Fokker revises anti-ice procedures after Austrian crash

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Dutch maintenance firm Fokker Services has issued a set of precautionary recommendations for airframe and engine anti-icing procedures on Fokker 70 and 100 aircraft following the forced landing by an Austrian Airlines aircraft outside Munich this month.

Fokker Services says that, although the precise circumstances of the 5 January accident have yet to be determined, the possibility that engine or wing icing contributed to the crash has prompted the company to reassess anti-icing recommendations on the type.

Investigators have so far determined that, although the pilots activated anti-ice systems on the aircraft, ice-impact protection panels inside the Rolls-Royce Tay engines broke away shortly before the twin-jet was due to touch down at Munich.

“The involved [investigating] parties have strong reasons to believe that the Austrian Airlines aircraft was operating in exceptional icing conditions,” says Fokker Services.

“This meant that, as far as can be seen at present, a substantial mass of ice was able to accumulate in a short time on the engine air intakes and possibly also on the wing leading edges.”

After the pilots switched on the anti-icing systems, it says, the accumulated ice could have broken away and caused the ice-impact panels to detach: “These are believed to have subsequently blocked the air flow in the engines, as a result of which the engines were unable to develop sufficient thrust and an emergency landing became necessary.”

Under the new advisory, engine anti-icing must be switched on during all ground or flight operations where the total air temperature is below 6°C, irrespective of the presence of visible moisture.

Airframe anti-icing systems must be switched on during flight operations when any of three possible conditions arise: ice build-up is observed, the aircraft’s icing alert is activated, or icing conditions are anticipated. Icing conditions occur when the total air temperature is below 6°C and visible moisture is present.

“These precautionary measures are recommended until further notice, pending further results from the investigation,” says Fokker Services. The advisory applies to Rolls-Royce Tay 620- and Tay 650-powered aircraft.

Austrian Airlines commenced an immediate inspection of its Fokker 70 fleet in the wake of the accident and has been replacing a number of ice-impact panels in the engines of its aircraft.