These "Flying Boats" Were Built To Carry a Nuclear Payload

These "Flying Boats" Were Built To Carry a Nuclear Payload

The Seaplane Striking Force was intended to deploy long-range nuclear bombers, obviating the need for large aircraft carriers or land-based runways.

Key Point: While the SSF concept had its ardent and articulate advocates, it was probably never going to perform a primary role in the Navy’s nuclear strike mission.

The first few years after World War II were challenging ones for the U.S. Navy. Massive demobilization of personnel and rapid scrapping or retirement of ships created internal disruptions. Formation of a new Defense Department, combined with sharp reductions in defense spending, led to bitter rivalries among the American military services, each seeking its proper share of increasingly limited resources. Birth of an independent Air Force eager to gain control over all airpower accelerated an internecine struggle with the Navy, leading to the sudden 1949 cancellation of a proposed new aircraft carrier, USS United States.

In this milieu, the Navy faced a concurrent operational challenge: the adaptation of larger, heavier, and faster jet-powered aircraft to existing carriers that had supplanted battleships as primary projectors of naval power during the war. Senior naval aviators were concerned that the new supersonic jet aircraft, with their greater weight and higher takeoff and landing speeds, might not be able to operate safely from available carriers—or even new ones of any reasonable size. One theoretical solution was the Seaplane Striking Force (SSF), in which newly developed seaplanes and vertically launched and recovered aircraft would be unshackled from the need for land-based runways or large aircraft carriers.

As envisioned by Navy planners circa 1950, the SSF included as its primary strike weapons high-performance, four-engine, jet-powered seaplanes. These would be supported by a system of technologically advanced, water-based, or short takeoff and landing aircraft in defensive roles, large long-range flying boats for resupply, and relatively inexpensive surface ships and diesel-powered submarines as supporting tenders and refueling and maintenance stations. The centerpiece of the 1950s concept was the P6M SeaMaster flying boat, designed by the Glenn L. Martin Company of Baltimore. In support of the SeaMasters’ conventional or nuclear long-range attack mission were three aircraft proposed by Consolidated Vultee Aircraft Corporation of San Diego (Convair). These included the vertical takeoff and landing XFY-1 Pogo tail-sitter defensive fighter aircraft; the F2Y-1 Sea Dart, an innovative delta-winged jet fighter that could take off and land from water; and the R3Y Tradewind, a sleek, large, four-engine turboprop flying boat.

The Convair XFY-1 Pogo

The Convair XFY-1 Pogo was perhaps the least significant among the aircraft elements of the proposed SSF. Designed as a vertical takeoff and landing fighter that could operate from a relatively small platform ashore or on a ship, the Pogo would be a fighter liberated from the need for a land runway or aircraft carrier flight decks. It would ostensibly be used to  flight decks. It would ostensibly be used to defend SSF forward operating bases and strike aircraft or convoys at sea. As originally designed by Convair, Pogo was an innovative tail-sitter with stubby delta wings and fins above and below the fuselage. Four small landing wheels were affixed to hydraulic pegs at the ends of the wing and vertical stabilizers.

The Pogo had three major flaws. First, the XFY-1 was powered by a huge turboprop engine in an era when American manufacturers were experiencing seemingly insoluble problems developing such engines with satisfactory power and reliability. The Pogo mounted the Allison YT40-A-16, which consisted of two coupled Allison T38 engines producing 5,500 estimated shaft horsepower driving two three-bladed, contra-rotating propellers. The propellers were intended to operate as helicopter rotors while the aircraft was in or near vertical mode during landings and takeoffs. Second, the vertical takeoffs and landings were foreign to pilots who were used to landing on runways or ships while flying forward with full view of the landing area and its periphery. Landings in particular were challenging and hazardous for fledgling pilots because a Pogo aviator had to land by looking over his shoulder or into rearview mirrors while descending to the pad. Third, even if the engine problems were resolved, maximum flight speeds for Pogo would barely exceed 550 miles per hour, far less than the speed of the new jet fighters deployed by the most probable enemy, Soviet MiGs. In addition, the relatively slow but lightweight Pogo lacked spoilers and air brakes and could not slow down efficiently after flying at high speeds.

