What happened
On March 7, 2001, at approximately 00:30 local time, a Boeing 707, registration PT-MST, operated by Skymaster Airlines, was performing a cargo flight for the Brazilian Postal Service (Correios) from Brasília to Guarulhos. While executing an ILS approach to runway 09R, the crew first noticed that the stabilizer trim control was inoperable at 10,000 feet. Although the system briefly returned to normal operation, the failure recurred between 6,000 and 4,700 feet.
The commander elected to proceed with the landing. During the short final phase, the aircraft assumed a severe nose-down attitude and collided violently with the ground. The impact caused the nose and main landing gear to collapse. The aircraft slid approximately 800 meters, eventually coming to a stop perpendicular to the runway on the grass. All three crew members escaped the wreckage uninjured, though the aircraft sustained extensive damage to the engines, landing gear, and fuselage, rendering it a total loss.
The investigation
CENIPA's investigation focused on the mechanical failure of the flight control systems and the crew's decision-making. Maintenance inspections of the stabilizer trim components revealed that the trim servo was seizing and lacked output torque, while the stabilizer trim actuator showed excessive wear. Notably, investigators found that the control cables had become unguided and wrapped around the pulleys.
Furthermore, the investigation identified that the Flight Data Recorder (FDR) had been incorrectly installed, which prevented the retrieval of critical flight parameters. The investigation also noted that the airport's emergency response was hindered by the lack of specialized fuel suction equipment and the absence of decision-making personnel at the scene, which delayed the removal of the aircraft.
Findings
- The primary cause was the crew's decision to continue the landing approach despite the stabilizer trim failure, which led to an unmanageable nose-down attitude.
- The crew failed to execute the prescribed "Jammed Stabilizer Landing" checklist, specifically neglecting the use of flaps and spoilers to help maintain the aircraft's pitch.
- Deficiencies in Crew Resource Management (CRM) were present, characterized by poor coordination, a lack of landing briefings, and a failure to utilize the emergency checklist.
- The crew's perception of the emergency was skewed by the critical phase of flight, leading them to prioritize landing over performing a go-around to stabilize the aircraft.
- Maintenance deficiencies were suspected, as the unguided cables and pulley issues were not detected during previous inspections.
- The FDR was improperly installed, making it impossible to analyze the aircraft's flight parameters during the final moments of the approach.