What happened
On May 3, 2003, at approximately 16:45 UTC, a Velocity XLRG Elite experimental aircraft, registration CS-XAM, departed from runway 19 of the Évora Aerodrome for a test flight. The aircraft was operated by a single pilot.
After completing one circuit of the airfield, the pilot performed a second approach. During this second pass, as the pilot applied power to execute a go-around, flames erupted from the engine area. The aircraft continued on a straight path and collided with a 7-meter-tall concrete utility pole approximately 2 km from the runway. The impact caused an explosion and a subsequent fire that consumed the aircraft. The pilot sustained fatal thoracic injuries in the accident.
The investigation
The GPIAAF investigation examined the aircraft's construction and the pilot's experience. The investigation focused on a significant modification made to the aircraft's exhaust system. The pilot had designed a custom noise-reduction system by installing exhaust mufflers inside the wings. This involved creating tunnels within the wing structure using STYROFOAAM (extruded polystyrene) to house the mufflers.
Investigators found that the exhaust pipes, which reached high temperatures, were placed in close proximity to the aileron control cables and surrounded by the polystyrene foam. Testing revealed that the STYROFOAM structure began to deform irreversibly at temperatures near 300°C and was highly flammable. The investigation also noted that the modification had not been reviewed or approved by the engine manufacturer, Lycoming, or the kit manufacturer, Velocity Inc.
Findings
- The primary cause of the accident was the inadequate management of an in-flight engine fire.
- A contributing factor was the fire originating in the right wing root, likely caused by the incorrect design of the modified exhaust system.
- The use of highly flammable polystyrene foam around high-temperature exhaust components created a significant fire hazard.
- The lack of national legislation in Portugal regulating experimental aircraft construction meant there was no formal mechanism to prevent or oversee such unauthorized modifications.
- The pilot's limited flight experience, totaling only 96:30 hours, may have limited the ability to effectively mitigate the emergency.