On February 28, 1985, a Cessna 421C (registration N98487) was involved in an aviation accident near Butte, MT. Investigators recorded the probable cause as: The swivel hose aluminum fitting on the hydraulic line failed for undetermined reasons. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
During level flight, the pilot observed smoke from the left engine, followed by hydraulic fluid and warning lights. On approach, the nose gear failed to extend. The pilot secured the engine, used emergency gear extension, and landed. Investigation found a broken hydraulic line fitting.
Incident Description
During level flight, the pilot noticed a puff of smoke emanating from the left engine. Shortly after, hydraulic fluid appeared, and both the left and right hydraulic flow lights illuminated. As the aircraft approached for landing, the pilot lowered the landing gear, but the nose gear did not extend.
Pilot Actions
Flames were then observed burning through the top of the left engine cowling. The pilot secured the engine and utilized the emergency extension system for the nose gear, which allowed it to extend. The pilot subsequently landed the aircraft.
Investigation Findings
Post-incident investigation revealed that the fire originated from hydraulic fluid that sprayed from a broken hydraulic line onto the supercharger. The failure occurred on a swivel hose aluminum fitting (part number AE70101JZ174) on the hydraulic line. The reason for the fitting failure could not be determined.
Probable cause
The swivel hose aluminum fitting on the hydraulic line failed for undetermined reasons.