Subject: New Fighter Series--Douglas F-6 Skyray (1 of 4)

From: [email-masked]
Date: 15 Aug 94 16:23:11 GMT

>From [email-masked]

The Douglas F4D Skyray (later redesignated F-6) was the first 
carrier-based fighter to break the world's absolute speed record and 
was the first Navy fighter capable of exceeding Mach 1 in level 
flight.  Although it served with the Navy for only a short time and 
never fired its weapons in anger, it is still fondly remembered as an 
extremely attractive airplane.  

The Douglas F4D Skyray (later redesignated F-6) was the result of a 
1947 Navy design competition for a new aircraft based on delta wing 
planforms.  Analysis of the studies carried out by Dr. Alexander 
Lippisch on delta winged aircraft in Germany during the war attracted 
a considerable amount of interest on the part of both the US Army Air 
Forces and the US Navy, since such aircraft offered particular promise 
in the design of fast-climbing interceptors.  

Several manufacturers submitted proposals for interceptor aircraft to 
the Navy that embodied a delta-winged format.  On June 17, 1947, the 
US Navy Bureau of Aeronautics (BuAer) selected the Douglas proposal as 
being the best of the lot, and a contract was awarded for a 
preliminary design study.  

Douglas engineers E. H. Heinemann and C. S. Kennedy directed the 
preliminary design study.  Very early on, the pure delta planform was 
abandoned in favor of a tailless aircraft with a pair of mid-mounted, 
low aspect-ratio, highly-sweptback wings with round tips.  The single 
turbojet was fed by a set of lateral air intakes located in the wing 
roots.  The tricycle undercarriage had to be supplemented by a small 
retractable tailwheel mounted under the rear fuselage because of the 
aircraft's high angle of incidence during takeoff and landing.  The 
tailhook extended from the base of the tailwheel assembly.  The 
armament was to be four 20-mm cannon, the guns being mounted in the 
wing roots just outboard of the main wheels, their muzzles being 
located slightly below and behind the wing leading edges.  The cockpit 
was situated well forward in the lose and was equipped with an ejector 
seat.  

The engine was to be the afterburning Westinghouse J40 turbojet, which 
was the powerplant of choice for the next generation of 
high-performance Navy aircraft such as the McDonnell F3H-1 Demon, the 
Grumman F10F Jaguar, and the Douglas A3D Skywarrior.  With this 
engine, it was estimated that the Douglas design should be able to 
achieve a maximum speed in level flight slightly greater than Mach 1, 
and would have an initial climb rate exceeding that of all other 
contemporary fighters.  

On December 16, 1948, Douglas was awarded a contract for the 
construction and testing of two prototypes.  The designation XF4D-1 
was assigned.  The BuAer serials were 124586 and 124587.  

The airframe was completed in 1950, but the 7000 lb.s.t. Westinghouse 
XJ40-WE-6 engine that was intended for the XF4D-1 had experienced 
serious development delays and was not yet ready for flight.  Rather 
than wait until the J40 was completed, Douglas decided to install a 
5000 lb.s.t. Allison J35-A-17 turbojet in the two XF4D-1 airframes 
for the initial testing.  XF4D-1 BuNo 124586 took off on its maiden 
flight on January 23, 1951, test pilot Robert Rahn being at the 
controls.  The similarly-powered second prototype flew shortly 
thereafter.  The first prototype had a clamshell- type canopy, whereas 
the second had a rearward-sliding canopy.  The clamshell canopy was 
adopted for the production version.  The Navy ordered an initial 
production batch of 12 F4D-1s in February of 1951.  

With the J35, the XF4D-1 was seriously underpowered.  The XF4D-1 
prototypes were both re-engined with the 7000 lb.s.t. non- 
afterburning XJ40-WE-6 when it finally became available.  This was 
later replaced with a 11,600 lb.s.t. afterburning XJ40-WE-8 turbojet.  

The XJ40 turbojet was highly temperamental and was prone to sudden 
inflight failures, but it did enable the high-speed performance 
profile of the XF4D-1 to be explored.  On October 3, 1953, BuNo 124587 
flown by Navy Lt-Cdr James B. Verdin set a new world's air speed 
record of 752.944 mph over a three-kilometer course above the Salton 
Sea in California.  This was the first time in history that the world 
air speed record had been captured by a carrier-based aircraft.  On 
October 16 of that year, Douglas test pilot Bob Rahn used the same 
aircraft to set a 100-km closed course speed record of 728.11 mph over 
Muroc Dry Lake.  

In the meantime, the problems with the J40 were beginning to get very 
serious.  The engine would not deliver the expected thrust output, and 
was notoriously unreliable, being subject to sudden inflight failures, 
fires, and explosions.  By March of 1953, the J40's problems were 
beginning to make the Navy very nervous, and in that month the 
decision was made to adapt the Skyray to the Pratt & Whitney J57 axial 
flow turbojet as insurance in case the J40 project should fail.  The 
J57 was not only more reliable than the J40, it was also more 
powerful.  However, it was also quite a bit larger and heavier than 
the J40, requiring that up to 80 percent of the airframe be modified 
in order to accommodate it.  

It was a good thing that this decision to replace the J40 was made, 
because the J40's problems proved to be insoluble, and the entire J40 
program had to be cancelled.  The J40 episode was a sorry experience 
for all concerned, especially for Westinghouse, which was driven out 
of the jet engine manufacturing business altogether.  

In October of 1953, while work on the J57-powered production F4D-1 was 
getting underway, the XJ40-WE-8-powered XF4D-1 was used for carrier 
qualification trials aboard the USS *Coral Sea*.  

The second XF4D-1 (BuNo 124587) was loaned to General Electric in 1956 
for use as a test bed for the J79 turbojet and later for the CJ805-3 
turbojet which was intended for the Convair 880 commercial jet 
transport.  

BuNo 124586 and 124587 		Douglas XF4D-1 Skyray 

Sources:

  The Aircraft of the World, William Green and Gerald Pollinger,
  Doubleday, 1965.

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

  United States Navy Aircraft Since 1911, Gordon Swanborough and
  Peter M. Bowers, Smithsonian, 1989.

  McDonnell Douglas Aircraft Since 1920: Volume 1, Rene J. Francillon,
  Naval Institute Press, 1988.

  Ray Wagner, American Combat Planes, Third Enlarged Edition,
  Doubleday, 1982.

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