Wind gusts

October 21, 2011 by Tim McAdams

 Wind is defined by Webster’s dictionary as a strong current of air. Although simple in definition, the affects of wind on a helicopter can be profound. To a pilot who clearly understands this, wind can be very helpful. Yet, helicopter pilots sometimes underestimate the risks of flying in gusty wind conditions.

On March 27, 2002, the pilot of a Hughes 269 helicopter lost control while hovering at the Fort Collins Downtown Airport. The flight instructor reported that the wind was about 2 knots at takeoff, but forecasted to be gusty in the afternoon. While hovering at about 3 ft with the student pilot at the controls, the helicopter encountered a very strong gust and began to wobble. The instructor took control of the helicopter and climbed to about 15 ft when another gust hit the helicopter, turning it sideways and then downwind. The instructor stated he was attempting to get it on the ground, but the wind continued to drive the helicopter forward with excessive nose-over tendency. With the tail rotor into the wind, creating a high power demand and limited tail-rotor authority, the helicopter skipped along the dirt two or three times. The helicopter traveled forward 180-200 ft. The right strut failed, and the helicopter rolled over on its right side.

The instructor reported that he thought the wind was gusting to 60 knots at the time of the accident. The reported weather at the Fort Collins-Loveland Municipal Airport, 8 nm south of the accident site, was wind from 260 deg at 13 knots, gusting to 25.

Extra care should be taken when sitting on the ground with less than 100% rotor rpm in windy conditions. Wind can affect the flexing of a rotor blade at low rpm much more than at normal speed. An Enstrom 280FX helicopter was substantially damaged when the main rotor blades struck the tail boom while sitting on the ground. In an interview with the NTSB, the pilot stated he landed in a corn field and got out of the helicopter while the rotors were still under power. Then, he said a gust appeared and the main rotor severed the tail boom.

It should go without saying that leaving the pilot station of a helicopter with power still applied to the rotor system is just a really bad idea under any circumstances.

  • Avi Weiss

    Concur that leaving the controls while the rotor system is under power not advisable, but assuming the situation is as the Enstrom pilot recounted it, it seems doubtful the pilot would have been able to take corrective action fast enough if he were at the control, especially if they were frictioned.

  • http://AOPA Jim Borger

    There’s nothing wrong with frictioning down the controls and getting out with the rotor turning as long as you know what you are doing. There are times when it shouldn’t be done. I regulary start up and shut down in 35kts of wind, you can do it in 60kts in a Boelkow, but I would never leave the controls unattended in such windy conditions. Also, I’ve never seen the wind just start blowing for no reason. It can come up rapidly when there are storms in the area. As long as you keep up with current and forecast connditions you can avoid unpleasant surprises.

  • Jeff Johnson

    Jim Borger is correct. It does not “go without saying that leaving the pilot station of a helicopter with power still applied to the rotor system is just a really bad idea under any circumstances”. There are situations where it is an acceptable procedure for a pilot to properly friction the controls and leave the pilot station. Not of course in adverse wind conditions. Thousands upon thousands of Army helicopter pilots were taught this procedure in primary helicopter training. It is less safe to leave a helicopter that is shut down and still has blades turning, particularly in a high wind situation.

  • Danny Wallace

    Something I found helpful as a training aid is practice hovering in a tail wind when ever safely possible. The article didn’t mention the hour level of the pilots at the time of the hovering accident. It does make a difference in comfort level especially when operating light helicopters. When we avoid tail wind hover like the plaque we’re possibly depriving ourselves of a great training work out. After time you’ll know by feel just how much tail wind you and your bird can handle. Keep in mind tail wind gusts could cause your tail rotor to be too close to the ground if you don’t adjust hover altitude appropriately. With enough practice you will easily recognize the onset of loss of tail rotor effectiveness. That will be very helpful when operating close to or at max gross weight and slow speeds. None of this practice is substitute for proper preflight planning for all conditions expected.

  • Pierre duPont

    While leaving the controles of an operating helicopter is often done. Technisally this procedre is not legal on most helicotpers. In the rotor craft flgiht manual, in the limitations section you will often find minimum crew lsiting. In the Enstroms, it is listed as One Pilot.

