What happened
On June 8, 2001, at approximately 17:12 UTC, a Cessna 152, registration CS-AUI, crashed into the terrain in the Peninha area of the Sintra Mountains. The aircraft, operated by Aerocondor Aviation School, was conducting a flight training mission focused on instrument flight maneuvers. The crew consisted of a student pilot and a flight instructor.
After departing from Cascais (Tires) aerodrome, the aircraft was operating under Visual Flight Rules (VFR) within an assigned training area. During the maneuvers, the student pilot used a view-blocking device to simulate instrument conditions, while the instructor maintained visual separation from other traffic. As the flight progressed, weather conditions deteriorated, with a continuous cloud layer forming below the aircraft's altitude.
Seeking to descend to 1,500’ AMSL, the instructor guided the aircraft through a gap in the clouds. During this descent, Lisbon Approach (LIS APP) instructed the crew to expedite their descent due to other traffic in the area. As the aircraft descended through 1,900’ and entered the clouds, visibility dropped to between 20 and 30 meters. While attempting to maneuver to avoid the terrain, the aircraft entered a sequence of pitch changes that led to a loss of airspeed and altitude, ultimately striking the ground at approximately 1,600’ AMSL.
The investigation
The GPIAAF investigation examined the flight planning, weather conditions, and the sequence of events leading to the impact. Investigators found that while the flight was properly authorized and the crew was qualified, the aircraft had drifted approximately 4 km outside its assigned training area. The investigation also reviewed the communications between the crew and Lisbon Approach, noting that the controller's instruction to expedite the descent did not account for the high terrain in the area.
Findings
- The primary cause of the accident was the collision with the ground resulting from a descent below the minimum safe altitude for the area.
- The instructor decided to continue the descent into clouds without ensuring VFR separation minima could be maintained.
- Air Traffic Control (ATC) issued an instruction to expedite the descent without considering the underlying terrain elevation.
- The flight crew failed to notify ATC when they could no longer maintain VFR conditions, effectively operating in a state that required IFR procedures without requesting them.
- Deteriorating meteorological conditions and the aircraft's deviation from the assigned training area contributed to the accident.