AD/F50/94 Engine Mount Tubing and End Fittings (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.

Fokker F50 (F27 Mk 50) Series Aeroplanes

AD/F50/94 Engine Mount Tubing and End Fittings 6/2006

Applicability:

Model F27 Mk 050, Mk 0502, and Mk 0604 aircraft, all serial numbers, unless the engine mount frames have been inspected previously in accordance with the Fokker 50/60 MRB Document, Task Numbers 712000-00-09 and 712000-00-10.

Requirement:

1.    Perform an X-ray inspection on the engine mount tubing and end fittings in accordance with Section 3. Accomplishment Instructions of Fokker Service Bulletin SBF50-71-047, dated 15 February 2006, or later EASA approved revision.

2.    Following accomplishment of the Requirement 1 inspection, report all inspection results to Fokker Services in accordance with the procedure described in SBF50-71-047.

3.    No spare engine mount may be installed on any aircraft as a replacement part, unless it has been X-ray inspected in accordance with Section 3. Accomplishment Instructions of Fokker Component Service Bulletin F8200-035-71-12, dated 15 February 2006, or later EASA approved revision.

Note:  CAA-NL AD NL-2006-005 refers.

Compliance:

1.    Within 2 years after 8 June 2006.

2.    Within 7 days of accomplishment of Requirement 1 inspection.

3.    After 15 June 2006.

This Airworthiness Directive becomes effective on 8 June 2006.

Background: During scheduled MRB mid-life X-ray inspections of Fokker 50 engine mount frames, severe internal corrosion of the tubes was discovered.  In some locations, the depth of the corrosion spots appeared to be more than 50 percent of material thickness.  Premature degradation of the synthetic preservation oil film that protects the interior of the tubes and end fittings of the engine mount frames is considered to be the cause of the corrosion.  This condition, if not corrected, could ultimately lead to failure of the engine mounting frame in cases where multiple tubes are severely affected.

Richard Castles
Delegate of the Civil Aviation Safety Authority

18 April 2006