target 350 miles away, why wouldn't you load up on 996 gallons gallons of fuel in the internal and external tanks? (Yes, that's right. That's the maximum internal and external fuel load carried ny the P-47N) It would be for the same reason you wouldn't load up the internal tanks to a 570 gallon capacity. Too much weight.

When you're in a fur ball with late model Me-109's and Fw-190's, the last thing you'd be thankful for is that extra margin of safety of being able to fly to Greece should you not feel like returning to base.

That's, funny But I gotta disagree David. Weight comes into the equation on fighters/ fighter bombers when trying to lift something (like bombs) or if your operating out of a high elevation airport on a short strip. Once in the air, utopia is to be over the target, full of gas. Sure you're going to be able to maneuver better if you were on half tanks, but I'm willing to bet dollars to donuts that most WW2 fighter pilots would trade that little margin of maneuverability for endurance - whether it be used over target or to be able to make it home!

 

[DAVIDICUS]

",but I'm willing to bet dollars to donuts that most WW2 fighter pilots would trade that little margin of maneuverability for endurance "

I agree with you Flyboy but I think we need to bear in mind that the "N" carries 50 more gallons internally than the "M" carries both internally and with external drop tanks combined!

The "N" model empty weighs only 556 lbs more than the "M" model empty. The Combat Gross Weight armament configuration and capacityof both aircraft is the same. At Combat Gross Weight (full internal ammunition and fuel load), the "N"weighs 3,055lbs more. (That's 2,500lbs [2,499lbs] of extra internal fuel.) That translates to a climb rate at 5,000 ft of 2,950fpm for the "N" and 3,775fpm for the "M".

I don't think we're talking about a "little margin of manueverability".

 

[FLYBOYJ]

",but I'm willing to bet dollars to donuts that most WW2 fighter pilots would trade that little margin of maneuverability for endurance "

I agree with you Flyboy but I think we need to bear in mind that the "N" carries 50 more gallons internally than the "M" carries both internally and with external drop tanks combined!

50 gallons x 6 = 300 lbs. I would guess that the -N or -M would cruise at at least 80 gph. A forty minute flight to a target would eat this up alone. That would equal to the "M" internal and external fuel load as stated after 40 minutes in the air assuming normal climb and cruise settings are used.

The "N" model empty weighs only 556 lbs more than the "M" model empty. The Combat Gross Weight armament configuration and capacity of both aircraft is the same. At Combat Gross Weight (full internal ammunition and fuel load), the "N"weighs 3,055lbs more. (That's 2,500lbs [2,499lbs] of extra internal fuel.) That translates to a climb rate at 5,000 ft of 2,950fpm for the "N" and 3,775fpm for the "M".

Again, I think if you gave a fighter pilot the choice - extra range or an extra climb rate of 825 fpm at 5000 feet, I think he'll take the extra range, especially if he's dropping bombs first!

Also consider this - 2500 Lbs of fuel = 416.6 gallons. War emergency burn has to be at least 200 gph. Between climb, war emergency, maneuvering, etc., the extra fuel will could go quick, but considering the extra weight vs. the extra range, I think its a worth-wild luxury.

I don't think we're talking about a "little margin of maneuverability".

825 fpm vs the extra security of knowing that if you loiter target too long you'll still make it home? Again, I think the prudent measure is the extra gas.

But think about this - if you're in the heavier "N" (2950 fpm) and you want to get to the "M" (3775 fpm) climb numbers based on weight, you simply have to do one thing - run slightly rich and slightly above cruise settings (you just got to watch you don't foul spark plugs). The best power settings for cruise with tanks on the "N" is 33.5" mp @ 1950 rpm, that will probably give you 80 gph. Use a higher rpm setting at the same RPM and that R2800 will suck down that fuel (@ 6 pounds per gallon) quicker than a starving vampire at at blood bank!

 

[DAVIDICUS]

"Also consider this - 2500 Lbs of fuel = 416.6 gallons. War emergency burn has to be at least 200 gph. Between climb, war emergency, maneuvering, etc., the extra fuel will could go quick, but considering the extra weight vs. the extra range, I'll take the range."

Where did that 200gph figure from again? Is it in the Pilots Manual? I left it at work and don't have it with me. Anyway, based on that 200gph figure, you are talking about a full two hours and five minutes of of WEP flight in a single mission. That doesn't seem quick to me at all.