    The Rotor Craft Flght Manual is an FAA approved document, so if you are seen leaving the controles or have an incident, you could be looking at a violation.

    The Enstrom series helicopters have no cyclic friction but the only time it is possible to strike the tail boom on the ground is with extremely windy conditions and low rotor RPM.

  • Allen Lambert

    I disagree with duPont on leaving a running helicopter being illegal. It isn’t wise in many situations, but the crew member is required for the helicopter IN FLIGHT, not frictioned down and idlig. I was in flight training with the Army and this was regularly practiced to insure safe take offs could be made from the LZ when you used the maximum space available to land and had to back the helicopter up to get a safe take off run, you got out placed markers to be able to safely back up and not hit an obstacle. In an airport environment with ground guides available and most obstacles noted, no real reason to leave it alone and idling, even in calm conditions.

  • Brad

    I have a question for Danny or any pilot for that matter. I am a new pilot that is just passed the private stage and am looking for all the info I can get from the more experienced pilots. You said it is good training to put the tail into the wind and I understand that but would that be something you would want to try with a 12kn gust spread and peak gust at 25kts in a smaller acft such as the hughes? Aslo wouldnt that pilot have been better off to continue the climb and put the nose into the wind if he experinced a “nose over” situation like that instead of trying to put the aircraft on the ground? I understand things happen fast I was just wondering your thoughts.

  • Michael Jay Jones

    Thank you for discussing this issue. I vividly recall the first time I turned my back to a relatively gusty wind in the R-22. It was an eye opener. The horizontal tail surface can apply a significant amount of pitch force in a stationary hover in gust tail wind. I have asked my instructor to give me more tail into the wind experience when condition permit and as the previous poster mentioned, this improved my ability to not only recognize potentially hazardous winds but to improve aircraft control in safe but “challenging” winds conditions.

    The R-22 manual forbids operating in winds in excess of 25kts or 15kt gusts without 200 hours of experience in the aircraft. At my level of experience, I find 14G22 a challenge in a tail wind or left wind hover in the R-22.

    Setting personal minimums for wind and sticking to them is also a good idea.

  • Lex Marasek

    In my experience sometimes , just to hook up a longline or take off a jacket .a pilot could get out of the seat .How ever trusting frictions is a risky business.Creeping collectives could kill you,never less the ship . With fully articulated rotor systems ground resonance is always possible no matter how flat you think your sitting. As for light [training helicopters] an eagle flying buy could upset the apple cart. Dynamic rollover with no one in the ship explain that to the insurance company and flight school!

  • Mark

    sounds like a IFE , I agree with what you said

  • Vedair

    I own and fly a bell 47 G. It is safe to fly in tail wind conditions and this comes
    With experience and training because of the heavy weight and heavier blades
    Tailwind hover is not that difficult! It is common and depends on pilot
    In command decision to have blades turning and get into and out of the helicopter
    As. Needed off hot fueling is done this way as well, common sense is needed
    And all must remember rules to regulate safety do not stop accidents, cannot cover all scenarios
    And are way you cannot ride anywhere fast in an airline now! Opinions
    Of anyone but the pilot in command at the time are destroying general
    Aviation as we know it!!

  • Alan D. Resnicke

    As a former USAF helo instructor (at Mother Rucker), we often taught our students downwind hovering. In a UH-1H it’s still an interesting manuever. As Brad asked, above, I’d be curious to know the thought process of the IP involved in the mishap. Sometimes putting the aircraft down isn’t the best idea… a go around might have been better called for in this gusty situation. As far as exiting the helo with it running – that’s what crew chiefs and flight engineers are for (thanks, guys)! Still – I have exited the helo a few times, but frictions shouldn’t be trusted (I never walked away from the open door), wind shouldn’t exist (a breeze off the nose might be okay), and the rotor should always be at 100% – or shut ‘er down! The “saved” expense of a restart isn’t worth the safety compromise.

  • Charleston Wedding

    Wow. That’s serious business right there. By the way, why would you exit with the engine still running, not very smart? They were blessed to have survived this crash. I can’t imagine. -Philip

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