N4112K

On January 12, 2020, about 1223 Alaska standard time, a Piper PA-31-350 airplane, N4112K, sustained substantial damage when it was involved in an accident at Fairbanks International Airport (FAI), Fairbanks, Alaska. The airline transport pilot and seven passengers were uninjured. The airplane was operated as a Title 14 Code of Federal Regulations Part 135 scheduled commuter flight.

The pilot reported that as the airplane approached the destination airport, the landing gear did not extend, the landing gear indicator lights did not illuminate, and the selector did not return to the neutral position. She repeated the landing gear extension procedures again; however, the landing gear still did not extend. She then checked that all the circuit breakers were in and used the checklist to perform the emergency landing gear extension procedure. The pilot pumped the hand-operated emergency gear extender about 70 times, but there was low feedback pressure in the system. When the landing gear still did not extend, she diverted back to FAI, where emergency services and a maintenance crew were available.

As the airplane approached FAI, the pilot activated the emergency blowdown pneumatic system for both the main and nose landing gear. The green down-and-locked indicator lights for the nose and left main landing gear illuminated, but the right main landing gear (MLG) light did not illuminate. The pilot performed a fly-by of the control tower and the tower controller reported that the right MLG door was open, but the gear remained retracted. The pilot then flew to a nearby training area, climbed to 5,000 ft, and attempted to swing the right MLG out with higher-G maneuvers, but was unsuccessful.

The pilot performed a straight-in visual approach to FAI runway 2L. Once the landing was assured, she shut down and secured both engines. During the landing roll, the right wing impacted the runway, resulting in substantial damage to the right wing and aileron. All occupants evacuated normally.

The airplane was recovered to the company hangar, where a Federal Aviation Administration inspector examined the hydraulic system. The hydraulic reservoir was almost depleted and minimal fluid existed in the system. After servicing and testing the hydraulic system, a leak was observed at the fitting between the right main landing gear door close line and the right MLG unlock actuator. The hydraulic line was removed, and the threads on the actuator assembly connection were stripped. The fitting was capped and the system functioned normally.

The company also tested the pneumatic blowdown system and discovered that the right MLG shuttle valve was stuck in place. The shuttle valve was removed and disassembled, and water and corrosion were present inside.

According to the maintenance records, all of the landing gear hydraulic lines were replaced during a recent phase inspection about one week before the accident.