Forum: Rotary Wing Aircraft

"The technical challenge of rotating an airplane's wings and engines in midair led to delays"

TEG,
I know the Osprey can fold itself up almost like a transformer when stowed on the flight deck, but the author was asserting that the wings rotated in midair which they don't do. The LTV XC-142 had wings that rotated in midair, maybe that was what the author was thinking of.

F-16.net Sponsor

Tiltwing is better at VTOL, Tiltrotor is better at STOL. This was considered during V-22 development.

So maybe Bell's Magellan needs some tilt-tech and therefore is being built in Amarillo?

http://www.star-telegram.com/2012/01/09 ... er-in.html

hcobb wrote:

Tiltwing is better at VTOL, Tiltrotor is better at STOL. This was considered during V-22 development.

So maybe Bell's Magellan needs some tilt-tech and therefore is being built in Amarillo?

http://www.star-telegram.com/2012/01/09 ... er-in.html

A Tilt-Wing is absolutely not better at VTOL. The primary reason is the high disc loading inherent in the design. It also is poorer in the hover and is more limited in the transition phase, which is a more complicated process. Where it is better is at the upper end of the high speed cruise, since that same high disc loading provides less drag then.

Given that ever since contract award the V-22 and its predecessor JVX have been a Tilt-Rotor (a Tilt-Rotor was the only concept that could meet the requirements), I'm not sure how Tilt-Wing was considered in V-22 development.

The new Bell 525 (Magellan) may turn out to be all new (if Textron doesn't keep siphoning off R&D money) or it may be an upgraded 412. Hope it's the former.

Some other points relative to older posts:

Like most large transport V/STOLs (i.e. helicopters), the Osprey's autorotation to a full stop characteristics are not that good. However, the ability to autorotate to a complete landing was never a requirement. The requirement was to achieve a certain level of survivability to the ground from a total engine loss through either autorotation or gliding. The V-22 team chose the latter. The V-22 can actually land with the nacelles full forward. With the blades stopped at the 12, 4 and 8 o'clock positions the blades don't impact the ground. If they are rotating, the blades are designed to break off in such a way that they are thrown away from the aircraft.

The inability to hover with one proprotor in ground effect and one out will certainly be a surprise to those crews that have done it. Of course, if your field is high enough, that would be true, but then a conventional helo also as a limit on how high it can HOGE as well. For the V-22, HOGE is 5,400 ft., according to NAVAIR. So, if you're sailing an LHD along at say, 6,000 ft., and you let one proprotor go over the side...yep, you're going to have a problem. The issue is where you run out of roll control to offset the limited difference in lift. Tandem rotor helicopters also have a differential lift issue, yet somehow they manage to survive.

The CSAR community went with conventional designs because when the specifications were announced, there would be no credit given for speed or range above conventional helo capabilities and the V-22 would clearly be more expensive. Downwash is absolutely an issue. It's worthy of note, though, that USAF picked the H-47, which is not known for gentle breeze-like conditions under it in the hover. In fact, data coming back from its use by the Brits indicate a problem on rescue missions or insertions where it's downwash is setting off IEDs and mines. Frankly, though, for CSAR, it's probably more effective and less dangerous to actually land than hover whenever possible for the rescue. V-22 is actually too big for classic CSAR, but there's no money to develop a more optimally sized bird. SAR, BTW, is one of the roles envisioned for the smaller AW-609. In fact, that's the reason its door is on the starboard, rather than port side as is more normal in civilian executive transport.

As far as a joint program to survive, originally the Marine requirement was embodied in a program called HXM. It likely would have been a Tilt-Rotor as well, but that would be because of the range required, not speed. The great speed would be a fortuitous fallout. DoD turned it inot a joint program, JVX, and that added a bunch of requirements the plane had to try and meet that made it more complex and expensive. As far as the folding wing goes, that was essential for Marine and Navy use (they still have an unfunded requirement for 48 for COD and CSAR). For USAF's requirement alone, it would cost too much to make a 2nd fixed wing version. After all, even though they didn't need it, the outer wings on all Air Force F-4s retained the outer wing folding mechanism, they just deleted the power folding motor.

The Time magazine article was, as are so many things it does, a hit piece.

USMC V-22 Crash

Does anybody know how much weight the drive-shaft and gearboxes add, and how much work is lost to them under normal conditions?
I saw someone suggest that the next generation might be electric, with turbo-shaft engines in the main body that drive generators and electrically driven rotors. I can see a number of problems that might solve, but I'm curious how the weight and efficiency trade-offs would come out.

There are pallets that can be loaded into cargo planes that let them launch Griffin missiles from their rear loading ramp. Could something like that be adapted for the V-22?

http://www.defenseindustrydaily.com/Ray ... les-07182/

Quote:

Does anybody know how much weight the drive-shaft and gearboxes add, and how much work is lost to them under normal conditions?

The drive shafts are most likely pretty lightweight as they are made of light metals like aluminum and are hollow inside.

Quote:

I saw someone suggest that the next generation might be electric, with turbo-shaft engines in the main body that drive generators and electrically driven rotors. I can see a number of problems that might solve, but I'm curious how the weight and efficiency trade-offs would come out.

That posses challenges to weight and battle damage tolerance.

Any CV-22 maintenance guys on this forum?

Would anyone in AFSOC do online forums, period?

Forum: Rotary Wing Aircraft

The V-22 Osprey