That 416.6 gallons you referenced is the amount of fuel over and above the full internal fuel capacity that an "M" could carry. Under such a scernario, an "N" model, after spending two hours and five minutes at WEP would still have a fuel load left equivalent to an "M" model with a full internal fuel load.

Te reason I am having a hard time with this is that the P-47N really carries a truly enormous fuel load. In fact, with full internal fuel and drop tanks, it carries 22 more gallons of fuel than a B-25J with her tanks topped off. With a range of 1275 miles with 3,200 pounds of bombs, the B-25 wasn't a short range aircraft by any measure.

From: http://www.b25.net/#specifications

The fuel capacity consisted of four tanks in the inner wing panels, with a total capacity of 670 US gallons. In addition, 304 US gallons of fuel could be carried in auxiliary tanks in the outboard wing panels, for a normal total fuel load of 974 US gallons.

Here's another example. The P-47N with full internal fuel and drop tanks could carry 54 more gallons of fuel than a B-26G with a full fuel load.

You mentioned something interesting. "f you're in the heavier "N" (2950 fpm) and you want to get to the "M" (3775 fpm) climb numbers based on weight, you simply have to do one thing - run slightly rich and slightly above cruise settings"

I think you are saying (I may be misunderstanding you) that the "N" model at Combat Gross Weight could increase its climb rate from 2,950fpm to the the 3,775fpm rate of climb of the "M" model (even though the "N" weighs 3,055lbs more) simply by doing one thing - "run slightly rich and slightly above cruise settings".

This doesn't sound possible. Did I misunderstand you? If not, can you elaborate on how this would be possible? How can you increase the climb rate by 825fpm at 5,000ft when the aircraft weighs 3,055lbs more?

 

[plan_D]

I don't know how closely this applies to this discussion but it was always unsafe to let an aircraft take off or be stored without being full. It might just be the EE Lightning but my dad informed me that they used to fill up the Lightnings before putting them away for the night and they always had to be full when taking off. It wasn't because of the dismal range of the Lightning, it was because fuel vapour is extremely dangerous and more volatile than fuel itself. So, when the crackers started the engine, if it wasn't full, the engine may have just exploded.

That's why I think it really wouldn't have been ideal to take off without full fuel. On bombers and big aircraft it's different because they have many seperate tanks.

Maybe it's just the EE Lightning though because people think the Me-163 was just a rocket with wings, try going in a Lightning.

 

[FLYBOYJ]

"Also consider this - 2500 Lbs of fuel = 416.6 gallons. War emergency burn has to be at least 200 gph. Between climb, war emergency, maneuvering, etc., the extra fuel will could go quick, but considering the extra weight vs. the extra range, I'll take the range."

Where did that 200gph figure from again? Is it in the Pilots Manual? I left it at work and don't have it with me. Anyway, based on that 200gph figure, you are talking about a full two hours and five minutes of of WEP flight in a single mission. That doesn't seem quick to me at all.

The 200 gph is a wag from what I know about large radial engines. it might even be higher. An Allison burns close to 175 gph @ WE.

I've flown on aircraft (S-2, PBY, DC-3) with large radial engines and excluding the posted performance for the particular aircraft, it's amazing how quick the fuel goes, especially at start, taxi, run-up, takeoff and climb.

t 416.6 gallons you referenced is the amount of fuel over and above the full internal fuel capacity that an "M" could carry. Under such a scernario, an "N" model, after spending two hours and five minutes at WEP would still have a fuel load left equivalent to an "M" model with a full internal fuel load.

The reason I am having a hard time with this is that the P-47N really carries a truly enormous fuel load. In fact, with full internal fuel and drop tanks, it carries 22 more gallons of fuel than a B-25J with her tanks topped off. With a range of 1275 miles with 3,200 pounds of bombs, the B-25 wasn't a short range aircraft by any measure.

From: http://www.b25.net/#specifications

Those are the numbers posted! All I did was do the math with the posted numbers.

You mentioned something interesting. "f you're in the heavier "N" (2950 fpm) and you want to get to the "M" (3775 fpm) climb numbers based on weight, you simply have to do one thing - run slightly rich and slightly above cruise settings"

I think you are saying (I may be misunderstanding you) that the "N" model at Combat Gross Weight could increase its climb rate from 2,950fpm to the the 3,775fpm rate of climb of the "M" model (even though the "N" weighs 3,055lbs more) simply by doing one thing - "run slightly rich and slightly above cruise settings".

