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Gazelle Accident Database

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  • Gazelle Accident Database



    Loss of Fenestron Authority (aka Tail-Swing Bite) Accidents:

    This phenomenon is also known as ..

    - Loss of fenestron effectiveness
    - New Gazelle pilot's syndrome
    - Not knowing one’s left from one’s right
    - Fenestron stall

    Here are some examples of accidents related to this condition:


    1) SA341G YU-HEW JAN 2008

    Pilot Experience
    Total Experience (Helicopter): 56
    Total Hours (On Type): 46

    Comments from Accident Report

    In the absence of any significant technical defect, it is considered that the pilot lost control of the helicopter in yaw due to the strength, direction and gusty nature of the wind acting on the aircraft whilst flying at low forward airspeed.

    However, it is considered that the main contributing factors to this accident were the pilot’s lack of experience and probable inadequacies in his training.
    Injuries from Accident

    Two fatalities.

    AAIB Accident Report


    2) SA342J F-GJSL MAY 2005

    Pilot Experience
    Total Experience (Helicopter): 600
    Total Hours on Type: 12

    Comments from Accident Report

    Pilots who are inexperienced on the Gazelle need to be particularly aware of this apparent loss of tail rotor control. Unlike several helicopter types routinely used for training, the man rotor rotates in a clockwise direction (when viewed from above) and right pedal rather than left pedal is needed to oppose main rotor torque.

    Also, the fenestron-equipped Gazelle requires greater pedal deflection than that required for manoeuvring other training helicopters. Additionally, the tail fin is considerably larger than non-fenestron equipped helicopters, leadng to more challenging spot turns in windy conditions. In view of these characteristics, the statement in the MoD FM of: "Whenever possible, the first turn should be made to the right to check the maximum rotor torque required.”
    Injuries from Accident

    Two seriously injured.

    AAIB Accident Report


    3) Westland Gazelle HT2 G-BZOS JUL 2002

    Pilot Experience
    Total Experience (Helicopter): 167
    Total Hours on Type: 21


    Comments from Accident Report

    The pilot anticipated the need for right yaw pedal during the takeoff, but just after becoming airborne the helicopter yawed to the left and despite the use of more right yaw pedal, the rate of yaw increased. As the aircraft passed through 180° the rate of yaw was too high to land and the pilot became confused. He applied right cyclic to try to counter the yaw but the aircraft rolled to the right and the main rotor blades struck the ground.

    Both the Eurocopter Service Letters and the Ministry of Defence Flight Manual emphasise that very high yaw rates can rapidly develop in the hover in light wind conditions with only very small applications of left yaw pedal.
    Injuries from Accident

    Two persons with minor injuries.

    AAIB Accident Report


    4) Westland Gazelle HT3 G-BXZE

    Pilot Experience
    Total Experience (Helicopter): 180
    Total Hours on Type: 2

    Comments from Accident Report

    The pilot reported that the wind was calm and he lifted to a hover about 6 to 8 feet above the ground. He began a left pedal turn to position the helicopter for transition over the open arena area to the east. As the turn approached 180° from the initial heading, the pilot felt that he was unable to stop the helicopter turning left. The rate of turn began to increase
    rapidly.

    After some 10 to 12 rotations, the pilot elected to land the helicopter immediately while still turning rapidly to the left. On touchdown, the right skid broke and damage was sustained during the rotational deceleration.

    EUROCOPTER remind you that in some configurations (hover flight, flight at low speed in light wind etc), starting a turn to the left can induce a high-rate turn if the pilot does not apply quickly the suitable position to the yaw pedal. If the pilot attempts to counter this high-rate turn by applying the amount of right yaw pedal.
    Injuries from Accident

    One person with minor injuries.

    AAIB Accident Report



    5) SA341G G-BCHM JUL 1997

    Pilot Experience
    Total Experience (Helicopter): 68
    Total Hours on Type: 29

    Comments from Accident Report


    The initial lift-off was normal but at a height of about 3 feet the helicopter yawed to the left. The pilot believes that he took the necessary corrective actions with the yaw pedal but the left yaw continued through approximately 2 revolutions with the helicopter climbing to about 9 feet and rolling to the right. The pilot elected to carry out an immediate landing by lowering the collective lever. Ground contact was firm but the helicopter remained upright and came to rest on the original take-off heading.

