Sikorsky S-67 Blackhawk
Encyclopedia
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.
The Army awarded Lockheed and Sikorsky with contracts for further study on 19 February 1965. On 3 November 1965, the Army announced Lockheed as the winner of the AAFSS program selection. The Army perceived Lockheed's design as less expensive, able to be available earlier, and that it would have less technical risk than Sikorsky's Rotorprop.
The S-67 featured a five-bladed main rotor
and tail rotor
. The main rotor was taken from the 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 causes variations in tip track at high Mach numbers. These allowed the S-67 to achieve and maintain high cruise speeds. To reduce drag at high speed, the main wheels retracted fully into the stub wing sponsons. It had speed brakes on the wing trailing edges that could be used to decrease speed or increase maneuverability.
The S-67 was fitted with a moving map display, a hands-on-collective radio tune control, and night vision systems. Its armament included a Tactical Armament Turret
(TAT-140) with a 30 millimetres (1.2 in) cannon, and could carry 16 TOW missiles
, 2.75 inches (69.9 mm) rockets, or AIM-9 Sidewinder
air-to-air missile
s. The Blackhawk was powered by two General Electric
T58-GE-5
1500 shp engines.
"King Cobra", was put through a series of flight test evaluations in 1972 by the U.S. Army
. Neither aircraft was selected to replace the AH-56 Cheyenne. Instead, the Army chose to create the new Advanced Attack Helicopter
program, which would lead to 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 14 December 1970 by flying at 348.97 km/h (216.8 mph) over a 3 km (1.9 mi) course, and 355.48 km/h (220.9 mph) on 15 to 25 km (9.3 to 15.5 mi) course on 19 December 1970. These records stood for 8 years.
As part of internal Sikorsky R&D efforts, in 1974 the S-67 had a 3.5 feet (1.1 m) diameter ducted fan
fitted instead of its original conventional tail rotor. The S-67 with fan was tested over 29 flight hours to compare to the conventional tail. In this configuration it reached a speed of 230 mph (370.1 km/h) in a test dive. The original tail rotor and vertical tail fin were re-installed in August 1974.
, the nose dropped below the horizon resulting in a momentary descent which eliminated the altitude safety margin for a safe completion of the maneuver. The aircraft struck the ground in a level attitude and immediately burst into flame. Sikorsky test pilot Stu Craig died on impact, and test pilot Kurt Cannon died nine days later from his injuries. Development work on the S-67 ceased after this accident.
The United States Army assigned the name Black Hawk to the Sikorsky UH-60 Black Hawk
helicopter.
Sikorsky Aircraft
The Sikorsky Aircraft Corporation is an American aircraft manufacturer based in Stratford, Connecticut. Its parent company is United Technologies Corporation.-History:...
S-67 Blackhawk was a private-venture, prototype attack helicopter
Attack helicopter
An attack helicopter is a military helicopter with the primary role of an attack aircraft, with the capability of engaging targets on the ground, such as enemy infantry and armored vehicles...
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
Sikorsky S-61
The Sikorsky S-61L and S-61N are civil variants of the successful SH-3 Sea King helicopter. They are two of the most widely used airliner and oil rig support helicopters built.-Design and development:...
, it was designed to serve as an attack helicopter or to transport up to 8 troops into combat.
AAFSS and S-66 bid
The US Army issued a request for proposals (RFP) for its Advanced Aerial Fire Support System (AAFSS) program on 1 August 1964. Lockheed offered its CL-840 design, a rigid-rotor compound helicopter. Sikorsky submitted the S-66, which featured a "Rotorprop" serving as a tail rotor but as speeds increased would rotate 90° to act as pusher prop. The S-66 had short, fixed wings and was powered by a 3400 shp Lycoming T55 turboshaft engine. The design was to have a speed of 200 knots (392 km/h) with the ability for 250 knots (490 km/h) for brief periods.The Army awarded Lockheed and Sikorsky with contracts for further study on 19 February 1965. On 3 November 1965, the Army announced Lockheed as the winner of the AAFSS program selection. The Army perceived Lockheed's design as less expensive, able to be available earlier, and that it would have less technical risk than Sikorsky's Rotorprop.
S-67 development
When the Armed Aerial Fire Support System program was delayed, Sikorsky offered an armed SH-3 Sea King (Sikorsky S-61) version initially. After further AAFSS problems, the company developed an intermediate, high-speed, attack aircraft named the Sikorsky S-67 Blackhawk in 1970. Design work on the S-67 began in November 1969 with manufacturing following in February 1970. The Blackhawk first flew on 20 August 1970.The S-67 featured a five-bladed main rotor
Helicopter rotor
A helicopter main rotor or rotor system is a type of fan that is used to generate both the aerodynamic lift force that supports the weight of the helicopter, and thrust which counteracts aerodynamic drag in forward flight...
and tail rotor
Tail rotor
The tail rotor, or anti-torque rotor, is a smaller rotor mounted so that it rotates vertically or near-vertically at the end of the tail of a traditional single-rotor helicopter. The tail rotor's position and distance from the center of gravity allow it to develop thrust in the same direction as...
