Tilt rotor and eng fail
 

How do they (assuming it's possible) control the aircraft if an engine fails? Surely it's impossible in a vertical take off? If that's the case, is the aircraft then limited to short field take offs only? Where you would have enough speed to maintain control with rudder?

:confused:

I believe you'll find that there's a shaft across the front of the wing linking both prop/rotor systems to prevent assymetric in the event of an engine failure.

It's done with driveshafts and some fancy gearboxes. The obvious difference between a Chinook and a tilt-rotor is that the Chinook has both engines at the rear while the tilt-rotor has them at the wing tips.

Basically same problem.

RatherBeFlying

You forgot one other obvious difference to the CH-47.............the proprotors do not overlap so no phasing required due to intermesh. :E

There's been a fair amount of discussion about the particular vices of the Osprey in Rotorheads - a search over the last few years should trawl up a fair amount of info.

The single engine failure case shouldn't be too much of a problem as, has been described, there are drive linkages between the engines.

However, asymmetric vortex ring is much more of a worry - especially at low level. But I'm not tilt-rotor pilot, read the threads and judge for yourselves.

Aren't the Osprey rotors contra-rotating to get around this? I'd be very surprised if they weren't as the low speed vortex would have wildly different effects on each wing.

Thanks
 

Obvious solution, one that I didn't even think about.

Thanks!

Notso :

Vortex ring doesn't care which way a helicopter rotor turns - it's a condition caused by low airspeed, a reasonable rate of descent, and having power applied.

The Osprey and similar have high disc loadings compared to a helicopter, and this exacerbates the problem.

Any news as to a competitor to the tilt rotor - we have been hearing some news about compound helos? Any comments?

RatherbeFlying

Your comparison with the Chinook does not end up as 'basically the same problem'. The Chinook has both engines at the rear, so there is no shock-loading on the long driveshaft in the event of an engine failure. The Belvedere had a similar arrangement to the tilt-rotor, in that the shaft was a 'synchronisation' shaft, with an engine at each end of the aircraft, but if one of the donkeys took a break, then the shaft normally did too.

I thought another difference with Chinook is that the x-shaft is only loaded when an engine fails. However would that not create a sudden torque increase?

Wastelands had a plan for a Lynx with two RTM322s (!) as a compound demonstrator in the mid 90s. Budget cuts at MOD(PE)?

Nr Fairy,

Sorry to contradict but the higher the disc loading, the LESS likely is vortex ring to occur for a given rate of descent, not more likely. :8

Vortex ring occurs when the velocity of the flow caused by vertical descent approaches the rotor down wash flow velocity. It allows a "doughnut" shaped vortex to encompass the outer part of the rotor disc reducing the effective angle of attack of the blades. :)

So bigger, beefier and heavier aircraft with a rapid / heavy downwash don't tend to suffer as badly as small, lightly loaded aircraft. Not to be confused with "running out of sufficient power to arrest a rate of descent" which has occurred before, not actually VRS.

However, the tilt rotor apparently needs very cautious handling at the low speed end, especially when rolling into a turn as the inner (down going) rotor, sees a higher effective ROD on that side. Coupled with an already high ROD, it might give rise (sink :hmm: ) to VRS on that rotor, causing a loss of control.

Can't imagine one ever going into EGLW Heliport...