AAIB Special Bulletin – Inadvertent nose landing gear retraction
Whilst the aircraft was being loaded with cargo in preparation for a flight to Frankfurt, and whilst carrying out a Dispatch Deviation Guide (DDG) procedure to clear maintenance messages relating to an existing Acceptable Deferred Defect (ADD), the Nose Landing Gear (NLG) retracted. This caused damage to the lower nose, NLG doors and engine cowlings. Door 2 left (Door 2L) struck the top of the mobile steps which resulted in the door separating from the fuselage and one person, operating the cargo loader positioned at the forward cargo hold, received minor injuries.
The DDG procedure required the cockpit landing gear selection lever to be cycled with hydraulic power applied to the aircraft. To prevent the landing gear from retracting, the procedure required pins to be inserted in the nose and main landing gear downlocks. However, the NLG downlock pin was installed in the NLG downlock apex pin bore which was adjacent to the correct location to install the downlock pin. When the landing gear selector was cycled the NLG retracted.
An Airworthiness Directive had been issued, with a 36-month compliance from 16 January 2020, to install an insert over the apex pin bore to prevent incorrect installation of the downlock pin, but this had not yet been implemented on G-ZBJB.