AIRWORTHINESS DIRECTIVE
For the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/B737/188 and issues the following AD under subregulation 39.1 (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/B737/188
Amdt 1
Main Wheel Well Electrical Connectors 12/2004
Applicability: Model 737-600, -700, -700C, - 800, and -900 series aeroplanes.
Requirement: 1. Either:
- Determine exposure of the aeroplane to runway deicing fluids containing potassium formate by reviewing airport data on the type of components in the deicing fluid used at airports that the aeroplane may have operated from.
Note 1: In particular, details of runway deicing employed at foreign airports that aeroplanes may have operated from pre delivery to Australia should be checked.
or,
b. Perform a detailed inspection of the line replaceable units (LRU) electrical connectors (including the contacts and backshells) in the wheel well of the main landing gear (MLG) for corrosion (the presence of moisture, corrosion pits, or white coloured material build-up), in accordance with Boeing Alert Service Bulletin (ASB) 737-24A1148 dated 6 December 2001 or Revision 1 dated 10 July 2003.
2. For aeroplanes that have been determined to be exposed accomplish the following:
- If the determination was accomplished in accordance with Requirement 1.a. of the original issue of this Directive - Perform a detailed inspection of the LRU electrical connectors (including the contacts and backshells) in the wheel well of the MLG for corrosion (the presence of moisture, corrosion pits, or white coloured material build-up), in accordance with ASB 737- 24A1148 or Revision 1.
b. If the determination was accomplished in accordance with Requirement 1.a. of this Amendment - Perform a detailed inspection of the LRU electrical connectors (including the contacts and backshells) in the wheel well of the MLG for corrosion (the presence of moisture, corrosion pits, or white coloured material build-up), in accordance with ASB 737-24A1148 or Revision 1.
Note 2: For the purposes of this Directive, a detailed inspection is defined as: "An intensive visual examination of a specific structural area, system, installation or assembly to detect damage, failure or irregularity. Available lighting is normally supplemented with a direct source of good lighting at intensity deemed appropriate by the inspector. Inspection aids such as mirror, magnifying lenses, etc., may be used. Surface cleaning and elaborate access procedures may be required."
3. Carry out the following in accordance with ASB 737- 24A1148 or Revision 1:
- If no corrosion is found, clean the LRU connector.
b. If any corrosion is found, replace the LRU connector with a new connector.
c. Apply D5026NS corrosion inhibiting compound, or equivalent, to the affected areas.
Note 3: FAA AD 2002-16-03 Amdt 39-12842 refers.
Compliance: For Requirement 1 - Prior to the issue of a Certificate of Airworthiness.
For Requirement 2.a. - Before further flight and thereafter repeat the detailed inspection at least every 12 months.
For Requirement 2.b. - Within 12 months after the inspection accomplished in accordance with AD/B737/188 Requirement 2 and thereafter repeat the detailed inspection at least every 12 months.
For Requirement 3 - Before further flight after doing any inspection specified in Requirement 1 or 2.
This Amendment becomes effective on 25 November 2004.
Background: The United States Federal Aviation Administration (FAA) has advised of receiving reports indicating that significant corrosion of the electrical connectors located in the main wheel well has been found on some model 737 series aeroplanes. These aeroplanes are known to land on runways treated with deicing fluids containing potassium formate which has been determined as the cause of the corrosion. Tests conducted by the aeroplane manufacturer revealed that corrosion inhibiting compounds (CIC) can be used to form a shield against such corrosion and will not affect the electrical components or the systems. Corrosion of the electrical connectors could result in incorrect functioning of critical aeroplane systems essential to safe flight and landing of the aeroplane.
This Directive requires the determination of exposure to runway deicing fluids containing potassium formate and, for exposed aeroplanes, repetitive inspections of certain electrical connectors in the wheel well of the main landing gear for corrosion, and follow-on actions. This Directive, due to Australian operating conditions, does not require the repetitive inspection of aeroplanes that have been determined not to have been exposed.
This amendment introduces ASB 737-24A1148 Revision 1 as an alternate method of compliance.
The original issue of this Airworthiness Directive became effective on 3 October 2002.
James Coyne
Delegate of the Civil Aviation Safety Authority 14 October 2004
The above AD is notified in the Commonwealth of Australia Gazette on 3 November 2004.