My biggest problem with Time's crap cover story on the V-22 is that it gives reasoned criticism of the Bell-Boeing tiltrotor a bad name.
To best view the V-22's shortcomings as a hybrid helicopter-airplane, it helps to look at an aircraft design that may do vertical and short takeoff and landing manuevers better.
Thankfully, Boeing received a patent on September 11 that proposes such a design. Behold:
This is a single-engine vertical takeoff and landing aircraft that uses split-torque face gears to drive three lift fans for vertical lift and two pusher propellers for forward thrust. Gone is the cumbersone complexity of the V-22's tilting wings and two engines.
The key new technology proposed in the patent is the split-torque face gear, which comes from Boeing's recent upgrades of the AH-64 Apache helicopter. As my colleague The Woracle explained to me, this device allows the engine to drive the fan and the pusher-prop simultaneously. The trick will be to figure out how to manage the power loads going to either the fan or the prop. Here's how it looks:
And this is a drawing of the complete system:
on October 4, 2007 9:25 PM | Reply
Wow, that is ugly.
I don't care how it looks...can it auto-rotate?
on October 5, 2007 3:54 PM | Reply
No. That's direct thrust, not lift. That means you glide on whatever fixed wings you have, not autorotate.
IANAE, but I don't see how you transition shaft power from fan to prop with this getup. There are also the usual issues (debris, brownout, etc.) with fan vs. rotor. That said, the overarching concept is definitely something that we need; vertical mechanized envelopment is a big deal.
Really stupid non-engineer idea. Use a large, hollow, composite rotor up top, and a high-bypass turbofan on each side that can divert thrust into the rotor head and out through the rotor tips. No transmission, and in level flight the diversion is turned off, allowing the rotor to spin freely, generating some small lift without entering dangerous tip speeds.
I assume there's a reason why that won't work; but I don't know enough engineers to find out why.
on October 5, 2007 5:39 PM | Reply
Ha. Nice try.
Look up Sikorsky X2 technology. Theres a reasonsable answer to high(er) speed VTOL craft.
All I think of when I look at that layout is - parasitic driveline loss.
on October 5, 2007 6:22 PM | Reply
It will be very interesting to follow the development of this concept with strong potential military AND commercial potential. No doubt the $millions will come from Boeing and not from NASA and other US Quangos. Where did Boeing get the plastic weaving technology for the 787 fuselage & why,therefore, can they so confidently sell so many to a normally conservative, from the passenger safety perspective, aircraft buying industry. Could there be a 'stealth' connection? Surely not.
on October 6, 2007 7:46 AM | Reply
Looks like a high priced, high maintenance UAV to me. They might have designed the V-22 this way if didn't have payload and pilots to accommodate.
And absent any stealth.
on October 7, 2007 9:35 PM | Reply
Yes, I am very aware of X-2, and have been following the old Advancing Blade Concept for several years now. However, ABC in general is aimed at a helicopter that can lift and cruise more like an airplane, not an airplane that can do VTOL. The cargo/range/speed just don't compare to, say, a C-130.
That said, some of the X-2 designs look like "the best we've got" right now, and at least they're clearly enough helicopters that the AF would have a hard time shooting them down under Key West.
on October 8, 2007 7:00 PM | Reply
Sorry Big D, my comment wasnt targeted towards yours (apparent delay between comment posting and approval) but towards boeing's concept.
on February 12, 2008 10:00 AM | Reply
Big D's suggestion of hollow rotor and high bypass turboprops reminds me of the Fairey Rotodyne of the 1950s. It needed tip-jets for best performane, which were judged too noisy, but with 2 RR Tynes and a fairly capacious fuselage it was a concept which could have been further developed if the "city centre-to-city-centre" idea hadn't been felt to be a step too far for civil aviation at the time ...
What goes around comes around?