Shutting down in high winds

[TheFlyingSquirrel]

Which machine can sustain the highest windspeed on shutdown and why does it have advantages over others? I am always facinated with pics of blades chopping off tailbooms and riding through cabins when aircraft have come to misfortune in extreme conditions. Also, apart from cyclic into wind and parking crosswind, what other techniques can possibly reduce a strike?

TFS

[Devil 49]

Rotor brake required!!!!

Park with the wind dead on the nose, works up to 50 knots or so. That's the easiest way to keep the disk under control. Don't get excited about keeping the back clear- pushing the tip down in front eventually means the blades start bouncing, and things get random after that (bad).

Personal preference is against a teetering head, they get interesting as the NR drops. Really, really hate(!) the Longrangers, with the vertical fins on the horizontal stabs.

[Aesir]

When landing in high winds, which in my neck of the woods is 40 kts and above, its preferable to land with the nose into wind otherwise the forces on the side and tail of the helicopter could cause a dangerous situation.

In flight scool it´s often taught to land with the wind from the RH side so the wind will lift the rotor over the tailboom. It works fine in 20+ winds but anything above that and you want to have the nose into wind!

I have seen a JetRanger turn itself 90° into the wind in 50G60 kts winds with no damage at all.

I usually use the rotorbrake to stop the rotor at the 1/7 o´clock position to avoid it flapping into the tailboom.

Its not been a problem shutting down in high winds in the years I have flown B206 / 222 / 212 helicopters.

[delta3]

Flying a lot in "Mistral country", 20-30knts would be an average day. Never any problem with any position in R44, provided you keep cyclicking the rotor well.

Above 30 knts, I put it straight in the wind, especially if gusting. Putting it side ways also tends to create important vibrations in the tail rotor (never seen it visually, just hear the vibrations)

Fully agree with rotor brake.

Some times luck is involved, taking a nasty gust just at the wrong moment, might cause concern.


Some time ago there was an interesting thread on this subject.


D3

[cyclicpushover]

Aesir

It works fine in 20+ winds but anything above that and you want to have the nose into wind!


Why? Surely this would increase the probability of a tailboom strike. If it works fine at 20k why not at higher wind speeds?

In reply to TFS's first question, would a rigid system be better? Less flap?

[KENNYR]

Yes, a rigid system is better in high winds. The use of the rotor brake is essential........but once you have applied it dont play with it, let the blades stop quickly and in whatever position they arrive at. Be sure that you dont stop the rotors with a blade sitting over an exhaust outlet if the engine is still running!

The other thing you can do is to land behind a high or a large obstacle to act as a wind-break. (in the Falklands we used to land downwind of Bristows S61s).

[TeeS]

Hold on a second -

If we are talking about a symmetrical blade at zero pitch, the wind is not necessarily going to increase the lift! Any lift component (up or down) is going to occur because the blade is flapping or because there is a vertical component to the wind.

TeeS

[delta3]

Tees

Take a minute


Collective down is not zero angle of attack.
The blades tend most of the time to be twisted.

Kennyr

See the older thread.

Building etc can also create problems if they provoque extra turbulence, so I look rather for trees and not hangars, unless I could get very close.


D3

[Devil 49]

kissmysquirrel-
I was calling the typical Bell semi-rigid, two-blade rotor, a "teetering" head. Because they tilt freely at the head and mast, they seem to be more problematic in the wind. If a gust tips the disc with enough energy to encounter the droop stops, the disc can start bouncing off the stops. That cycle's phase becomes is the strongest influnce on disc tilt and isn't easily controlled once excited, as it occurs at low RPM when cyclic is ineffective. If the blade hits the stop at the most inopportune time, the aft blade will flex and strike tailboom, winglets, whatever, in spite of the fuselage being aligned with the wind, cross wind, or down wind.

[Gomer Pylot]

I prefer the wind slightly from the right, if possible, but it depends on lots of things. Onshore, there usually isn't too much problem, but offshore, with slick metal decks and the wind being swept up or down over the deck, it can be exciting. I've had 206s turn drastically both on start and shutdown, and the blades hit the droop stops regularly. All you can do is keep the cyclic into the wind to some extent, apply the brake as hard as possible, and hope. With the wind from the left, you start getting the blades heading downward as they approach the tailboom, and that is never good.

A 412 is about as good as you can get, because the blades are mounted very high, and I've never seen them come near the tailboom or anything else. The S76 has an advantage for startup, because you can start an engine with the rotor brake on and then release the brake for a rapid spinup. I don't normally do that onshore because there is no need, but offshore in 40+ kt winds, blowing up and down as much as horizontally, it works well.

[ConwayB]

In the Chinook, after 30 knots, that's when you pull out the charts and see if the windgust speeds will take you out of limits for rotor shutdown. The Chinook has 30inch blades and like to sail in very gusty winds... but I've found the charts pretty conservative. Having said that, if you don't obey the charts, then you do so at your own peril (and the Accident Investigation Board will have your guts for garters!)

Because both rotors intermesh and (almost) meet over the mid-cabin, the charts show you the best wind azimuths to try and get the blades to sail UP as they approach mid-cabin an thus afford the greatest clearance from blade and fuselage. Where possible, you park so as to keep the mean wind direction within these 'preferred' azimuth arcs if the wind speed is of concern.

CB

[Galapagos]

65 kts for the Super Puma.

Cdn Driver has a great story about shutting down in high winds... may be he could tell us!

:ok: