Aircraft
Certification Service Washington, DC U.S. Department of Transportation Federal Aviation Administration
AIR-21-07
March 30, 2021
This is information only. Recommendations
aren’t mandatory.
Introduction
This Special Airworthiness Information Bulletin requests that owners
verify the correct washer style prior to the installation of wing spar
attach bolts when complying with AD 2020-26-16.
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
AD 2020-26-16 requires the replacement of four wing spar attach bolts
following eddy current inspection of the subject bolt holes. Although
not required by the AD, it is common practice to install new washers
with the new bolts. Some of the washers listed in the various model
Illustrated Parts Catalogs (IPCs) for the wing spar attach bolts are
designed with rounded edges on one side intended to provide additional
clearance between the washer and the wing spar structure. These washers
are normally used in conjunction with flat washers but are placed with
the rounded side against the spar surface in locations where structural
clearance cannot be maintained by the use of a flat washer. Piper
Aircraft, Inc. (Piper) has made the FAA aware of recent shipments of
incorrectly manufactured washers. Even though the washers may be
identified with the part number that matches the IPC washer part
number, the incorrect washers were manufactured without the rounded
edges on one side. Installation of a non-rounded “flat” washer where a
rounded washer is intended may decrease or eliminate the clearance
between the washer and the spar structure.
Recommendations
The FAA recommends that any owner/operator ordering and receiving Piper
part number 96352-003 (Piper purchase order code 494-284) washers for
use in the wing spar attach bolts of any aircraft applicable to AD
2020-26-16 verify that those washers have the required radius on one
surface. If the washers do not have the radius as shown below, do not
install the wing spar attach bolts until the correct washers are
obtained.