Serious incident to the Cessna 525 registered F-HMSG operated by Valljet on 28/10/2023 at Paris - Bourget airport

The aeroplane was returned to service following maintenance operations that included a visual inspection of the nose landing gear well. However, the task relating to closing the doors of the nose landing gear, after its inspection, was not completed. Three technicians from the maintenance workshop worked on the aeroplane, one of them not type-rated for the aeroplane, assumed the role of team supervisor, in the absence of the only team supervisor of the Citation sector in the workshop.

The technicians all indicated that, in hindsight, they were very tired at the end of their week’s work, accentuated by a reorganisation of the tasks requested by Valljet’s Fleet Technical Manager. According to the technicians, this situation led to aeroplanes being moved several times in the hangar and on the apron, thus increasing the overall workload.

To move F-HMSG without damaging the nose gear doors, whose rods were not connected, one of the technicians closed them with aluminium adhesive strips and a red flag was put in position.

Before the aeroplane’s run-up on the apron, the technician assuming the role of team supervisor removed the red flag without noticing the aluminium adhesive strips. He thought that the maintenance task on the nose landing gear had been completed in full.

At the end of the maintenance operations, the technician responsible for the CRS did not linger over the nose landing gear and did not identify that the task associated with the nose landing gear inspection had not been completed. In fact the rods actuating the gear doors were not attached and the screws were still hanging in a bag from the nose landing gear. The work card filled in by the technician who carried out the inspection did not show this information.

Following these maintenance operations, the two agents in charge of towing the aeroplane between the maintenance workshop apron and the operator’s apron did not notice the aluminium adhesive strips. Furthermore, the two pilots did not notice them either when they carried out the pre-flight external inspection of the aeroplane at night.

After take-off, when the crew controlled the retraction of the landing gear, as the rods of the nose gear doors were not attached, this affected the movement of the doors, and resulted in them blocking the nose gear.

Complying with the emergency procedures did not correct the problem. The crew then decided to burn as much fuel as possible before landing in order to limit the consequences of a landing with an unlocked nose gear. On landing, the contact of the aeroplane’s nose with the runway did not result in any particular incident.

Throughout the flight, which lasted around three hours and during which the landing gear failure was not an emergency, numerous suggestions from controllers, pilots and the fire services were discussed and considered, or even improvised, without being assessed or given a concrete form by a structured decision-making process.

Finally, the observations made by OSAC following the serious incident revealed, among other things, deviations within the maintenance workshop, that were consistent with the information gathered during the BEA investigation, in particular deviations relating to:

·the management of the technicians and their supervision;

·proper checking of the work cards by support and certifying staff.

These deviations have since been the subject of corrective actions by the workshop, approved
by OSAC.