What happened
On September 13, 1998, a Cessna 208B Caravan, registration PT-OTM, operated by Penta Pena Transp. Aéreo S.A., was performing a ferry flight from Mundico Coelho to Alta Floresta. Approximately 18 minutes into the flight, the pilot reported an oscillation in engine torque. In response to this perceived issue, the pilot elected to land at an uncertified airstrip known as Pista do Conforto in Itaitube, Pará.
The aircraft approached the uncertified runway with a high glide slope, landing after having missed the first portion of the runway. During the landing roll, the pilot utilized reverse thrust only briefly. As the aircraft approached the end of the runway, the pilot determined that stopping within the remaining distance was impossible. In an attempt to steer the aircraft away from the runway limits, the pilot feathered the propeller, shut down the engine, and executed a sharp left turn (a "cavalo de pau"). This maneuver caused the aircraft to leave the runway and plunge into a nearby ravine. The aircraft sustained severe damage to the landing gear, propeller, right wing, and various onboard systems, but both crew members emerged uninjured.
The investigation
CENIPA investigators examined the engine and torque instruments, as well as the aircraft's braking system. Technical analysis by the Instituto de Aeronáutica e Espaço (IAE) found no anomalies in the engine or the torque indicator that would explain the reported fluctuation. Furthermore, testing of the torque pressure tube and brake assembly at PAMA-BE revealed that while the brakes were functional, the brake discs were below the minimum thickness specified in the maintenance manual.
The investigation also scrutinized the crew's emergency procedures. While the aircraft was equipped with an emergency power lever to manually override the fuel control unit (FCU) during torque fluctuations, the crew's use of this system was ineffective. Additionally, the investigation noted that the pilot did not cross-check the torque indication with other engine instruments to verify the validity of the reported fluctuation.
Findings
- Improper use of aircraft controls: The pilot's decision to feather the propeller and shut down the engine actually created a forward impulse that worsened the overrun situation.
- Inadequate braking performance: The brake discs were below the minimum thickness required by the maintenance manual, reducing braking efficiency.
and the pilot's decision to execute a sharp turn at the end of the runway.
- Lack of instrument cross-checking: The pilot failed to verify the torque fluctuation against other engine parameters to confirm a genuine engine failure.
- Deficient supervision and training: The operator failed to properly supervise maintenance standards regarding brake thickness and did not ensure the crew was proficient in using the emergency power lever or managing high-approach landings.
- Ineffective crew coordination: The co-pilot remained a passive observer during the emergency, failing to actively participate in managing the situation.