Ariel
PH-SAM
Pathfinder I
The Pathfinder was an interesting Compound Helicopter concept that was carried out during the 1960s by Piasecki Aircraft. There was interest from both the Army and Navy who shared a joint development contract.
The Compound Pathfinder used a standard helicopter-style overhead rotor which was off-loaded by a small low-mounted fixed wing when the craft transitioned to high-speed horizontal flight. The three-bladed rotor was mounted on a streamlined pylon which was powered by turbine engine. The small tapered low wing was equipped with standard flaps. To the rear of the fuselage were cruciform fins which supported an annulus which contained a propeller. That rear installation performed the function of anti-torque and directional control. The model also mounted a retractable landing gear carriage.
In operation, the Pathfinder took off like a standard helicopter. Acceleration was then achieved by directing power from the rotor into the rear propeller, then as the speed increased, the fixed wings took on a larger share of the lift. It should also be noted that the Pathfinder could also be used in a STOL mode, which greatly increased its payload capability. The reverse transition for landing exactly reversed the take-off process.
There were actually two versions of the Pathfinder, the first of which was the -1 version, which first flew in 1962. The similar Pathfinder II, the 16H-1A, was completed in 1965.
The 37 foot long privately-developed Piasecki 16H-1 weighed 11,000 lb and had a wingspan of 20 ft. The five-seat Pathfinder I was originally powered by a 550 hp Pratt & Whitney PT6B-2 turboshaft engine. The engine powered a 41 foot fully articulated three-bladed rotor and a 5.5 ft three-bladed ducted propeller in the tail (called a "ring-tail") to provide forward thrust and directional and anti-torque control with four vertical vanes in the duct. Gross weight was 2,611 lb and fuselage length was 25 foot. The 16H-1 made its first flight on 21 February 1962. Overall, the Pathfinder I had the handling qualities of a conventional helicopter, but used its wings and pusher propeller to off-load the rotor and increase its maximum forward velocity to 148 kt. 185 flight hours were accumulated before May 1964, when Piasecki was contracted to test a high speed modification, the 16H-1A Pathfinder II. It was equipped with a 1,250 shp T58 turboshaft engine, a new drive system and propeller to handle the increased power. The rotor size was increased to 44 foot diameter, and the fuselage was stretched to accommodate eight seats. Flight testing resumed on 15 November 1965 and it accrued over 40 hours in the air by May 1966, reaching speeds of 195 kt. Later, it was redesignated the 16H-1C when the engine was upgraded to a 1,500 shp T58-GE-5. The -1A version was considerably larger than the initial prototype, with a three-foot bigger diameter rotor at 13.4m, and its maximum speed was much faster at 360km/h, compared to 287 with the first version. The gross weight of the 1A model was 1037kg heavier than the first model. The two models used different powerplants; the first used a United Aircraft of Canada PT6B engine, while the later version used a General Electric T58 turbine engine.
The Pathfinder was an interesting Compound Helicopter concept that was carried out during the 1960s by Piasecki Aircraft. There was interest from both the Army and Navy who shared a joint development contract.
The Compound Pathfinder used a standard helicopter-style overhead rotor which was off-loaded by a small low-mounted fixed wing when the craft transitioned to high-speed horizontal flight. The three-bladed rotor was mounted on a streamlined pylon which was powered by turbine engine. The small tapered low wing was equipped with standard flaps. To the rear of the fuselage were cruciform fins which supported an annulus which contained a propeller. That rear installation performed the function of anti-torque and directional control. The model also mounted a retractable landing gear carriage.
In operation, the Pathfinder took off like a standard helicopter. Acceleration was then achieved by directing power from the rotor into the rear propeller, then as the speed increased, the fixed wings took on a larger share of the lift. It should also be noted that the Pathfinder could also be used in a STOL mode, which greatly increased its payload capability. The reverse transition for landing exactly reversed the take-off process.
There were actually two versions of the Pathfinder, the first of which was the -1 version, which first flew in 1962. The similar Pathfinder II, the 16H-1A, was completed in 1965.
The 37 foot long privately-developed Piasecki 16H-1 weighed 11,000 lb and had a wingspan of 20 ft. The five-seat Pathfinder I was originally powered by a 550 hp Pratt & Whitney PT6B-2 turboshaft engine. The engine powered a 41 foot fully articulated three-bladed rotor and a 5.5 ft three-bladed ducted propeller in the tail (called a "ring-tail") to provide forward thrust and directional and anti-torque control with four vertical vanes in the duct. Gross weight was 2,611 lb and fuselage length was 25 foot. The 16H-1 made its first flight on 21 February 1962. Overall, the Pathfinder I had the handling qualities of a conventional helicopter, but used its wings and pusher propeller to off-load the rotor and increase its maximum forward velocity to 148 kt. 185 flight hours were accumulated before May 1964, when Piasecki was contracted to test a high speed modification, the 16H-1A Pathfinder II. It was equipped with a 1,250 shp T58 turboshaft engine, a new drive system and propeller to handle the increased power. The rotor size was increased to 44 foot diameter, and the fuselage was stretched to accommodate eight seats. Flight testing resumed on 15 November 1965 and it accrued over 40 hours in the air by May 1966, reaching speeds of 195 kt. Later, it was redesignated the 16H-1C when the engine was upgraded to a 1,500 shp T58-GE-5. The -1A version was considerably larger than the initial prototype, with a three-foot bigger diameter rotor at 13.4m, and its maximum speed was much faster at 360km/h, compared to 287 with the first version. The gross weight of the 1A model was 1037kg heavier than the first model. The two models used different powerplants; the first used a United Aircraft of Canada PT6B engine, while the later version used a General Electric T58 turbine engine.
