WHAT IF: Longer range P-47 from start

[gjs238]

What if the USAAC, recognizing the historically expeditionary nature of the US military, and the need to reach out to the enemy rather that wait for the enemy to come to you, had specified "P-51 like" ranges in fighters such as the P-40 and P-47?

P-38 had long range, but development was protracted.
P-39 could be kept short range point-defence and other such duties.

 

[tomo pauk]

Even if P-38 had a more protracted development, P-47 saw combat 1 full year after P-38 did. So, for Allied war effort, P-38 had the edge in that category.

Despite that, having another fighter type with long legs would've been beneficial IMO. If the doctrine was shifted, in early/mid 1943, to the deep fighter sweeps into German-held air space, and the force used being of great size in numbers, the combat attrition would've come earlier for Luftwaffe.
Another US-built plane that have had long range decent performance (in mid 1943) was the P-51A/Mustang II. It was deployed piecemeal, however - in Italy, India China for example, despite rather small numbers produced.

 

[gjs238]

Even if P-38 had a more protracted development, P-47 saw combat 1 full year after P-38 did. So, for Allied war effort, P-38 had the edge in that category.

Yet the P-38 didn't successfully fulfill the escort job for 8th AF.
If P-47 had the legs...............

 

[Shortround6]

P-40 and P-47 already had longer ranges than most (all?) European fighters. P-36 could hold 158 US gallons of fuel as could the P-40 prototype, early P-40s without self-sealing tanks could hold the same or more.

The problem is that the P-40 airframe has higher drag than the P-51 so even if you can get the same amount of fuel inside the plane you still won't go as far because at the same power levels (fuel burn) you are going slower.
By the time you stuff in even more fuel to compensate you wind up with a rather heavy airplane with the same power which affects both take-off performance (field length) and climb.

The earliest P-47s could hold 305 US gallons (254imp) which means it held about 3 times the fuel of an early Spitfire or 109. It was also quite possible to cruise a P-47 for almost 900 miles as long as you stayed under 12,000ft and under 200mph indicated airspeed. Which was better than either of those two fighters could do.

See: http://www.zenoswarbirdvideos.com/Images/P-47/47TOCL.gif

But subtracting a combat allowance of about 90 gals for 5 minutes of Military power and 20 minutes of MAX continuous power and cruising the plane at a more reasonable 315mph true airspeed at 20,000ft cuts the range to 380 miles the radius to 190 miles without any reserve. To get "P-51 like" ranges is going to need a lot more fuel and at the the time the P-47 was being spec'd the US Army seemed to have something against drop tanks even though they had used them in the late 20s/early 30s under some of their biplane fighters. The R-2800 was going for 2000hp with no water injection of WER ratings and it had the toothpick prop. What I haven't seen is a field requirement for the P-47. What the Army was willing to accept for runway length in 1943/44 may not have been what they were specifying in 1940-41.

 

[drgondog]

Had the P-47 been designed with a wet wing/wing tank hardpoint and feed from the beginning, and used the wing tank fuel only for escort purposes it would have been superb in 1943.

 

[Shortround6]

Another US-built plane that have had long range decent performance (in mid 1943) was the P-51A/Mustang II. It was deployed piecemeal, however - in Italy, India China for example, despite rather small numbers produced.

Trying to escort bombers by flying thousands of feet below them wasn't going to work.
OK, it wasn't that bad but with Allison engines the rate of climb and "surplus" power needed to maneuver or accelerate once speed had bled off in a maneuver wasn't there once the altitude was much over 20,000ft.

 

[gjs238]

Trying to escort bombers by flying thousands of feet below them wasn't going to work.

But this thread isn't limited to high-altitude bomber escort. Long range/endurance can have many applications.

 

[Shortround6]

Yet the P-38 didn't successfully fulfill the escort job for 8th AF.
If P-47 had the legs...............

The P-38 wasn't really allowed to perform the escort job for the 8th AF. The early P-38s were siphoned off to North Africa to support operation Torch and the North Africa campaign which didn't allow for build up of experience or demand for changes to made earlier (like better cockpit heating). Changes in equipment and even fuel blends affected the P-38s in Europe. The US changed the specification for 100/130 octane fuel in 1943 and allowed heavier components to be used which affected the volatility. Under certain temperature conditions it lead to fuel separation and fuel puddling in the intake manifolds, This affected ALL Allison engines but most especially the P-38s because they flew in colder temperatures more often and longer than the non-turboed Allison engines. Allison new of the problem and was working on new intake manifold designs to correct it in late supper of 1943. Put that together with the improper flying technique common in the 8th AF for cruising the P-38 and put it together with the introduction of new models of the P-38 using new models of the turbo and new/different turbo controls and you had a real recipe for finger pointing/playing the blame game for a few months. By the time it was sorted out the P-51 had been chosen to be the standard escort fighter and in hindsight the choice was the right one but the difference between the P-51 and a properly performing P-38 may not be quite as large as many people believe.
The P-38 doesn't really go operational in Europe for bomber escort until the Fall of 1943 when 7 P-47 groups are already operational.

