An A300 spoiler system faulted as the spoiler handle was being retracted and caused severe roll oscillations. Aircraft control was regained after the three faulting spoilers switches were deactivated. The faulting spoilers should have; but did not automatically deactivate.
Synopsis
An A300 spoiler system faulted as the spoiler handle was being retracted and caused severe roll oscillations. Aircraft control was regained after the three faulting spoilers switches were deactivated. The faulting spoilers should have; but did not automatically deactivate.
Narrative
[We were] descending from 9;000 to 6;000 MSL on initial approach; 245 KTS; 30 air miles from the runway; autopilot on; NAV engaged; 5 miles from turn point. From wings level flight; aircraft rolled abruptly 20 degrees to the right; then through neutral to approximately 20 degrees to the left. First Officer turned autopilot off and attempted to level wings. Captain then took control of aircraft. Roll oscillations continued. First Officer complied with ECAM and turned off Spoiler 7 switch and Spoiler 3 & 2 switch (both showed faults). Roll oscillations ceased when faulted switches were deselected. Since aircraft was now under control; Captain elected to continue to landing without further troubleshooting. Calculated landing distance with spoilers inoperative at 1.3x normal distance and determined landing distance not a factor. [I] Selected Medium Brakes as a precaution. Informed Approach control; due to the short duration between recovering aircraft control and landing; elected to not declare an emergency so as to devote our attention to the aircraft and checklists. After being cleared the approach; Approach Control queried us as to souls on board and fuel. Offered this info and were informed crash/rescue would be standing by; ready to assist. After landing uneventfully; informed outbound Captain of maintenance issue. Later learned a part was changed to remedy anomaly. Maintenance informed outbound Captain the faults should have rendered corresponding spoilers deactivated (or de-powered). Either this did not happen (since roll oscillations only stopped when faulted spoilers were deselected) or they were de-powered and the speed brakes that were still extended caused the rolling moment. In either case; uncontrollable adverse roll was the result. In this case; since we were descending; altitude was necessary before aircraft control was regained. If the aircraft was on short final; this situation may not have been recoverable. Accordingly; due to the potential threat to flight safety: recommend that spoiler fault lights; accompanied by un-commanded roll moments be incorporated as A300 memory items. This incident demonstrates 'whatever the cause' that an uncontrollable situation can result from spoiler switches remaining on; with fault lights illuminated.
NASA callback
The Reporter stated that he was in the process of stowing the speed brake handle or had just completed stowing the handle when this event occurred. He was uncertain exactly what he had done because the severity of this event obscured his memory of his exact actions prior to the roll beginning. The roll rate was found to be 17 degrees per second; so it was very violent. The reporter is uncertain whether the faulted spoilers retracted while the operating spoilers were in the process of retracting or if the faulted spoilers failed to retract as the operating spoilers were fully retracted. As stated in the report; if this event has occurred near landing it may not have provided enough time for the crew to recover.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.