The Spoilers Left in Maintenance Mode — G-KMAM

To change a damaged right-hand outer flap, engineers put the A320's spoilers into maintenance mode and moved them — using an incomplete procedure. The collars and flags that lock and placard a spoiler actuator in maintenance mode were never fitted, so nothing visible marked the spoilers as unsafe, and the purpose of the collars was not fully understood by engineers more familiar with other types. Across the shift handovers of a job that overran its 0700 return-to-service estimate — amended at least twice, with the team under pressure — the spoilers' status never got briefed. After flap fitment, the re-instatement and functional check of the spoilers were not carried out. The airplane was handed to the crew at about 1500. During the flight-control check, spoilers 2 to 5 on the right wing failed to answer right-roll demands on the ECAM — neither pilot noticed, and the operator had given its pilots no specified procedure for the check. On rotation at 1530 the aircraft rolled right undemanded; the co-pilot needed full left sidestick, handed control to the commander at about 300 feet, and past 1,700 feet the ECAM finally declared F/CTL ALTN LAW and F/CTL SPLR FAULT. The crew flew a 37-minute circuit and landed back at Gatwick.

The AAIB's causal factors climb the whole ladder: an incomplete maintenance-mode procedure on the floor, line management that did not enforce a rigorously procedural approach, engineers whose mental model came from other aircraft types, a handover that never carried the spoiler status, and a functional check — the last defence — that neither maintenance nor the flight crew performed to a standard that would catch four dead spoilers (AAIB AAR 2/95, causal factors i–v). It produced fourteen safety recommendations, including specific warnings in the Airbus manuals to re-instate and function the spoilers after deactivation, and an additional flag on the maintenance device itself. The card teaches the iron rule of maintenance mode: a system you deactivate is not back until you have re-instated it and proven it.

1. Put a flight-control system into maintenance mode only by the complete maintenance manual procedure — on the A320 spoiler actuator that includes fitting the collars and flags that physically lock and visibly placard the deactivated state.
2. Deviation from the maintenance manual requires design-authority consultation and approval — an engineer who cannot achieve full compliance is not empowered to certify the work.
3. Carry the deactivation status across every shift handover, explicitly: which systems are in maintenance mode, what remains to re-instate.
4. After the job, re-instate the system by the book and perform the full functional check — surfaces answering the correct command, in the correct direction, on indication and on the wing.
5. Stage-sheet the task so re-instatements, inspections and function checks each carry an authorised signature before the Certificate of Release to Service.

Frequency of flight-control systems left in maintenance mode is not quantified in public sources — but the UK CAA canon puts incorrect installation of components at the top of its published listing of frequently recurring maintenance discrepancies (UK CAA CAP 718, Chapter 2 §1.5).

An undemanded right roll from liftoff, with spoilers 2 to 5 on the right wing extended out of control; full left sidestick to contain it; reversion to alternate law with the spoiler fault annunciated only past 1,700 feet. The crew retained control, flew a 37-minute circuit and landed safely back at Gatwick; the flight-control system was degraded by the loss of spoiler control throughout (AAIB AAR 2/95, Synopsis and §1.1). No injuries; the incident, notified to AAIB at 2030 that evening, became one of the defining human-factors investigations in UK maintenance.