AD NUMBER: 2011-27-51

MANUFACTURER: Hawker Beechcraft Corporation
SUBJECT: Airworthiness Directive 2011-27-51

Background: This emergency AD was prompted by the following reported problems of the elevator bob-weight (stabilizer weight) traveling past its stop bolt, which allowed the attaching linkage to move over-center, reducing nose down elevator control. In one instance, a Model 1900C airplane experienced jammed elevators on take-off after a loud bang was heard in the cockpit shortly after rotation. The flight crew noticed that they were unable to move the control column to a nose down position. Elevator movement was only available between neutral to full deflection nose up. The airplane pitch was controlled with the elevator trim and the airplane returned to base, landing safely. Upon inspection, mechanics noticed that the bob-weight interconnect link, part number (p/n) 101-524112-1, was upside down and trailing FORWARD from the control column weld assembly instead of trailing AFT as it should. With the link travel over-center, the geometry of the bob-weight was completely changed relative to its stop. This condition made the bob-weight hit its stop mid-travel, where it should actually have positive clearance from its stop at the full nose down position. The elevator could now only move between nose full up and neutral.

In another instance, on a Model 1900D airplane, during the takeoff roll the elevator controls felt heavy and appeared to be jammed/sticking, requiring more force than usual to rotate. The crew then aborted the takeoff run. Subsequent investigation revealed that the elevator bob-weight attaching link assembly traveled over-center, thus preventing full nose down elevator control authority.
The Model 1900 airplanes have the same type design and thus are subject to this unsafe condition.

This condition, if not corrected, could result in reduced nose down elevator control and loss of airplane control.

FAA’s Determination: We are issuing this AD because we evaluated all the relevant information and determined the unsafe condition described previously is likely to exist or develop in other products of the same type design.

AD Requirements: This AD requires inspecting the elevator bob-weight and attaching linkage for correct installation and for damage or deformation to the weight and/or weight bracket with corrective action as necessary.

Interim Action: We consider this AD interim action to address the immediate unsafe condition affecting these airplanes. We may take further AD action at a later date.

FMI: AD NUMBER: 2011-27-51