AD/B737/307 Main Slat Downstop Assembly (Cth)

AIRWORTHINESS DIRECTIVE

For the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.001(1) of CASR 1998.  The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.

Boeing 737 Series Aeroplanes

AD/B737/307 Main Slat Track Downstop Assembly 11/2007 DM

Applicability:

All Model 737-600, -700, -700C, -800, -900, and -900ER series aircraft.

Requirement:

1.    Accomplish a detailed inspection of each main slat track downstop assembly to verify proper installation of the slat track hardware (the bolt, washers, downstops, sleeve, stop location, and nut shown in Figure 1 of Boeing Service Letter 737-SL-57-084-B, dated 10 July 2007; and in this Directive).  If any part is missing or installed incorrectly, before further flight, install a new or serviceable part using a method approved in accordance with the procedures specified in paragraph (g) of FAA AD 2007-18-51; and accomplish a detailed inspection of the inside of the slat track housing for foreign object debris (FOD) and damage.  Before further flight, remove any FOD found and repair any damage found using a method approved in accordance with the procedures specified in paragraph (g) of FAA AD 2007-18-51.

Using Boeing Correspondence (Multi-Operator Message) Service Request ID
1-523812011, issued 25 August 2007, is one approved method for verifying proper installation; installing a new or serviceable part; and inspecting for damage and FOD; and removing FOD and repairing damage.

2.    Apply a torque between 50 to 80 inch-pounds to the nut.  The bolt head must be held when the torque is applied to the nut.

Figure 1

Note:  FAA Emergency AD 2007-18-51 refers.

Compliance:

For Requirements 1 and 2: Within 24 days after 28 August 2007.

Repeat the Requirement 1 actions at intervals not to exceed 3,000 flight cycles.

This Airworthiness Directive becomes effective on 29 August 2007.

Background: The FAA received reports of parts of the main slat track downstop assembly coming off the main slat track.  In one case, a nut fell into the slat track housing and, during a subsequent slat retraction, the track made contact with the nut, pushing it into the wall of the housing and puncturing it.  In a recent case, an initial investigation revealed that following retraction of the slats after landing on a Model 737-800 aircraft, loose parts of the main slat track downstop assembly punctured the slat track housing, which resulted in fuel leakage and a fire that ultimately destroyed the aircraft.

David Villiers
Delegate of the Civil Aviation Safety Authority

27 August 2007