Aircraft of the Month for December 1999

Chance Vought F7U Cutlass

Photo Courtesy of National Museum Of Naval Aviation

Overview
The F7U Cutlass was an aircraft of remarkable innovation. The tricycle landing gear and pressurized cockpit were some of its advanced features for the time. The Cutlass was the first production tailless military aircraft, the first swept-wing naval aircraft, the first production aircraft with afterburning engines, the first naval aircraft with a high-pressure hydraulic system (3,000 psi) and, in the advanced F7U-3M version, the first fighter in the world to carry air-to-air radar guided missiles, the Sparrow I (then called the AAM-N-2, but now known as the AIM-7A), and the first fighter to exceed the Mach 1 while delivering weapons in a diving attack. The F7U-3 easily outmaneuvered the F9F-5 Panther and the Navy's version of the F-86, the FJ-1 (later F-1) Fury. Most pilots loved flying the Cutlass despite its numerous shortfalls, poor accident record and excessive maintenance needs - they found the it seemingly unbreakable in high-G maneuvers, exciting to fly, and an excellent aerobatic machine. The cockpit was very comfortable, and in flight it possessed excellent visibility.
During the short service life of the F7U, deploying squadrons would usually fly most of their aircraft to shore bases in the vicinity of the ship, leaving only a few F7U's aboard for fleet defense and carrier qualifications. The risk to pilot and aircraft was reduced. A technical change was later introduced that strengthened the nose gear by 30 percent, allowing for increased saftey in landing, where some earlier aircraft had their nose gear snap in two during landing. The cockpit was 4.3 m (14 ft) off the ground, so a snapping nose gear usually either critically injured or killed the pilot.
The twenty millimeter cannons were mounted two to a side, just above the engine air intakes. In earlier aircraft, both engines tended to flame out when the guns were fired. At first the problem was thought to be caused by ingestion of gun gases but later was proved to be caused by pressure resonance (when both sets of guns fired simultaneously, a pressure wave was created at the engine intakes, which caused a resonance which traveled to the aft section of the engine's compressor, creating a stall. The resulting air mass led the compressor blades to over temp, perhaps causing the engine to either burnout or disintegrate). The problem was solved by installing circuits that prevented the left and right pairs of guns from firing simultaneously, but not before a number of aircraft and pilots were lost while firing the guns.

Two F7U-1's during their stay with Blue Angles History
In 1945 the USN issued a request for a high performance jet fighter, capable of speeds of 970 km/h (515 kts/600mph) and able to reach altitudes of 12200 m (40000 ft). Chance Vought won the contract in June 1946. The new fighter was described by the Navy as an "experimental, tail less fighter designed for carrier operations and equipped with two 24C turbojet engines."
The design featured swept wings, tricycle landing gear, a pressurized cockpit, and four twenty millimeter cannons. The requests for the four cannon and the tricycle landing gear were radically new; in 1946, very few aircraft a nose wheel. Most aircraft still had a tail wheel, straight wings and were unpressurized. Much of the technology used in this new design evolved from allied technical evaluations of German aircraft following World War II.
The F7U was the first USN aircraft designed with swept wings. Its delta wing featured radically different control surfaces than any seen before. Ailerons joined with horizontal stabilizers to form "elevons." The F7U featured twin tails and rudders. Since the tailless design demanded a critical center of gravity, an unusually long nose strut was applied to the aircraft to give it a very high angle of attack during takeoff and landing. However, the unusual design produced the highest roll rate of any of the USN's jets - up to 576 degrees a second! Also, the pilot was provided with a ejection seat and a pressurized cockpit.
The F7U was designed for more powerful engines than it ever reveived, and the afterburning Westinghouse J34-WE-32 jet engines, which were installed in the side by side in the read fuselage and which powered the prototype, didn't provide enough power to make the F7U safe to fly. The design was quickly changed to use the more powerful J46 jet engines. Although the F7U-3 version first flew in December 1951, a lack of J46 engines kept the first F7U-3's from reaching service until fall, 1954. Even the initially promising J46 design proved a disappointment - the J46 design promised 10,000 lb in afterburner, but in reality the thrust was less than half that. The J46's also had a very high maintenance to flight time ratio and they wore out quickly, which meant a lot of maintenance time for the aircraft; but altering the design again to adapt to more powerful engines was out of the question - Turbojet technology was evolving too quickly for airframe designers to keep up.
The Blue Angles received two F7U-1's, which they only used in the 1951 season. The F7U's new pressurized hydraulic system was unreliable, and if it went out, it took 11 seconds for the manual override to activate. This made airshows dangerous. During 1955, production was canceled in favor of the newer and far superior F8U Crusader, also made by Vought and still used today by France.
F7U-3s equipped 13 fleet squadrons, four test squadrons, and one reserve attack squadron, VA-212 at NAS Moffett Field, California. The "Rampant Raiders" of VA-212 made a six month cruise aboard the carrier "Bonne Homme Richard", returned early in 1957, and traded their "Cutlasses" in for F9F-8 "Cougars." One VA-212 "Cutlass" survives today, restored and on static display at the US Navy's National Museum of Naval Aviation in Pensacola, Florida. The Marines operated only two F7U-3's from NAS Miami, now Coast Guard Air Station, Opalocka.