    It is therefore most likely that the helicopter suffered the sudden loss of yaw control which can occur in the Gazelle in light wind conditions.
    Injuries from Accident

    No serious injuries.


    AAIB Accident Report


    6) SA341G G-HAVA JUL 1997

    Pilot Experience
    Total Experience (Helicopter): 170
    Total Hours on Type: 25

    Comments from Accident Report


    The wind was from the left and the intended departure directionwas to the west. The pilot was therefore conscious of the need to turn to the left after take off and may inadvertently have applied left pedal during the take off process. The helicopter's behaviour would then have been consistent with the skid marks indicative of it yawing whilst still in ground contact and with witness descriptions of it turning immediately on leaving the ground. Conditions would then have been conducive to the rapid increase in yaw rate experienced in other Gazelle accidents and incidents, particularly if the wind had been modified by adjacent hangars to provide a less favourable local wind component from the right. It is therefore likely that the pilot experienced a sudden loss of yaw control induced by her early left pedal input.

    It is therefore recommended that the Civil Aviation Authority (CAA) reconsider the type-rating training requirements for the Gazelle to determine whether additional emphasis needs to be placed on yaw control during take off, landing and low speed manoeuvres.
    Injuries from Accident

    Two persons seriously injured.


    AAIB Accident Report


    7) SA341G G-TURP SEP 1991

    Pilot Experience
    Total Experience (Helicopter): 108
    Total Hours on Type: 9

    Comments from Accident Report


    The Gazelle has a history of suffering unexplained loss of fenestron effectiveness, commonly known as ‘fenestron stall’. Know previous cases include .. 11 accidents plus 11 incidents in the UK military fleet. The majority of documented ‘fenestron stalls’ have occurred in the hover during an attempted left turn in conditions of wind speeds of 10 kts+ from astern or from the right but there have also been cases in a variety of other wind and flight conditions.
    Injuries from Accident

    No serious injuries.


    AAIB Accident Report

    8) SA341G G-SFTA MAR 1984

    Pilot Experience
    Total Hours (Helicopter): 6,000
    Total Hours on Type: 120

    Comments from Accident Report

    The helicopter took off from Carlisle Airport at 0800 hrs on a navigational training sortie which was to simulate the pick-up of troops at various points on the route. About 18 mins after take-off the student had identified a pick-up point near a barn and was told by his instructor to look for a suitable landing area. They flew past the barn at 40-50 kts with a slight left bank at about 100-150 ft agl. The helicopter started to yaw to the left at an increasing rate with the airspeed reducing. The instructor reached for the controls and asked the student what he was doing. The student replied that he had lost control. By now despite the full right pedal and forward cyclic applied by the instructor the helicopter was rotating to the left and descending. The instructor raised the collective just before the helicopter hit the ground nose down and right skid low. The helicopter, after contacting the ground., rolled over onto its right side.
    Injuries from Accident

    No serious injuries.


    AAIB Accident Report

    From these reports it seems to me that the UK’s AAIB and CAA both believe in the existence of ‘Fenestron Stall’ (even if that isn’t the best phrase to describe it).

    I think the moral of the story may be to ensure that new Gazelle pilots are thoroughly acquainted with the potential for the Gaz to deliver an unwanted ‘tail swing bite’ .. and for the need to be aware of those conditions which can induce this.

  • #2
    Date: 20th August 2011
    Operator: Tunisian Army
    Model: SA342L1
    Registration: L611

    The two crew members aboard this Tunisian Army Gazelle were killed when the aircraft went down near the Libyan border in southern Tunisia.

    The cause of the accident was cited as being a technical malfunction while unofficial reports cited poor weather as a factor.



    Tunisian Army SA342L1 L611 in which two military personnel were killed on 20th August 2011

    Comment


    • #3
      Date: 10th January 2012
      Operator: Cropspray Ltd, UK
      Model: SA341G
      Registration: G-WDEV

      The pilot reported a loss of power followed by an uncontrolled descent into trees while manoeuvring at slow speed and low height over a remote landing site near Salisbury in Wiltshire in the UK.