 

[gjs238]

Regardless, the escort need wasn't satisfied until Merlin Mustangs arrived in force.
P-47's, AFAIK, weren't having the fuel issues the P-38 was.

 

[Shortround6]

But this thread isn't limited to high-altitude bomber escort. Long range/endurance can have many applications.

Yes, it can have many applications, but if you have to fight at altitudes over 20,000ft over the target area or in the middle of the mission all the range/endurance in the world isn't going to do you much good if the plane won't perform at those heights. Early Mustangs made good photo-recon planes with their high speed and long range, it was valuable work but it didn't contest control of the air much. It might have been useful in the Pacific where there were long stretches of flight path over open water with no radar/spotters/aa guns and the Japanese aircraft didn't tend to fight in the upper 20,000ft range that much.
Planes that are designed to hold large quantities of internal fuel for long range tend to be larger, heavier, poorer climbing that shorter ranged planes with the same power engines. The Mustang is a almost singular exception to this. It is a bit larger, it is heavier and it is poorer climbing than may planes with similar engines but it's low drag allows for higher level speed and less bled off in manuvers.

 

[gjs238]

The title of the thread is the P-47, not the P-51.

 

[Shortround6]

Regardless, the escort need wasn't satisfied until Merlin Mustangs arrived in force.
P-47's, AFAIK, weren't having the fuel issues the P-38 was.

That is true but P-40s and Allison Powered Mustangs did, just not to the extent the P-38s did. And there was no way to know in 1940/41 when the aircraft specs were being written that the fuel specifications/standards would change 2 years after the plane specifications were issued.

 

[Shortround6]

True, but I am trying to point out some of the differences. You want "P-51 like" range you have to understand why the P-51 got that range and some other planes did not. You also have to understand that without the P-51s low drag numbers there will be a bigger penalty to be paid in weight and overall performance in order to get that range.

 

[gjs238]

That is true but P-40s and Allison Powered Mustangs did, just not to the extent the P-38s did. And there was no way to know in 1940/41 when the aircraft specs were being written that the fuel specifications/standards would change 2 years after the plane specifications were issued.

No one said we're stuck with the Allison.
The long endurance of the P-51 married well with the Merlin.
Conceivably, the same could go for another Allison powered plane.

 

[gjs238]

True, but I am trying to point out some of the differences. You want "P-51 like" range you have to understand why the P-51 got that range and some other planes did not. You also have to understand that without the P-51s low drag numbers there will be a bigger penalty to be paid in weight and overall performance in order to get that range.

Somehow we got away from the P-47.

 

[davebender]

Early P-47s (P-47B and P-47C) had teething problems of their own. Early P-47s were lacking in performance, especially climb and acceleration. Both aircraft were relatively expensive with the single engine P-47 costing almost as much as a twin engine P-38.

IMO the P-38 has the potential to develop into a decent long range bomber escort by early 1943, exactly when such an aircraft was needed by the U.S. 8th Air Force. The P-47 does not.

Better yet, the U.S. Army Air Corps should purchase the Fw-187 tooling from Focke Wulf during 1939. Power it with a pair of Packard built Merlin engines.

 

[Lighthunmust]

If the wing tanks and drop tanks of the P-47N were available for P-47Cs in 1943, I am not so sure the Mustang would have ever been developed into an escort fighter. The 47 was getting the job done in all aspects other than escort range.

 

[Shortround6]

Better yet, the U.S. Army Air Corps should purchase the Fw-187 tooling from Focke Wulf during 1939. Power it with a pair of Packard built Merlin engines.

There is no Fw-187 tooling, at least in the mass production sense. A half dozen prototypes don't have much in the way of jigs/fixtures made for them. one reason prototypes take so long to build.
Without a time machine there is no knowledge of Packard built Merlins in 1939. And even if you have a "what IF" that Packard is approached a year early, which Merlin are they approached to build? The Merlin III of the Merlin X? the Merlin XX that they signed on to build first doesn't exist yet. A different supercharger intake and set up than on the X engine let alone the different boost ratings.

 

[Shortround6]

If the wing tanks and drop tanks of the P-47N were available for P-47Cs in 1943, I am not so sure the Mustang would have ever been developed into an escort fighter. The 47 was getting the job done in all aspects other than escort range.

A P-47 N weighed 1100lbs more than a P-47C when both were empty. It could hold another 250 gallons of fuel, that is another 1500lbs. Your clean but full 12500lb P-47 is now up to 15,100lbs (a 20.8% increase) with no increase in power and still has the toothpick prop.

 

[tomo pauk]

Seen that coming

(sorry for derailing the thread)
The USA has a potential Merlin-bearer, the P-38. The Merlin XX can do some 1100 HP @ 18kft @ MIL, 15% less than turbo V-1710s from 1942-mid 1943. The lower power can be canceled out by using the exhaust thrust (almost impossible for turboed engines) and perhaps some 500-600 lbs less weight for 2 engines installed. The WEP rating for Merlin XX was what, 1420 @ 15K; never used by such USAAC engines? The nominal advantage of turboed Allison in that tine frame was hampered by many things, while Merlin was mature. We still lack some 10-15 mph vs. German opposition, but the edge vs. Japanese Italian planes mostly remains.