Airbus is to modify its A320 and A319 alpha protection control law for a second time after a landing accident in windshear showed it to be oversensitive to sudden changes in angle of attack combined with rapid pilot sidestick input. This follows analysis of a 7 February hard landing on runway 30 at Bilbao, Spain, by an Iberia A320, in which one of the 136 passengers and seven crew were injured and the aircraft was severely damaged.
Bilbao is infamous for windshear on final approach, and the crew encountered an updraft with indicated airspeed (IAS) increase while passing through 200ft (70m), where they increased nose-down attitude to compensate.
Passing 50ft the aircraft was hit by a downdraft and loss of IAS, there was a sink-rate warning and the alpha protection overrode the pilot's nose-up selection because the system detected a stalling angle of attack. The pilot selected take-off/ go-around power, but when the aircraft hit the ground at a descent rate which Airbus puts at 1,200ft/min, all three gear legs hit the ground almost simultaneously, the nosewheel collapsed, and the airframe and engines suffered serious damage.
Meanwhile, Airbus has put out a service bulletin advising crew who expect windshear to use maximum 30° flap and slightly increased IAS. In this case the crew were advised only of moderate turbulence and relatively light wind.
Source: Flight International
