Undetected Ground Ice and Bird Avoidance felled Fokker 100

 - January 29, 2009, 4:04 AM

The crash of a Régional Fokker 100 shortly after takeoff from Pau, southwest France, in January 2007 was caused by undetected ground ice and excessive rotation on liftoff, according to the French air accident investigation board. The accident killed one driver on the road the aircraft traversed.

According to the report issued by the Bureau d’Enquêtes et d’Analyses (BEA), the French air accident investigation office, there is a cultural issue among French pilots about ground icing. Some of them believe, for example, that there is no risk of ground icing if there is no in-flight icing, BEA investigators determined. The report recommends improving training to enhance pilot awareness of this issue. The Régional accident is the first recorded accident involving ground icing in France.

The BEA also recommends that operators provide crews with suitable equipment for preflight checks. Although Régional’s operations manual requires it to do so, the crew did not check the wing’s upper surface, an inspection that would have required a stepladder. According to investigators, procuring the means to check the wings’ upper surface should become de rigueur for French pilots. The fact that the weather was ordinary for a winter day in France contributed to the crew’s lack of awareness about the potential for icing. However, during the same period of time in Pau, two other crews requested de-icing before takeoff, the report noted.

According to investigators, birds in the area were also a factor in the crash. When the pilot saw the birds at V1 (decision speed), he pulled back on the control wheel more sharply, taking the angle of attack beyond 11 degrees. Tests conducted after similar accidents have shown that the wing can stall at an AOA of 10 degrees, according to the BEA. The investigators also noted that aircraft without leading-edge slats, such as the Fokker 100, are more sensitive to ice contamination.