Piaggio P.7

Piaggio

Industry	Aerospace
Headquarters	Italy , Italy
Products	Aircraft

The Piaggio P.7, also referred to as the Piaggio-Pegna P.c.7, was an Italian racing seaplane developed and constructed by Piaggio specifically for competition in the 1929 Schneider Trophy contest.

Design and development

File:Piaggio P.7 afloat.jpg

The P.7 on water. While stationary, the aircraft floated up to its wings due to its watertight fuselage, with the hydrofoils submerged beneath and its wings resting on the surface.

In an effort to eliminate the aerodynamic resistance caused by traditional floats on seaplanes of the floatplane type, Ing Giovanni Pegna at Piaggio engineered a highly unconventional seaplane to represent Italy in the 1929 Schneider Trophy race. This cantilever shoulder-wing monoplane, known as both the Piaggio P.7 and Piaggio-Pegna P.c.7, featured a long, narrow watertight fuselage that supported the aircraft afloat up to its wings, which rested on the water’s surface. It utilized a pair of high-incidence hydrofoils mounted beneath the fuselage to lift itself from the water during takeoff runs.

There is some discrepancy regarding the P.7’s powerplant; it has been identified as either an Isotta Fraschini Special V6 engine rated at approximately 723 kilowatts (983 PS; 970 hp) or as an Isotta Fraschini AS-5 delivering around 745 kilowatts (1,013 PS; 999 hp). The engine drove two separate propellers via distinct shafts: a two-bladed automatic variable-pitch tractor propeller at the front through a long metal shaft, and a smaller marine-style propeller positioned under the tail via another shaft. For waterborne acceleration, the pilot would initiate engine operation with the flight propeller feathered and carburettor air intake closed, engaging a clutch to power only the rear marine propeller, propelling the aircraft forward through water. The hydrofoils, attached on struts ahead of the wings akin to floatplane float mounts, would swiftly raise the aircraft above water level. Once airborne on its hydrofoils and with the flight propeller clear of water, the pilot opened the carburettor air intake while disengaging the marine propeller via clutch, then engaged another clutch to activate the flight propeller which automatically adjusted from feathered to flight pitch. With thrust now provided by its flight propeller, the aircraft performed a conventional takeoff run while skimming atop its submerged hydrofoils until achieving lift-off speed.

By removing both the drag and additional mass linked with floats, Pegna anticipated that the P.7 would achieve exceptional velocities. Estimates of its projected top speed vary between approximately 580 km/h (360 mph) and 700 km/h (435 mph).

Testing

File:Piaggio P.7 above.gif

View of the P.7 from above while floating on water.

Piaggio produced a single P.7 prototype, which was handed over to the Italian Schneider Trophy racing squad. Despite hesitation from several pilots to operate the aircraft, Tommaso Dal Molin of the Italian Schneider team performed a series of water trials on Lake Garda in northern Italy. The hydroplane spray during takeoff severely impaired visibility, and ongoing clutch malfunctions plagued the tests. Ultimately, the aircraft failed to achieve flight.

Due to its incomplete status, the P.7 did not participate in the 1929 Schneider Trophy competition, where Italy was represented by a Macchi M.52R and two Macchi M.67 seaplanes. Subsequently, Piaggio and Pegna discontinued efforts to develop a second P.7 unit.

Operators

Template:Country data Kingdom of Italy

Specifications

File:Piaggio Pegna P.C.7 3-view.svg

References

• Vašiček, Radko. "When Seaplanes Ruled the Sky." Aviation History, September 2002.