What happened
While cruising at altitude, the flight crew of an unidentified aircraft discovered that the control wheel could not be moved for lateral aileron control. While the elevator and rudder remained functional, the crew was unable to extend the trailing edge wing flaps as they approached their destination, although the leading edge slats did extend. The aircraft subsequently performed a landing in this degraded configuration.
The investigation
Post-flight inspections of the aircraft revealed ice accumulations located within all three wheel wells. This ice had accumulated on both the aertoon control cables and the flap extension cables, physically preventing the movement of the cables.
Investigators traced the source of the moisture to a leak in the potable water system. A rubber hose attached to a water line fitting beneath the floorboard, near the 3R door, was found to be misting water. When the floorboard was lifted, the upward movement was restricted by this specific water line. Further inspection showed that the water line pulled loose from its fitting during the examination. The failure of the rubber hose was attributed to excessive load applied to the crimped joint between the flexible hose and the end fitting.
It was noted that the aircraft manufacturer had installed water lines to the underside of the floorboards. However, the maintenance manuals lacked instructions for identifying if a water line was attached to the underside of a floorboard or procedures for disconnecting such lines before lifting the panels.