Piper PA-46-350P N117KR accident near Redmond, Oregon

Probable cause

An undetermined hydraulic system malfunction in the engine compartment during descent from cruise flight which resulted in an in-flight fire.

NTSB analysis

The pilot reported that during the approach to the airport, the landing gear down and locked indicator lights (3-green) did not illuminate when the landing gear handle was placed in the down position. The pilot cycled the landing gear; however, the landing gear lights did not illuminate and the pilot activated the emergency landing gear extension system and declared an emergency. After the emergency was declared, the pilot noted flames emanating from the engine cowling and the cockpit began to fill with smoke. Shortly thereafter tower personnel reported that the airplane was trailing smoke and the pilot was cleared to land. The pilot reported that on short final to the runway the "engine experienced a significant, uncommanded decrease in power, but continued to provide partial power." After landing, the pilot and passenger exited the airplane and the fire was extinguished by airport fire department personnel. Examination of the airframe and engine revealed that the nose landing gear hydraulic actuator hose was separated from its corresponding B-nut coupler. The B-nut fitting remained attached to the threaded end of the hydraulic actuator; however, the hose was separated from the coupler at the coupler flange. The hose was covered by dark soot and extensive thermal damage was noted. The opposing end of the hydraulic hose was secured to its associated coupler and fitting. The hydraulic hose is positioned below the engine, adjacent to the turbo charger and exhaust. The examination also revealed that the upper right crossover exhaust pipe was separated from the intermediate crossover exhaust pipe. Fire damage was noted on both the internal and external exposed ends of both the intermediate and right crossover exhaust pipes in the area where they were intended to be connected. The hydraulic hose and associated coupler were removed from the airframe and examined by Safety Board investigators. Due to the extensive thermal damage, the failure mode of the hose was not determined, and the correlation between the exhaust leak and separated hydraulic hose was not established. Subsequent to the accident, the manufacturer amended the maintenance manual for the airplane to reflect changes in the service life limits for nose landing gear hydraulic hoses. The amendment states "Replace nose gear hydraulic hoses (gear actuator/door actuator/ sequence valve), as required; but do not exceed 1,000 hours time-in-service, or eight (8) years, whichever comes first."

Text from the NTSB. Open the NTSB docket for WPR09LA361 for the full record.