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F70, vicinity Munich Germany, 2004

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Summary
On 5 January 2004, a Fokker 70, operated by Austrian Airlines, carried out a forced landing in a field 2.5 nm short of Munich Runway 26L following loss of thrust from both engines due to icing.
Event Details
When January 2004
Actual or Potential
Event Type
Airworthiness, Loss of Control, Weather
Day/Night Day
Flight Conditions IMC
Flight Details
Aircraft FOKKER F70
Operator Austrian Airlines
Domicile Austria
Type of Flight Public Transport (Passenger)
Origin Vienna International/Schwechat
Intended Destination Munich Airport
Take off Commenced Yes
Flight Airborne Yes
Flight Completed No
Flight Phase Descent
ENR / APR
Location - Airport
Airport vicinity Munich Airport
General
Tag(s) Inadequate Airworthiness Procedures
LOC
Tag(s) Loss of Engine Power,
Environmental Factors
WX
Tag(s) In Flight Icing - Turbine Engine
AW
System(s) Ice and Rain Protection,
Engine - General
Contributor(s) Maintenance Error (invalid guidance available),
OEM Design fault
Outcome
Damage or injury Yes
Aircraft damage Major
Non-aircraft damage Yes
Injuries Few occupants
Off Airport Landing Yes
Causal Factor Group(s)
Group(s) Aircraft Technical
Safety Recommendation(s)
Group(s) Aircraft Airworthiness
Investigation Type
Type Independent

Description

On 5 January 2004, a Fokker 70, operated by Austrian Airlines, carried out a forced landing in a field 2.5 nm short of Munich Runway 26L following loss of thrust from both engines due to icing.

Synopsis

This is an extract of the synopsis from the official report into the accident published by the German Bundesstelle für Flugunfalluntersuchung (Germany) (BFU):

"On 5 January 2004 at 07:27 hrs a Fokker 70 certificated in Austria departed from Vienna with four crew members and 28 passengers aboard for a scheduled flight to Munich. It had been an uneventful flight until the airplane was transferred to the air traffic control unit Munich. Suddenly, at FL 90, heavy vibrations on the RH engine were indicated during the approach to airport Munich. When additionally unusual noises were coming from the rear of the airplane, the crew declared an emergency due to severe engine problems and requested to be cleared for an immediate landing. Thus the airplane was immediately cleared for a descent to 3,500 ft and by means of several heading instructions guided to a short approach of approximately 8 NM to the instrument landing system of runway 26L. Because the airplane could not maintain the glide slope it touched down at 08:16:35 hrs approximately 2.5 NM short of the beginning of the runway on a snow covered field with the landing gears partially extended. After a sliding distance of 220 m, the airplane came to rest lying on its severely damaged fuselage. All occupants were able to leave the airplane without assistance.

The accident was due to the following immediate causes:

  • After a prolonged time under moderate icing conditions and low engine thrust, ice developed on the rotors of the low pressure compressors of both engines.
  • The bonded joints of the ice impact panels on both engines failed due to strains caused by ice-induced vibrations of the engines and by ice which had shedded from the rotors of the low pressure compressor.
  • The loose ice impact panels became trapped in front of the outlet guide vanes of the low pressure compressor and affected the airflow in the by-pass duct in such a way that the engines now only produced low thrust.
  • The runway was no longer within reach of the aircraft as the loss of thrust on both engines had not triggered any warnings and was not indicated until the necessary demand of thrust at an altitude of 3,500 ft.
  • Due to its nature the terrain within reach was not suited for the landing of a transport airplane."

Safety Recommendations:

"As a result of the forced landing the Luftfahrt-Bundesamt (LBA) responsible for the type support of the Rolls Royce TAY 620-15 engine issued on 16 January 2004 the Airworthiness Directive D-2004-055 requiring visual inspections of the ice impact panels of all affected engine versions. According to information provided by the engine manufacturer approximately 30% of the ice impact panels were replaced in the scope of these inspections."

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