Pilot Commands TOGA; A320 lands anyway
From this week's "Aviation Week":
Incident Prompts Airbus
To Alter A320 AOA Limits
PIERRE SPARACO/TOULOUSE, FRANCE
Revised software, to be implemented soon, will increase pilots' authority over automated systems
In the wake of a serious landing incident, Airbus plans to revise the A319/A320 twinjets' automated angle-of-attack (AOA) protection.
Recently, a 150-seat A320, operated by an unspecified European carrier, made a hard landing, in nose-down attitude, despite the pilot-in-command's decision to go around and the application of maximum power. The aircraft's front landing gear collapsed, and the engine nacelles were damaged. Light turbulence but no wind shear had been reported to the flight crew before the nighttime ILS approach began.
An investigation team, supported by the European manufacturer's flight operations department, determined that during the final approach, the A320 entered into heavy turbulence at about 200 ft. altitude. Wind conditions were significantly more severe than initially reported to the flight crew, with up- and downdrafts and gusts that also involved an inversion of wind direction. The digital flight data recorder and additional inputs helped investigators determine that the A320 encountered strong tailwinds, a 1.25g-updraft, then a downdraft followed at 50 ft. by a tailwind gust.
DURING THE UPDRAFT, the flight crew applied a forward side stick input, then aft input to reduce the aircraft's increasing sink rate. As the Ground Proximity Warning System (GPWS) sounded, they moved engine throttles to takeoff/go around power, but the aircraft nevertheless touched down, according to Capt. Michel Brandt. He is Airbus' deputy director of flight operations support. He added that the A320's estimated vertical speed, when it impacted the runway, was 1,200 ft./min.
The recently completed investigation has shown that the combination of up and down wind gusts and the flight crew's actions on flight controls led the aircraft to hit the automated systems' high angle of attack protection and prevented a normal flare.
The incident was reproduced here in a full-flight simulator and led Airbus to a decision to modify the AOA protection's control laws to increase the flight crew's authority. Such a modification, which has been ratified by DGAC French civil aviation authority and European Joint Aviation Authorities, will cover all in-service A319s and A320s, but will not affect the stretched-fuselage A321.
The revised software is expected to be validated in June, and the retrofit program will be implemented rapidly, Brandt said. He added that in the shorter term, A319/A320 operators will temporarily apply precautionary measures in gusty wind conditions such as a slightly higher approach speed and immediate go-around in case of sink rate GPWS warning below 200 ft.
In an unrelated development, the British transport ministry's Air Accident Investigation Branch (AAIB) this month completed the investigation of a tail strike accident that occurred last year to a Lufthansa German Airlines A321.
DURING THE FINAL approach to Heathrow airport, the aircraft went below nominal glidepath, and the flight crew increased the attitude to reduce the rate of descent. The sink rate GPWS sounded, full aft side stick was applied, and the aircraft bounced on the runway after touching down for the second time. AAIB investigators determined that the aircraft's attitude peaked at 10.6 deg., just above the 9.7-deg. touch down limit with the main landing gear's oleos fully compressed. A similar incident occurred at Heathrow a few months earlier. Brandt noted that A321 landing tail strikes are not a noticeable concern and largely remain within tolerable limits.