Description

On 10 July 2002, a Saab 2000 being operated by Swiss Air Lines on a scheduled public transport service from Basel to Hamburg encountered extensive thunderstorms affecting both the intended destination and the standard alternates and due to a shortage of fuel completed the flight with a landing in day Visual Meteorological Conditions (VMC) at an unmanned general aviation airstrip where the aircraft collided with an unseen obstruction. After the aircraft came to a stop with the landing gear torn off, the two cabin crew conducted the passenger evacuation on their own initiative. There was no fire and only one of the 20 occupants was injured. The aircraft was declared a hull loss due to the damage sustained relative to the location.

Investigation

An Investigation was carried out by the German BFU. It noted that on the afternoon of the accident day, an active cold front had been moving eastwards over Germany but that the pre flight briefing received by the flight crew had only mentioned isolated Cb clouds and had not included the then-valid SIGMET for the Berlin FIR or, in particular, the SIGMET issued at 1500Z for the destination Bremen FIR which contained a warning of a squall line reaching FL380 even though the aircraft remained on the ground until 1609Z.

It was established that the approach to the intended destination Hamburg had been abandoned 90 minutes after departure from Basel due to the weather conditions. The crew had then decided to divert to their planned alternate of Hannover but did not first obtaining a comprehensive weather overview of those airfields within range and as yet unaffected by the front. After a 20 minute flight in a south-easterly direction in advance of the squall line, the crew decided against trying to reach Hannover by flying around the thunder cells and instead began a diversion to Berlin Tegel on the basis of their weather radar display, flying at a maximum of 5000ft. The Tegel Automatic Terminal Information Service (ATIS) broadcast did not, at that time, indicate that the existing CAVOK weather would significantly worsen by the ETA. Upon nearing Tegel, the crew requested a “priority approach” because they had “just observed a low fuel warning light”. However at this time, the weather reports for all the Berlin airports included imminent thunderstorms with heavy precipitation and winds gusting up to 55 knot and a few minutes later, the approach to Tegel was discontinued because of the thunderstorms.

The aircraft then set course for the airfields at Finow and Neubrandenburg northeast of Berlin but this plan was soon abandoned because of the weather in the vicinity and the distance away in relation to estimated fuel endurance. ATC advised that Werneuchen Special Airfield was reported as currently unaffected by the line of thunderstorms and the crew decided to fly there. ATC referred to the AIP and advised the crew of the length, width and nature of the runway surface. This airfield was not licensed or equipped for public transport flights and although the runway was long enough, the airfield chart did not, in the view of the Investigation, provide absolute clarity in respect of a non-usable portion of the runway. It was also not clear whether the crew had understood that part of the original runway length was no longer in use. The airfield radio frequency was not passed to the crew nor was it requested.

A direct visual approach was made to runway 08 at Werneuchen without any radio contact with the airfield and, because of the overall weather situation and the low fuel endurance, without first inspecting the runway from the air. The markings on the disused portion of the old full-length (2400m) runway had not been removed, nor had the disused portion been marked as such. The touchdown zone markings on the old full-length runway were still in good condition and misled the crew to use this as a touchdown target marker. A low earth bank extending the full width of the runway at the boundary of the disused and available (1500m long) parts of the runway was not, in the prevailing poor lighting, noticed by the crew during the final stages of their approach and, after a normal touchdown, it was too late for the aircraft to avoid a collision with the bank.

The track followed by the aircraft is depicted on the map below:

The Investigating Agency stated that it was not provided with any evidence that the crew had taken part in Line Oriented Flight Training exercises, which “might have improved their in flight responses to the circumstances encountered, as part of their flight training”.

The Findings of the Investigation included:

• The Swiss AL Operational Control Centre provided insufficient pre flight information to the crew.

• According to the Swiss Operations Manual Part ‘A’, Crew Resource Management training for the crew had not included LOFT.

• The extra fuel above minimum requirements loaded by the crew was reasonable given the weather briefing they had received.

• Short term weather forecasting for the Berlin airports at the time of the event was deficient.

• The active and disused runway markings at Werneuchen were not in accordance with the requirements of ICAO Annex 14 or with applicable Germany regulations.

• The last airfield inspection made by the responsible CAA prior to the accident had produced no criticism with respect to the runway or the disused runway markings.

The Investigation concluded that the accident was due to the following ‘Immediate Causes’:

• The extent and intensity of the thunderstorm frontal system, plus the speed of change in the weather system.

• Insufficient use (by the flight crew) of available resources when making decisions in flight.

• The loss of alternative landing options, coupled with increasing time pressure.

• The aircraft touched down outside the operational area of an airfield.

• The earth wall was not detected and collision with same followed.

It was also concluded that the accident could be associated with the following ‘Systemic Causes’:

• Insufficient information with respect to weather situation and development, both prior to and during the flight.

• Insufficient information about Werneuchen Special Airfield due to inadequate chart illustration plus absence of and misunderstood communications.

• Insufficient signs and markings of operational and non-operational airport areas (at Werneuchen).

After an unexplained substantial delay, the Final Report: Accident Investigation Report AX002-0/02 of the Investigation was completed in October 2010 and published in English in December 2010. No Safety Recommendations were made as a result of the Investigation.

Further Reading

• Runway Excursion
• Runway Availability
• Runway Visual Perspective
• Weather Forecast
• Decision-Making (OGHFA BN)
• Flight Preparation and Conducting Effective Briefings (OGHFA BN)