What happened
On 27 August 2024, a Bell 206L-1 LongRanger helicopter with a single pilot on board was conducting a ferry flight with the doors removed, from Mitchell Falls campground to a coastal landing site on Nat Beach, Western Australia.
The helicopter departed at 0615 local time and climbed to an altitude of 1,800 feet AMSL. During the flight, the seat located in the rear row on the right side fell out of the helicopter. The pilot was unaware that the seat had fallen out until after the helicopter landed at Nat Beach and the pilot was preparing to pick up the passengers for the next flight.
The seat did not impact the tail rotor or stabilisers and there was no damage to the helicopter.
The helicopter had finished a 100 hourly maintenance inspection the day prior to the incident flight. It then conducted a ferry flight to Mitchell Falls with the doors on. The doors were removed at Mitchell Falls campground and the seat base was lost on the next flight (Figure 1).
Figure 1: Missing seat after landing at Nat Beach
Source: Operator
The operator’s internal investigation revealed that the seat had been incorrectly installed prior to release from the 100 hourly inspection. During installation, the brackets on the seat were most likely not installed fully onto the locating pins before the securing pin was installed (Figure 2), or the brackets missed the securing pin (Figure 3).
Figure 2: Incorrect installation – seat brackets not installed on locating pins
Source: Operator, annotated by the ATSB
Figure 3: Incorrect installation – securing pin not fully engaged
Source: Operator, annotated by the ATSB
Safety action
The Head of maintenance briefed the engineer who completed the 100 hourly inspection and reiterated to all engineering staff during a toolbox meeting the necessity of ensuring proper seat installation. The helicopter was inspected by the maintenance team and no damage was found. The Fleet Service Manager raised an alert relative to this occurrence to remind both pilots and engineers on the seat installation instructions.
Safety message
The Bell 206L rear seats are not standardised and have several different ways that they may be secured. Personnel installing seats need to be vigilant in understanding and double‑checking that seats are installed correctly, which usually requires a close visual inspection and a pull on the seat to check security, as seemingly minor tasks in nature can have a substantial impact.
Pilots accepting aircraft from maintenance should conduct a particularly thorough pre-flight inspection. Errors in maintenance can and do occur, and that first pre-flight inspection is a critical part in capturing those errors.
About this report
Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, no investigation has been conducted and the ATSB did not verify the accuracy of the information. A brief description has been written using information supplied in the notification and any follow-up information in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions.