What happened
On October 30, 2006, an ATR 42-500, registration F-GPYM, operated by Airlinair, was performing a scheduled passenger flight from Rouen to Le Havre. During the approach to runway 23, the crew was informed of a 25-knot wind. Two minutes prior to touchdown, the aircraft was subjected to significant turbulence and wind gusts.
The pilot flying (PF) increased the approach speed by 5 to 10 knots to account for the wind conditions. The aircraft touched down slightly left of the centerline, with the right main gear making contact first. As the aircraft decelerated to 70 knots, the PF transferred control of the yoke to the pilot not flying (PNF) to focus on managing the nose wheel steering (NWS) and rudder, while maintaining control of the brakes and pedals.
During the rollout, the aircraft experienced a lateral excursion. The aircraft initially drifted left before a sudden correction caused it to swing toward the right, tending to weathercock into the wind. Despite efforts to use the NWS to correct the trajectory, the nose wheel skidded on the pavement, causing the aircraft to veer off the runway and into the grass, where it became bogged down. The incident resulted in damage to the brake units and two wheels, but there were no injuries to the 16 passengers or the 3 crew members on board.
The investigation
The investigation examined the meteorological conditions, the accuracy of wind transmissions, and the crew's control techniques. Investigators found that while the crew was aware of forecasted strong winds, the actual instantaneous wind gusts reached up to 34 knots, exceeding the demonstrated maximum crosswind component of 30 knots for the ATR 42-500.
Analysis of the wind data revealed that the controller's information was based on two-minute averages. While a more precise instrument for instantaneous wind was available at the aerodrome, its position made it difficult for the controller to use during the shift. Furthermore, the investigation noted that the proximity of the runway to coastal cliffs creates significant rotors and turbulence for arrivals from the northwest.
Regarding aircraft handling, the investigation reviewed the coordination between the two pilots. It was noted that the airline's operating manual did not explicitly mirror the manufacturer's FCOM instructions regarding the specific timing of control transfers and the use of NWS to prevent tire skidding at high speeds.
Findings
- The aircraft was subjected to a crosswind component that exceeded its demonstrated operational limits.
- The crew was not informed of the peak instantaneous wind gusts, only the averaged values.
- The primary cause was the difficulty in controlling the aircraft during the deceleration phase, where the high crosswind increased the weathercock effect on the vertical stabilizer.
- The coordination of flight controls between the two pilots was complicated by the specific use of the NWS during a high-wind rollout.
- Excessive use of the NWS at higher speeds contributed to the nose wheel skidding on the runway surface.