Ad/B737/57 Amdt 3 - MLG Actuator Beam (Cth)

AIRWORTHINESS DIRECTIVE

On the effective date specified below, and for the reasons set out in the background section, the CASA delegate whose signature appears below revokes Airworthiness Directive (AD) AD/B737/57 Amdt 2 and issues the following 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/B737/57 Amdt 3 MLG Actuator Beam 11/2005

Applicability:

All Model 737-100, -200,-300,-400 and -500 series aircraft.

Requirement:

Inspect in accordance with the inspection requirements of Boeing Alert Service Bulletin 737-32A1314.

Note 1.  Boeing Alert Service Bulletin 737-32A1314 replaces Boeing Alert Service Bulletin 737-32A1224 and previous terminating action is rescinded.  Further, the ultrasonic inspection techniques in Boeing Alert Service Bulletin 737-32A1314 vary depending on beam arm part number.  Use of the incorrect inspection technique may result in erroneous results.

Note 2.  FAA AD 99-10-12 Amdt 39-11165 refers.

Compliance:

a.    For undercarriage that have been inspected in accordance with Amendment 1 of this AD, inspect within 90 days (in service) or 600 landings of that inspection, whichever occurs first.  Re-inspect every 90 days (in service) or 600 landings, whichever occurs first.

b.    For all other undercarriage, inspect prior to the accumulation of 10,000 landings or 4 years (in service) since new or overhaul, whichever occurs first.  Re-inspect every 90 days (in service) or 600 landings, whichever occurs first.

Note 3.  The inspection interval listed here includes a calendar time in service inspection interval as well as the previously required landing cycle interval.  The failure, whilst originating from a corrosion problem also is fatigue based, and there have been failures in Australia.  The compliance period therefore reflects the manufacturers SB.

Note 4.  CASA accepts previous inspections carried out under Amendment 1 of this AD.  However, all inspections subsequent to the validity of this AD must be of the revised type.

This Amendment becomes effective on 27 October 2005.

Background:

An Australian aircraft recently had a MLG actuator beam component fail in flight.  The failure caused damage to the aileron and spoiler cables, the hydraulic lines and rear wing spar.  Subsequent inspection of the remaining aircraft in the operator’s fleet found one other MLG actuator beam with significant cracks.

The problem has also been reported on overseas aircraft.  These aircraft had similar failures.  Boeing has now released a new Service Bulletin dealing with the problem.  Amendment 2, effective 12 August 1999, required use of this latest data from the manufacturer.

This amendment clarifies the calendar time inspection interval as calendar time in service.

Amendment 1 of this Airworthiness Directive became effective on 29 March 1999.

The original issue of this Airworthiness Directive became effective on 16 May 1991.

David Villiers
Delegate of the Civil Aviation Safety Authority

15 September 2005