N9267P

On February 20, 2023, about 1425 Pacific standard time, a Piper PA24-260, N9267P, sustained substantial damage when it was involved in an accident in San Jose, California. The pilot and passenger were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 flight.

The pilot departed from his home base of Reid-Hillview Airport (RHV) with a destination of Half Moon Bay Airport (HAF) and reported that the flight was uneventful.

While on the landing approach, he performed the pre-landing checks and realized that he had not heard any movement of the landing gear. He checked the landing gear light, and it was not green, and the emergency extension handle had not moved forward to the landing position.

The pilot cycled the landing gear switch, but the gear did not extend so he decided to abort the landing and fly out over the ocean to troubleshoot. During that time, he checked the landing gear circuit breaker and it had not tripped and did not appear to be hot. He then cycled landing gear switch but the gear still did not extend.

He decided to return to RHV where there were emergency and maintenance services, rather than proceed with a landing at HAF. Once within the San Jose area, he released the emergency release arm in accordance with the emergency procedures. The landing gear still did not extend and the telescoping emergency extension bar was jammed and did not move forward. He decided to perform a series of high-G maneuvers to help the gear extend and during each pull-up he pushed the extension handle. After multiple attempts the handle finally moved forward to what appeared to be the fully extended position; however, the green landing gear light still did not illuminate.

He then decided to land at RHV after tower controllers at San Jose International Airport and RHV reported that the gear was down. The landing was uneventful; however, when the pilot retarded the throttle the nose gear started to retract, followed by the main gear.

The airplane sustained structural damage to both lower center beams and multiple bulkheads during the ensuing ground roll.

The airplane was equipped with retractable tricycle landing gear operated through an electrically controlled retraction system. The system consisted of an electrical motor and transmission that drove a torque tube and bellcrank connected to push-pull cables for each main and nose gear strut assembly. All three landing gear move simultaneously when activated and were held down and locked with over-center links. In the event of an emergency, such as when the gear cannot be extended due to a failure in the motor or transmission, a release arm can be used to disconnect the motor, and the gear can then be extended manually by pushing the emergency extender bar fully forward.

The airplane was examined by the National Transportation Safety Board investigator-in-charge at RHV airport following the accident.

During the examination, it was found that the landing gear motor would intermittently stop operating and pause at the retracted position. During multiple cycles it was found that the fault would not always be accompanied by the landing gear circuit breaker tripping. The transmission jackscrew assembly was coated in grease and did not show any evidence of binding and the motor did not emit any smoke. There was no evidence in the maintenance records that the motor had ever been replaced.

Examination of the emergency gear release system revealed that the emergency disengage arm and links exhibited wear to their pivot pins and holes, such that when the arm was pulled it did not provide the leverage required to consistently release the motor transmission from the landing gear bellcrank assembly. Under this condition, because the bound motor remained connected, it inhibited movement of the bellcrank assembly and the landing gear could not be extended with the emergency extension bar.

Even when the disengage assembly opened and the gear could be extended by the emergency extension bar, due to a worn and out of adjustment drag link assembly in the nose landing gear a firm forward application of force to the nosewheel would cause the nose gear to unlock. Due to the simultaneous design, this would also unlock the main gear. This condition had been masked by the landing gear motor transmission assembly, which under normal operation drove the drag links into the locked position.

Further examination revealed that the entire landing gear system appeared to be dirty and coated in old grease and grime. The nose landing drag link assemblies were slightly loose at their fuselage fittings and could be seen to move with landing gear movement.

Airworthiness Directive (AD) 77-13-21 was issued in 1977 to prevent collapse of the landing gear after manual extension as in the accident scenario. The AD required a specific landing gear inspection at 1,000-hour intervals and the installation of a second nose gear downlock spring, both in accordance with Piper Aircraft Service letter 782. The AD also required periodic inspection of the main landing gear bungee cords, with replacement at 500-hour intervals.

The inspection portion of the AD was last completed in 2007, and not due for another 306 hours. The second spring was present, and the bungees were replaced in June 2020, 78 flight hours before the accident. The mechanic, who performed the most recent annual inspection one week before the accident, stated that he performed a functional check of the landing gear while the airplane was on jacks, with no anomalies noted.

The airplane’s maintenance logbook indicated the airplane was examined in accordance with “FAR Part 43 appendix D.” Subpart (e) of those regulations is devoted to the inspection of the landing gear group, and makes multiple specific references, including, “All units—for poor condition and insecurity of attachment,” “Linkages, trusses, and members—for undue or excessive wear fatigue, and distortion,” and “Retracting and locking mechanism—for improper operation.”