Description

On 30 November 2001, a BAe Jetstream 31 operated by European Executive Express ran off the side of runway 19 on landing at Skien Airport, Geiteryggen, Norway. The runway excursion was the consequence of an unstable non-precision approach, with airframe ice accretion, and a very heavy touchdown, which caused severe aircraft damage and loss of control.

Synopsis

The following is an extract from the official Report into the Accident investigated by the Aircraft Accident Investigation Board Norway (AIBN):

"On Friday, 3 November 2001, SE-LGA (radio call signal EXC 204) was on its way to Skien with a crew of two and 11 passengers. During the flight, ice was observed on the aircraft’s wings, but the ice was considered to be too thin to be removed. During descent towards runway 19 at Geiteryggen the aircraft’s ground proximity warning system (GPWS) sounded a total of three times. The aircraft was then in clouds and the crew did not have visual contact with the ground. The warnings, combined with somewhat poorly functioning crew coordination, resulted in the crew forgetting to actuate the system for removing ice from the wings. The subsequent landing at 1828 hrs was unusually hard, and several of the passengers thought that the aircraft fell the last few metres onto the runway. The hard landing caused permanent deformation of the left wing so that the left-hand landing gear was knocked out of position, and the left propeller grounded on the runway. The crew lost directional control and the aircraft skewed to the left and ran off the runway. The aircraft then hit a gravel bank 371 metres from the touchdown point. The collision with the gravel bank was so hard that the crew and several of the passengers were injured and the aircraft was a total loss."

The Investigation

"Information from the FDR and CVR indicates that the aircraft maintained an indicated speed of approx. 110 - 115 kts when the aircraft encountered an abnormally high sink rate and hit the runway. Both of the crew members thought that they were a little high on final approach because the white light (PLASI 3.30L) flashed a few times. According to the Commander, the aircraft developed a high rate of descend in flare at the same time as the Power Levers were pulled back to Flight Idle 2.5 - 3 seconds before landing. According to the passengers, the landing was especially hard, and several thought that the aircraft fell the last metres down onto the runway. The breath was knocked out of one passenger momentarily when the aircraft hit the ground. According to a printout from the FDR, the load was 6 g at the moment of landing. […]

The investigation shows that it is probable that ice on the wings was the initiating factor for the accident. The AIBN has not formed an opinion on whether the ice resulted in the high sink rate after the first officer reduced the power output of the engines, or whether the aircraft stalled before it hit the runway. Investigation has to a large extend focused on the crew composition and training. A systematic investigation of the organisation has also taken place. In the opinion of the AIBN, the company has principally based its operations on minimum standards, and this has resulted in a number of weaknesses in organisation, procedures and quality assurance. These conditions have indirectly led to the company operating the route Skien - Bergen with a crew that, at times, did not maintain the standard that is expected for scheduled passenger flights. The investigation has also revealed that procedures for de-icing of the aircraft wings could be improved…"

Causal and Contributory Factors

The Report identifies the following factors (Significant Investigation Results) that led to the accident:

• "The decision was made to wait to remove the ice from the wings because, according to the SOPs, it should only be removed if it had been “typically half an inch on the leading edge”. This postponement was a contributory factor in the ice being forgotten.
• At times, the relationship between the flight crew members was very tense during the approach to Skien. This led to a breakdown in crew coordination.
• Among the consequences of the warnings from the GPWS was a very high workload for the crew. In combination with the defective crew coordination, this contributed to the ice on the wings being forgotten.
• It is probable that the aircraft hit the runway with great force because the wings were contaminated with ice. The AIBN is not forming a final opinion on whether the wings stalled, whether the aircraft developed a high sink rate due to ice accretion or whether the hard landing was due to a combination of the two explanatory models.
• The company could only provide documentary evidence to show that the Commander had attended an absolute minimum of training after being employed within the company. Parts of the mandatory training had taken place by means of self-study without any form of formal verification of achievement of results.
• The company’s operation was largely based on minimum solutions. This reduced the safety margins within company operations.
• The company’s quality system contributed little to ensuring ‘Safe Operational Practices’ in the company.
• Authority inspection of the company was deficient.

Safety Recommendations

As a result of its investigations, the AIBN submitted 7 safety recommendations:

• "During the investigation, the AIBN has become aware that pilots have received warnings from the Ground Proximity Warning System (GPWS) during apparently normal approaches to runway 19 at Skien airport Geiteryggen. This can undermine respect for the warning system. Inadvertent GPWS warnings were also a factor relating to the accident in question here. The AIBN recommends that Avinor should undertake a review of approach procedures (LLZ DME) for runway 19, among other things, with a view to reducing the opportunity for inadvertent GPWS warnings (SL recommendation no. 10/2005).
• The investigation has discovered that the Swedish Civil Aviation Authority largely based its inspection work on inspections of the company’s manuals, and to a lesser extent verified the company’s actual practices. The AIBN recommends therefore that the Swedish Civil Aviation Authority should assess whether, to a greater extent than previously, its inspection activities should also be directed towards verifying the actual practices within a company (SL recommendation no. 11/2005).
• A review of the quality system at European Executive Express has uncovered a series of weaknesses. The AIBN recommends that the Swedish Civil Aviation Authority should undertake a new assessment of the quality system at European Executive Express AB (SL recommendation no. 12/2005).
• The accident in question can, with great probability, be linked to the fact that the aircraft was landing with ice on the wings. Current procedures for this aircraft type do not contain any items that would guarantee a maximum possible degree of ice-free wing before landing. The AIBN therefore recommends that the Civil Aviation Authority in the UK (CAA-UK) should order BAE Systems to introduce a procedure that would reduce the possibility of landings with wings contaminated with ice (SL recommendation no. 13/2005).
• The procedures for removing ice on the wing are based on the crew being able to assess the thickness of the ice without having a specific tool to undertake such as assessment. The AIBN therefore recommends that the Civil Aviation Authority in the UK (CAA-UK) should order BAE Systems to assess whether a form of ice accretion meter should be installed on this aircraft type. (SL recommendation no. 14/2005).
• The Jetstream 31 is equipped with a stall warning system which activates on the basis of the wing’s angle of attack. If the aircraft’s wings are contaminated with ice, stalling can occur at smaller angles of attack than the criteria for issuing a warning. This is not discussed in the Approved Flight Manual (AFM), and the flight crew in this instance were apparently unfamiliar with the situation. The AIBN recommends therefore that the Civil Aviation Authority in the UK (CAA-UK) should order BAE Systems to inform and warn operators of the fact that the stall warning systems do not function as assumed when the wings are contaminated with ice (SL recommendation no. 15/2005).
• The investigation has discovered that the Joint Aviation Authorities (JAR-OPS 1) have very general requirements for training when a company employs flight crew members with adequate type rating and possibly authorisation to act as Commander. These requirements form the basis for the training that the Commander was given within the company, and which the AIBN believes was marginal. The AIBN therefore recommends that the JAA should assess whether the requirements for training should be increased within the CRM, the company’s OM and the company’s quality system. (SL recommendation no. 16/2005)."

Related Articles

Runway Excursion

• Runway Excursion

Human Factors

• Crew Resource Management

Further Reading

• AIBN Accident Report (SL REP. 11/2005)