Sikorsky S-67

infobox Aircraft
name = S-67 Blackhawk
type = Attack/assault helicopter
manufacturer = Sikorsky



caption = S-67 Blackhawk in 1972, flown by Sikorsky Test Pilots Kurt Cannon (rear seat) and Byron Graham (front seat).
designer =
first flight =
introduced = 1970
retired =
status = Destroyed (1974 crash)
primary user =
more users =
produced =
number built = 1
unit cost =
developed from = S-61
variants with their own articles =

The Sikorsky S-67 Blackhawk was a private-venture, prototype attack helicopter built in 1970 with Sikorsky Aircraft R&D funds. A tandem, two-seat aircraft designed around the dynamic drive and rotor systems of the Sikorsky S-61, it was designed to serve as an attack helicopter or to transport up to 8 troops into combat.

Development

Following the cancellation of the Armed Aerial Fire Support System program and prior to the Advanced Attack Helicopter program, Sikorsky offered an intermediate high-speed attack aircraft based on dynamic components of the S-61 (which evolved into the Sea King helicopter).cite book|last=Apostolo, G.|year=1984|title=The illustrated encyclopedia of helicopters|location=New York|publisher=Bonanza Books]

The result was the Sikorsky S-67 Blackhawk, which featured a five-bladed main rotor and tail rotor. The main rotor was taken from the Sikorsky S-61, but was modified to have a hub fairing, swept main rotor blade tips and a special "alpha-1" linkage which was added to the main rotor controls to increase collective pitch sensitivity and so extend the collective pitch range. The 20° swept main rotor blade tips help to overcome a phenomenon called sub-multiple oscillating track (SMOT) that that cause variations in tip track at high Mach numbers. [Leoni, Ray (2007) "Black Hawk: The Story of a World Class Helicopter", AIAA, p. 70.] [ [http://www.freepatentsonline.com/3721507.pdf US Patent: Blade for High Speed Helicopter] ] These allowed the S-67 to achieve and maintain very high cruise speeds. To reduce drag at high speed, the main wheels were made fully retractable. It had speed brakes on the wing trailing edges that deployed as commanded by the pilot, or automatically at a set airspeed to improve dive speed control and reduce pilot targeting workload during firing runs.

The S-67 was fitted with a moving map display, a hands-on-collective radio tune control, night vision systems, a Tactical Armament Turret (TAT-140) with a 20 mm cannon, 16 130 mm TOWs, and 2.75 inch rockets or Sidewinder air-to-air missiles. The Blackhawk was powered by two General Electric T58-GE-5 1500 shp engines.

Operational history

The S-67 Blackhawk, along with a specially modified Bell 309 "King Cobra", was put through a series of flight test evaluations in 1972 by the Army. Neither aircraft was selected to replace the AH-56 Cheyenne. Instead, the Army chose to create a new program to select an attack helicopter, which would become the AH-64 Apache several years later.

The S-67 performed a series of aerobatic maneuvers during its various marketing tours, including rolls, split-s, and loops. The S-67 was reputed to be very smooth and responsive, in spite of its size and speed.

Piloted by Sikorsky Test Pilots Kurt Cannon and Byron Graham, the S-67 established two E-1 class world speed records on December 14, 1970 by flying at 216.84 mph (188.4 knots) over a 1.86 mile (3 km) course, [cite web|url=http://records.fai.org/documents.asp?from=rotorcraft&id=9962|title=Speed over a straight 3 km course at restricted altitude : 348.97 km/h|publisher=Fédération Aéronautique Internationale|accessdate=2007-08-05] and 220.85 mph (191.9 knots) on a 15/25 kilometer course on 19 December, 1970. [cite web|url=http://records.fai.org/documents.asp?from=rotorcraft&id=9965|title=Speed over a straight 15/25 km course : 355.48 km/h|publisher=Fédération Aéronautique Internationale|accessdate=2007-08-05] These records stood for 8 years. As part of internal Sikorsky R&D efforts, in 1974 the S-67 Blackhawk had a 3.5 foot diameter fan-in-fin fitted instead of its original conventional tail rotor. In this configuration it reached a speed of 230 mph (199.9 knots) in a test dive. The original tail rotor and vertical tail fin were re-installed in August 1974.

Fatal crash

The lone S-67 prototype crashed while conducting a low-level aerobatic demonstration at the Farnborough Airshow in September 1974, killing Sikorsky test pilots Kurt Cannon and Stu Craig. [http://www.aaib.dft.gov.uk/publications/formal_reports/1_1976__n671sa.cfm "1/1976 Sikorsky S-67 Blackhawk, N671SA, Report on the accident at Farnborough, Hampshire"] , UK Air Accidents Investigation Branch, September 1974.]

Development on the S-67 ceased after this accident.cite book|last=Donald|first=David|year=1998|title=The Complete Encyclopedia of World Aircraft|location=New York|publisher=Barnes & Noble Books]

Legacy

The aft fuselage and vertical tail design of the S-67 was used as a basis for the Sikorsky S-72 Rotor Systems Research Aircraft (RSRA), which later became the test bed for the X-Wing Stopped Rotor Program.Fact|date=August 2007

In 1976, Sikorsky Aircraft lifted the trademark on the name "Blackhawk" and allowed the US Army to assign that name to the UH-60 Black Hawk Utility Tactical Transport System (UTTAS).Fact|date=August 2007

Specifications (S-67 Blackhawk)

aircraft specifications

plane or copter?=copter
jet or prop?=prop

ref=

crew= 2
capacity= 8 troops
payload main= 8,000 lb
payload alt=
length main= 74.15 ft
length alt= 22.6 m
span main= 62 ft
span alt= 18.9 m
height main= 5.0 m
height alt=
area main=
area alt=
airfoil=
empty weight main=12,524 lb
empty weight alt=5681 kg
loaded weight main=
loaded weight alt=
useful load main=
useful load alt=
max takeoff weight main=24,272 lb
max takeoff weight alt=11,010 kg
more general=

engine (prop)= T58-GE-5
type of prop= turboshaft engine
number of props= 2
power main= 1500 shp
power alt=
power original=

max speed main=
max speed alt=
cruise speed main=
cruise speed alt=
stall speed main=
stall speed alt=
never exceed speed main=
never exceed speed alt=
range main=
range alt=
ceiling main= 17,000 ft
ceiling alt=
climb rate main=
climb rate alt=
loading main=
loading alt=
thrust/weight=
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armament=
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ee also

aircontent
related=
* SH-3 Sea King

similar aircraft=
* Bell 309
* AH-56 Cheyenne
* AH-64 Apache
* Mil Mi-24

see also=

lists=
* List of helicopters

References

* Derived from text at [http://tri.army.mil/LC/CS/csa/aahist3.htm#hist3 Historic U.S. Army Helicopters - Modern era helicopters]

External links

* [http://www.aviastar.org/helicopters_eng/sik_s-67.php Sikorsky S-67 page on aviastar.org]
* [http://www.helis.com/70s/h_s67.php Sikorsky S-67, First Blackhawk on helis.com]
* [http://www.liveleak.com/view?i=7c1_1178647292 Early 1970s industry commercial for the S-67] Copyvio link