An Evaluation of the V22 Tiltrotor Aircraft With Variable Diameter Propeller Blades

摘要

At the request of the Defense AdvancedrnResearch Projects Agency (DARPA), thernSystems Analysis Branch at the NASArnAmes Research Center is conducting arnstudy to evaluate the mission potential ofrnthe V22 aircraft modified to have a variablerndiameter rotor blade system. The variablerndiameter tiltrotor (VDTR) is not a newrnconcept, and in this case, it is beingrnevaluated specifically for the Marine Corpsrnland assault mission.rnThree different variations of the mission arernbeing evaluated: (1) A VDTR V22 aircraftrnwith an increased rotor diameter for verticalrntakeoff (VTO) and hover; (2) A VDTRrnV22 aircraft with a short takeoff (STO) andrnclimb replacing vertical takeoff andrnconversion at the beginning of the mission;rn(3) A VDTR V22 aircraft with a shortrntakeoff and climb replacing vertical takeoffrnand conversion at both the beginning of thernmission and at the mission mid-point. The optimum rotor diameter is largest forrnmission (1) and somewhat less for missionsrn(2) and (3). All three missions benefit fromrna rotor diameter larger than that of thernbaseline V22. A larger rotor diameterrnpermits a higher gross weight at liftoff,rnwhich translates to increased missionrnradius. Constraints in maximum allowablernaircraft gross weight, maximum allowablernfuel weight, and maximum allowablernengine shaft horsepower are applied in allrncases.rnIt has been determined that the VDTR V22rnaircraft design with all VTO has a distinctrnpay off in increasing the mission radiusrncapability of the V22 aircraft operatingrnwith all VTO. The latter two VDTR V22rndesigns, which have partial or completernSTO replaceing VTO, also show an increasernin mission radius over the baseline V22rnoperating in these STO modes. However,rnthe improvement is slight.