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Subject: V22 - Why propellers instead of jet propulsion
Miketer Binderty     11/22/2005 11:26:58 PM
Why did they design the V-22 with propellers instead of jet propulsion?
 
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flamingknives    RE:V22 - Why propellers instead of jet propulsion   6/23/2005 10:14:59 AM
Jet engines aren't very efficient in static thrust, which is required for hover and descent. Descend too fast and your engines will flame out and stop. While propellers can get caught in their own bad air and lose power, the engine will keep going, giving you a better chance of getting out of it.
 
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phrogdriver    RE:V22 - Why propellers instead of jet propulsion   1/13/2006 11:24:55 PM
Besides all the aero factors, a turbojet or turbofan would have extremely hot gases hitting the deck. Even the turboshaft engines in the V-22 are pretty hot immediately under the nacelles, and they use coanda exhaust deflectors to spread the exhaust out from the aircraft. True jet exhaust would set an LZ on fire or buckle a LHD flight deck.
 
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westwords2020    RE:V22 - Why propellers instead of jet propulsion   1/17/2006 1:44:58 PM
Stop/Fold Tiltrotor might help as it is capable of supersonic speeds with enough power. Concept has been around for years. Basically you have an engine side fuelsalage mounted that can output shaft horsepower to wingtip proprotors or produce thrust out of a standard afterburner tailpipe. The trick is to produce an engine that can switch between shaft operation and jet exhust operation. F-35B engine is hybrid in that it produces both shaft rotation to the lift fan and tailpipe exhust during STO and VL ops..SFT uses it's engine in shaft mode to takeoff short/vertically and then tilts props like MV-22 for flight at up to around 300knots in airplane mode. The engine then converts to jet thrust mode and the proprotors fold back smoothly along their nacelles for miniumum drag; nacelles contain the gearing but not the engine. The a/c then accelerates to high subsonic speed and with afterburning, supersonic speed. Such a combatant aircraft as a fighter/attack bird offers significant VTO fuel/payload which Harrier and JSF cannot match. Their specs call for only recovery of plane, fuel reserve and a few weapons, nothing in VTO like a payload/fuel to do anything worthwhile with.
 
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