      G-WDEV post crash


      Three people were onboard the aircraft at the time of the crash, all of whom sustained minor injuries

      AAIB Report

      Comment


      • #4

        SA342J F-GJSL after crashing at Ockington Farm, Dymock, Gloucestershire on 8th May 2005

        This Gaz fell victim to the 'Tail Swing Bite' syndrome and ended-up hitting the corner of a house.

        You may read about this accident under item No. 2 in the Tail Swing Bite accident summary at the top of this page.


        Gazelle Accident Summary 2014-15

        2 June 2014 - Boscombe Down, UK - XZ936 cn. WA1743 / Substantially damaged when fenestron was 'sliced off' from tailboom by main rotor following practice autorotation.

        19 September 2014 - St. Petersburg, Russia - RA1233G cn. 1020 / Destroyed after flying into the sea at speed while pilot was drunk. One fatality.

        6 July 2015 - Stapleford Aerodrome, UK, - YU-HET cn. 1204 / Substantially damaged when aircraft inadvertently became airborne during a post-maintenance 'ground' run.

        15 July 2015 - Abbeyshurle, Longford, Ireland - G-BXTH cn. WA1120 / Destroyed after hitting building while trying to execute landing in unreasonably confined area.


        XZ936 (cn WA1743) as seen after her autorotational 'landing' at Boscombe Down on 2nd June 2014

        Comment


        • #5
          Accident Date: 8th March 2011
          Operator: Honister Mine
          Model: SA341G
          Registration: HA-LFB
          C/N: 1074

          Accident Summary

          On the evening of 8th March 2011 at approximately 7 pm, a Gazelle helicopter (registration HA-LFB), crashed while attempting to depart from the Honister slate mine in Cumbria. Having lifted-off, the helicopter was flown at low level and slow speed within the valley immediately below it's point of take-off. In what appears to have been an attempt to negotiate a departure route in reduced visibility conditions, the helicopter's main rotor struck the side of the valley resulting in the destruction of the aircraft and the fatal injury of the pilot.

          The pilot’s ability to maintain a safe flight path may have been affected by diminished situational awareness or a loss of control, and there was evidence of poor lighting and weather conditions that might have contributed to these difficulties, especially if the helicopter had inadvertently entered cloud. In addition, canopy misting, distracting illumination of cloud by the landing light or strobes, turbulence, and windshear are factors that may be associated with the prevailing conditions but for which there was no direct evidence.

          The pilot’s difficulties may have been compounded by the helicopter’s handling characteristics at low speed, the degraded performance of the yaw damper and the possibility that the helicopter entered vortex ring. There was no evidence that the pilot had received training in night flight. His decision to depart in the prevailing weather conditions, and from a site with no cultural lighting, suggested either a lack of awareness of the inherent risk or an acceptance of the risk.


          The remains of HA-LFB at the crash site
          Accident Report

          Comment


          • #6
            Accident Date: 16th January 1991
            Operator: Royal Navy
            Model: SA341C
            Registration: XW886
            C/N: WA1157

            Accident Summary

            On 16th January 1991 an SA341C Westland Gazelle belonging to No. 705 Naval Air Squadron at Culdrose crashed into a field in the Goonhilly Exercise area, near Predannack, Cornwall after the pilot lost yaw control during a semi-wing-over manoeuvre when avoiding another Gazelle. The pilot escaped from the wreckage but was seriously injured.


            Fleet Air Arm Westland Gazelle XW886 (cn WA1157) as seen in a field near the Traboe Cross-Ruan Minor road on 16th January 1991

            The pilot was was recovered by a Sea King helicopter and then sent to the AIU at Lee-on-Solent by road.

            The aircraft had been flown into an undefined area of the flight envelope known as the 'Fenestron Vortex'. The Fenestron, a shaft driven 13 blade fan, replaces the conventional tail rotor.

            This was the twelfth accident to a British Forces Gazelle attributed to this effect.
            Accident Summary

            Comment


            • #7

              Accident Date: 2nd May 2010
              Operator: Shuttle Air
              Model: SA341H
              Registration: YU-HEH
              C/N: 011


              Accident Report
              Accident Summary

              Comment

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