Tuesday, August 27, 2013

Tiltrotors Take AHS Design Prizes, X-VTOL Next

AHS International's student design competition, this year sponsored by Eurocopter, has been won by a pair of tiltrotor designs. The competition to design a disaster-rescue rotorcraft was won by the University of Maryland's HeliX variable-diameter tiltrotor in the graduate category and Pennsylvania State University's Griffin tiltrotor in the undergraduate category.
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UMD HeliX (Concept: University of Maryland)

The 280kt HeliX has several noteworthy features. The proprotor blades extend for hover and reatract for cruise using Kevlar staps wound out and in by an electric motor in the hub. The twin engines are mounted in the center fuselage, driving privoting gearboxes at the wing tips, to reduce wing weight. Aerodynamically deployed outboard wing extensions reduce cruise drag and fold down in the hover to reduce downwash. The "II-tail" design improves structural efficiency and reduces the weight of the ramp, says the UMD team.

Penn State's Griffin is distinguished by a slender, reduced-thickness composite tailored wing to reduce weight, drag and downwash. Blackburn slotted flaps  increase lift during transition and incorporate active flow control to prevent separation when fully deployed to reduce download in the hover. Outboard wing sections provide roll control and tilt with the nacelles to reduce drag and download.
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Penn State Griffin (Concept: Pennsylvania State University)

Runners up in the 2013 competition were the Sterna compound helicopter from Georgia Institute of Technology in the graduate category and the HealCopter tiltrortor from Texas A&M University in the undergradiate category, with an honorable mention for India's Kiran Ganesh and his extraordinary rotor-in-wing Kurara - inspired by the osprey (the bird, not the tiltrotor). This is a tailless M-wing configuration with gull-wing profile, embedded rotors and jet engines.

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Kurara (Concept: Kiran Ganesh)

And while on the subject of whacky, out-there concepts, AHS International's 2014 student competition (sponsored this time by AgustaWestland) is to design an experimental vertical take-off and landing aircraft meeting the same "transformational" performance requirements as DARPA's VTOL X-Plane program. These include: speed between 300kt and 400kt; hover efficiency with 25% of ideal power loading; cruise lift-to-drag ration no less than 10; and useful load fraction no less than 40% of gross weight (payload fraction no less than 12.5%). Here's the RFP - happy designing!


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