User:Born2flie/Piasecki 16H

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The Piasecki Aircraft 16H was a series of compound helicopters developed by Piasecki Aircraft Corporation in the 1960s. The 16H-1 Pathfinder, first flown on 21 February 1962, was the world's second, single rotor compound helicopter. The larger 16H-1A Pathfinder II was completed in 1965, in response to a research contract for the United States Army, and first flown on 15 November 1965.

Development
After leaving Piasecki Helicopter, Frank Piasecki established the Piasecki Aircraft Corporation. He guided the new company into research of compound helicopter technology, believing that such aircraft would be beneficial for short-haul air operations. Piasecki built a prototype of a compound helicopter, as a privately-funded venture, known as the 16H-1 Pathfinder (registration number N616H), which first flew on 21 February 1962.

In 1965, the Army's Technical Research Command (TRECOM) issued a contract to Piasecki to assess the technical capabilities of the Pathfinder design. To assess the ability of the aircraft to meet the Army's requirements, Piasecki lengthened the fuselage and installed a 1,250 shp (1250 hp) General Electric T58 turboshaft engine. The company designated the modified aircraft as the 16H-1A Pathfinder II.

<!--The Pathfinder achieved first flight on February 21, 1962. This flight, along with the first few subsequent flights, was made with the cockpit and cabin unenclosed, the wings unfitted, and the landing gear in the down position. By early fall of the same year, flight tests had progressed enough to allow the cabin enclosure and wings to be fitted for testing at higher speeds. During testing, the Pathfinder attained a total of 185 flight hours and a top speed of 170 mph. The success in flight testing attracted the interests of the military, giving rise to a joint Army/Navy program to jointly fund flight demonstrations of a modified 16H-1 as part of an ongoing study of advanced high-speed rotorcraft technology. The jointly-funded program began in May 1964 with the goal of gathering information on the characteristics of a compound helicopter flying at speeds greater than 225 mph. In order to achieve this, Piasecki funded several modifications to the Pathfinder. The engine was replaced with the much more powerful 1,250 shp General Electric T58-GE-8 shaft-turbine engine, a new drive system and propeller were installed to absorb the increased power, and a larger 44 ft diameter main rotor was fitted, the same as that used on the Vertol H-21 Shawnee/Workhorse helicopter. In addition, the fuselage was lengthened, allowing accommodation for eight people. These extensive modifications warranted a new designation and a new name, resulting in the 16H-1A Pathfinder II.

Army/Navy-funded ground tests of the Pathfinder II began in early May 1965 and the first tethered hover took place on November 13 that year. Two days later, the first free-flight occurred on November 15, 1965. By April 1966, the Pathfinder II had logged more than 40 flight hours under the Army/Navy contract and attained speeds up to 225 mph while demonstrating a high degree of maneuverability. Backwards and sideways flight had also been explored with speeds as high as 32 and 35 mph respectively. As the Pathfinder II entered the final stages of its flight test program in the Summer of 1966, new air intake ducts were fitted for improved efficiency and the powerplant was replaced with a still larger 1,500 shp General Electric T58-GE-5 turboshaft engine. Although the aircraft retained the name Pathfinder II, the company changed the aircraft designation to 16H-1C.

At the conclusion of the program later that same year, the Army and Navy had collected a vast amount of research data in the field of compound helicopters, much of which was used in the development and testing of other research aircraft and remains as a useful resource for future efforts. A more advanced commercial variant of the aircraft, tentatively called the Pathfinder III, was planned, but emerging interests within the military took precedence over further commercial development. Today, the Pathfinder II remains in storage with Piasecki for future use in high-speed compound helicopter research, which continues as an active program to this day. --> Robb, Raymond L. "Hybrid helicopters: Compounding the quest for speed", Vertiflite. Summer 2006. American Helicopter Society.

Design
The five-seat aircraft featured a monocoque fuselage with a small, low wing, a fully-articulated three-bladed main rotor and an annular tail duct, called a Ring-Tail, which housed a three-bladed pusher propeller and directional vanes. The Ring-Tail provided thrust, yaw, and anti-torque control by vectoring the thrust of the ducted propeller through four vertical vanes

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Text 1
Beginning in early 1964 the Army and Navy jointly funded modifications to Piasecki Aircraft's Model 16H-1 Pathfinder compound research helicopter as part of an ongoing study of advanced high-speed rotorcraft technology. The 16H-1 had originally been developed as a company private venture and, as such, had first flown in February 1962. The modified version, designated the 16H-1A Pathfinder II by Piasecki, made its first tethered test ascents in October 1965.

Like its predecessor, the Pathfinder II was a high-speed compound rotorcraft which utilized a conventional fully articulated, three-bladed main rotor for vertical lift and a tail-mounted, dueled 'ringtail' pusher propeller for directional and anti-torque control. After takeoff, power was applied to the pusher propeller for forward propulsion, and in cruising flight the craft's small wings helped off-load the rotor and increase forward speeds.

The Pathfinder II differed from the earlier 16H-1 primarily in having a more powerful General Electric T58 shaft turbine engine, a longer and more streamlined fuselage with increased cabin accommodation, a larger main rotor, increased-span stub wings, strengthened main landing gear, redesigned engine air intakes, and upgraded electronics.

The Pathfinder II made its first free flight in November 1965, and quickly proved itself to be an extraordinarily fast and manoeuvrable machine. Forward speeds in excess of 360kph were not uncommon, and the 16H-1A was capable of flying backwards and sideways at speeds of up to 55kph. The evaluation programme provided a wealth of valuable information on compound rotorcraft technology and operations, much of which was later used in the development and testing of the AH-56 Cheyenne. Joint Army-Navy sponsorship of the 16H-1A ended in late 1966, at which time the craft was returned to Piasecki for further company-funded research.

S.Harding "U.S.Army Aircraft since 1947", 1990

Text 2
The Pathfinder was an interesting Compound Helicopter concept that was carried out during the 1960s by Piasecki Aircraft. Although the project never reached fruition, the concept did show promise during its flight test program. 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 -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.

S.Markman & B.Holder "Straight Up: A History of Vertical Flight", 2000 -->

Variants

 * Model 16H-1 Pathfinder : one Pratt & Whitney Canada PT6B-2 turboshaft engine; 405 shp (302 kW)
 * Model 16H-1A Pathfinder II : lengthened to accomodate eight personnel (two crew + six passengers) and upgraded engine to 1,250 shp (930 kW) General Electric T58-GE-8
 * Model 16H-1C Pathfinder III : upgraded engine to 1,500 shp (1,100 kW) T58-GE-5
 * Model 16H-3J : planned commercial design capable of carrying nine passengers.