USAF Penetration Fighter Program

[Zipper730]

The program started in August, 1945 and primary specifications were dictated as of late November, and called for the following

• Operating Altitude: 35000 feet
• Top speed at 35000 feet: 550 mph
• Top speed at S/L: 600 mph
• Climb: Must be able to go from S/L to 35000 feet in 10 minutes
• Radius of action: 900 nm
• Armament: 6x0.50, or 6x20mm
• Must use already existing engines: Not sure if this meant designs that were already running in testing stages at least, or in the pipeline for development.

Convair, Curtiss-Wright, Goodyear, Lockheed, Northrop, and McDonnell submitted designs, of which McDonnell and Convair initially were selected the winners. Since Convair was working on the B-36, they were told to stand down, and to keep a competitor in the game, they added Lockheed provided they switched engines (originally they were planning on using the L-1000/XJ37 at first), which they did (they picked the J34).

Starting in August 1947, requirements were changed to...

• Operating altitude was increased to 50,000 feet
• Time to operating altitude was the same as before, but requiring a higher climb-rate to reach the altitude
• Top speed was now specified as 690 mph (presumably at sea-level as that'd be supersonic at altitude)
• Radius of action was now 1500 nm

 

[Zipper730]

North American submitted a design of it's own in late 1947 which was based on the F-86 with a bifurcated NACA type duct feeding a J48 in the middle, and allowing a new nose with an SCR-720 in it. The engine was equipped with an afterburner, and the wings were the same. The design was fairly easy to submit because it was considered a modification of a design already flying, and was originally called the P-86C/F-86C, and later YF-93 (presumably because they got their way ).

The first design to fly was the XF-88, which flew October 20, 1948; The XF-90 flew next on June 3, 1949; the XF-93 flew last in January, 1950.

The XF-90 might very well have looked the sleekest of all of them: It didn't perform the best, but on the bright side, it was tough. It was actually the only design built to the g-requirements the USAAF/USAF required (12g ultimate load), unfortunately living up to the obligation didn't pay off very well for them -- the aircraft was overweight.

The XF-93's engine inlets proved to be a problem, so it went from the NACA duct, to a pseudo-NACA duct (a term I created to best describe it), to a regular D-inlet. The aircraft was said to have a good rate of climb, and a maximum range of over 2000 nm. It wouldn't shock me if it didn't maneuver so good at high altitude with extra weight on the same wing. The radar was a nice-feature though -- and offered to combine day/night fighter into one design.

The XF-88 won, but for one reason or another it was cancelled...

 

[swampyankee]

Well, the XF-88 did turn into the F-101.

 

[fubar57]

McDonnell XF-88 Voodoo Escort Fighter / Penetration Fighter Prototype - United States

 

[Zipper730]

Well, the XF-88 did turn into the F-101.

True, but I could imagine a number of B-29 pilots that would have greatly appreciated having the F-88 as protection over the F-84

That being said, I'm not sure how long it'd take to get it online

• The XF-88 first flew 10/20/1948
• The XF-88A first flew 4/26/1949 (unsure if this was a de-facto YF-88)
• The XF-90 first flew 6/3/1949
• The XF-93 first flew 1/24/1950
• The XF-88 won on 8/15/1950

 

[Graeme]

Convair initially were selected the winners. Since Convair was working on the B-36, they were told to stand down,

What did that winning project look like? Any more info on it Zipper?

 

[Shortround6]

Unfortunately, as built with Westinghouse J-34 engines the XF-88 as a penetration fighter..............wasn't.

even with 1434 gallons of fuel on board the tactical radius was figured at 521 nautical miles. and that is with about 700 gallons in drop tanks.

The engines just weren't powerful enough or fuel efficient enough to allow for the range needed.

 

[Zipper730]

What did that winning project look like?

My scanner doesn't work at this moment, but it's covered in Convair -- Advanced Designs II: Secret Fighters, Attack Aircraft and Unique Concepts (1929-1973) on pages 53-55.

There were two designs which differed in the landing-gear configuration: The preferred design for Convair was a bicycle landing gear because it permitted more fuel in the wings, but they also had a design that was equipped with tricycle gears as well.

The basic statistical figures were as follows

• Dimensions
  • Length: 46'1.5"
  • Wingspan: 47'5"
  • Wing-Area: 375 square feet
  • Aspect Ratio: 5.996
  • Wing-Sweep: 30-degrees at the 25% chord
• Engines
  • 3 x J34
  • 2 x mounted side by side under the mid-fuselage
  • 1 x in the rear fed by NACA intake
• Weights
  • Empty: 12048 lbs
  • Design: 19546 lbs
  • Takeoff Weight: 26548 lbs with drop-tanks
• Performance
  • Speeds
    • Cruise: 450 mph
    • Maximum speed with military power: 657 mph @ sea-level, 613 mph @ 35,000'
    • Maximum speed with war-emergency power (120% RPM): 686 mph @ sea-level; 627 mph @ 35,000 feet
  • Altitudes
    • Cruise: 35,000 feet
    • Service Ceiling: 47,000 feet

 

[Zipper730]

Unfortunately, as built with Westinghouse J-34 engines the XF-88 as a penetration fighter..............wasn't.

even with 1434 gallons of fuel on board the tactical radius was figured at 521 nautical miles. and that is with about 700 gallons in drop tanks.

I didn't know that was the combat-radius with drop-tanks. If I recall, that would compare unfavorably with the F-86 (I think they could do around 600 nm with tanks)...

The engines just weren't powerful enough or fuel efficient enough to allow for the range needed.

The J34's weren't, but the J47 might have been viable. It was considerably more powerful, and would eliminate the afterburner requirement.

 

[Zipper730]

Graeme

Here's an online picture...
Consolidated Vultee Downey Penetration Fighter Proposal - United States