This doesn't sound possible. Did I misunderstand you? If not, can you elaborate on how this would be possible? How can you increase the climb rate by 825fpm at 5,000ft when the aircraft weighs 3,055lbs more?

Simple - you're burning off the extra fuel (1 gallon of aviation fuel = 6 pounds), remember the extra weight? You're getting both aircraft to the same weight by burning more fuel on one, this is done by running rich. These are based on the numbers in your previous post. Get an "M" and an "N" close to the same in gross weight in flight, I would think they would climb close to the same.

Bottom line - combat missions flown with these aircraft were done so at maximum capacity fuel. The only time you're going to leave fuel behind if you're going to be carrying something (like bombs) or if you're operating at a high density altitude. The 825 fpm climb difference between the 2 aircraft is something that is just lived with.

Plan D also brought up something interesting and very correct - once an aircraft lands, it is usually topped off with fuel for 2 reasons - build up of fuel vapors in the tank and water condensation. With that, I would assume that these aircraft in question were flown with full tanks 99% of the time!

 

[DAVIDICUS]

"Plan D also brought up something interesting and very correct - once an aircraft lands, it is usually topped off with fuel for 2 reasons - build up of fuel vapors in the tank and water condensation. With that, I would assume that these aircraft in question were flown with full tanks 99% of the time!"

I hadn't thought of that but it does sound right.

 

[DAVIDICUS]

I am at work again and have the Pilot's Manual. More interesting data.

Page 28:

At cruise, the P-47N can go 900 miles on the two wing tanks.

If the belly tank is employed as well and used to take off and climb, it will then last for another 220 miles of cruise if climb is at 33.5". If 43.5" s used, it will last for 150 miles of cruise.

Page 29:

After dropping the external tanks, the internal gas load will last for 1,800 miles.

Page 30:

Twenty minutes of combat will take 90 gallons from the internal tanks. Range for the return home will be more than 1,400 miles for a clean airplane at 33.5".
----------------------------------------------------------------------

It would appear that at a rate pf 90 gallons in 20 minutes, the gph figure would be more like 270!

 

[FLYBOYJ]

It would appear that at a rate pf 90 gallons in 20 minutes, the gph figure would be more like 270!

And that equates to 540 pounds in 20 minutes, 1620 pounds in 1 hour!

Oh and remember, when you show MP, there will be an rpm shown as well. Those two numbers together will equate to the fuel burn.

 

[DAVIDICUS]

More data from Republic Aviation Corporation's dimensional, specification and performance data on the P-47M and "N" models:

Bomb load data:

Two 1,600lb bomb loadings under the wings for both the "M" and "N" models.

The "M" can carry one 1,000lb bomb loading under the belly.

The "N" can carry one 500lb bomb loading under the belly.
________________________________________________

- Question for everyone -

When, for example, an aircraft is described as carrying a 1,000lb bomb under each wing, does that refer to the true weight of the bombs themselves or does it refer to the explosive power of the bombs in terms of pounds of TNT?

 

[the lancaster kicks ass]

it would refer to the total weight of the bomb.........

 

[FLYBOYJ]

- Question for everyone -

When, for example, an aircraft is described as carrying a 1,000lb bomb under each wing, does that refer to the true weight of the bombs themselves or does it refer to the explosive power of the bombs in terms of pounds of TNT?

"It is the weight of the ordnance hung on the bomb rack."

 

[DAVIDICUS]

Thanks.

 

[wmaxt]

Here is a site with some great P-47 data: http://www.geocities.com/pentagon/quarters/9485/P-47M.html?200526
If you go to the home page there are a number of other articles concerning the P-47, F4U-4, P-38 and other WWII aircraft.

wmaxt

 

[Sal Monella]

Just wondering. A little while back there was an issue about if the Republic P-47-N ended up in the European theatre. Someone said that it would have had to had to keep a full fuel load in its internal tanks which would have made it so heavy that its high performance would have been downgraded.

Didn't it have some sort of vaccuum system that would have allowed it to operate with less fuel without condensation forming?

 

[syscom3]

I just posted some P47 photo's in my "Chino Pix" album. Check them out.