Today, the U.S. Marine Corps has the leading role in developing and fielding short takeoff/vertical landing (STOVL) warplanes like the AV-8B Harrier II and F-35B Lightning II Joint Strike Fighter. In the 1950s, the U.S. Navy – seeking to expand the role of, and to protect, its surface warships – took an initiative all its own to develop a combat aircraft that wouldn’t require a concrete runway or a carrier deck. The Navy wanted a combat aircraft with full vertical takeoff and landing (VTOL) capability, and its solution was unusual in the extreme.
Rather than an aircraft like the Harrier that remains horizontal in all modes of flight, the Navy wanted a “tail sitter” fighter able to take off from a platform on the afterdeck of a surface warfare vessel or an ordinary cargo ship. The tail sitter would be able to deploy aboard any vessel that could handle a helicopter.
Memories were fresh of the battle between Allied surface ships and German U-boats in the Battle of the Atlantic. The new fighter would be an ideal way to protect shipping convoys. The Navy also saw many other uses for an aircraft that could take off and land in a small space.
Pogo and the XFV-1
American industry came up with two planes for the job. Convair designed the XFY-1 “Pogo,” a tail sitter with stubby delta wings and fins above and below the fuselage.
Lockheed developed the straight-wing, X-tailed XFV-1 (initially known as the XFO-1). Both planes reflected brilliance and initiative in an era of free spending on defense that encouraged experimentation. Both, in the end, were icons for an original idea whose time never quite came.
The XFY-1 and XFV-1 both relied on huge turboprop engines in an era when the Navy was having enormous difficulty developing turbine engines. Both were tested with versions of the Allison XT40-A, which consisted of two coupled T38 engines together producing 6,500 estimated shaft horsepower and driving three-bladed, contra-rotating propellers, intended to work like helicopter rotors when the aircraft was in the vertical mode.
The XFY-1 sat atop the trailing edges of its two wings and dorsal and ventral fins. Convair fitted a small, castering wheel onto the end of a strut several feet long and mounted four of these to form an improvised landing gear at the tips of the wings and fins. At touchdown, the struts compressed several feet, like a child’s pogo stick, to dampen impact forces. There were no brakes and the wheels rolled freely, so the aircraft had to be flown when there was no wind – a severe limitation that would have been corrected on an operational version.
There were plans on the drawing boards for more advanced versions of both the aircraft and the engines.
Convair’s triangular-shaped “Pogo” began tethered tests beneath the 184-foot roof of the dirigible hangar at Moffett Field just south of San Francisco in 1954. Ultimately, it flew 250 times inside the hangar.
On Aug. 1, 1954, back at the manufacturer’s home base at Lindbergh Field in San Diego, Convair test pilot James F. “Skeets” Coleman made the first untethered vertical flight in the XFY-1, reaching an altitude of 40 feet.
Except for helicopters and autogyros, no aircraft had ever before made a flight that included a vertical takeoff and landing. Coleman achieved this feat on Nov. 2, 1954, taking off in the “Pogo,” transitioning to the horizontal mode, flying over San Diego for 20 minutes, and landing inside a 50-foot square. He was later awarded the Harmon Trophy for the effort. Coleman said the XFY-1 was nose-heavy and was difficult to land, in part because the pilot needed to look over his shoulder while descending for a landing.
John Knebel, the only other pilot to fly the XFY-1, said he “almost wrecked” the aircraft trying to maintain control of it while in a hover in free flight near Lindbergh Field.
The pilot’s seat in both tail sitters rotated for safety and comfort in both vertical and horizontal flight. In case of an off-field or emergency vertical landing, Convair thoughtfully provided about 25 feet of rope tied inside the cockpit so the pilot could dismount safely.
Less Likely Lockheed
The Lockheed craft was the less successful of the two tail sitter designs.
Lockheed test pilot Herman “Fish” Salmon piloted the other ship, the XFV-1. Beginning in December 1953, Salmon flew the XFV-1 using a test rig that resembled conventional landing gear and enabled the plane to take off from a runway like a conventional aircraft.
The XFV-1 made 32 flights, logging 23 hours, using the undercarriage. Although it demonstrated the ability to transition from vertical to horizontal mode at high altitude after takeoff, the XFV-1 never took off or landed vertically.
The XFY-1 “Pogo” logged 40 hours of flying.
Had an operational version been built for fleet duty, the XFY-1 and XFV-1 would have been armed with four 20-mm cannon or 46 2.75-inch folding-fin aircraft rockets (FFAR). But, contrary to expectations, neither of the tail sitters was able to hover, helicopter-style, for more than a minute or two. A 7,500-horsepower Allison T54-A-3 engine would have powered proposed XFV-2 and FV-2 versions of the Lockheed aircraft. This “monster” engine was also proposed for other aircraft, including a Lockheed patrol bomber, but the engine was never completed or tested.
By the time both tail sitter fighters were being tested, the Navy had decided that there would be no gain in attempting to overcome engine and other problems. Neither aircraft was capable of flying faster than 580 miles per hour, not enough speed to assure survival in any conflict where an adversary possessed jet air power. The XFY-1 and XFV-1 made the cover of Collier’s magazine and were well known to every teenaged aviation buff in the 1950s, but they were doomed by their complexity, handling problems, and relatively low speed. Conventional American jets and Soviet MiGs of the period were considerably faster. The XFY-1 and XFV-1 were retired from service and are now in museums.