V-22 Osprey Tiltrotor

Wikipedia:  The Osprey is the world's first production tiltrotor aircraft, with one three-bladed proprotor, turboprop engine, and transmission nacelle mounted on each wingtip. It is classified as a powered lift aircraft by the Federal Aviation Administration.  For takeoff and landing, it typically operates as a helicopter with the nacelles vertical and rotors horizontal. Once airborne, the nacelles rotate forward 90° in as little as 12 seconds for horizontal flight, converting the V-22 to a more fuel-efficient, higher-speed turboprop airplane. STOL rolling-takeoff and landing capability is achieved by having the nacelles tilted forward up to 45°. For compact storage and transport, the V-22's wing rotates to align, front-to-back, with the fuselage. The proprotors can also fold in a sequence taking 90 seconds.  Composite materials make up 43% of the V-22's airframe. The proprotors blades also use composites.

The V-22's development process has been long and controversial, partly due to its large cost increases. The V-22's development budget was first planned for $2.5 billion in 1986, then increased to a projected $30 billion in 1988.  As of 2008, $27 billion have been spent on the Osprey program and another $27.2 billion will be required to complete planned production numbers by the end of the program.

The aircraft is incapable of autorotation, and is therefore unable to land safely in helicopter mode if both engines fail. A director of the Pentagon's testing office in 2005 said that if the Osprey loses power while flying like a helicopter below 1,600 feet (490 m), emergency landings "are not likely to be survivable". But Captain Justin (Moon) McKinney, a V-22 pilot, says there is an alternative, "We can turn it into a plane and glide it down, just like a C-130".  A complete loss of power would require the failure of both engines, as one engine can power both proprotors via interconnected drive shafts.  While vortex ring state (VRS) contributed to a deadly V-22 accident, the aircraft is less susceptible to the condition than conventional helicopters based on flight testing.  But a GAO report stated the V-22 to be "less forgiving than conventional helicopters" during this phenomenon.  In addition, several test flights to explore the V-22's VRS characteristics in greater detail were canceled.  The Marines now train new pilots in the recognition of and recovery from VRS and have instituted operational envelope limits and instrumentation to help pilots avoid VRS conditions.

With the first combat deployment of the MV-22 in October 2007, Time Magazine ran an article condemning the aircraft as unsafe, overpriced, and completely inadequate.  The Marine Corps, responded with the assertion that much of the article's data were dated, obsolete, inaccurate, and reflected expectations that ran too high for any new field of aircraft.

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