Chance Vought F7U Specifications

F7U-1 F7U-3

Type Naval air superiority fighter

Powerplant Two Westinghouse J34-WE-32 turbojets Two Westinghouse J34-WE-8A turbojets, 4600 lb thrust each

Accommodation Pilot only

Armament Four 20mm cannon + three three-packs of Mighty Mouse (FFAR 2.75 in) rockets (two on the wings, one under the fuselage) Four 20mm cannon and up to 5,500 lb of disposable stores, including four AIM-7A Sparrow I's or Mighty Mouse Rockets

Performance

Max speed Mach 1.02 (1082km/h; 584kt) Mach 1.03 (1095 km/h; 591 kts)

Combat radius 970km (520nm) 1063 km (574 nm)

Ceiling 12625m (41400ft) 12200 m (40000 ft)

Climb Rate 3962.21 m/min (13000 ft/min)

Weights

Empty 7645kg (16,840 lb) 8258 kg (18210 lbs)

MTOW 14365 kg (31642 lb)

Dimensions

Wingspan 11.79 m (38ft 8in)

Length 13.49 m (44ft 3in)

Height 3m (9ft 10in) 4.45m (14 ft 7.5 in)

Wing Area 46.08 sq m (496 sq ft)

Chance Vought F7U Specifications
	F7U-1	F7U-3
Type	Naval air superiority fighter
Powerplant	Two Westinghouse J34-WE-32 turbojets	Two Westinghouse J34-WE-8A turbojets, 4600 lb thrust each
Accommodation	Pilot only
Armament	Four 20mm cannon + three three-packs of Mighty Mouse (FFAR 2.75 in) rockets (two on the wings, one under the fuselage)	Four 20mm cannon and up to 5,500 lb of disposable stores, including four AIM-7A Sparrow I's or Mighty Mouse Rockets
Performance
Max speed	Mach 1.02 (1082km/h; 584kt)	Mach 1.03 (1095 km/h; 591 kts)
Combat radius	970km (520nm)	1063 km (574 nm)
Ceiling	12625m (41400ft)	12200 m (40000 ft)
Climb Rate		3962.21 m/min (13000 ft/min)
Weights
Empty	7645kg (16,840 lb)	8258 kg (18210 lbs)
MTOW		14365 kg (31642 lb)
Dimensions
Wingspan		11.79 m (38ft 8in)
Length		13.49 m (44ft 3in)
Height	3m (9ft 10in)	4.45m (14 ft 7.5 in)
Wing Area		46.08 sq m (496 sq ft)

Links
Fiddlers Green F7U
Free Downloadable/Printable/Flyable F7U Model from Fiddlers Green