AD/At/29 Engine Mount (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.

Airtractor AT-300, 400 and 500 Series Aeroplanes

AD/AT/29 Engine Mount 7/2008

Applicability:

Model AT-400, AT-400A, AT-402, AT402A, and AT-402B aircraft, serial numbers 0001 through 1175.

Model AT-502, AT-502A, AT-502B, and AT-503A aircraft, serial numbers 0001 through 2597.

Requirement:

For all aircraft with less than 5,000 total hours time in service that do not have gussets installed on the engine mount in accordance with Snow Engineering Co. Service Letter (SL) No. 253 Revision A, dated 16 October 2007, Snow Engineering Co. SL No. 253 Revision B, dated 30 November 2007, or Snow Engineering Co. SL No. 253 Revision C, dated 17 April 2008:

1.    Visually inspect the engine mount as follows:

a.     For all Model AT-502A aircraft, visually inspect in accordance with Snow Engineering Co. SL No. 253 Revision B, or Snow Engineering Co. SL No. 253 Revision C.

b.    For all Model AT-400, AT-400A, AT-402, AT-402A, AT-402B, AT-502, AT-502B, and AT-503A aircraft, visually inspect in accordance with Snow Engineering Co. SL No. 253 Revision B, or Snow Engineering Co. SL No. 253 Revision C.

2.    For all aircraft:  Where crack damage is detected during any Requirement 1 inspection, repair and modify the engine mount by installing gussets in accordance with Snow Engineering Co. SL No. 253 Revision B, or Snow Engineering Co. SL No. 253 Revision C.  This modification terminates the Requirement 1.a. and 1.b. repetitive inspections.

3.    For all aircraft:  Unless already accomplished in accordance with Requirement 2, inspect, repair if cracked, and modify the engine mount by installing gussets in accordance with Snow Engineering Co. SL No. 253 Revision B, or Snow Engineering Co. SL No. 253 Revision C. at the compliance time(s) specified in the compliance section of this Directive.  This modification terminates the Requirement 1.a. and 1.b. repetitive inspections.

4.    For all aircraft:  The Requirement 3 modification may be delayed, provided the following is accomplished in accordance with the service information provided in Snow Engineering Co. SL No. 253 Revision B, or Snow Engineering Co. SL No. 253 Revision C:

Initially inspect upon reaching the applicable compliance time in Requirement 3.a. or 3.b., unless accomplished within the last 100 hours time in service;

Repetitively inspect thereafter at intervals not to exceed 100 hours time in service; and,

If cracks are detected during any inspection, before further flight, repair the cracked part and install the gussets.

Note 1:  As a terminating action to the Requirement 1 inspections, the gussets modification may be installed before detecting cracks or reaching the times specified above provided an inspection assures the area is crack free before installing the gussets.

Note 2:  FAA AD 2008-10-12 Amdt 39-15518 refers.

Compliance:

1.a. Initially before the aircraft reaches a total of 1,300 hours time in service or within 100 hours time in service after 3 July 2008, whichever occurs later.  Inspect thereafter at intervals not to exceed 300 hours time in service.

1.b. Initially within 12 months after 3 July 2008.  Inspect thereafter at intervals not to exceed 12 months.

2.    Before further flight.

3.    At whichever of the following times occurs later:

a.     Before the aircraft reaches 5,000 hours total time in service; or,

b.    Within 100 hours time in service after 3 July 2008.

4.    Until 30 April 2009, at which time the modification must be incorporated.

This Airworthiness Directive becomes effective on 3 July 2008.

Background: Since the issue of FAA AD 2007-13-17, which affected Models AT-602, AT-802, and AT-802A aircraft, Air Tractor has received a report of a Model AT-502B aircraft with a crack located where the lower engine mount tube is welded to the engine mount ring.  In addition, Air Tractor has developed gussets that, when installed in accordance with certain service letters, terminates the repetitive inspection requirement.  Consequently, new FAA AD 2008-10-12 establishes new inspection actions for the AT-400 and AT-500 series aircraft and incorporates a mandatory terminating action for the repetitive inspections.  The actions required by this Directive are intended to detect and correct cracks in the engine mount, which could result in failure of the engine mount and possible separation of the engine from the aircraft.

David Villiers
Delegate of the Civil Aviation Safety Authority

23 May 2008