In September 2007, two separate accidents due to similar landing gear failures occurred within three days of each other on
Bombardier Dash 8 Q400 aircraft operated by
Scandinavian Airlines System
The Scandinavian Airlines System (SAS), commonly known as Scandinavian Airlines, is the Flag carrier, national airline of Denmark, Norway, and Sweden. It is part of SAS Group and is headquartered in Solna Municipality, Solna, Sweden.
Including ...
(SAS). A third accident, again with an SAS aircraft, occurred in 27 October 2007, leading to the withdrawal of the type from the airline's fleet.
Scandinavian Airlines System Flight 1209
Scandinavian Airlines System Flight 1209, a
Bombardier Dash 8 Q400 registered as LN-RDK, took off from
Copenhagen Airport
Copenhagen Airport, Kastrup (, ) is an international airport serving Copenhagen, the capital of Denmark, as well as the wider Øresund Region, including Zealand and the southern Sweden, Swedish province of Scania. In 2023 it was the largest ai ...
, Denmark, on 9 September 2007. It was on a domestic flight to
Aalborg Airport.
Prior to landing, the right main landing gear failed to lock and the crew circled for an hour while trying to fix the problem then preparing for an emergency landing. After the aircraft touched down, the right landing gear collapsed, the right wing hit the ground, and a fire broke out. The fire went out before the aircraft came to rest and all passengers and crew were evacuated. Five people had minor injuries, some from parts of the propeller entering the cabin and others from the evacuation.
Investigation
When the handle for lowering the landing gear was activated, the indicator showed two green and one red light. The red light indicated that the right main gear was not locked in position. The landing was aborted. Attempts at lowering the gear manually were also unsuccessful. An investigation into the cause of the failure to deploy revealed that the right main gear
hydraulic actuator
A hydraulic cylinder (also called a linear hydraulic motor) is a mechanical actuator that is used to give a unidirectional force through a unidirectional stroke. It has many applications, notably in construction equipment ( engineering vehicles ...
eyebolt had broken away from the actuator. A further analysis of the actuator showed
corrosion
Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engine ...
of the threads on both the inside threads of the piston rod and the outside threads of the rod end, leading to reduced mechanical strength of the actuator and eventual failure.
On 19 September 2007, the
prosecutor
A prosecutor is a legal representative of the prosecution in states with either the adversarial system, which is adopted in common law, or inquisitorial system, which is adopted in Civil law (legal system), civil law. The prosecution is the ...
of
Stockholm
Stockholm (; ) is the Capital city, capital and List of urban areas in Sweden by population, most populous city of Sweden, as well as the List of urban areas in the Nordic countries, largest urban area in the Nordic countries. Approximately ...
commenced a preliminary investigation regarding suspicion of ''endangering another person''.
Maintenance procedures
Scandinavian Airlines
The Scandinavian Airlines System (SAS), commonly known as Scandinavian Airlines, is the national airline of Denmark, Norway, and Sweden. It is part of SAS Group and is headquartered in Solna, Sweden.
Including its subsidiaries SAS Link and ...
System (SAS) was accused of cutting corners in the maintenance of its Q400 aircraft. As the
Swedish Civil Aviation Administration began an investigation of the accident, it brought renewed focus on SAS maintenance procedures. (Only two weeks previously, Swedish authorities had levelled a scathing critique at the airline after an aircraft of the same model nearly crashed because its engine accelerated unexpectedly during landing.) The outcome of the investigation was that the cause was not a lack of maintenance but over-cleaning of the landing gear, with pressure washers being used that washed out the corrosion preventative coatings between the eyebolt and the actuator rod end. The airline reportedly made 2,300 flights in which safety equipment was not up to standard, although the airline denied this.
AIB Denmark (Havarikommissionen) noted that the use of different alloys in the bolt and surrounding construction was most probably a contributing factor:
Scandinavian Airlines System Flight 2748
A second accident occurred when a Bombardier Q400, operating as Scandinavian Airlines System Flight 2748, took off from Copenhagen Airport, Denmark, on 12 September 2007. It was headed to
Palanga
Palanga (; ; ) is a resort town, resort city in western Lithuania, on the shore of the Baltic Sea.
Palanga is the busiest and the largest summer resort in Lithuania and has sand, sandy beaches (18 km, 11 miles long and up to 300 metres, 10 ...
, Lithuania, but was diverted to
Vilnius International Airport when landing gear problems were discovered before landing. Again, the right landing gear collapsed immediately after the aircraft touched down. All passengers and crew were evacuated safely. The local officials at Vilnius International Airport noted that this was the most serious accident in recent years. This accident was also caused by corroded threads in the piston rod and rod end.
