ERA24LA386

The pilot reported that during climb out, he noticed a flicker of both the left and right hydraulic flow lights. He thought the airplane was losing hydraulic pressure, so he tried to extend the landing gear before all pressure was lost. Only the left main landing gear position green light illuminated. The hydraulic flow lights then illuminated steadily. He returned to the airport and performed the emergency landing gear extension checklist; however, the right and nose landing gear did not extend, and he landed with only the left main landing gear extended. A postaccident examination of the airplane revealed that a solid hydraulic line connected to the hydraulic filter was fractured and the system contained no hydraulic fluid. It is likely that the fracture of the hydraulic line and the subsequent loss of hydraulic fluid resulted in the partial landing gear extension. A review of the airplane’s maintenance records could not determine the age of the hydraulic line or if any maintenance had been performed on the hydraulic line. Postaccident testing of the emergency landing gear extension system revealed that if functioned normally when the activation handle was fully extended. Based on this information, it is likely the pilot did not pull the emergency handle out far enough to activate the system.

On September 17, 2024, about 1730 eastern daylight time, a Cessna 402C, N18VV, was substantially damaged when it was involved in an accident near Boston, Massachusetts. The pilot and two passengers were not injured. The airplane was operated by Cape Air as a Title 14 Code of Federal Regulations Part 135 scheduled passenger flight. According to the pilot, during climb out, he noticed a flicker of both the left and right hydraulic flow lights. He thought the airplane was losing hydraulic pressure, so he tried to extend the landing gear before all pressure was lost. Only the left main landing gear position green light illuminated. The hydraulic flow lights then illuminated steadily. He made the decision to return to the departure airport, notified air traffic control of the situation, and asked for delaying radar vectors to the airport in order to run the checklists. The pilot then followed the "Landing Gear Will Not Extend Hydraulically" checklist. He noted that the landing gear position indicating lights were working when he checked the “press to test,” just as they were on the ground before takeoff. He slowed the airplane to under 130 knots with the landing gear switch already in the down position. He then pulled the “GEAR HYD” circuit breaker and pulled the emergency landing gear extension handle. There was no change of position indicator lights or any indication/noise that the landing gear had extended. He subsequently landed on the left main landing gear and began lowering the airplane’s nose. During the landing roll, the airplane’s right wing contacted a runway light, after which it started to leak fuel. The airplane came to rest upright on the right side of the runway, at an intersection of the runway and taxiway. Further examination of the airplane’s hydraulic system by the operator’s maintenance department revealed that a solid hydraulic line connected to the hydraulic system filter was fractured, and that all of the hydraulic fluid had drained out of the system. The maintenance personnel performed the emergency landing gear extension procedure by pulling the landing gear emergency extension handle all the way out and observed all three landing gear come down and lock. A review of the airplane’s maintenance records could not determine the age of the hydraulic line or if any maintenance had been performed on the hydraulic line. Following the accident, the operator issued a Technical Notice to all maintenance personnel to stress the importance of general inspection criteria while performing maintenance on the airplanes.