Initial flight tests for the radical Pogo, perhaps unsurprisingly, were conducted indoors and tethered at Naval Air Station Moffett Field, California, in early 1954. Convair engineering test pilot and Marine reserve Lt. Col. James F. “Skeets” Coleman made the first untethered test flight at Lindbergh Field, San Diego, in August, reaching an altitude of 40 feet. Coleman continued takeoff and landing practice at Naval Auxiliary Air Station Brown Field, California, logging nearly 60 flight hours in 70 such drills, one of which attained an altitude of about 150 feet. In November, he became the first American pilot to finish a complete flight in the aircraft. He executed a vertical takeoff in Pogo, transitioned to horizontal flight over San Diego for about 20 minutes, then landed vertically within a square measuring 50 feet on each side. Attesting to the difficulty of flying the aircraft, Coleman was awarded the 1954 Harmon trophy, given annually to the world’s outstanding aviator.

During its brief career, the sole experimental Pogo logged only about 80 flights. By late 1954, it had become obvious that the aircraft would never overcome its three major problems. The XFY-1 program was terminated by the Navy in August 1955. Convair continued briefly with limited testing of the aircraft, which was grounded for good in November 1956. The single prototype of the unsuccessful Pogo was later transferred to the National Air and Space Museum at Suitland, Maryland, where it currently remains.

The XF2Y-1 Sea Dart

In early 1948, the Navy initiated a design contest for a high-performance, supersonic seaplane fighter that could operate from forward areas without the need of either carriers or land air bases. Convair entered the contest in October 1948 via its proposal for a delta-winged design with streamlined hull that rested on the water and rose up on a pair of retractable hydro-skis for takeoffs and landings. After two years of extensive testing and empirical revisions of seaplane designs, Convair was awarded a contract  in January 1951 for two prototypes, which were assigned the designation XF2Y-1, Sea Dart, and became an essential element of the SSF concept. The Sea Dart was to be powered by two afterburning Westinghouse J46 jet engines, providing 6,000 pounds of thrust each, fed by a pair of air intakes mounted high on the sides of the fuselage above the wing and behind the cockpit. This configuration was chosen to prevent water spray from entering the intakes during takeoffs and landings. The plane was fitted with a set of dive brakes on the lower rear fuselage, which also doubled as water brakes and rudder while taxiing on the surface.

Sea Darts took off and landed on a pair of retractable hydro-skis that extended outward on hydraulic legs from recesses cut into the lower hull, one ski on each side of the hull. The Navy had such confidence in the design that it ordered 12 production F2Y-1 aircraft in August 1952. Pending the availability of the J46 jets, the first prototype XF2Y-1 was fitted with two non-afterburning Westinghouse J34 engines providing only 3,400 pounds of thrust each. Initial flight tests in April 1953 revealed that the aircraft was severely underpowered for its weight. In addition, the hydro-skis vibrated so much during takeoffs and landings that the aircraft was extremely difficult to control. To cure the vibration problem, the skis were redesigned and their hydraulic legs improved. But inadequate thrust and seemingly insoluble vibration problems with the hydro-skis continued to plague the Sea Dart. In October 1953, the Navy canceled the remaining XF2Y-ls.

The first of four contracted YF2Y-1 service test aircraft joined the program in early 1954. It was powered by a pair of afterburning Westinghouse J46 turbojets. In overall appearance, the YF2Y-1 was similar to the XF2Y-1 except for the revised nacelles housing more powerful J46 engines. Convair test pilot Charles E. Richbourg made the initial flight tests of this Sea Dart. In August 1954, at an altitude of 34,000 feet, he took the first YF2Y-1 through the sound barrier while in a shallow dive, making the Sea Dart the first and to date the only seaplane to go supersonic. Since the Sea Dart had been designed before the application of the fuselage area rule, the aircraft experienced high transonic drag and remained unable to exceed the speed of sound in level flight.

The Fatal End of the Sea Dart Program

By the fall of 1954, both the Navy and the manufacturer were confident that all three aircraft being developed by Convair were ready for a public demonstration of their capabilities. In November 1954 the Navy scheduled a daring but, in retrospect, premature flight demonstration in San Diego for all three aircraft. Invited for the performance were high-ranking Navy officers and Defense Department officials, Convair management and engineering personnel, and a large press contingent. The first act was performed by the XFY-1 at Naval Auxiliary Air Station Brown Field, where the experimental Pogo made a successful vertical takeoff, conversion to level flight, and safe vertical descent on its quadruple landing wheels. Following this performance, guests were transported to Convair’s seaplane ramp on San Diego Bay, where they were treated to an impressive flyby from the R3Y Tradewind.