Loss of engine power after takeoff
On the morning of 25 June 2021, the Cessna 208B with registration PH-FST was parked inside the hangar of a maintenance organisation. A mechanic under supervision of a licenced engineer was tasked to replace the magnetic pick-up. The mechanic followed steps one through four. Steps five through eight were not noticed by the mechanic and as a result not carried out.
After the system was found to be functioning correctly, the mechanic left the aircraft and the pilot taxied to the skydive organisation’s building to pick up parachutists. Following the boarding of seventeen parachutists, the pilot taxied to runway 26 and commenced the takeoff roll. Shortly after takeoff, without any warning, the engine lost power at approximately 400 feet above field level. The pilot made an emergency landing in a field whereby the aircraft sustained substantial damage to the fuselage, wings, landing gear and propeller. One parachutist suffered minor injuries.
Gear design and maintenance procedure allowed incorrect installation
The damage was caused by contact between the magnetic pick-up and rotating parts of the propeller governor (the toothed gear). Metal debris restricted the free movement of the ball head assembly in the governor housing, likely displacing the metering valve aft and allowing all oil to drain from the propeller dome and causing the propeller to continuously move to the feather position. This increasing pitch of the propeller led to an increasing power demand, which the engine could not deliver. This resulted in a power reduction that reinforced itself until the engine flamed out.
It was determined that prior to the accident flight most probably the magnetic pick-up was installed in the governor assembly in between two gear teeth of the rotating gear. This was not noticeable during the normal engine autostart and SRL check (systems which also use magnetic pick-up input). The design of the propeller governor toothed gear makes it possible to position the magnetic pick-up in between two teeth. The maintenance manual did not specifically mention or address this possibility.
Preliminary report and safety actions
On 30 December 2021, the Dutch Safety Board published a safety alert on its website in the form of a preliminary report to present initial findings and highlight the possibility of positioning the magnetic pick-up in between the teeth of the ball head gear.
in July 2022, the engine manufacturer issued a revision of the engine maintenance manual regarding the procedure for replacement of the magnetic pick-up. The maintenance organisation has taken safety actions to improve planning of maintenance and prevent distraction of mechanics while performing maintenance tasks. Because of the corrective actions already taken, the Safety Board does not issue safety recommendations.
