Piasecki PV-3 / HRP / PV-17
On 1 February 1944 Piasecki received a contract to develop a tandem-rotor utility transport and rescue aircraft for the U.S. Navy.
Given the factory designation PV-3, this machine was a development aircraft for the US Navy's HRP Rescuer transport and rescue helicopter. Powered by a Wright R-975 piston engine, the tandem-rotor PV-3 first flew at Morton, Pennsylvania in March 1945. It was followed by two XHRP-1 airframes, one of which was used for static tests while the other undertook the U.S. Navy flight development programme, during the course of which the company changed its name to Piasecki Helicopter Corporation.
In June 1946 Piasecki received an initial order for 10 production HRP-1 helicopters. The test programme was completed in the spring of 1947, by which time work had already begun on an initial batch of ten HRP-1 Rescuers. The first of these flew on 15 August 1947, powered by a 447kW / 600hp Pratt & Whitney R-1340-AN-1 engine
A second batch of ten was built later, the final machine being delivered in 1949, with a metal-skinned rear fuselage and fabric covering over the main cabin section, although they were often flown with the fabric removed.
Service evaluation was undertaken by US Navy Squadron VX-3 and US Marine Corps Squadron HMX-1. Twelve of the HRP-1's were eventually assigned to the U.S. Marine Corps for assault training, while three others, as HRP-1G's, were used as rescue craft by the U.S. Coast Guard. After withdrawal of the Rescuer from military service in the early 1950s, about six appeared on the U.S. civil register.
The HRP-1 carried a crew of 2 sitting in tandem, and its 11.33cu.m cabin could accommodate 8 passengers, 907kg of cargo or 6 stretchers. The single engine was mounted in the rear part of the fuselage, with a clutch and gearbox amidships from which drive shafts ran to reduction gearboxes below each of the rotor hubs.
In June 1948 the U.S. Navy ordered five examples of the much-developed PV-17 with the designation HRP-2. The much-improved HRP-2 (PD-17) featured a streamlined metal fuselage offering better visibility for two pilots, who now sat side by side ahead of the front rotor. The most significant improvement was the HRP-2's all-metal stressed-skin construction, and modified rotor heads.
It used the same engine and rotors as the HRP-1, but was slightly shorter and lighter. The Piasecki team used a thinner skin and had the longitudinal members shaved down, as well as other extruded parts that could not be manufactured thinly enough.
Jim Ryan lifted the new Navy helicopter into the air for the first time October 29, 1949. While it was indeed better than the HRP-1, the fast pace of helicopter technology had already passed it by, and better helicopters could now be built. With a gross weight of 3260kg, the HRP-2 was simply too light to offer much utility and only five were built.
The HRP-2 formed the basis of the later PD-22 model which became the military Vertol H-21 series.
Robert Cummings, 23.02.2009
HRP-1 / PV-14
Engine: 1 x Pratt & Whitney R-1340-AN-1, 600 hp / 445kW
Rotors: 2 x 3-blade main rotors in tandem
Rotor diameter: 12.50m / 41 ft
Fuselage length: 14.63m / 47 ft 2 in
Take-off weight: 3629kg / 6,900 lb
Max speed: 193km/h
Service ceiling: 3658m / 12,000 ft
Normal range: 483km
Typical range: 264 miles at 85 mph with 100 USgals fuel
HRP-2 / PV-17
Engine: 1 x Pratt & Whitney R-1340, 600 hp