What happened
On April 11, 2017, an Aero Commander 690A, registration HK1771G, was conducting a flight for a pilot annual check accompanied by an instructor and an aviation authority inspector. During the flight, the crew performed a simulated engine failure maneuver. Upon restoring power to the right engine, the aircraft experienced a significant leftward yaw. The crew declared an emergency due to the pedals becoming jammed.
While attempting an emergency landing at Yariguíes Airport, the aircraft touched down on runway 04. During the deceleration phase, the aircraft experienced a lateral runway excursion to the left, exiting the paved surface into the safety area. The impact caused significant damage to the nose gear assembly. All three (03) occupants evacuated the aircraft safely without injuries.
The investigation
The GRIAA investigation focused on the mechanical failure of the directional control system. Investigators examined the aircraft's maintenance history and found that the rudder had become obstructed by a loose component. Specifically, the "Anti Icer Rudder Horn" had partially detached and was interfering with the vertical stabilizer, which severely limited the pilot's ability to maintain directional control.
Findings
- The primary cause of the runway excursion was the loss of directional control resulting from the rudder jamming.
- The rudder jam was caused by the partial detachment of the Anti Icer Rudder Horn, which interfered with the vertical stabilizer.
- The detachment occurred because of deficient maintenance procedures where three of the five required screws (P/N: MS27039-0806) were omitted during a previous maintenance task.
- A contributing factor was the lack of detailed, step-by-step instructions from the manufacturer regarding the removal and installation of the Anti Icer Rudder Horn (P/N: 5E1487-2) during inspections.
Safety action
- The investigation recommended that maintenance programs for the Aero Commander include complete procedures for the visual inspection of the anti-ice system and the verification of correct fastener installation.
- It was recommended that the manufacturer, Rockwell International, revise Service Bulletin SB235 Revision 2 to include specific instructions for inspecting and installing the Anti Icer Rudder Horn and its associated hardware.