Convair FY/F-3 Delta DashThe Convair Delta Dash fleet defence fighter could easily have been a flash-in-the-pan abortion in the history of aircraft design, but instead it would go on to earn a deserved reputation for speed and manoeuvrability.
The revolutionary XFY design, competing with Lockheed’s XFV for a United States Navy contract, had delta wings and three-bladed contra-rotating propellers powered by a 5,500 hp (4,100 kW) Allison YT40-A-16 turboprop engine. It sat on four wheels, one on the trailing edge of each wing and vertical stabiliser, and the pilot had to climb a ladder to reach the nearly two-storey-tall cockpit. The aircraft was intended to provide a ship-borne VTOL defence for naval vessels beyond the reach of an aircraft carrier.
Landing the XFY-1 prototype (BuAer 138649) was difficult as the pilot had to look over his shoulder while carefully working the throttle to land. Another issue found during flight testing by Convair test pilot and Marine reservist James F “Skeets” Coleman was that due to the XFY's lightweight design, and the lack of spoilers and air brakes, the aircraft lacked the ability to slow down and stop efficiently after moving at high speeds. Otherwise, performance was comparable to the more conventional designs of the day.
Although experiments were conducted with prone-pilot cockpits, the solution to the landing issue was found to be a simple one: a rearview mirror was installed above the windscreen. To ease the speed issues, perforated speed brakes were installed on both the upper and lower inner wing surfaces. These fixes – implemented in the third XFY-1, BuAer 138650, which had previously been a static testbed – were proven to remedy these issues during a series of test flights by Skeets Coleman during March 1955. By now the aircraft had been nicknamed “Pogo” by Convair engineering staff, although the company gave it the more dignified moniker “Delta Dash” to fit in with its interceptor designs serving with the US Air Force.
Now designated XFY-2, both 138650 and the newly-modified 138649 were flown together at Edwards AFB for the first time in April ahead of a much-publicised fly-off against the sole complete Lockheed XFV. However the trials were never to occur as the Lockheed was incapable of vertical take-off due to insufficient engine power, and that company announced the cancellation of its VTOL programme in late June.
On 1 August the USN formally placed an order for 100 FY-2 Delta Dashes. These service examples were armed with either four 20mm Colt Mk.12 cannon or 48 2.75in folding-fin rockets, the change being accomplished by use of so-called “quick change” pods on the wingtips. The rear portion of each pod was a fixed fuel tank. The service aircraft also had longer-stroke undercarriage legs (to absorb the movement of the ship and heavy landings) which were now retractable.
The Delta Dashes were assigned to entirely new units: VFD-1 through -6, the VFD designation standing for Fixed-wing Fleet Defence in naval parlance. Each squadron would serve with a Fleet, rather than aboard a single ship or Naval Air Station as with standard fixed-wing units, with the aircraft and pilots of the squadron being dispersed among the cruisers, destroyers and frigates of the Fleet. Each Delta Dash-capable ship received a “clam-shell” protective housing for the aircraft which acted as a custom-sized hangar, and provision was made to house three pilots and two maintenance crews.
Although landing vertically on a pitching deck at sea was difficult and a handful of examples were lost in early accidents, USN aviators soon became comfortable with the procedure. As well as the nickname Pogo from the Lockheed testing days being used by pilots and crews, the aircraft’s unique stance on the ground led to FY-2 flying duties being called “sitting in the High Chair”. The type was also called “Blender” and “Mixmaster” due to the distinctive contraprop.
As the aircraft entered active service Convair continued to tweak the design. In mid-1957 they tested the FY-3 Delta Dash, which forwent the quick-change pods in favour of fixed units housing the new Hughes Falcon guided missile. Similar to the installation on the Northrop F-89D Scorpion, the FY-3’s Falcons were stored in the streamlined pods and extended out when needed. Rather than purchase new aircraft the USN instead opted to have the existing FY-2 fleet modified to FY-3 standard.
On 18 September 1962, under the Tri-Service aircraft designation system, the Delta Dash was redesignated F-3. Under the new system the surviving FY-2s became F-3Bs and the FY-3 became F-3Cs. By 1970 the last Delta Dashes had been replaced in US service by Hawker-Northrop AV-8B Sea Harriers.
