User:Born2flie/Piasecki 16H

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Main article: Piasecki 16H
Pathfinder

Piasecki 16H-1 Pathfinder
Type Experimental high-speed helicopter
Manufacturer Piasecki Aircraft
Designed by Frank Piasecki
Maiden flight February 21, 1962 (16H-1)
November 1965 (16H-1A)
Primary user United States Army
Variants Piasecki X-49

The Piasecki Aircraft 16H was a series of compound helicopters produced in the 1960s. There first version of the Pathfinder, the -1 version, first flew in 1962. The similar but larger Pathfinder II, the 16H-1A, was completed in 1965.

Contents

[edit] Development

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

Text 3

A high-speed compound helicopter built in 1965 as a private venture for research into fast rotary wing craft. After a two-year development period, the aircraft was modified at the request of the US Army and Navy and redesignated Pathfinder II.

G.Apostolo "The Illustrated Encyclopedia of Helicopters", 1984

Text 4

Having left the Piasecki Helicopter Corporation, Frank Piasecki set up Piasecki Aircraft Corporation and became involved in the Agusta 101G large transport helicopter and also embarked on research under government contracts into compound helicopters. The company built a prototype of the Pathfinder 16H-1 (N616H) which first flew on 21 February 1962. This machine had an all-metal monocoque fuselage with a small low wing, a forward-swept pylon mounting a three-bladed rotor and an annular tail duct with a pusher propeller and directional vanes. It was subsequently modified with a stretched fuselage and a 1250shp General Electric T58 turboshaft engine to become the Model 16H-1A and then to Model 16H-1C Pathfinder III configuration with a 1500shp T58-GE-5. A nine-seat development, the Model 16H-3J was not proceeded with.

R.Simpson "Airlife's Helicopter and Rotorcraft", 1998

[edit] Piasecki X-49

Text 1

Trials to start using Piasecki-modified Sikorsky H-60 helicopter planned to achieve speeds of up to 200kt.

Piasecki Aircraft is preparing its X-49 experimental compound helicopter for a first flight before the end of June.

The modified Sikorsky H-60, with wings and tail-mounted variable-thrust ducted propeller (VTDP), has been moved to Boeing's Wilmington, Delaware facility for ground and flight testing.

© Piasecki SpeedHawk has wings and tail-mounted variable-thrust ducted propeller

Dubbed the SpeedHawk by Piasecki, the X-49 is being developed with incremental funding from the US Army's Aviation Applied Technology Division to demonstrate the ability to increase the speed of existing helicopters to 200kt (360km/h).

The VTDP replaces the tail rotor and provides thrust for forward flight, while the wing unloads the rotor and allows the helicopter to fly faster.

Initially the aircraft will be flown within the SH-60's existing flight envelope, but the company then plans to install a third engine and push the helicopter to 200kt, says vice-president John Piasecki.

In forward flight most of the more than 2,100shp (1,560kW) from the two main engines will go to the VTDP, says Piasecki.

The third engine, called a secondary power unit, will replace the existing auxiliary power unit and provide another 600-700shp to the ducted propeller to push the compound helicopter to higher speed.

"This technology gives the helicopter the ability to productively use the extra power in forward flight," says Piasecki.

"Traditionally we add power to lift more, but we are at the outer edge of the envelope on the H-60, where a marginal increase in power brings a significant reduction in forward speed."

This is because the heavily loaded rotor stalls at higher speeds.

"The UH-60 is a 90kt helicopter in Afghanistan," claims Piasecki. "The power that goes into the high/hot hover cannot be used in forward flight."

While the SpeedHawk wing and tail add weight and download, "the aircraft has adequate margin in the hover to carry the payload, then can harness the power to fly at 200kt", he says.

Funding permitting, Piasecki plans about 100h of flight testing in the X-49 programme's first phase.

Funding to install the SPU and perform a nine-month drag clean-up for high-speed flight testing, which includes fitting retractable gear and a rotor-hub fairing, has yet to be secured.

[edit] Variants

Model 16H-1 Pathfinder 
one PWC PT6B-2 405 shp turboshaft engine
Model 16H-1A Pathfinder II 
larger version with one 1,250shp T58-GE-8
Model 16H-1C Pathfinder III 
proposed conversion of the 16H-1A with one 1500shp T58-GE-5 [1]
Model 16H-3J 
nine-seat development, not built.

[edit] Specifications (16H-1A)

Piasecki's 16H-1A Pathfinder II
Piasecki's 16H-1A Pathfinder II

Data from U.S. Army Aircraft Since 1947[2], Avia.Russian.ee Website[3]

General characteristics

  • Crew: 2
  • Capacity: up to six passengers
  • Length: 37 ft 3 in (11.35 m)
  • Rotor diameter: 44 ft 0 in (13.41 m
  • Wingspan: 10.0 m)
  • Height: 11 ft 4 in ()
  • Empty weight: 4,800 lb (2,165 kg)
  • Loaded weight: lb (kg)
  • Useful load: lb (kg)
  • Max takeoff weight: 10,800 lb (4,870 kg)
  • Powerplant: 1× General Electric T58-GE-8 turboshafts, 1,250 shp (930 kW)
  • Propellers: ducted propeller both, 1 per engine
    • Propeller diameter: 5 ft 6 in ()
  • *Rotor: 1 three-bladed

Performance


[edit] See also

[edit] References

Notes
  1. ^ Note: While some sources read as if this variant was completed and flown, Piasecki Aircraft's history site makes no mention of this variant at all.
  2. ^ Harding, Stephen (1997). U.S. Army Aircraft Since 1947. Atglen, PA, USA: Schiffer Publishing Ltd., 251. ISBN 96-69996. 
  3. ^ Piasecki 16H "Pathfinder". Retrieved on 2007-07-01.
Bibliography

[edit] External links

{{aviation lists}}

Category:VTOL aircraft X-49, Sikorsky Piasecki Category:Helicopters