Austrian Airlines flight 111
| Austrian Airlines flight 111 | |
|---|---|
.jpg) The affected machine in 2001 |
|
| Accident summary | |
| Accident type | Crash landing due to loss of thrust |
| place | Travel , Germany |
| date | January 5 (January 5) 2004 |
| Aircraft | |
| Aircraft type | Fokker 70 |
| operator | Austrian Airlines |
| Mark | OE-LFO |
| Departure airport | Vienna Airport |
| Destination airport | Munich Airport |
| Passengers | 28 |
| crew | 4th |
| Lists of aviation accidents | |
Austrian Airlines flight 111 was a scheduled flight of Austrian Airlines from Vienna to Munich , on which on January 5th (January 5th) 2004 a Fokker 70 had to make an emergency landing in a field a few kilometers from the runway in Munich after a loss of thrust from both engines.
Flight history
After taking off from Vienna at 07:27 a.m., the Fokker 70 with 28 passengers and four crew members flew over Salzburg towards Munich. At 7:54 a.m., the flight was taken over by the Munich air traffic control and the pilots instructed to descend to flight level 100 and reduce the speed to 220 knots . During the descent to flight level 100, which was reached at 07:59, the ice warning system responded and ice crystals formed on the edges of the windshield. The de-icing system was then activated. However, the pilots could not detect any ice accumulation on the wings.
Six minutes after reaching the flight level, there was a temporary increase in vibrations on the right engine. During the descent to flight level 90, there were increased vibrations on the right engine, which caused the pilots to extend the air brake in order to maintain speed with higher engine power. The purpose of increasing the power (and thus the speed) is to accelerate the removal of icing in the engine. After there were no further fault indications on the right engine, it was not switched off.
After loud noises and vibrations from the rear part of the cabin and simultaneous vibrations of the right engine, one of the pilots declared at 08:08:14 an air emergency due to severe engine problems . The crew was immediately given permission to descend to 5000 ft . At the same time, the engine pressure ratio (a measure for the power output of an engine; English Engine Pressure Ratio ; EPR) on the left engine fell from 1.5 to values around 1.0. During the descent, the engine pressure ratio on the right engine was also reduced within four minutes.
After the clearance to descend to 3500 ft, the crew again set the air brake to reduce the speed to around 170 kn. At this point in time, the aircraft was 8 NM from the runway and was on a landing course. The landing gear and flaps were extended. When trying to increase the power of the engines (to compensate for the increased air resistance), 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 landing flaps partially retracted again. After the speed had increased to 135 knots, the landing flaps were extended again.
At 08:16:10, the pilot informed the crew that the machine was 500 ft below the glide slope. A radar measurement only showed an altitude of 500 ft above ground and the GPWS issued warnings. The crew then informed the controller that the runway could no longer be reached. The aircraft reached the lower edge of the cloud at a height of 400 ft and the landing gear lever was operated 13 seconds before the impact. Five seconds before landing, one of the pilots informed the cabin crew by shouting Brace for impact several times .
At 8:16:35 a.m., the plane touched down about 4.5 kilometers from the runway on a snow-covered field between Reisen and Schwaig ( 48 ° 20 ′ 55.6 ″ N , 11 ° 51 ′ 45.1 ″ E, ) and slipped 220 meters before coming to a stop. The fully extended and locked nose landing gear was torn off and the aircraft was severely damaged, especially at the transition between fuselage and wings. The main landing gear, which was not fully extended at the time of the impact, was then back in the landing gear shaft. The hull itself remained intact. Three passengers were slightly injured on landing. All passengers could exit the plane unaided through the front door.
Rescue operation
The alarm was triggered at 08:09:31 by air traffic control. The rescue workers ( Munich airport fire brigade and other forces) then took up their positions on the runway. After the aircraft crew announced the emergency landing outside the airport, the tower gave a new alarm for an accident outside the airport . At this point in time, however, the command line monitoring the radio traffic had already given the order to leave the airport grounds to the east. Due to a false report, the location of the emergency landing could not be located immediately. With the help of the crew, the control tower was then able to bring the rescue workers to the scene of the accident, where the first rescuers arrived at 8:34 am.