Scandinavian Airlines System Flight 2867
On 27 October 2007, a Q400 registered as LN-RDI was operating SAS Flight 2867 from
Bergen
Bergen (, ) is a city and municipalities of Norway, municipality in Vestland county on the Western Norway, west coast of Norway. Bergen is the list of towns and cities in Norway, second-largest city in Norway after the capital Oslo.
By May 20 ...
, Norway to Copenhagen, Denmark with 40 passengers and 4 crew members when problems with the main landing gear were discovered. After waiting about two hours in the air to burn fuel and troubleshoot, the pilots attempted a prepared emergency landing. The pilots were forced to land the aircraft with the right main landing gear up. The right engine was shut down prior to the landing, because in the previous landings the propeller had hit the ground and shards of it ripped into the fuselage. This was not on the emergency checklist, rather it was the pilots making a safety-based decision. The aircraft stopped on the runway at 16:53 local time with the right wing touching the surface. It did not catch fire and the passengers and the crew were evacuated quickly. There were no serious injuries. The aircraft in question was one of six that had been cleared to fly just a month before, following the grounding of the entire Scandinavian Airlines Q400 fleet due to similar landing gear issues. The entire fleet was grounded again following the accident.
The preliminary Danish investigation determined this latest Q400 accident was unrelated to the airline's earlier corrosion problems; in this particular case being caused by a misplaced
o-ring
An O-ring, also known as a packing or a toric joint, is a mechanical gasket in the shape of a torus; it is a loop of elastomer with a round cross section (geometry), cross-section, designed to be seated in a groove and compressed during assembl ...
found blocking the orifice in a hydraulic restrictor valve.
Accordingly, the
European Aviation Safety Agency
The European Union Aviation Safety Agency (EASA) is an agency of the European Commission with responsibility for civil aviation safety in the European Union. It carries out certification, regulation and standardisation and also performs inve ...
announced that "...the Scandinavian airworthiness authorities will reissue the Certificates of Airworthiness relevant to this aircraft type in the coming days".
The final report stated:
Aftermath
After the second accident in Vilnius, SAS grounded its entire Q400 fleet consisting of 27 aircraft, and a few hours later the manufacturer
Bombardier Aerospace recommended that all Q400 aircraft with more than 10,000 flights stay grounded until further notice, affecting about 60 of the 160 Q400 aircraft then in service worldwide. As a result, several hundred flights were cancelled around the world.
Horizon Air grounded nineteen of its aircraft and
Austrian Airlines
Austrian Airlines AG, often shortened to Austrian or AUA, is the flag carrier of Austria and a subsidiary of Lufthansa, the flag carrier of Germany. The airline is headquartered on the grounds of Vienna International Airport in Schwechat where i ...
grounded eight.
On 13 September 2007,
Transport Canada
Transport Canada () is the Ministry (government department), department within the Government of Canada responsible for developing regulations, Policy, policies and Public services, services of road, rail, marine and air Transport in Canada, tra ...
issued an
Airworthiness Directive applicable to Bombardier Q400 turboprop aircraft instructing all Q400 aircraft operators to conduct a general visual inspection of the left and right main landing gear systems and main landing gear retract actuator
jam nuts. This effectively grounded all Q400 aircraft until the inspection had been carried out.
On 14 September 2007, Bombardier issued an All-Operators Message (AOM) recommending new procedures concerning the landing gear inspection for all aircraft with more than 8,000 flights. Bombardier acknowledged the likelihood of corrosion developing inside the
retract actuator.
Previous maintenance procedures mandated checking this component after 15,000 landings. The new maintenance schedule affected about 85 of the 165 Q400 aircraft worldwide. Some operators found that spare parts for this unexpected actuator replacement program were not available, grounding their aircraft indefinitely.
Investigators detected corrosion inside actuators on 25 of 27 aircraft they checked. Accordingly, SAS decided to continue the grounding of its Q400 fleet until all the affected parts were replaced.
On 28 October 2007, SAS announced that it would retire its entire fleet of Q400 aircraft after a third accident involving the landing gear occurred the day prior.
On 10 March 2008, a multi-party agreement was announced, attempting to finalize the roles of maintenance and manufacture in causing the SAS accidents; as settlement the airline and its partners ordered a replacement set of short-haul aircraft from Bombardier, and in turn received a US$164 million discount.
It has been speculated that a November 2007 shakeup of Bombardier management was spurred by the Q400 landing gear issues.
References
External links
VG Newspaper article
Video of the SAS Dash8-Q400 accident at AALHavarikommissionen (Danish Accident Investigation Board) report on the accident of the aircraft LN-RDK
Havarikommissionen (Danish Accident Investigation Board) report on the accident of the aircraft LN-RDI even though it says Danish
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