Limit in the wind?

[voodoo2]

It seems that most helicopter manuals don’t publish a max wind limit. There usually is a demonstrated wind condition (I think it’s a legal matter). I guess it’s up to the pilot or company procedure. What limits do you guys use? Off course it varies dependent on the job at hand and what aircraft. Not to long ago I was flying B206 in Greenland through a valley shaped like a venturi tube. Before I entered the valley the wind was only 20-30 kts but in the valley it increased to about (GPS showed 30 kts and IAS 100 kts) 70 kts. A passenger asked if it was safe to fly in such bad turbulence. I answered”Sure, no problem, just uncomfortable ". This answer was more a reflex. Because sometimes I felt like I was not in control of the helicopter. Needles to say, me and my passengers did not enjoy it very much. When we landed, the passenger sitting next to me said that he could see that I was also affected by the turbulence (witch was true).This incident have left its mark on me. Whenever the wind starts blowing more then 30-40kts, I get a bit nervous. But where do you draw the line? Most people I talk to are more concerned with start-ups. Anybody with experience flying in mountains condition, who could give me some pointers to ease my mind, would be appreciated.

[Do Drop In]

Hi,

Just take a look at the Rig guys for wind limitations ! 60Kts no problem.

You are quite correct on startup/shut down limits, but flying mountains in high wind can have serious complications. The machine will cope - but can you ? One downdraft off a windward side and bye bye sooty.

Just steady on there partner.

There are old pilots and bold pilots, but no old bold pilots !

[S76Heavy]

I'd say that in steady wind conditions, the only concern would be start up, shut down and fuel required. Although on offshore decks I would not want my pax to get blown over the side after they leave the helicopter either.

But I would take great caution with turbulence, especially in the vicinity of the surface and/or obstacles. Also, if you become uncomfortable, it is time to chicken out before you become too distracted by it and suffer an avoidable incident or worse.

[Shawn Coyle]

It might be worth looking at the definitions of turbulence in the enroute supplements.
I've heard of severe turbulence that can generate sufficient G loading to put you at zero G. You definitely don't want to do that in a Jet Ranger or R-22/44.
Common sense says that if you have a choice to not fly in moderate to severe turbulence, you would be wise to do that.
Ask yourself how you would answer the question at the board of inquiry (if you were there to answer), - why did you continue the flight into severe turbulence?
You will also note that no fixed wing airplane has any wind limits published.

[Ascend Charlie]

In a teetering-head chopper, and moderate turbulence is forecast, you want a good reason to go flying. Your customers could lose their breakfast, and the ride will be uncomfortable. Plus, as you have found, in local areas the effects can take it to "severe" or even "bloody hell!"

If severe turbulence is forecast, leave it in the hangar and get another cup of coffee.

Rigid and articulated heads are another matter. In a BK117 I was flipped to 120 degrees bank in turbulence - might not have survived that in a 206.:eek:
(We terminated the search at that stage and landed until the 50kt winds in the Blue Mts died down):p

[ShyTorque]

In my experience people are more badly affected than aircraft in any event but I have a reputation for not being too badly affected (no sense, no feeling, no doubt :D)

I've flown the S-76 in winds up to Typhoon strength and IMHO a high wind speed isn't a major problem provided the turbulence isn't too bad, that obviously depends on the stability of the air mass and what it's blowing over. It can be a problem for the SAR winchman on the cable though as he gets blown back towards the tail rotor in very high wind speeds and it becomes too risky to continue to winch.

I did once have the interesting experience of my S-76 not wanting to land, even at minimum collective I just couldn't get it on the ground. It took about 3 or 4 minutes for the updraughting to reduce a bit so we could touch down. The waiting passengers got the idea and jumped on in about 5 seconds flat! On the way home we saw 230 kts groundspeed at low level, it still wasn't too turbulent and our pax didn't complain, they were just grateful to be out of the predicament they had been in before we picked them up.

In a steady wind the aircraft doesn't actually know it's blowing; airspeed is airspeed. As folk already said, it's the startup and shutdown that are the bigger problem.

Today we had a 2000ft wind of 54 kts at times in central UK and the air was still as smooth as silk most of the time for our 7 flights, including a couple over the Southern Pennines.

Flew past Leeds Bradford a couple of times and listened with glee to all the planks diverting to Teeside. At least we don't have to worry about crosswind limits, hehe.

