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2. Bell XV-15 - Wikipedia

   en.wikipedia.org/wiki/Bell_XV-15

   The first XV-15 prototype aircraft, N702NA, was transferred back to Bell for company development and demonstration use. On 20 August 1992, the aircraft crashed while being flown by a guest test pilot. He was lifting off for a final hover when a bolt slipped out of the collective control system on one pylon, causing that rotor to go to full pitch.

3. Helicopter flight controls - Wikipedia

   en.wikipedia.org/wiki/Helicopter_flight_controls

   Helicopters with fly-by-wire systems allow a cyclic-style controller to be mounted to the side of the pilot seat. The cyclic is used to control the main rotor in order to change the helicopter's direction of movement. In a hover, the cyclic controls the movement of the helicopter forward, back, and laterally.

4. McDonnell XV-1 - Wikipedia

   en.wikipedia.org/wiki/McDonnell_XV-1

   The XV-1 began tethered hovering flight tests on 11 February 1954, with test pilot John R. Noll. The tether had lead weights intended to keep the aircraft in ground effect until issues with the rotor's tip-jet propulsion system were solved. On 14 July 1954, the lead weights were removed and the XV-1 conducted its first free hovering flight. [1]

5. BERP rotor - Wikipedia

   en.wikipedia.org/wiki/BERP_rotor

   In the case of fighters, this was a concern, especially at landing, but in the case of helicopters, this is less of an issue because the rotor tips do not slow significantly, even during landing. Such swept-tips can be seen a number of helicopter types from the 1970s and 80s, notably the UH-60 Blackhawk and the AH-64 Apache.

6. Blade-vortex interaction - Wikipedia

   en.wikipedia.org/wiki/Blade-vortex_interaction

   Helicopter blade tip vortex simulation by DLR Tip vortex rollup A blade vortex interaction ( BVI ) is an unsteady phenomenon of three-dimensional nature, which occurs when a rotor blade passes within a close proximity of the shed tip vortices from a previous blade.

7. Helicopter height–velocity diagram - Wikipedia

   en.wikipedia.org/wiki/Helicopter_height...

   The FAA states "The height–velocity diagram or H/V curve is a graph charting the safe/unsafe flight profiles relevant to a specific helicopter. As operation outside the safe area of the chart can be fatal in the event of a power or transmission failure it is sometimes referred to as the dead man's curve ."

8. Bell XV-3 - Wikipedia

   en.wikipedia.org/wiki/Bell_XV-3

   XV-3 in forward flight Bell XV-3 in a hover, 1955. This was first version with 3-blade rotors and crashed. XV-3 test, in vertical flight with 2 blade rotors. In 1951, the Army and Air Force announced the Convertible Aircraft Program and released the Request for Proposals (RFP) to solicit designs from the aircraft industry.

9. Human-powered helicopter - Wikipedia

   en.wikipedia.org/wiki/Human-powered_helicopter

   The American Helicopter Society (AHS) International's Igor I. Sikorsky Human Powered Helicopter Competition was a competition to achieve the first human-powered helicopter flight to reach an altitude of 3 m (10 ft) during a flight lasting at least 60 seconds, while remaining within a 10 m (32.8 ft) x 10 m (32.8 ft) square, and complying with other competition requirements. [1]