AD 99-09-12 64 FR 20150 Active

This amendment adopts a new airworthiness directive (AD), applicable to all British Aerospace (Jetstream) Model 4101 series airplanes, that requires repetitive inspections to detect damage of the structure associated with the engine nacelle fairing attached to the wing flaps, and repair of any damage found; drilling a new drain hole in each engine nacelle fairing; and applying a sealant to the gap between the wing flap and engine nacelle fairing. This amendment also requires correction of discrepancies, and modification of the wing flap structure, which terminates the repetitive inspections. This amendment is prompted by reports of fatigue cracks found in the structure that attaches the engine nacelle fairing to the wing flaps. The actions specified by this AD are intended to prevent such fatigue cracking, which could result in the partial or complete separation of the fairing from the wing flap, and consequent additional structural damage to the airframe and/or reduced controllability of the airplane.