Thu, Dec 29, 2011
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.
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