Tilt rotor and eng fail

[ManaAdaSystem]

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:

[idg]

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.

[RatherBeFlying]

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.

[Travelling Toolbox]

RatherBeFlying

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

[The Nr Fairy]

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.

[Notso Fantastic]

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.

[ManaAdaSystem]

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

Thanks!

[The Nr Fairy]

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.

[46Driver]

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

[Pub User]

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.

[zalt]

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)?

[ShyTorque]

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...