. The main rotor was taken from the 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 causes variations in tip track at high Mach numbers. These allowed the S-67 to achieve and maintain high cruise speeds. To reduce drag at high speed, the main wheels retracted fully into the stub wing sponsons. It had speed brakes on the wing trailing edges that could be used to decrease speed or increase maneuverability.
The S-67 was fitted with a moving map display, a hands-on-collective radio tune control, and night vision systems. Its armament included a Tactical Armament Turret
U.S. Helicopter Armament Subsystems
The United States military has developed a number of Helicopter Armament Subsystems since the early 1960s. These systems are used for offensive and defensive purposes and make use of a wide variety of weapon types including, but not limited to machine guns, grenade launchers, autocannon, and rockets...
(TAT-140) with a 30 millimetres (1.2 in) cannon, and could carry 16 TOW missiles
BGM-71 TOW
The BGM-71 TOW is an anti-tank missile. "BGM" is a weapon classification that stands for "Multiple Environment , Surface-Attack , Missile ". "TOW" is an acronym that stands for "Tube-launched, Optically-tracked, Wire command data link, guided missile"...
, 2.75 inches (69.9 mm) rockets, or AIM-9 Sidewinder
AIM-9 Sidewinder
The AIM-9 Sidewinder is a heat-seeking, short-range, air-to-air missile carried mostly by fighter aircraft and recently, certain gunship helicopters. The missile entered service with United States Air Force in the early 1950s, and variants and upgrades remain in active service with many air forces...
air-to-air missile
Air-to-air missile
An air-to-air missile is a missile fired from an aircraft for the purpose of destroying another aircraft. AAMs are typically powered by one or more rocket motors, usually solid fuelled but sometimes liquid fuelled...
s. The Blackhawk was powered by two General Electric
General Electric
General Electric Company , or GE, is an American multinational conglomerate corporation incorporated in Schenectady, New York and headquartered in Fairfield, Connecticut, United States...
T58-GE-5
General Electric T58
|-See also:-References:* and...
1500 shp engines.
Evaluation and records
The S-67 Blackhawk, along with the Bell 309Bell 309
|-See also:-References:* Verier, Mike. Bell AH-1 Cobra. Osprey Publishing, 1990. ISBN 0-85045-934-6.-External links:*...
"King Cobra", was put through a series of flight test evaluations in 1972 by the U.S. Army
United States Army
The United States Army is the main branch of the United States Armed Forces responsible for land-based military operations. It is the largest and oldest established branch of the U.S. military, and is one of seven U.S. uniformed services...
. Neither aircraft was selected to replace the AH-56 Cheyenne. Instead, the Army chose to create the new Advanced Attack Helicopter
Advanced Attack Helicopter
The Advanced Attack Helicopter was a United States Army program to develop an advanced ground attack helicopter beginning in 1972. The Advanced Attack Helicopter program followed cancellation of the Lockheed AH-56 Cheyenne. After evaluating industry proposals, the AAH competition was reduced to...
program, which would lead to 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 14 December 1970 by flying at 348.97 km/h (216.8 mph) over a 3 km (1.9 mi) course, and 355.48 km/h (220.9 mph) on 15 to 25 km (9.3 to 15.5 mi) course on 19 December 1970. These records stood for 8 years.
As part of internal Sikorsky R&D efforts, in 1974 the S-67 had a 3.5 feet (1.1 m) diameter ducted fan
Fenestron
A Fenestron is a shrouded tail rotor of a helicopter that is essentially a ducted fan. The housing is integral with the tail skin, and, like the conventional tail rotor it replaces, is intended to counteract the torque of the main rotor...
fitted instead of its original conventional tail rotor. The S-67 with fan was tested over 29 flight hours to compare to the conventional tail. In this configuration it reached a speed of 230 mph (370.1 km/h) in a test dive. The original tail rotor and vertical tail fin were re-installed in August 1974.
Fatal crash and afterwards
The lone S-67 prototype crashed while conducting a low-level aerobatic demonstration at the Farnborough Airshow in September 1974. During a low-level roll maneuverBarrel roll
A barrel roll is an aerial maneuver in which an airplane makes a complete rotation on its longitudinal axis while following a helical path, approximately maintaining its original direction. It is sometimes described as "a combination of a loop and a roll"...
, the nose dropped below the horizon resulting in a momentary descent which eliminated the altitude safety margin for a safe completion of the maneuver. The aircraft struck the ground in a level attitude and immediately burst into flame. Sikorsky test pilot Stu Craig died on impact, and test pilot Kurt Cannon died nine days later from his injuries. Development work on the S-67 ceased after this accident.
The United States Army assigned the name Black Hawk to the Sikorsky UH-60 Black Hawk
Sikorsky UH-60 Black Hawk
The UH-60 Black Hawk is a four-bladed, twin-engine, medium-lift utility helicopter manufactured by Sikorsky Aircraft. Sikorsky submitted the S-70 design for the United States Army's Utility Tactical Transport Aircraft System competition in 1972...
helicopter.