Cause of accident
In the existing engine ( Rolls-Royce Tay 620-15 ), so-called ice protection panels made of foam encased with glass fiber are glued to the inner wall of the housing between the fan and guide vanes . They are designed to protect the engine casing from ice breaking away from the fan (diagram on page 38 in the investigation report).
Due to inaccuracies and inconsistencies in the repair instructions of the adhesive manufacturer and the engine manufacturer (with regard to curing temperature and duration, fixing during curing, cleaning and surface treatment before bonding), the panels were incorrectly attached. Over a longer period of time, the panels kept peeling off due to moisture penetration and the lack of flexibility of the adhesive.
As only the southern runway was available at Munich Airport at the time of the approach (the northern runway was closed due to snow clearing work), the aircraft remained in the zone up to flight level 140 for a long time with the moderate icing forecast by the weather forecast. Because of this and the low speed of the engines at this point in time, a layer of ice formed on the fan in both engines.
The imbalance caused by the ice and the associated vibrations, the peeling off ice and the faulty adhesive connections on the ice protection panels led to the panels becoming detached. The panels wedged themselves in front of the guide vanes and blocked the bypass flow . Subsequently, only a small amount of thrust was available (pictures p. 39 f in the investigation report). However, the crew was only able to notice this when the power demand was made after the landing flaps and landing gear had been extended, since the aircraft had previously been descending and the flight warning computer did not provide for a comparison of the ratios between engine speed and engine pressure ratio. Due to the loss of thrust, it was no longer possible to reach the runway and the crew had to make an emergency landing in the field.
In the original version of the engine, the panels consisted of 36 segments. There were also some incidents with these panels. However, these incidents were always due to foreign object damage ( FOD ) and in most cases the engines had to be shut down anyway due to strong vibrations. None of these incidents resulted in a comparable loss of thrust, as the panels were small enough not to become wedged if they peeled off.
According to a service bulletin from the engine manufacturer, it was possible to replace the panels with new ones. These only consisted of six segments. This modification was made to the engines of the affected machine in 1999 and 2001, respectively. In January (January) 2005, an incident with such an engine on a Fokker 100 in Italy from 2003 became known. Since only one engine was modified on the machine, it could land safely in Rome. During the inspection, the ice protection panels were found wedged in front of the guide vanes. However, the reason for this was not recognized during the investigations.
Recovery and repair
A few days after the accident, the machine was taken out of the field and onto a nearby dirt road. There it was dismantled in the following weeks, brought to Woensdrecht in individual parts and stored there. In 2007, the decision was made to restore the machine to an operational state. The aircraft has been owned by Fokker Services since 2008 and completed its first flight in more than six years under the new Dutch registration (PH-ZFT) in mid-July 2010. The machine was put back into service on September 15, 2010 and flew for a while as ZS-SKA for the South African AirQuarius Aviation , which ceased operations on February 7, 2012.
Web links
- Investigation report of the Federal Bureau of Aircraft Accident Investigation
- Aircraft accident data and report in the Aviation Safety Network (English)
- Report from the Süddeutsche Zeitung
Individual evidence
- ↑ Investigation report p. 5 f
- ↑ Investigation report p. 17 f
- ↑ Investigation report p. 8 f
- ↑ Investigation report p. 21 f, p. 23 ff
- ↑ Investigation report p. 10 f, p. 20
- ↑ Investigation report p. 10, p. 16 f
- ↑ Investigation report p. 20 f
- ↑ FOKKERfleetlist. Fokker F27, Fokker 50 & Fokker 60. (No longer available online.) De Stichting Airnieuws Nederland, September 1, 2010, archived from the original on August 27, 2010 ; accessed on October 15, 2010 (English). Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ ZS-SKA AirQuarius Fokker F70 - cn 11559. Planespotters.net, accessed on October 15, 2010 (English).
