Tim van Beveren/MIAMI

A Lufthansa Airbus A320 almost crashed shortly after take-off because of reversed wiring in the captain's sidestick flight control. Quick action by the co-pilot, whose sidestick was not faulty, prevented a crash.

The 20 March Frankfurt-Paris schedule service hit turbulence just after rotate and the left wing dipped. The captain responded with a slight sidestick input to the right but the aircraft banked further left. The pilot followed up with a stronger right input. The aircraft responded with more left bank, reaching 21í. Realising the problem, the copilot switched his sidestick to priority and recovered the aircraft.

According to sources close to the investigation, the flight data recorder revealed that the left wing dipped to within 0.5m (1.6ft) of the ground. "If this had continued for 5s more, the aircraft would have definitely crashed," says the source. A full report by the German BFU aircraft accident investigation board is expected shortly. Airbus declines to comment and Lufthansa would not make anyone available for comment.

The crew say they had performed their pre-take-off checks and that all electronic centralised aircraft monitor (ECAM) indications seemed normal. According to the A320 manual, the pilot flying (PF) should check his sidestick for full lateral and fore/aft movement, holding it in each position until the control surfaces have reached full travel, and the pilot not flying (PNF) should check the ECAM to see that the control surfaces are moving correctly. The roles are then reversed while the PNF checks his controls.

After performing handling checks at 12,000ft (3,650m) and confirming that the captain's sidestick was reversed in roll, the crew returned to Frankfurt.

The investigation has focused on maintenance on the captain's controls carried out by Lufthansa Technik just before the flight. During the previous flight a problem with one of the two elevator/ aileron computers (ELAC) had occurred. An electrical pin in the connector was found to be damaged and was replaced. It has been confirmed that two pairs of pins inside the connector had accidentally been crossed during the repair. This changed the polarity in the sidestick and the respective control channels, "bypassing" the control unit which might have sensed the error and would have triggered a warning. Clues might have been seen on the ECAM screen during the flight control checks, but often pilots only check for a deflection indication, not the direction. Before the aircraft left the hangar a flight control check was performed by the mechanic, but only using the first officer's sidestick.

Source: Flight International