Tuesday, December 14, 2010

Qantas jet's 'lucky escape' after water leak

This happened in 2008 but apparently the final report on it has just been released

LEAKING water knocked out electricity to a number of systems during a Qantas 747's flight to Bangkok, forcing the crew to land using limited battery power in a race against the clock.

The plane, with 346 passengers and 19 crew, was on descent in 2008 when the flight crew were alerted to a “substantial” water leak in the galley. As a result of the leak many of the aircraft‘s communication, navigation, monitoring and warning, and flight guidance systems were affected.

Had the event occurred more than 30 minutes flying time from the nearest suitable airport, or if there had been a delay prior to landing, numerous flight-critical systems would have become unavailable, placing the flight at “considerable” risk, air safety investigators warned.

The aircraft‘s batteries were available to provide power to critical systems for a limited period of time if the primary power sources were lost. “The limited battery power available restricted the amount of time that the aircraft‘s remaining functional instrumentation and communication systems were available to the crew, which necessitated an expedited descent and landing in order to reduce the risk of those systems failing,” a report by the Australian Transport Safety Bureau (ATSB) said.

At the end of the taxi to the passenger terminal the plane had been using battery power for approximately 21 minutes. The crew was unable to determine the time at which the aircraft had switched to battery power, or when the 30 minutes of minimum battery life would elapse.

If the plane had missed its approach or been at a different point in the flight when the use of battery power became necessary, the amount of battery power left could have been critical to the safe operation of the aircraft, the investigators said.

The investigation found that the galley leak was caused by an overflowing drain after a drain line was blocked with ice that had formed due to an inoperable drain line heater. The water flowed into the aircraft’s main equipment centre before leaking onto three of the plane’s four generator control units, causing them to malfunction and shut down.

The flight crew manuals did not contain information on means to extend the limited battery life or on managing the aircraft if the batteries were depleted.

The ATSB has issued two safety recommendations and a safety advisory notice as a result of the investigation.


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