Austrian Airlines Flight 111

Austrian Airlines Flight 111 was a scheduled Austrian Airlines flight from Vienna to Munich on which, on 5 January 2004, a Fokker 70 had to make an emergency landing in a field a few kilometres short of the runway in Munich after a loss of thrust in both engines.

Course of the flight

After taking off from Vienna at 07:27, the Fokker 70, carrying 28 passengers and four crew members, flew via Salzburg towards Munich. At 07:54 the flight was taken over by Munich air traffic control and the pilots were instructed to descend to flight level 100 and reduce speed to 220 knots. Already during the descent to flight level 100, which was reached at 07:59, the ice warning system activated and ice crystals formed at the edges of the windshields. The de-icing system was then activated. However, the pilots could not detect any ice accretion on the wings.

Six minutes after reaching the flight level, there was a temporary increase in vibrations in the right engine. During the descent to flight level 90 there were then again increased vibrations in the right engine, which prompted the pilots to extend the airbrake in order to maintain speed at a higher engine power. Increasing the power (and thus the rotational speed) serves to accelerate the shedding of ice inside the engine. Since no further fault indications appeared on the right engine, it was not shut down.

After loud noises and vibrations from the rear part of the cabin and simultaneous vibrations of the right engine, one of the pilots declared an emergency at 08:08:14 due to severe engine problems. The crew immediately received clearance to descend to 5000 ft. At the same time, the engine pressure ratio (a measure of the power output of an engine; English: Engine Pressure Ratio; EPR) of the left engine dropped from 1.5 to values around 1.0. During the descent, the engine pressure ratio of the right engine also decreased within four minutes.

After clearance to descend to 3500 ft, the crew again deployed the airbrake to reduce speed to about 170 kn. At this point the aircraft was 8 NM from the runway and on the landing course. The landing gear and flaps were extended. When attempting to increase engine power (to compensate for the increased drag), the crew noticed that this did not have the desired effect and that the engine pressure ratio, and thus the power of both engines, did not increase. In order to increase the speed, which had dropped to 115 knots, the landing gear was retracted and the flaps were partially retracted again. After the speed had increased to 135 knots, the flaps were extended again.

At 08:16:10 the controller informed the crew that the aircraft was 500 ft below the glide path. A radar measurement showed a height of only 500 ft above ground and the GPWS issued warnings. The crew then informed the controller that the runway could no longer be reached. At a height of 400 ft the aircraft reached the cloud base, and 13 seconds before impact the landing gear lever was operated. Five seconds before the landing, one of the pilots informed the cabin crew by repeatedly calling out Brace for impact.

The aircraft touched down at 08:16:35 about 4.5 kilometres short of the runway in a snow-covered field between Reisen and Schwaig and slid 220 metres before coming to a stop. In the process, the fully extended and locked nose landing gear was torn off and the aircraft was heavily damaged, especially at the junction between the fuselage and the wings. The main landing gear, which had not yet been fully extended at the time of impact, was afterwards back in the landing gear bay. The fuselage itself remained intact. Three passengers were slightly injured in the landing. All passengers were able to leave the aircraft without assistance via the front door.

Cause of the accident

In the engine concerned (Rolls-Royce Tay 620-15), so-called ice impact panels made of fibreglass-covered foam are bonded to the inner wall of the casing between the fan and the guide vanes. They are intended to protect the engine casing from ice breaking away from the fan (schematic drawing on page 38 of the investigation report).

Due to inaccuracies and inconsistencies in the repair instructions of the adhesive manufacturer and of the engine manufacturer (with regard to curing temperature and duration, fixing during curing, cleaning and surface treatment before bonding), the panels were attached incorrectly. Over a longer period of time, the panels became increasingly detached due to penetrating moisture and the insufficient flexibility of the adhesive.

Since at Munich Airport at the time of the approach only the …