SAIB

SPECIAL AIRWORTHINESS INFORMATION BULLETIN

Aircraft Certification Service
Washington, DC
U.S. Department of Transportation
Federal Aviation Administration

NM-07-39

June 28, 2007

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. The forward bearing fitting is manufacturer’s part number (p/n) G23-EJ-4013, and the original attach bolt is p/n NAS6205-48 (see Figure 1). The bolt failures have not caused any flight or ground incidents and were found during routine maintenance.

ILLUSTRATION (Figure 1)

Background

This SAIB is 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 attach bolt and allow binding on the ejector rails. In one case, a bent translating link resulted. During subsequent review, the following items appear to have contributed to failure of the bolts:

Material of NAS6205 bolts may not have met all the requirements of the NAS standard, potentially reducing the fatigue life of the bolts.

The installation may allow the subject bolts to be loaded in a reverse bending fatigue condition, potentially reducing the fatigue life of the bolts.

The current data show that the quickest failure occurred at approximately 350 hours since installation (HSI)/230 flight cycles since installation (CSI), whereas the highest time failure occurred at 1,500 HSI/850 CSI. All failures were noted during routine maintenance and did not cause a flight or ground incident.

As a result of these findings, QTA has released Service Bulletin QTA-002 and is in the process of revising its Illustrated Parts Catalog (IPC) and Aircraft Maintenance Manual (AMM) to show replacement of NAS6205-48 bolts with NAS6705-48 bolts. The NAS6205-48 bolts will no longer be acceptable and are one-way forward interchangeable with the NAS6705-48 bolts.

Recommendations

The FAA recommends that you, an aircraft owner or operator, perform the following:

1. Replace the forward bearing fitting bolt in accordance with Service Bulletin QTA-002, and accomplish the following items:

Visually inspect the bull nose and side fairings for signs of damage.

Inspect the thrust reverser translating link for damage such as being bent, yielded, or cracked.

Inspect the ejector rails for signs of wear or damage caused by binding.

With the NAS6205-48 bolts removed, visually inspect for:

a. Damage to the forward bearing fitting.

b. Roundness of the forward bearing fitting attach bolt holes.

c. Inspect the bearing retainer nuts/nut plates.

Visually check the forward upper edge of the ejector for signs of contact with the thrust reverser aft skins.

If damage is noted on the ejector, visually inspect the thrust reverser aft skins for signs of damage.

2. Evaluate any noted damage using published allowable limits. Replace or repair components accordingly.

The FAA also recommends replacement using only NAS6705-48 bolts. QTA is currently revising their manuals to remove the NAS6205-48 option. We recommend tracking bolt replacements to prevent inadvertent de-modification using NAS6205-48 bolts until the manuals are revised. Additionally, a QTA-specific replacement bolt, manufacturer’s p/n G23-EJ-4024 is being developed; however, at the time of this writing, this bolt was not yet approved for installation.

Currently, we are still evaluating the forward bearing fitting bolt installations, including the various bushing configurations (manufacturer’s p/n G23-EJ-4012-15/-25/-27), to determine what, if any, contribution they might be having on the bolt failure, and if a life limit is warranted for the subject bolts.

Note: Based on current information, we only recommend these actions. We will continue this investigation and analyze any added information. If warranted, we may develop additional
actions based on this analysis.

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