Aircraft
Certification Service Washington, DC U.S. Department of Transportation Federal Aviation Administration
NM-07-39 R1
October 10, 2008
This is information only. Recommendations
aren’t mandatory.
Introduction
This Special Airworthiness Information Bulletin (SAIB) alerts you, an
owner or operator of Gulfstream Model G-1159 (G-II), G-1159A (G-III),
and G-1159B (G-IIB) series airplanes equipped with Quiet Technology
Aerospace (QTA) supplemental type certificate (STC) ST02618AT Stage 3
Hushkits, that several forward bearing fitting attach bolts have been
found failed, cracked, or yielded. This situation was reported
originally in SAIB NM-07-39, dated June 28, 2007. This revised SAIB
provides revised service recommendations.
SAIB NM-07-39 was a result of findings of several failed, cracked, or
yielded forward bearing fitting attach bolts on QTA Stage 3 Hushkits
installed in accordance with STC ST02618AT. The bolts are located
adjacent to the thrust reverser translating link attach point and
connect the forward bearing fitting to the ejector. Note that the
subject bolt is installed on both the inboard and outboard side of each
engine; however, it is located on the top of the forward bearing
fitting on one side, and on the lower side of the forward bearing
fitting on the other side of the engine.
Failure of these bolts can lead to overload on the opposite side
forward bearing fitting attach bolt and allow binding on the ejector
rails. In one case, a bent translating link was found. QTA released
Service Bulletin QTA-002 to specify replacing NAS6205-48 bolts with
NAS6705-48 bolts.
Since the issuance of SAIB NM-07-39, QTA and the FAA worked to
determine the cause of the cracking and the aircraft level effect of
such failures. Fatigue testing and analysis were accomplished on
several configurations of bolt installations. The conclusion of that
investigation is that if the subject bolts are replaced every 400
flight cycles, in-service cracking and failure will be prevented. The
examined failures result in a configuration that does not endanger the
flight crew, passengers, or the public, and thus 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.
Recommendations
We recommend that aircraft owners or operators replace the subject
forward bearing fitting bolts every 400 flight cycles with an approved
replacement. Currently, the approved replacement bolts are NAS6705-48
and QTA part number G23-EJ-4024. We do not recommend re-installation of
the NAS6205-48 bolts.
QTA is revising its Instructions for Continued Airworthiness to reflect
the replacement time limit and the approved bolt part numbers. We
recommend compliance with this information to prevent in-service bolt
cracking and failures.
The 400-flight-cycle limit is the same for any of the approved QTA
configurations. This includes several bushing configurations
(manufacturer’s part numbers G23-EJ-4012-15/-25/-27) matched with
either NAS6705 bolts or QTA part number G23-EJ-4024 bolts.
For aircraft with bolt installations already exceeding 400 flight
cycles, we recommend replacing the bolts within 6 months to minimize
the risk of an in-service bolt failure.
For Further Information Contact
Michael Cann, Aerospace Engineer, FAA, Central Region, Atlanta Aircraft
Certification Office, One Crown Center, 1895 Phoenix Boulevard, Suite
450, Atlanta, GA 30349; phone (770) 703-6038; fax (770) 703-6097;
email: michael.cann@faa.gov
Ron Wissing, Aerospace Engineer, FAA, Central Region, Atlanta Aircraft
Certification Office, One Crown Center, 1895 Phoenix Boulevard, Suite
450, Atlanta, GA 30349; phone (770) 703-5978; fax (770) 703-6097;
email: Ronald.wissing@faa.gov