Thursday 12 May 2016

HAVE WE FORGOTTEN THE BASICS OF SAFETY?

Let me start by saying categorically that I am not pointing any fingers in this post. I am just highlighting a concern that we might, as an industry, have taken our collective eye off the ball when it comes to managing the operational safety of our aircraft.

Last week I read on twitter that an Airbus A330 had encountered an airspeed discrepancy between left and right instruments during take-off at Brisbane airport. The pilots correctly abandoned the take-off as they were still below decision speed V1, and returned to the parking stand for maintenance investigation. The engineers did something with the air data computers, which process raw air data into information for the instruments. I forget what they did - re-racked or swapped them I think - and selected one unit off in accordance with the minimum equipment list (MEL). The aircraft was then dispatched. After getting airborne the crew again observed an airspeed discrepancy and returned to land.

Less than 2 years ago an Airbus A320 suddenly disappeared from ATC radar, after apparently making a very rapid climb above the cleared cruising level and then plummeting into the sea below. There was much speculation that the flight had encountered severe turbulence or icing and the pilots had been unable to maintain control.

In the first case it was found that mud wasps had started to build a nest in one pitot probe during the 2 hour stopover prior to the first take-off attempt but apparently no-one had thought to look into the probe for obstructions. Instead they went straight for a technological fix. In the second case the investigation found that, in an attempt to rectify a recurring fault with the rudder travel limiter, the captain pulled and reset the circuit breakers for both flight augmentation computers (FAC), contrary to abnormal procedures. The aircraft’s flight control logic immediately reverted from ‘normal law’ to ‘alternate law’, the autopilot disengaged and much of the automatic flight envelope protection was lost. The aircraft was manually flown into a steep climb and stalled – it never recovered.


It feels to me like we may have forgotten the basics of how our aircraft work…

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