On September 27, 1985, a Cessna 177RG (registration N2637V) was involved in an aviation accident near Ennis, TX. Investigators recorded the probable cause as: The hydraulic fluid supply had been depleted through a fatigue cracked aluminum pressure line, thus causing the hydraulically operated landing gear system to be inoperative by use of its normal or emergency extension systems. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A pilot unable to lower landing gear normally made an emergency landing at night. Nose gear remained down but unlocked; main gears folded. The aircraft veered off runway, striking a post. Investigation found hydraulic fluid lost via a fatigue-cracked pressure line.
Incident
During a nighttime operation, the pilot attempted to lower the landing gear using the normal extension system but was unable to do so. The emergency extension system was then used, which allowed partial lowering of the gear. The pilot subsequently performed an emergency landing at the departure airport. Upon touchdown, the nose gear remained down but unlocked, while the main landing gear folded back into their respective wheel wells. The aircraft veered off the runway, and the right side of its horizontal stabilator struck a short wooden post, bringing the aircraft to a stop.
Investigation
Examination of the aircraft revealed that the hydraulic fluid supply had been depleted. The loss was attributed to a fatigue-cracked aluminum pressure line. This condition rendered the hydraulically operated landing gear system inoperative, affecting both the normal and emergency extension systems.
Probable cause
The hydraulic fluid supply had been depleted through a fatigue cracked aluminum pressure line, thus causing the hydraulically operated landing gear system to be inoperative by use of its normal or emergency extension systems.