Accident Overview
A twin-engine aircraft departed Madrid-Cuatro Vientos Airport on a private flight to Cascais, Portugal, carrying three passengers and one pilot. One of the reasons for the flight was to repair the weather radar at a Portuguese maintenance center that specialized in this equipment. The pilot delayed takeoff until 1557 local time due to adverse weather conditions. The aerodrome had been in instrument meteorological conditions (IMC), forcing its closure from 0900 until 1444 local time.
Flight Progression
At 1615 local time, the aircraft was en route, climbing from flight level 190 to its authorized cruise level of 210. Moments later, according to a detailed analysis of radar data, there was a yaw to the left, and the aircraft started to turn in this direction and suddenly lose altitude. After this event, the airspeed fell quickly and gradually until the aircraft stalled.
Spin and In-Flight Breakup
The aircraft entered a spin, which after some time became a flat spin. As the airplane descended out of control, with the spin fully developed, loads were placed on the horizontal tail that exceeded the design loads, causing the tail to break up in flight into five parts before the aircraft impacted the ground. The aircraft was completely destroyed by the impact and subsequent fire, and its four occupants were killed in the accident.
Official Findings
The investigation concluded that this accident was caused by the loss of control of the aircraft in flight due to a stall and subsequent spin. Due to the high degree of destruction of the wreckage after impact and fire, and the lack of other pertinent data, it was not possible to determine precisely the sequence of events leading to the stall/spin.
Contributing Factors Identified
The investigation identified the following contributing factors:
- The decision to make the flight with adverse meteorological conditions (IMC) along the planned route, considering that the weather radar was not operational.
- The forecast of moderate to strong icing conditions in areas of the route (presence of cumulonimbus with caps up to 35,000 feet and temperatures between -17°C and -19°C at flight level 180) suggests that ice formation or accumulation was a significant contributory factor.
- The use of the autopilot and the failure to disengage it when the emergency situation arose, as concluded from radar data analysis, could have contributed significantly to the loss of control.
- The inadequate training of the pilot (who lacked the type rating for the accident aircraft) in abnormal or emergency situations on the accident aircraft.