PRM1, vicinity Samedan Switzerland, 2010
PRM1, vicinity Samedan Switzerland, 2010
On 19 December 2010, a Raytheon 390 inbound to Samedan from Zagreb made a daylight approach to runway 21 at destination in marginal VMC which involved a steep and unstable descent from which a landing was not possible. The subsequent go around was followed by entry to a visual right hand circuit which was contrary to local procedures due to terrain constraints. Overbanking in the turn towards final approach was followed by a stall and loss of control which led to ground impact which, with the post crash fire, destroyed the aeroplane and fatally injured both occupants.
On 19 December 2010, a Raytheon (Hawker Beechcraft) 390 being operated by German Air Taxi operator Windrose Air Jetcharter on a positioning flight from Zagreb to Samedan with just the two pilots on board cancelled Instrument Flight Rules (IFR) and made a daylight approach to runway 21 at destination in marginal Visual Meteorological Conditions (VMC) which involved a steep and evidently unstable descent from which a landing was not possible. The subsequent go around was followed by entry to a visual right hand circuit which was contrary to local procedures due to terrain constraints. Controlled flight was exited during an overbanked turn towards final approach and in the subsequent ground impact and fire, the aeroplane was destroyed and both occupants were fatally injured.
An Investigation was carried out by the Aviation Division of the Swiss AIB. The Investigation was heavily dependent on the successful downloading of the NVM from the Terrain Avoidance and Warning System (TAWS) equipment since no Flight Data Recorder (FDR) was fitted (or required to be fitted) and the search for the 2 hour CVR was unsuccessful.
It was concluded that the First Officer had been PF during at least the final stages of the flight and that the AP had not been engaged. Both pilots were found to have been qualified on the aircraft types which was certified for single pilot operation but required by the operator to be flown by two pilots. It was noted that both pilots worked part time for the operator involved as well as also working part time for other operators.
It was established that on the day of the accident, several operators had planned to make flights to Samedan and a total of 13 inbound aircraft were notified. Eight of these flights were filed as business jets, four as turboprop aircraft and one using a single-engine piston aircraft. An analysis of the prevailing weather showed that stable conditions for approach had existed but there had been considerable layer cloud at fluctuating heights creating restricted visibility on the runway 21 approach. Three other aircraft had completed successful approaches and landings prior to the arrival of the accident aircraft but the other nine had either abandoned their approaches and diverted or had not attempted an approach at all. The last of the three aircraft that did land did so just under half an hour prior to the accident occurring and had reported “very challenging weather conditions during the approach”.
After cancelling IFR during the descent, the accident aircraft had begun an approach down the valley to runway 21 passing through “areas with greatly reduced visibility” before apparently obtaining a late sighting of the runway. At this point, a ‘land at your discretion’ was received from the FISO and a steep descent reaching and maintaining over 2000 fpm was commenced and maintained until just below 250 feet agl when the aircraft was over the runway threshold with a speed of 150 KCAS. This descent was steep enough to have activated two EGPWS ‘Sink Rate’ Alerts and a ‘PULL UP’ Hard Warning without any crew response.
A climb was initiated to approximately 600 feet agl with the landing gear extended and probably the flaps also still set to 20º. At the end of the runway, a right turn was made onto a downwind leg during which the bank angle reached 55º and airspeed increased from 110 to 130 knots. Abeam the threshold of runway 21, a turn direct to final approach was begun during which the bank angle reached up to 62 degrees without any significant increase in airspeed. The aircraft then turned upside down and crashed almost vertically, severing a power line which caused a power failure in the Upper Engadine valley. A post crash fire followed the impact and completed the destruction of the aircraft.
The improvised right hand visual circuit attempted was noted to have been contrary to the prescribed missed-approach procedure (see the copy of the Samedan Visual Approach Chart applicable at the time of the accident below) and it was concluded that it became so challenging because of the topography and the handling characteristics of the jet aircraft involved, that it was no longer manageable.
The Operating procedures employed by the aircraft operator were found to be substantially different to the manufacturers standard SOPs, in many cases without obvious reason. It was also noted that the Operator had published procedures which allowed crucial EGPWS warnings to be suppressed for no justifiable reason which was potentially dangerous. Records of completion for operator qualification to operate into Samedan were found to be incomplete, raising the question of whether they had been complied with by both pilots.
In relation to the provision of weather information pertinent to decisions by aircraft pilots on whether to commence or continue approaches to Samedan were considered by the Investigation. These included the fact that weather observations at the aerodrome were not necessarily any guide to conditions likely to be encountered during the (visual only) approach and the fact that conditions reported by an approaching aircraft were not consistently passed on by the FISO. It was also found that FIS employees at Samedan were unable to append TREND information to their METARs and since it was as a result only possible to terminate a METAR with ‘NOSIG’, there was the potential for crews to be misled.
It was also noted that the transmitted Automatic Terminal Information Service (ATIS) recording did not always correspond to the current METAR because it was only updated once an hour whereas the METAR was produced every half hour and that SPECI reports were neither broadcast via the ATIS nor transmitted over the radio.
There was also particular concern that “the…..weather minimums applicable at the time of the accident involved a considerable risk”.
The Investigation concluded that Cause of the accident was that the aircraft collided with the ground after control of the aircraft was lost due to a stall. This outcome was attributable primarily to “the risky conduct of the crew” concerning which two Causal Factors were identified:
- The crew continued the approach under weather conditions that no longer permitted safe control of the aircraft.
- The crew performed a risky manoeuvre close to ground instead of a consistent missed-approach procedure.
A Contributing Factor was found to be that the flight information service did not consistently communicate to the crew relevant weather information from another aircraft. And a Systemic Factor was found to be that “the visibility and cloud bases determined on Samedan airport were not representative for an approach from (the north east) because they did not correspond to the actual conditions in the (runway 21) approach sector”.
Safety Action taken by the Swiss Aviation Regulator FOCA during the course of the Investigation to introduce a comprehensive system of mandatory pilot pre-qualification for Samedan was noted as was their introduction of new approach minima there for all aircraft in ICAO PANS-OPS Category ‘B’ or higher of a minimum visibility of 5km and a minimum cloud ceiling of 2200 feet aal with the stipulation that whenever those values are not met, the runway will be unavailable.
One Safety Recommendation as a result of the Investigation as follows:
- that the Federal Office of Civil Aviation together with the Operator of Samedan airport should improve weather observation and transmission of important weather information so that approaching crews have all necessary information at their disposal for decision-making
The Final Report No. 2140 of the Investigation was completed on 23 April 2012 and approved by the Board on 12 June 2012