The Sikorsky S-69 was an experimental compound co-axial helicopter developed as part of the Advancing Blade Concept (ABC) program.

Design and development

Also known by the military designation XH-59A, the S-69 was part of the Advancing Blade Concept (ABC) program. This Advancing Blade Concept system consisted of two rigid, contra-rotating rotors which made use of the aerodynamic lift of the advancing blades. At high speeds, the retreating blades were offloaded, as most of the load was supported by the advancing blades of both rotors and the penalty due to stall of the retreating blade was thus eliminated. This system did not even require a wing to be fitted for high speeds and to improve manoeuvrability, and also eliminated the need for an anti-torque rotor at the tail.

Specifications (S-69)

See also

References

External links

• Sikorsky S-69
• Global Security.org Sikorsky XH-59 page
• Sikorsky X2
• "X2 marks the spot for radical rotor designs" FlightGlobal