What happened
On February 10, 2001, a Mitsubishi MU-2B-25, registration PT-LEW, operated by Heringer Táxi Aéreo Ltda, was performing a check flight for a command rating. The flight departed from Belém (SBBE) bound for Macapá (SBMQ) with three crew members and two passengers. During the instrument approach, weather conditions at the destination deteriorated, with heavy rain and mist reducing visibility below the minimum descent altitude (MDA).
As the aircraft approached the missed approach point, an explosion occurred in the left engine, followed by an intense in-flight fire. The crew attempted emergency procedures, including feathering the propeller and activating the fire extinguishing system. However, the fire persisted and intensified. Due to the loss of altitude during the emergency maneuvers, the crew was able to regain visual contact with the runway. The instructor decided to proceed with a landing despite an unstabilized approach. The aircraft landed on the grass on the right side of the runway with the landing gear retracted. All five occupants escaped without injuries, though the aircraft sustained severe damage and was a total loss.
The investigation
CENIPA investigators examined the wreckage and the left Garrett TPE331-6251M engine. Analysis by the propulsion subdivision revealed a failure of the second-stage turbine disk. The investigation also focused on why the fire could not be extinguished. Investigators found that a fuel tank puncture, likely caused by engine fragments during the explosion, may have fed the fire. Furthermore, while the crew attempted to use the fuel shut-off valve, the valve failed to close because a misplaced hose clamp obstructed the control lever.
Findings
- The primary cause of the fire was sparks resulting from friction caused by the failure of the second-stage turbine disk.
- The fire could not be extinguished because the fuel shut-off valve was obstructed by a misplaced clamp, allowing continuous fuel flow.
- A puncture in the left wing fuel tank may have contributed to the fire's intensity.
- The decision to perform a forced landing on the grass was made to maintain aircraft controllability and ensure occupant safety.
- The engine failure could have been related to manufacturing defects or improper handling during assembly, though the damaged state of the disk prevented a definitive conclusion.
Safety action
Following the investigation, several safety recommendations were issued:
- The manufacturer of the Garrett turbine was notified of the disk failure to assist in trend analysis.
- Operators of the MU-2B-25 were advised to inspect the area around the fuel shut-off valve for any misplaced clamps that could obstruct the mechanism.
- The operator was advised to re-evaluate pilot training, specifically regarding asymmetric power and engine fire emergencies, and to review maintenance supervision processes.