What happened
On the night of January 6, 1998, a Piper PA-31, registration PT-DGD, was conducting a night flight from Campo Grande International Airport (SBCG) to Cuiabá (SBCY). The aircraft was carrying a crew of two and five passengers at flight level 080. Approximately 67 nautical miles from Campo Grande, the aircraft experienced a sudden and significant power loss in the right engine, with power dropping from 30 to 18 inches.
The crew attempted to execute a 180-degree turn to return to the departure airfield. However, the aircraft was unable to maintain level flight on a single engine, descending at a rate of 500 feet per minute before stabilizing at a descent rate of 150 feet per minute. Approximately 20 nautical miles from Campo Grande, the pilots performed an emergency landing in a pasture on irregular terrain. During the landing, the aircraft struck a fence. Following the evacuation of all seven occupants, a fire broke out on the ground, completely consuming the aircraft. Of the occupants, one person sustained minor injuries while the remaining six were uninjured.
The investigation
CENIPA investigators examined the engine components and the maintenance history of the aircraft. While the pilots' licenses and medical certificates were valid, and the crew was experienced, the investigation focused on the fuel system and aircraft weight.
During the disassembly of the right engine's fuel injector, investigators discovered that the bypass spring in the fuel strainer assembly was deformed, a condition resulting from improper assembly. This deformation could prevent the bypass valve from opening, thereby restricting fuel flow in the event of a filter clog. Although the exact cause of the initial blockage could not be confirmed due to fire damage, the improper assembly was a significant finding. Additionally, the investigation considered the possibility that the aircraft's weight exceeded the limits required for single-engine level flight, despite the pilots' assertions that the aircraft was within weight and balance limits.
Findings
- Improper component assembly: The bypass spring in the right engine's fuel strainer assembly was found to be deformed, which likely restricted fuel flow.
- Single-engine performance uncertainty: While the aircraft's certification requires a 1/12 climb gradient, the crew was unable to maintain level flight following the power loss.
- Potential weight or handling issues: The investigation could not rule out that the aircraft was overweight or that flight controls were applied inadequately during the single-engine operation.
- Post-landing fire: The aircraft was destroyed by a fire that ignited on the ground after the forced landing.