BTW, with experience you can work out where the roughest air in the hills is likely to be found and avoid it. Normally, one side of a valley will be rougher than the other etc, fly on the updraughting side where possible because that's where the air is usually smoother.

[moosp]

Shaun

This is not to bug you but you write above that, "I've heard of severe turbulence that can generate sufficient G loading to put you at zero G".

In 'The Art and Science...' you quote that, "I have never seen a gust that can give anywhere close to zero G in a helicopter, and I've been in some pretty strong turbulence in lots of helicopters."

Should I be worrried in my teetering head machine round the back of the hills or not? In a brisk wind it seems to get towards a small positive G sometimes, can it go negative?

Thanks

[HeliMark]

I can understand the nervousness. Little over a year ago I was in an updraft in the mountains that sent me climbing over 3,000' a minute. That was with the collective as far down as I could with out overspeeding Nr. Even with the turning around I was doing, I still climbed over 5,000' before I got out of it. The thought that was scary was what the downdraft was going to be like on the other side. Really opens your eye's.

It may take you a little time to get back into that type of situations, but I like to think of it as learning yet another lesson. And maybe now seeing that it may not be as wise to go in all the situations that you had previously.

An interesting discussion would be, what speed are you going to use in moderate/severe turbulance. The book does not obviously have a "manuvering speed" like fixed wing, but too fast, a good bump, and you can experiance blade stall. In a 500, I like to keep it somewhere in the 90 kt. area (and slower if at high altitude).

[ATPMBA]

I good technique I heard of on shut down is to position the helicopter so the blade going over the tail boom is going into the wind. This would cause the blade flap up and not strike the boom.

On passenger embarkation or disembarkation it’s a good idea to keep the rotor RPM in the green so the blade won’t flap down in a gust of wind.

[Shawn Coyle]

God, somebody who's read my book.... The elusive other reader.

I used to think that you couldn't get enought turbulence to generate zero G, and then I heard about some fixed wing aircraft that had wings that failed in overload negatively, and helicopters that got mast bumping in turbulence, so i was obviously wrong in the book.
Sorry about that.

[GLSNightPilot]

ATPMBA, that's generally a good idea, but even that setup can be scary. I once was starting a 206B, with the wind from the right, & the wind suddenly increased by a lot. The wind was blowing the blade down in front, to the point that it was hitting the droop stops, hard. It was lifting the skids up in the rear, & the aircraft turned each time. I ended up with the aircraft turned 90 degrees by the time I had idle RPM. If I had been any closer to the edge of the platform, I'd have gone over backward into the water. Also, offshore you can get situations where the wind isn't blowing horizontally on the helideck, sometimes it's blowing straight down, especially if you're on the downwind side. Then it's a matter of luck whether or not the start is successful. So far I've always been lucky. :eek:

[kissmysquirrel]

If the turbine exhausts are facing more into wind, would this give a possible hot start?

[moosp]

Thanks for the reply Shaun. I'll even read your next book too ;)

[GLSNightPilot]

Kiss, IME a tailwind does raise the temp on starts, but only by a small amount. It shouldn't cause a hot start if the start were otherwise normal. Temperature isn't the most dangerous factor.

[Tail Bloater]

Voodoo2 Slow turbulence ahead was an article in the Flight Safety Bulletin Spring 1998 and covered the fixed wing and is worth a read if you can get hold of a copy.
For rotary wing the technique to adopt in windy, and therefore turbulent conditions is to reduce power/torque by 10% from the quoted max continuous figure. This will provide a larger power margin to control down draughts and equally give less rate of climb in up draughts. The pedals will also be better placed to off-set balance requirements. Vertical air will increase the a/a = more lift, therefore in up draughts the more the lever will have to be lowered to hold hight, and more forward cyclic to maintain airspeed as airspeed reduces in up draughts.
Mountain flying in winds of more than 15 knots does require some formal training. Where strong winds are a hazard is BEHIND buildings/dense woods during starting and stopping the rotor as cyclic control is unavailable at low RRPM, and can lead to blade strikes on the tail boom. If it's windy park in the open and accept the steady strong wind rather than the gusts around a building.
I hope this is of some help.

A second thought;- when making approaches it is wise to anticipate windshear by applying 1/2 wind speed to your approach speed and this should offset any windshear you may encounter