|Title:||Yaw problems on approach, Report on the Serious Incident at Bergen Airport Flesland (ENBR) ON 24 March 2003, involving SAS329, MD-81, LN-RMO, Operated By Scandinavian Airlines|
|Micro summary:||This MD-81 experienced a yaw problem on approach.|
|Event Time:||2003-03-24 at 1944 UTC|
|Publishing Agency:||Accident Investigation Board Norway (AIB)|
|Site of event:||Bergen airport Flesland, Norway (ENBR)|
|Departure:||Oslo Airport, Gardermoen, Norway|
|Destination:||Bergen Airport, Flesland, Bergen, Norway|
|Airplane Type(s):||McDonnell Douglas DC-9-81 (MD-81)|
|Type of flight:||Revenue|
|Executive Summary:||An MD-81, LN-RMO, with call sign SAS329 was on a scheduled flight from Oslo airport Gardermoen (ENGM) to Bergen airport Flesland (ENBR) with two pilots, three cabin attendants and 107 passengers on board. Due to low visibility at ENBR upon arrival, SAS329 entered a holding pattern north of ENBR. After 35 min in the holding pattern, visibility improved along RWY 35. The active runway (RWY) was changed from 17 to 35, and SAS329 was cleared for an ILS (Instrument Landing System) approach to RWY 35. The Commander was Pilot Flying (PF) and had planned to control the aircraft using the Autopilot (AP) down to 50 ft Radio Altitude (Rad alt) in accordance with SAS procedures. |
The pilots obtained visual contact with the approach lights when passing minima, approximately 200 ft above the runway threshold level.
At approximately 100 ft above the threshold level (Rad alt) the aircraft drifted to the right. The Commander disengaged the AP and corrected to the left using left aileron control. During flare for landing, the Commander observed a leftward drift and corrected with a powerful right rudder input in order to yaw the aircraft's heading towards the RWY centre line. The aircraft touched down hard on the RH main landing gear with a leftward skid. The aircraft still had a velocity vector to the left and towards the RWY edge. The Commander corrected this by holding full right rudder to correct the path towards the RWY centre line. In the right turn from the RWY edge, the outer left main wheel collided with a RWY edge light that broke. The aircraft turned towards the centre line, and the remaining rollout and taxiing to parking was uneventful. The Commander reported to the TWR that they had landed on the left side of the RWY and asked for an inspection of RWY 35. Nothing unusual was observed. After shutdown, it was discovered that a main wheel tyre was damaged, and the Commander called the TWR and asked for a new RWY inspection. This time airport personnel found one broken RWY edge light on the left side of RWY 35. The Commander also informed TWR about a suspected bend on the localizer beam (LZZ).
The AIBN has investigated three previous serious incidents involving MD-80 aircraft from Scandinavian Airlines landing at ENBR. Two of the incidents occurred during landing on RWY 35 and one incident occurred on RWY 17. All incidents occurred during reduced visibility and in darkness.
Common factors leading to the three incidents on RWY 35 were:
- reduced visibility,
- the SAS policy of controlling the aircraft by autopilot down to a minimum certified height of 50 ft above the runway,
- a small bend on the localizer causing a slight rightward drift at around 100 ft radio altitude causing the flying pilot to disconnect the autopilot and make a manual correction, overcorrecting to the left causing a leftward drift and touchdown on the extreme left side of the runway.
Contributory factors leading to the incidents were:
- lack of updated Runway Visual Range (RVR)
- lack of runway centre line lights at ENBR
- the Norwegian policy of painting runway surface markings yellow instead of white as recommended by ICAO
- SAS procedure of not using landing lights in the event of reduced visibility
The AIBN considers that during such circumstances the Pilot Flying (PF) is led to believe that the aircraft is more offset than it really is and makes an over-correction. This takes place during flare and in each case the Commander decided that a continued landing was the safest course of action. In all incidents the Commander has salvaged the landing by use of full opposite rudder in order to steer the aircraft back onto the centre-line of the runway. The AIBN is not aware of any similar problems being reported by other operators. A significant finding is that SAS is the only operator flying into ENBR that controls the aircraft by autopilot below the Category I (CAT I) landing minima at ENBR. The bend on the LLZ is well within the certification requirements for CAT I minima.
|Learning Keywords:||Operations - Airport Markings or Lighting|
|Operations - Upset - Uncommanded or excessive Yaw|
|Other - Workplace Culture or Management|
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