Piasecki 59 Sky-Car / Airgeep / Seageep / VZ-8
VZ-8 Airgeep I
While the Army was pursuing the flying platforms, they were also investigating larger rotorcraft along similar lines, called the "flying jeeps". Some sources imply that they were intended mostly for hovercraft operation, with an ability to fly over obstacles or impassable terrain when necessary, while other sources indicate they were regarded as helicopter-like utility vehicles that operated normally as flying machines. Whatever the case, the US Army Transportation Research Command began an investigation into the flying jeeps in 1956, leading to award of contracts for prototypes to Chrysler, Curtiss-Wright, and Piasecki in 1957.
The first of the Piasecki flying jeep was the Piasecki "Model 59H AirGeep", which was given the Army designation "VZ-8P". The craft was built around two tandem 2.4 meter (8 foot) diameter, three-bladed, ducted rotors driven by two 135kW / 180 hp Lycoming piston engines. Both powerplants were connected to a single central gearbox so that both rotors would continue to turn even if one engine failed. The "Sky Car" had fairly conventional helicopter-type controls which provided directional stability through a series of hinged vanes mounted under each rotor duct. Forward motion was achieved by pitching the aircraft nose-down. The craft had fixed tricycle wheeled landing gear, and accommodated its single pilot and one passenger in seats sited between the two rotor ducts.
The AirGeep was 7.9 meters long and 2.7 meters wide (26 feet by 9 feet), with three-bladed rotors in ducts in the front and the back. The pilot and passenger sat between the ducts. The rotors spun in opposite directions to reduce torque effects.
The first of two Model 59 AirGeep (58-5510) examples ordered by the Army was first flown on 12 October 1958. Apparently it proved grossly underpowered, barely able to fly over a fence, and it was sent back to the shop, where the piston engines were replaced by a single 317 kW (425 HP) Turbomeca Artouste IIB turbine engine. The upgraded AirGeep flew on 28 June 1959. It weighed 1.1 tonnes (2,500 pounds) and could carry a payload of 550 kilograms (1,200 pounds), including the pilot.
Turned over to the Army shortly, the machine was subsequently given the designation VZ-8P (the "P" indicating Piasecki). Shortly after being accepted by the Army the VZ-8P was fitted with a single 315kW Turbomeca Artouste IIB turbine engine in place of its twin Lycoming pistons, and its first turbine-powered flight took place in June 1959.
The AirGeep was put through trials for both the Army and the Navy over the next few years. The engine was upgraded again to a Garrett / Airesearch 331-6 engine, which had a higher power-to-weight ratio. For Navy trials, which began in June 1961, the rotorcraft was fitted with floats, and redesignated the "PA-59 SeaGeep".
The second VZ-8P incorporated several significant design changes and was designated the Model 59H "Airgeep II" by Piasecki and the VZ-8P (B) by the Army. The Army Transportation Research Command issuing a contract for the "Model 59K", which made its first non-tethered flight in the summer of 1962.
The AirGeep II was similar to the AirGeep, except that the aircraft was "bent" in the middle so that the rotors were tilted fore and aft, to improve forward flight characteristics. The AirGeep II used twin 298 kW (400 SHP) Turbomeca Artouste IIC turboshaft engines, once again linked so that if one failed the other would drive both rotors. One engine could also be coupled to the landing wheels to drive the machine on the ground. The increased power allowed a maximum take-off weight of 2.2 tonnes (4,800 pounds). The pilot and observer had "zero-zero" ejection seats, allowing safe escape if the machine was on the ground and standing still, and there were seats for up to passengers.
During 1961 it was used for a series of trials by the U.S. Navy, operating from water and from the deck of a destroyer. For these, pontoons replaced the wheeled undercarriage and the VZ-8 became known as the Seageep. Following completion of these trials, it was re-engined with an AiResearch Model 331-6 turboshaft.
Neither version of the VZ-8P was dependent upon surface effect lift for flight and, though intended to operate within a few feet of the ground in order to make the best use of natural cover, both were quite capable of flying at altitudes of several thousand feet. Both versions were found to be stable and relatively capable craft.
The Airgeep was ultimately judged by the Army to be mechanically ill-suited to the rigors of field operations. The "flying jeep" concept was eventually abandoned in favor of the further development of conventional battlefield helicopters, and both VZ-8P examples were dropped from the Army's inventory in the mid-1960s.
Piasecki VZ-8P Airjeep
Piasecki VZ-8P Airgeep II