The European Aviation Safety Agency (EASA) has mandated that operators of a large variety of Airbus aircraft fitted with Hamilton Sundstrand ram air turbines (RATs) perform inspections and part replacement on the backup devices.
The action comes after Hamilton Sundstrand, a subsidiary of United Technologies, reported a failure during a wind tunnel test of a balance weight fastening screw on a RAT turbine cover, according to an EASA airworthiness directive issued today.
"After investigation, it has been discovered that a batch of screws, which are used to attach the balance washers of the Hamilton Sundstrand RAT turbine assembly, have not been subject to the correct heat treatment and are consequently exposed to potential fracture," EASA states.
If the screws fracture and release the balance weights, EASA says the RAT vibrations can increase and possibly cause "detachment of RAT parts and consequent loss of RAT functionality".
In the worst case, the problem could leave pilots with no control over an aircraft if all engines were to flame out, says EASA. Airbus uses RATs to power the aircraft's essential systems in the absence of engine power.
The directive, which becomes effective on 24 December, applies to the A300-600, A310, A320, A330 and A340 families of aircraft.
Operators must identify the suspect RAT turbine assemblies and replace defective parts at the next RAT spin test or within a specified number of flight hours or months, whichever comes first.
Source: Air Transport Intelligence news
