Autorotation - using cyclic during the run on....

[unhappyhamster]

I may have asked this queston a while back, but I have forgotten what was said.

When on the auto run on and the T/R authority starts to run out and it's difficult to keep the aircraft straight, is it desirable depending on envronment and surface, to use cyclic to follow into the turn to keep the forces all going in the same direction ?


Thanks

UH

[MightyGem]

In my experience(Gazelles) I had no problems keeping it straight during the run-on.

[rotorfloat]

I would say that use of cyclic after an autorotative landing will have no effect. Rotor RPM has been consumed to cushon the landing, and there wouldn't be much thrust available from the disk afterwards (the same reason you aren't getting any directional control from the tail rotor).

It is important to let friction with the ground do it's job to slow the helicopter, lowering the collective slowly after touchdown . It may be instinctive to pull aft on the cyclic to slow the aircraft down, but this can lead to the main rotor striking the tailboom. It is also automatic for us to have a full bootful of pedal applied during the last portion of the run on, trying to keep the nose straight, which doesn't hurt at all.

[Teefor Gage]

unhappyhamster

I'm not sure what speed you are running on at during your autos, and how long your run on continues for as a result, but I would seriously try flaring off some of your speed before you touch down. You shouldn't be anywhere near running out of T/R authority before you are fully "landed".

[Thomas coupling]

Unhappyhampster:
Two things:

I agree with T4 gauge that your run on speed shouldn't be such that you're still having to drive the cab around the ground while TR authority is running out.

Secondly - don't even think of using cyclic to manouvre the head after the Nr and TR starts to decay. You will not be in control of the rotor head at this stage and your inputs will only exacerbate the tip path plane, possibly leading to banging droop stops at least or chopping the tail off at worst

[Matthew Parsons]

It depends...

Different techniques for different types. If you have a teetering rotor or low effective hinge offset then with little to zero lift being generated, the cyclic inputs will not be very effective. Also, with reduced Nr small cyclic inputs can lead to surprisingly large flapping amplitudes. With a rigid or semi rigid head, the cyclic may be effective, but whether it makes things better for you would be dependant on many things.

Your aircrew manual, etc. should specify what the best technique is. Don't try anything else.

T4 Gauge: run on speed and t/r authority are not directly linked. T/R authority would be more affected by relative wind and Nr.

MightyGem: did you try eols in Gazelles with relative winds from both sides?

Matthew.

[Teefor Gage]

Matthew Parsons

I wasn't suggesting that T/R authority is linked to run on speed, but implying that the NR decay experienced during a lengthy run on would give rise to reduction in T/R auth. Relative wind etc also need to be considered - something that unhappyhamster didn't alude to in his original post. Maybe he was landing on a runway with a reasonable x-wind component. etc

[griffinblack]

In a standard or normal auto at training weights, in normal DA with an appropriate touch down surface, there should be no reason to run out of pedal authority during touch down. That is, you should generally still have some authority (pedal remaining) until you have stopped. During the run on phase, cyclic and collective should be frozen, with the cyclic in a central position appropriate to touch down attitude (generally level). Direction of attention should be on the far distance (the horizon) to allow the aircraft to track straight (maintain heading).

Yaw control emergencies on the other hand may require some cyclic steering. But that’s not what was asked.

[Hughes500]

Leave the cylic alone, steer it with the pedals, do not push the lever down let friction slow the ac - progressively lower lever until she stops

[MightyGem]

MightyGem: did you try eols in Gazelles with relative winds from both sides?

Too long ago to remember, but I'm sure that it won't have been dead on the nose at all times.

[rotornut]

Don't use full aft cyclic in a Hughes 500 or you might lose your tailboom - the MR blades tend to flap down and can cut the thing in half.

[[email protected]]

In a heavy Gazelle (AAC not RAF or RN) it was not uncommon to get to the left pedal stop during the run on but only because you had used more Nr to cushion the landing.
I agree that a faster run on, especially if a little too much lever is used to cushion, can leave you with forward speed and little Nr left to steer with - then you do need to lower the lever a bit to let friction do its job and accept the yaw.
On the Gazelle, the usual result of waggling the cyclic around during the run on was hitting the frange and having the p*ss taken in the crewroom later.

[Spiritrider]

Autorotation - using cyclic during run-on

Gazelle is a piece of piss. Try the MD 520N then you will know about running out of T/R authority with the pedal against the stop with 10 knots through the disc and a short run-on!