AD/B717/20 Electrical Bonding (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 717 Series Aeroplanes

AD/B717/20 Electrical Bonding 5/2007

Applicability:	Model 717-200 airplanes, as identified in Boeing Service Bulletin (SB) 717-28-0011, Revision 2, dated 19 July 2006.
Requirement:	Replace attaching hardware of the bulkhead nipple assemblies of the left and right wing vent boxes with new electrical bonding attaching hardware, carry out resistance testing of the new electrical bonds and fuel leakage testing of the reworked nipple assemblies.  All actions are to be carried out in accordance with the Accomplishment Instructions of Boeing SB 717-28-0011, Revision 2.
Note 1:  Note (e) of Figure 1 of the service bulletin refers to a class `L' resistance test.  However, Section 20-50-01 of the Boeing Standard Wiring Practices Manual (SWPM) no longer refers to class `L.'  The class `L' resistance test was related to lightning protection and specified a maximum resistance of 0.0025 ohm, this appeared in earlier versions of the SWPM.  The term "class `L' " is not important in this context and the directions of note (e) of Figure 1 of the service bulletin are otherwise acceptable as written (ie the resistance must not exceed 2.5 milliohm [0.0025 ohm]).
Actions accomplished before the effective date of this Directive in accordance with Boeing SB 717-28-0011, dated 16 April 2004, or Revision 1, dated 24 January 2006; are acceptable for compliance with the corresponding actions specified in this Directive.
Later revisions of the SB 717-28-0011, Revision 2, approved by the United States Federal Aviation Administration (FAA) as an Alternate Method of Compliance (AMOC) to FAA AD 2007-05-06, are considered acceptable for compliance with the equivalent Requirements of this Directive.
Note 2:  FAA AD 2007-05-06 Amdt 39-14967 refers.
Compliance:	Within 78 months after the effective date of this Directive.
This Airworthiness Directive becomes effective on 10 May 2007.

Background:	This Directive requires replacing certain attaching hardware of the bulkhead nipple assemblies of the left and right wing vent boxes with new electrical bonding attaching hardware, together with accomplishing resistance testing of the new electrical bonds, and fuel leakage testing of the reworked nipple assemblies.  The Directive results from fuel system reviews conducted by the manufacturer.
The Directive is issued to ensure a conductive path is provided, from the bulkhead nipple assemblies of the left and right wing vent boxes to the airframe structure inside the wing fuel tanks, to dissipate high-amperage lightning-induced currents, which might otherwise create an ignition source for fuel vapours inside the wing vent boxes and lead to an explosion of the fuel tanks.

Charles Lenarcic
Delegate of the Civil Aviation Safety Authority

16 March 2007