What happened
On September 17, 2024, at approximately 1730 EDT, a Cessna 402C, registration N18VV, was involved in an accident near Boston, Massachusetts. The aircraft was operating as a scheduled Part 135 passenger flight for Cape Air.
During the climb out phase, the pilot observed the left and right hydraulic flow lights flicker. Fearing a loss of hydraulic pressure, the pilot attempted to extend the landing gear. While the left main landing gear position green light illuminated, the other gear did not indicate as down. The pilot then returned to the departure airport, requested radar vectors to allow time for checklists, and followed the "Landing Gear Will Not Extend Hydraulically" procedure. After slowing the aircraft to below 130 knots, the pilot pulled the "GEAR HYD" circuit breaker and pulled the emergency landing gear extension handle, but there was no change in the position indicator lights.
The pilot subsequently landed the aircraft on the left main landing gear and began lowering the nose. During the landing roll, the right wing struck a runway light, causing a fuel leak. The aircraft came to a stop upright at the intersection of the runway and a taxiway. There were no injuries to the pilot or the two passengers.
The investigation
Maintenance personnel from the operator examined the aircraft's hydraulic system and discovered that a solid hydraulic line connected to the hydraulic system filter had fractured. This fracture caused all hydraulic fluid to drain from the system. While maintenance staff were able to successfully extend all three landing gears using the emergency extension handle during post-accident testing, they noted the system functioned normally only when the handle was pulled all the way out.
A review of the aircraft's maintenance records did not provide information regarding the age of the fractured hydraulic line or any recent maintenance performed on it.