Helicopters downwind

[heights good]

Calling all QHI's this is from another thread on the rotorheads forum and i dont really know the answer.

Why do helicopters require more power out of wind in the hover?

[Cornish Jack]

Tail rotor power drain:(

[AllTrimDoubt]

Loss of translational lift.

[PTT]

Loss of translational lift.
http://smilies.jeeptalk.org/contrib/edoom/iamwithstupid.gif
(meant in the nicest possible way :) )

[pohm1]

Can it be "Loss of Translational lift" if you are in the hover and have not yet acheived translation?

:confused:

[swampy_lynx_puke]

See Cornish Jack's reply....
The a/c is designed to weather-cock into wind. To hold the a/c out of wind requires power from the tail rotor, hence tail rotor drain.
Now ask Westlands why the tail rotor on the early Lynx went the wrong way around......:confused:

[The Nr Fairy]

The thread "height's good" is alluding to can be found in Rotorheads, as Hovering Downwind (http://www.pprune.org/forums/showthread.php?s=&threadid=157371).

A lot of discussion undertaken, and the general consensus is that if there is a higher power requirement it's because of not a direct aerodynamic effect on the disk of hovering downwind, but rather associated effects such as lack of smoothness on the controls, some aerodynamic drag and other such effects. Well worth a read.

[Cornish Jack]

Swampy_Lynx_Puke
Re. the Lynx tail rotor query... possibly to avoid the Whirlwind tail rotor anomaly whereby it could be fitted back-to-front!!:(
This delightful peculiarity came to light, for one of our QHIs, well into the aircraft's service life, on a morning start-up at Tern Hill. On rotor engagement the airframe started to vibrate a bit like ground resonance. Instant shutdown and check for the problem. Took a while before the reversed tail rotor was spotted!!:( End result, thereafter, ... on walk-round check, confirm that the lower t/r blade had the same aerodynamic shape and airflow relationship as the adjacent tail pylon ... sorted!:ok:

[swampy_lynx_puke]

:8
My comment referred to the fact that the blades rotated with the main rotor downwash vice against, thus reducing the relative airflow over the blade thus requiring more pitch thus creating more drag....
;) What is the definition of a penguin?







An eagle designed by Westlands!

[Flypro]

I recall a certain Sea King MkV trying a hover with a reversed tail rotor - but not for long:ooh:

Wastelands made it possible - so somebody did it!:hmm:

[Muff Coupling]

A mate of mine who was an Army Pilot recounted an incident where his Gazelle Fenestron was fitted the wrong way round...apparently it led to some exciting maneouvres in a crowded dispersal and subsequent bent skids..oh and the wind was light and variable...especially from his a**se :eek:

[SandChopper]

Loss of translational lift? If you fly backwards you will still get the benefits of translational lift, if you fly the Chinook you can transition sideways and get even more of it - at least until the increased drag from the airframe becomes a factor.

What would happen to the Tq if you were sitting x-wind and using the good pedal (ie. the one that yaws the helicopter in the same direction as the rotor turns) to maintain heading, would you see a net gain in power available?

Time to go for a rest......