Aircraft
Certification Service Washington, DC U.S. Department of Transportation Federal Aviation Administration
CE-19-21
December 9, 2019
This is information only. Recommendations
aren’t mandatory.
Introduction
This Special Airworthiness Information Bulletin (SAIB) informs
registered owners/operators of an airworthiness concern for Air
Tractor, Inc., Models AT-602, AT-802, and AT-802A airplanes. (Note:
AT-802/AT-802A models with part number 71112-1 flap actuator installed
are NOT affected.) Specifically, this SAIB notifies owners and
operators of procedures to replace one configuration of the flap motor
mounting studs with an improved configuration, and to inspect for and
correct cracking and separation of the flap motor mounting studs, which
if left uncorrected, could result in loss of control..
At this time, the airworthiness concern is not an unsafe condition that
would warrant airworthiness directive (AD) action under Title 14 of the
Code of Federal Regulations (14 CFR) part 39.
Background
An incident occurred where the two mounting studs attaching the motor
to the flap actuator assembly cracked, resulting in separation of the
flap motor and loss of flap control on one of the above-referenced
airplanes. In addition, the separated motor fell downward and
interfered with the aileron controls. Other incidents of cracked
mounting studs have also been reported. Cracks were only reported with
one of the three possible stud configurations installed.
To address this, Air Tractor issued Service Letter (SL) #375, dated
April 9, 2019, which describes procedures for inspection of the flap
motor mounting studs for cracks, and for replacement of mounting studs
found to be cracked or susceptible to cracking. SL #375 describes the
stud configuration that is susceptible to cracking, as well as the
acceptable replacement configurations.
Recommendations
The FAA recommends that owners and operators perform a one-time
inspection of the flap actuator motor before further flight per Section
5, Action, of Air Tractor Service Letter #375, dated April 9, 2019.
In the event cracked studs, or stud configurations susceptible to
cracking, are found installed, the FAA recommends that owners and
operators replace the flap motor mounting studs with one of the other
two acceptable stud configurations described in Section 4, Summary, of
Air Tractor Service Letter #375, dated April 9, 2019. Instructions for
replacement should be performed in accordance with the Section 6,
Replacement Procedure, detailed in Air Tractor Service Letter #375,
dated April 9, 2019.
For Further Information Contact
Jacob Fitch, Aerospace Engineer, AIR-7F2, ACO Branch, FAA, 10101
Hillwood Pkwy, Fort Worth, TX 76177; phone: (817) 222-4130; email:
jacob.fitch@faa.gov.