Subject: Fighter Series--Vought XF8U-3 Crusader

From: [email-masked] (Joe Baugher)
Date: Sun, 2 Oct 1994 01:21:03 GMT

The Vought XF8U-3 Crusader III (known by the company as the Vought 
Model V-401) was an extremely advanced fighter interceptor of the late 
1950s.  Although the aircraft was designated XF8U-3, it was 
essentially a completely new design and bore only a superficial 
relationship to the earlier series of F8U-1 and F8U-2 carrier-based 
fighters.  

For some reason, the Navy decided not to designate the new Vought 
fighter XF9U-1, which would have been the logical choice.  Instead, 
they designated the aircraft XF8U-3, which may have been done for 
mysterious bureaucratic or budgetary reasons.  In addition, the Vought 
company began to refer to the aircraft as the Crusader III.  Why 
Crusader III?  The F8U-2 (F-8C) was considered such a major upgrade of 
the early Crusader that it was initially called Crusader II by the 
company, so it seemed logical to call the new aircraft XF8U-3 Crusader 
III.  

The XF8U-3 had the same general configuration as that of the earlier 
Crusader, and kept the variable-incidence wing.  However, the XF8U-3 
was appreciably larger and more powerful.  The fuselage was enlarged 
to accommodate a Pratt & Whitney J75 turbojet, with a thrust almost 60 
percent greater than that of the J57 of the F8U-1 and -2.  The lower 
lip of the chin-mounted intake was raked forward in order to achieve a 
Mach 2+ performance.  The vertical tail was appreciably broader, and 
an afterburner cooling intake duct was mounted in a forward extension 
of the vertical fin on top of the aft fuselage.  Perhaps the most 
distinctive feature of the XF8U-3 was the use of a pair of large 
ventral fins which were extended vertically downward when the aircraft 
was in flight.  These fins were retracted to a horizontal position for 
landings and takeoffs.  

The XF8U-3 was to have been equipped with an APQ-50 radar, and was to 
be armed with three Sparrow missiles mounted semi-recessed inside 
slots cut into the lower fuselage.  In a concession to tradition, the 
usual quartet of 20-mm cannon was to be fitted, even though the 
conventional wisdom of the time was that the air-to-air missile would 
make kills possible at such long ranges that cannon armament would 
never be used in combat.  

On July 25, 1955, the Navy authorized the construction of two XF8U-3 
prototypes.  Bureau of Aeronautics serials were 146340 and 146341.  
Three more prototypes were ordered later (147085/147087).  

The XF8U-3 found itself in competition against the F4H Phantom II.  In 
the spring of 1958, the Navy established two preliminary evaluation 
teams, one dedicated to the Phantom II and the other to the Crusader 
III.  

The first prototype XF8U-3 (BuNo 146340) took off on its maiden flight 
on June 2, 1958, test pilot John Konrad at the controls.  This was six 
days after the first flight of the rival McDonnell Phantom.  The 
aircraft was flown with three dummy Sparrow missiles mounted in slots 
cut into the fuselage, one on each side and one on the fuselage belly.  
The second prototype (BuNo 146341) took to the air on September 27, 
1958.  

The performance of the XF8U-3 was nothing short of spectacular.  
During flight testing, the XF8U-3 demonstrated speeds of Mach 2.2 and 
zoom climb altitudes of nearly 90,000 feet.  Sustained altitude levels 
of 60-65,000 feet could be achieved.  The Crusader III was never flown 
to its true limits becaused of the windshield construction, which was 
made of acrylic and could not take the high aerodynamic heating 
temperatures that would be generated by entry into the aircraft's 
upper performance envelope.  It was thought that without the 
windshield limitations the XF8U-3 could have reached speeds as high as 
Mach 2.7 or 2.9 at 35,000 feet.  

The flight test program went exceedingly well, and the XF8U-3 showed 
great potential.  However, there were some problems with intake duct 
"rumble" which depended in a complicated manner on the rate of 
acceleration, altitude, and attitude.  In a typical scenario, a 
rumbling sound would start to be heard by the pilot as the plane 
reached a speed of about Mach 1.35.  It initially appeared to come 
from somewhere behind and underneath the pilot and moved forward in 
the duct as the plane accelerated.  Eventually, the duct would 
suddenly "unload" with a explosive sound, which was very unnerving to 
the pilot.  The duct criticality was designed out of the airplane 
after the initial phase of the tests, and the rumble problem bothered 
pilots no more.  

Although the Crusader III showed great promise, the Navy chose the 
competing McDonnell Phantom as the winner of the contest.  The XF8U-3 
had been designed exclusively as a fighter/interceptor, but the 
Phantom had been designed to a more encompassing set of requirements 
which included interception, reconnaissance, and ground attack roles.  
The Vought development contract was cancelled in December of 1958.  At 
the time of project cancellation, the limiting windshield was in the 
process of being redesigned so that the upper region of the aircraft's 
performance envelope could be fully explored.  

Three XF8U-3s were actually flown.  Had it been accepted for 
production, the XF8U-3 aircraft would have become for a time the 
world's fastest jet aircraft in service, with a maximum speed perhaps 
approaching Mach 3!  It had excellent acceleration, maneuverability 
and high-speed stability.  Test pilots deemed it to have been a 
delightful airplane to fly, with excellent control harmony.  The 
aircraft was in every way a winner, and it is a pity that no place in 
the Navy could be found for it.  

Following the cancellation of the program, XF8U-3 BuNo 147085 was 
turned over to NASA/Ames in June of 1959, becoming NASA 225 

I do not know if any of the XF8U-3s survive today.  Details anyone?  

Serials of the XF8U-3:  

146340, 146341, 147085/147087 

Specification of Vought XF8U-3 Crusader III:  

One Pratt & Whitney J75-P-5A/6 turbojet, 16,500 lb.s.t.  dry, 29,500 
lb.s.t.  with afterburning.  Maximum speed 1457 mph (Mach 2.21) at 
50,000 feet, 800 mph (Mach 1.05) at sea level.  Cruising speed 575 
mph.  Stalling speed 154 mph.  Initial climb rate 32,500 feet.  Combat 
ceiling 51,500 feet, service ceiling 60,000 feet.  Combat range 645 
miles.  Maximum range 2044 miles.  Maximum fuel 2036 US gallons.  
Weights:  21,862 pounds empty, 32,318 pounds combat, 37,856 pounds 
gross, 38,772 pounds maximum takeoff.  Dimensions:  wingspan 38 feet 
11 inches, length 58 feet 8 inches, height 16 feet 4 inches, wing area 
450 square feet.  Projected armament was to have been four 20-mm 
cannon plus three air-to-air missiles carried in slots cut into each 
lower side of the fuselage and on the fuselage belly just behind the 
forward landing gear.  

Sources:

    Vought F-8 Crusader, Peter Mersky, Osprey, 1981.

    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.

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

    The World's Fighting Planes, William Green, Doubleday, 1968.

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