George Pereira built the single-seat flying boat GP2 Osprey 1, later known as the X-28A (US Navy 158766) in 1970. He started on the design and construction of a two-seat amphibian development in January 1972. Powered by a Franklin Sport the GP3 Osprey 2 (N3GP) made the first flight from water in April 1973, the aircraft becoming airborne after a take-off run of less than 800 ft (244 m).
The Osprey 2 had an unusual form of hull construction when after completing the all-wood fuselage structure and installing the controls the undersurface was given a deep coating of polyurethane foam. To produce the needed hull form the foam layer was sculptured and then protected by several layers of glass fiber cloth bonded with resin; after that it was polished and painted. This resulted in a light smooth but extremely strong structure, with good shock resisting characteristics.
The wingtip floats were constructed in the same manner as the aircraft hull; the wings aft of the main spar were fabric covered. The landing gear was manually operated; the engine was mounted on a steel tube pylon structure bolted to the wing truss.
After the initial flights from water the plane was tested from land and during the subsequent test flights a slight buffet aft of the cabin was observed. This occurred with retracted landing gear at a speed of 120 mph (193 kmh); and there was also an unacceptable high noise level.
To counter this a modification was made in early 1974 by lengthening the cabin by 7 in (0.18 m) and a Lycoming O-320 was installed in a new cowling. Also the vertical tail was altered by enlarging the fin above the tail plane, flight-testing was resumed and completed satisfactorily during 1974.
Through Osprey Aircraft the design plans and kits came available to the amateur constructors and over 500 have been built and flown. The Osprey 2 designer received an award from the publication "Mechanics Illustrated".
GP3 Osprey 2: prototype; many have been built by amateurs differing in detail only
Max T/O weight:
Two-seat light amphibian
One 150 hp Lycoming O-320 flat four-cylinder engine
26 ft 0 in (7.92 m)
20 ft 6 in (6.25 m)
6 ft 0 in (1.83 m)
130 sq.ft (12.08 sq.m)
970 lb (440 kg)
1,560 lb (708 kg)
150 mph (241 km/h)
1,200 ft (366 m)/min
500 mls (805 km)