Missing Control Rod Bushing Could Cause Excessive Vibration, Loss Of Control

The FAA has issued an Emergency Airworthiness Directive (EAD) (2010-12-51) for Agusta Model AW119 MKII helicopters. The EAD is the result of the report of a missing control-rod bushing (bushing) from a 90-degree tail rotor gearbox (TGB) installed on a Model AW119 MKII helicopter. The Agusta Model 119 helicopters also have the affected TGB installed; therefore, they are also included in the applicability of this EAD. This condition, if not detected and corrected, could result in abnormal vibration and damage to the tail rotor system, loss of the yaw control function, and subsequent loss of control of the helicopter.

Agusta Alert Bollettino Tecnico No. 119-38, dated March 25, 2010 (ABT), specifies inspecting the TGB, part number (P/N) 109-0440-06-103, to verify the presence of the bushing. If the bushing is not installed, the ABT specifies replacing the TGB and associated parts with a “new” TGB assembly, P/N 109-0440-06-105. Also, the ABT specifies if the bushing is installed, reidentifying the TGB “by installing an additional nameplate” with P/N 109-0440-06-105.

AW119 File Photo

EASA notified the FAA that an unsafe condition may exist on these helicopter models. EASA advises of a missing bushing in the TGB of a Model AW119 MKII helicopter. EASA also advises that “this condition, if not detected and corrected, could cause abnormal vibration of the tail rotor controls possibly leading to their damage and consequent loss of the yaw control function.” EASA classified the ABT as mandatory.

The FAA says the condition is likely to exist or develop on other helicopters of these same type designs. Therefore, this EAD requires, before further flight, removing the forward boot from the nut and inserting a 0.3 millimeter (mm) thickness gauge, not exceeding 10 mm in width, between the rod and nut until the gauge stops. This EAD requires, from the face of the nut, measuring the depth the gauge is inserted between the rod and the nut before it stops. If the depth measurement is between 4 mm and 6 mm, the bushing is installed, and this EAD requires reidentifying the TGB, P/N 109-0440-06-103, by using an etch pen to change the last three digits of the P/N from -103 to -105. If the depth measurement is greater than 6 mm, this EAD requires, before further flight, replacing the TGB and the associated parts with airworthy parts.

The actions must be accomplished by following specified portions of the ABT described previously. This rule is issued under 49 U.S.C. Section 44701 pursuant to the authority delegated to me by the Administrator, and is effective immediately upon receipt of this emergency AD.

FMI: www.faa.gov