Lockheed XH-51A Fastest Helicopter (300 mph)

The Lockheed XH-51A Compound Helicopter

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• CL-595

[hoserEAP]

The reality is that helicopter's support the majority of support missions and fly in a much more hostile environment, yet have received only a fraction of the funding for development when compared to the fixed-wing community.

[hoserEAP]

The root cause goes back to the military's interest in spending money to develop jet aircraft, while constantly overlooking the need to spend the money for development of rotorwing aircraft. Examples like the AV-8A Harrier show how despite poor initial performance and failure to meet expectations, the money was spend to continue development and refinement of the technology into the AV-8B, for a mission that is constantly being completed by AH-1W's because the AV-8B is so maintenance intensive.

[hoserEAP]

@benjyboba The forward thrust produced by either the Jet or prop has no effect on retreating blade stall. The lift generated by the XH-51A wings reduce the amount of pitch needed in the M/R at higher airspeeds, which in turn reduces the effect retreating blade stall.

The X-2 doesn't have any means of reducing or eliminating the effects of retreating blade stall (both rotors will still experience it) but reduce the vibrations by means of changing rotor RPM and having active vibration dampers.

[benjyboba]

@Jesusdragon737 This is pushed by a jet the other isn't. The thing i'm wondering about is the retreating blade stall effect from a single rotor, Do they reduce the power to compensate. I think the sikorski x2 helicopter managed 262 in a slight dive and that is normal powered with a fan on the back for thrust. Maybe the one you read is just a normal type helicopter as these have extra rear thrust.

[LouistheHedgehog]

That thing must be a real fuel guzzler...

[Spartan043]

If this aircraft seems a bit far ahead of its time, that's because it is. Not only do these early rigid-rotor compound helicopters often have maintenance and gearbox issues that crept out during testing, but this one has a fuel-hungry turbojet engine mounted to it, severely limiting its operational range. Helicopters like these don't enter service because no military force in the world can afford to maintain and operate them. With time and improved technology, that will change.

[Frosttty]

WTF has happened to our country? We're capable of building the most incredible tech, but where are we now? We don't have a lunar program nor a Mars program. There's a lack of affordable "green" energy. We should be miles ahead of anyone else here in the US. Not arrogance speaking, just the fact that we were so far ahead at one time.

[Jesusdragon737]

@hoserEAP Ok wow that's incredible. In the section below it has a different top speed. Strange. I wonder why this aircraft is so unheard of?

[hoserEAP]

@Jesusdragon737 ""The aircraft's first flight as a true compound helicopter took place on 10 April 1965.[3] and on 29 November 1967 achieved a speed of 263 knots (302.6 mph, 486.9 km/h).[4]""