Gearbox Fail Procedure for Osprey

[Yellow & Blue Baron]

Does anyone know whether the Osprey can sustain flight (and I certain the answer is no) in the event that one rotor stops through gearbox failure etc.

Also, what is the know single engine performance for this a/c?

http://cdn.wn.com/ph/img/07/06/c8a963e6a639503f16d0794fa482-grande.jpg

YBB

http://t0.gstatic.com/images?q=tbn:gMYIy_S3iLv1AM:http://media.expedia.com/media/content/expaus/flags-of-the-world/sweden-flag-small.gif (http://media.expedia.com/media/content/expaus/flags-of-the-world/sweden-flag-small.gif)

[Hell Man]

Where have you been Yellow?

The standard procedure for a rotor unit failure on the V22 is to place your head between you legs and kiss your a** goodbye!

HM

http://t0.gstatic.com/images?q=tbn:GGwQrBZbKaE2OM:http://thetroublemakertimes.files.wordpress.com/2009/03/bald_eagle_flag_small.jpg (http://thetroublemakertimes.files.wordpress.com/2009/03/bald_eagle_flag_small.jpg)



ps: Stop being so patriotic with your Swedish flags and sh*t! ;)

[ShyTorque]

The other one flies you straight to the scene of the accident.....

[SASless]

Darn....but that is a hard question to answer.....one rotor stopped due to a cast iron failure? Uh.....no problem mate! The fuel consumption would be reduced as the engines would only have to produce half the power but I think the specific range would take a beating.

Granted that is exactly the same result most helicopters have when they suffer a MGB failure!

One good thing is the aircraft would have one hell of a fuel reserve upon landing.....caused by a sudden increase in airspeed resulting in a reduced amount of time required to arrive at the landing destination.

[FH1100 Pilot]

YBB, you'll get nothing but flippant answers to your questions because the V-22 has been discussed to death in many other threads in this forum. The information you seek has been covered so thoroughly by the "regulars" that they sometimes forget that new people sometimes do actually come to places like this and moreover, those new people may not be as "up" on all the technical details of every rotorcraft ever made.

To answer your first question, you are correct, if one gearbox is compromised for any reason, it would result in a catastrophic accident. The V-22 is incapable of flying on one proprotor.

However! Your question does call to mind an interesting scenario. Suppose the V-22 was in high-speeed forward flight. If one gearbox did fail, could the pilots feather the proprotor on the good side (as any mediocre King Air pilot could do) and continue to a landing in airplane mode? The answer is probably moot. There is no such thing as a "simple" gearbox seizure/failure. Such an event would probably have a bunch of other things happening at the same time that would cause the aircraft to come apart rather dramatically. As far as I know, there is no way to uncouple the proprotors from each other.

Your second question about single-engine capability is more difficult to answer, because a lot depends on the aircraft's all-up weight at the time and the altitude at which it is operating. Are we talking about hover performance or forward flight? Like I say, it depends.

My beloved BO105 Bolkow could sure lift a lot of crap. But it did not have "fly away" capability on one engine until a certain airspeed was achieved. And even then, in cruise flight at sea level, if the day was hot and I was particularly heavy, all I could count on was a gradual descent - no ability to maintain altitude.

[Airmotive]

I would imagine it would be the same as a main rotor coming to a screaching halt on any other twin rotor helicopter. Fugly.

[The Sultan]

Airmotive

You left out what happens to any single main rotored helicopter when the gearbox seizes. Same result as demonatrated in the North Sea last year.

With the Osprey loss of the connecting shaft is a minor issue where on a tandem rotor like the Chinook it is instantly catastrophic.

The Sultan

[Yellow & Blue Baron]

FH100, thank you.

The scenario you pose is interesting. With the disc area of the second proprotor comes increased vulnerability and one wonders about the V22s surviveability in a combat situations. I wonder how quickly it can transit from hover to 200kts?

I found The Sultans comments interesting re: Chinook coupling. It seems that on both the Chinook and V22 all drives, couplings and gearboxes play a more critical role than in a standard twin engine helicopter configuration - in fact, if the integrity of any of these is compromised ... that you would be in serious difficulty?

[mckpave]

Yellow and Blue, PM sent

[sycamore]

Anyone got a transmission diagram ?

[Yellow & Blue Baron]

Sycamore, this is what I can find for now:

http://media.defenseindustrydaily.com/images/AIR_V-22_Cutaway_lg.jpg

YBB

[sycamore]

YBB,thanks,but the devil would be in the details; like, there must/should be `freewheel units` on each synchro shaft I ,would have thought,so in the event of a shaft/g-box failure both engines/rotors can still operate `manually` matching torques; I would think that with a prop failure and maybe an inability to feather that (in fwd flight) then it`s `curtains`..I don`t know if they can be feathered. However,again,if they can be,it may be possible to fly on one prop,at highish speed,then do a high-speed shutdown and glide landing; however,again,the prop rotation direction appears to be ` blades rotating upwards near the fuselage,which takes their `thrust centre`* outboard of the engine in an asymmetric condition(one rotor shut down)-not good.... Again,it would be interesting if someone who has flown it could come along and tell us the truth....B

* asymmetric blade effect,at small angles of attack- more appropriate to f/wing multi engines----just in case someone may not have flown those...

PS- does it have blade-tip `beta` lights,looking at the picture,or is it artistic licence ?

[mckpave]

sycamore, PM sent

[riff_raff]

It depends upon the nature of the gearbox failure. I'm not a V-22 pilot, so I'm just speculating. But if the gearbox is not seized, and has just lost the capability to drive its respective rotor, it might be possible. I believe the V-22 can sustain level flight on one rotor and/or one engine while the wing is producing lift (ie. flying like an airplane with the rotors positioned forward). The asymmetrical thrust yaw moment could be countered by the two large vertical tail surfaces and rotor cyclic.

I would imagine however that safe vertical flight (ie. with the rotors positioned vertically) on one rotor would definitely be out of the question. But remember, the V-22 also has a fairly substantial wing. So with the rotors feathered, it still has some glide ability if sufficient forward speed can be achieved.

The V-22 has a cross-wing drive shaft system that couples and synchronizes the two rotors, and also provides power to both rotors in the event of a single engine failure. There is no way to de-couple this cross-wing drive, so if one gearbox seizes then both gearboxes will quit rotating.

Here's a patent description for the V-22 drivetrain:
http://www.google.com/patents?id=yFojAAAAEBAJ&pg=PA1&img=1&zoom=4&hl=en&sig=ACfU3U12uLDlHbBq6jFjCnxZi6GjaVQb0w&ci=35%2C54%2C941%2C1265&edge=0

riff_raff

[BW109]

The Osprey has at least one service event of a non-catastrophic driveshaft failure. It was in 2000 or 2001... the pilots reported some minor RPM variations but otherwise landed uneventfully. They did a hover landing to LZ bluebird at Camp Lejeune.

The root cause of the failure was in the coupling between two drive shafts and not an actual failure of the composite shaft.

The comment about a tandem helo was on the mark... a driveshaft failure would be immediately catastrophic. With the Osprey, as long as both motors keep running, it's a non-event.