The Sikorsky S-75 was a proof-of-concept all-composite
helicopter
A helicopter is a type of rotorcraft in which lift and thrust are supplied by horizontally spinning rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forward, backward and laterally. These attributes ...
.
Sikorsky Aircraft used all-
composite material
A composite material (also called a composition material or shortened to composite, which is the common name) is a material which is produced from two or more constituent materials. These constituent materials have notably dissimilar chemical or ...
s to replace metal to provide greater strength, lighter weight, lower manufacturing costs, and reduce maintenance costs.
Design and development
The Sikorsky S-75 was developed under the
US Army's Advanced Composite Airframe Program (ACAP), the goal of which was the development of an all-composite helicopter fuselage, lighter and less costly to build than predominantly metal airframes in support of the
Light Helicopter Experimental (LHX) program.
[Historic US Army Helicopters](_blank)
In February 1981, contracts were awarded to Sikorsky and
Bell Helicopter
Bell Textron Inc. is an American aerospace manufacturer headquartered in Fort Worth, Texas. A subsidiary of Textron, Bell manufactures military rotorcraft at facilities in Fort Worth, and Amarillo, Texas, as well as commercial helicopters in M ...
, with Bell submitting its
Model D292. The S-75 flew for the first time in July 1984.
The S-75 mated an entirely new
composite
Composite or compositing may refer to:
Materials
* Composite material, a material that is made from several different substances
** Metal matrix composite, composed of metal and other parts
** Cermet, a composite of ceramic and metallic materials
...
airframe with the twin turboshaft engines, transmission, and main and tail rotors of Sikorsky's
S-76A civil transport helicopter.
[ The S-75's floors, roof and most exterior surfaces were of more ballistically-resistant ]Kevlar
Kevlar (para-aramid) is a strong, heat-resistant synthetic fiber, related to other aramids such as Nomex and Technora. Developed by Stephanie Kwolek at DuPont in 1965, the high-strength material was first used commercially in the early 1970s a ...
, while most of the aircraft's basic load-bearing structure was built of graphite
Graphite () is a crystalline form of the element carbon. It consists of stacked layers of graphene. Graphite occurs naturally and is the most stable form of carbon under standard conditions. Synthetic and natural graphite are consumed on lar ...
or a graphite/ epoxy blend. The machine was equipped with specially designed impact-resistant crew and passenger seats and high-strength pneumatic shock absorbers on its fixed tricycle landing gear, in keeping with the Army's requirement that the ACAP aircraft meet or exceed all existing military crashworthiness
Crashworthiness is the ability of a structure to protect its occupants during an impact. This is commonly tested when investigating the safety of aircraft and vehicles. Depending on the nature of the impact and the vehicle involved, different crit ...
standards. The aircraft was flown by two pilots, and could carry up to six passengers in the rear cabin.
Operational history
The S-75 underwent a 50-hour evaluation by the Army, and was found to have exceeded the weight- and cost-saving criteria set in the original ACAP specification.[ Sikorsky gained a wealth of data on the fabrication and use of composite airframes through building the S-75, and Sikorsky's later designs incorporated many of its features. Testing of the machine continued through April 1985, after which it was withdrawn from service and placed in long-term storage.
]
Specifications (S-75)
See also
References
External links
''The Sikorsky Legacy'' S-75 Advanced Composite Airframe Program
{{Sikorsky Aircraft
S-075
1980s United States helicopters
1980s United States experimental aircraft
Twin-turbine helicopters
Aircraft first flown in 1984