Subject: Number Ninety-Two in the Series--Convair XF-92A

From: [email-masked]
Date: 6 Oct 93 17:21:48 GMT

>From [email-masked]

In August of 1945, the USAAF announced a competition for a supersonic 
interceptor capable of reaching an altitude of 50,000 feet in four 
minutes and capable of achieving a maximum speed of 700 mph.  A tall 
order for 1945! 

A team from Consolidated Vultee Aircraft Corporation (better known as 
Convair) won the competition in May of 1946.  The Convair design 
proposal was for a ramjet-powered aircraft with wing sweep of 45 
degrees.  The designation XP-92 was assigned to the project.  

However, wind tunnel testing indicated that there would be problems 
with wing tip stalling at low angles of attack and with lateral 
control problems.  Consequently, the Convair team went back to some 
wartime German research by Dr.  Alexander Lippisch, who had been an 
early pioneer in delta wings.  

The Convair team decided to adapt their aircraft to a delta-winged 
configuration.  The aircraft that they eventually came up with was an 
interceptor with a delta wing and a V-shaped butterfly tail.  It was 
to be powered by a single 1560-lb.st.  Westinghouse J30-WE-1 turbojet 
plus no less than six 2000-lb.st liquid-fueled rocket engines.  The 
P-92 was envisaged as a very fast point-defense interceptor with range 
and endurance being sacrificed for all-out performance.  

In order to speed development of the P-92, in November 1946 the USAAF 
authorized Convair to build a delta-winged research aircraft to prove 
out the concept.  This aircraft was given the company designation of 
Model 7-002.  A USAF serial number of 46-682 was assigned.  In order 
to save time and money, extensive use was made of existing aircraft 
components where feasible.  The main undercarriage was taken from a 
North American FJ-1 Fury, the nosewheel was taken from a Bell P-63 
Kingcobra, the engine and hydraulics were taken from a Lockheed P-80 
Shooting Star, the ejector seat and cockpit canopy were taken from the 
cancelled Convair XP-81, and the rudder pedals were taken from a BT-13 
trainer.  The delta wing planform required that "elevons" be developed 
to replace the traditional elevators and ailerons.  All flight 
controls were hydraulically-activated and were irreversible.  

Construction was well underway when Vultee Field was closed down in 
the summer of 1947.  The airframe was then transferred out to 
Convair's plant in San Diego for completion.  The airframe was 
completed in the autumn of 1947, and in December it was shipped 
without an engine to NACA's Ames Aeronautical Laboratory at Moffett 
Field near Sunnyvale for wind-tunnel testing.  After the wind-tunnel 
testing was completed, the airframe was returned to San Diego, where 
it was installed with a 4250 lb.st.  Allison J33-A-21 turbojet.  

The Model 7-002 was then taken out to Muroc Dry Lake (later Edwards 
AFB) in April of 1948.  Tests were at first limited solely to taxiing 
and high speed ground runs, although a short hop was made on June 9, 
1948.  In the meantime, the USAF finally came to the conclusion that 
the F-92 point-defense interceptor concept was not a very practical 
idea, and decided to cancel the program.  However, the idea of a 
delta-winged aircraft was sufficiently interesting that the USAF 
decided to continue on with the flight testing of the Model 7-002, 
even though no production was envisaged.  The Model 7-002 aircraft was 
assigned the designation XF-92A.  

A 5200 lb.st. J33-A-23 engine was installed before the official 
flight testing began.  The XF-92A officially took to the air for the 
first time on September 18, 1948, Sam Shannon being the pilot.  The 
XF-92A was the world's first true delta-winged aircraft to fly.  

Iniial flight testing was performed by Sam Shannon and Bill Martin.  
They found the controls to be extremely sensitive.  Initial testing 
was completed by August 26, 1949.  The XF-92A was then turned over to 
USAF test pilots Capt. Charles E "Chuck" Yeager and Maj. Frank K.  
"Pete" Everest, who did most of the test flying with the aircraft 
until the end of the year.  The XF-92A was easy to land and was 
extremely stable at speeds of Mach 0.9.  However, the XF-92A could not 
exceed the speed of sound in level flight and could only exceed Mach 
1.0 in a dive, this being done at least once with Major Everest as the 
pilot.  

In 1951, the XF-92A was refitted with an Allison J33-A-29 engine with 
afterburner, offering a thrust of 7500 lb.st.  The re-engined XF-92A 
was flown by Chuck Yeager for the first time on July 20, 1951.  
However, there was very little improvement in performance.  In 
addition, there were maintenance problems with this engine and only 21 
flights were made during the next 19 months.  

A further engine change was made to the 8400 lb.st. J33-A-16, and on 
April 9, 1953, the test pilot A. Scott Crossfield began a series of 
flights on behalf of NACA.  These tests indicated a violent pitch-up 
tendency during high-speed turns.  Wing fences were added which 
partially alleviated this problem.  

On October 14, 1953, the XF-92A suffered a nosewheel collapse during a 
high-speed taxiing run.  The damage was sufficiently severe that the 
XF-92A had to be withdrawn from service.  Although the XF-92A never 
produced a useful combat aircraft, it nevertheless provide a lot of 
valuable data on delta wing aircraft, and was instrumental in the 
development of the later F-102 and F-106 delta-winged interceptors.  

Following the withdrawal of the XF-92A from test-flying work, it was 
eventually disposed of as a static exhibit, and was parked outside to 
weather away.  It was rescued from this fate by the USAF in 1962 and 
is currently in storage awaiting exhibit at the USAF museum at 
Wright-Patterson AFB.  I was there in June of 1992, but it was still 
not yet on display.  

Specification of the XF-92: 

One Allison J33-A-29 turbojet, 5900 lb.st. dry and 7500 lb.st. with 
afterburner.  Dimensions: wingspan 31 feet 4 inches, length 42 feet 6 
inches, height 17 feet 9 inches, wing area 425 square feet.  Weights: 
9078 pounds empty, 14,608 pounds gross.  Maximum speed: 718 mph at sea 
level, 655 mph at 35,000 feet.  Climb to 35,000 feet in 4.3 minutes, 
service ceiling 50,750 feet.  The XF-92A was never fitted with any 
armament.  

Sources: 

  Fighters of the United States Air Force, Robert F. Dorr and David 
  Donald, Temple Press Aerospace, 1990.  

  The American Fighter, Enzo Angelucci and Peter Bowers, Orion, 1987.  

  General Dynamics Aircraft and their Predecessors, John Wegg, Naval 
  Institute Press, 1990.  

Joe Baugher		AT&T Bell Laboratories   	
2000 North Naperville Road      Naperville, Illinois 60566-7033