Air accident investigation board (AAIB) calls on Boeing to modify Boeing 737 design to prevent leaks.

Citation

(1999), "Air accident investigation board (AAIB) calls on Boeing to modify Boeing 737 design to prevent leaks.", Disaster Prevention and Management, Vol. 8 No. 1. https://doi.org/10.1108/dpm.1999.07308aab.005

Air accident investigation board (AAIB) calls on Boeing to modify Boeing 737 design to prevent leaks.

Air accident investigation board (AAIB) calls on Boeing to modify Boeing 737 design to prevent leaks.

Britain last month called on US aircraft manufacturer Boeing Co to make urgent design modifications to its best-selling Boeing 737 passenger aircraft after a liquid leak played havoc with the electronics of a British Airways airliner.

An official report by the Air Accident Investigation Board said the unidentified liquid seeped into the aircraft's electrical and equipment bay during a test flight at 20,000 feet.

The liquid affected the yaw damper, which controls rudder movements, and caused the aircraft to roll uncontrollably from side to side for seven minutes. The pilot issued a mayday call and had to descend to 7,500 feet before regaining control and making a safe landing at London Gatwick Airport.

The incident occurred over southern England in October, 1995.

The AAIB report called on the US Federal Aviation Authority and Boeing to take quick steps to ensure similar incidents did not recur.

Review

It recommended they "conduct an urgent review of the measures incorporated into the Boeing 737 to prevent fluid ingress into the E&E bay, its equipment, connectors and wiring and, as necessary, require modifications to ensure the equipment, connectors and wiring are provided with protection consistent with reliable operation".

The location of the E&E bay, beneath the cabin floor in the area of the aircraft doors, galleys and toilets, "made it vulnerable to fluid ingress from a variety of sources", the report said.

The liquid had emerged from just aft of the forward lavatory, where a leak from the sink drain had been reported six months earlier.

The report said the Boeing 737 instruction manual should be reviewed to ensure it contained clear instructions enabling evidence of fluid leaks to be spotted during routine maintenance.

Corrosion

The particular electrical connection affected by the liquid had not been overhauled in the aircraft's 17-year life, the report said, describing "considerable build up of products of corrosion and electrolysis".

It also called on the FAA to order an inspection of all Boeing 737 E&E bays to check for possible leaks of fluid and signs of corrosion.

British Airways spokesman Iain Burns said the airline had checked its entire fleet of 68 B737s and had taken measures to ensure similar incidents did not recur.

"This is the only report of any such incident that BA has ever had", he said.

The AAIB report also recommended that the FAA and Britain's Civil Aviation Authority should look into aircraft design "with a view to requiring that the location of electronic equipment be arranged so as to minimise the potential for contamination by fluid ingress".

An aviation source involved in the investigation said the report had taken so long to produce because it was "an enormous piece of detective work done with the co-operation of other agencies here and abroad".

Boeing Co later said that a fluid leak of this kind could not have been involved in any unexplained accidents.

In a statement issued in Singapore, the manufacturer said: "Boeing believes that this incident was isolated, and that this issue could not have been involved in any unsolved aircraft accidents".

(Lloyd's Casualty Week, Vol. 311 No. 10, 6 March 1998.)