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.