AD 98-13-25
Unsafe Condition
Uncommanded trimming or failure of the trim system of the horizontal stabilizer, leading to reduced controllability of the airplane.
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Required Actions
Inspect the servo-valve sub-assembly rod-end bearing and servo-valve sub-assembly for movement within 20 days after September 9, 1992. Replace the horizontal stabilizer control unit if movement exceeds specified loads. Perform a one-time residual strength inspection within 6 months after the AD's effective date and replace the actuator if discrepancies are found. Replace the horizontal stabilizer actuator with an improved version within 3 years after the AD's effective date.
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Compliance Time
Within 20 days after September 9, 1992 (for part (a)), within 6 months after the effective date (for part (b)), within 3 years after the effective date (for part (c)), and as of the effective date (for part (d)).
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Affected Aircraft
Fokker Model F.28 Mark 1000, 2000, 3000, and 4000 series airplanes equipped with Menasco horizontal stabilizer actuators having part number 11100-( ).
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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