AD 97-03-09
Unsafe Condition
Corrosion on pivot bolts and bushings of the backlash remover lever mechanism on the elevator booster control unit (BCU) could result in backlash in the elevator controls and reduced elevator control authority in the manual mode.
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Required Actions
Perform repetitive operational checks to detect backlash in the elevator mechanical control system, inspect backlash remover bolts for freedom of movement and corrosion, and either replace affected BCU with improved units or modify BCU by installing corrosion-resistant bolts. If bolts are frozen/corroded, lubricate and free them, defer BCU replacement for 10 days if operational check is successful, but replace NAS6204C13D bolts immediately if issues are found.
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Compliance Time
Before further flight for NAS6200C13D bolt issues; otherwise, checks must be performed at specified intervals (e.g., 500-flight cycles for operational checks, 1,800-flight cycles for inspections per optional terminating actions).
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Affected Aircraft
Fokker Model F28 Mark 0100 series airplanes with elevator booster control units (BCU) containing pivot bolts and bushings in the backlash remover lever mechanism.
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Source: Official FAA Source ↗
Retrieved: Apr 8, 2026
Rights: U.S. Government Public Domain
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