Helicopter maintenance technicians reported that after scheduled maintenance they learned a pilot discovered during preflight inspection the tail rotor gearbox oil cap was not installed.

ACN 2061581 2023-12 Bell Helicopter Textron Undifferentiated or Other Model Maintenance Reports

Parked

What is ASRS?

The Aviation Safety Reporting System is NASA's voluntary, confidential, non- punitive incident-reporting system, established 1976. Pilots, controllers, dispatchers, and maintenance technicians file reports describing safety- relevant events. NASA de-identifies every report before adding it to the public database. Reports are not investigated by NASA, the FAA, or the NTSB — they represent the reporter's perspective.

Pilot narratives

Verbatim from the de-identified NASA record. First-person account by the reporter. NASA strips identifying details (names, company, specific time); anonymization placeholders are ZZZ, X, Y.

Reporter 1

I was performing scheduled maintenance on a Bell 206L1+ for a 300-hour event. I completed the Tail Rotor section and all that entailed. Our maintenance facility was recently made aware that the pilot was performing his preflight inspection after receiving the aircraft from scheduled maintenance when he noticed the tail rotor gearbox oil cap was not installed. I was the individual who installed the cap, and another AMT verified its installation by performing a Safety and Security Check (SSC). At this point, the aircraft was looked at by two individuals who verified the cap was installed. After receiving notification of the cap not being installed, we talked amongst ourselves here at our maintenance facility and there are several other people, to include 2 pilots, that saw that the cap was installed prior to the Operational Check Flight (OCF) and the aircraft's departure from our facility to its destination. The aircraft underwent ground-runs and an OCF prior to leaving our facility with no visible signs of oil coming from the gearbox or anywhere else.

Reporter 2

During 300 HR upon completion of servicing and inspection of the tail rotor gearbox area I was tasked with conducting a safety and security check (SSC) of the area prior to the cowling being installed. At the time of my inspection everything appeared and felt secure. After this action the aircraft underwent several ground runs with no evidence of oil leakage. It was also noted by other mechanics as well as pilots that the oil cap was installed at this time. The aircraft was then flown back to its destination. Upon arrival at its destination, during a preflight inspection, it was discovered the tail rotor gearbox servicing cap was not installed.

NASA classification — Anomalies

Aircraft Equipment Problem
Deviation / Discrepancy - Procedural

NASA classification — Assessments

Contributing Factors / Situations: Aircraft · Human Factors · Incorrect / Not Installed / Unavailable Part
Primary Problem: Incorrect / Not Installed / Unavailable Part

ASRS reports are voluntarily submitted, de-identified by NASA, and represent the reporter's perspective. The presence of reports on a topic cannot be used to infer prevalence in the National Airspace System. The authoritative source is the NASA ASRS Database Online at asrs.arc.nasa.gov ↗.