AD/F100/88 Engine Controls Reverse Thrust Control Normal Maximum (Second) Detent (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 F100 (F28 Mk 100) Series Aeroplanes

AD/F100/88 Engine Controls - Reverse Thrust Control Normal Maximum (Second) Detent 7/2008

Applicability:

Fokker Services B.V. F28 Mark 0100 aircraft, fitted with Rolls-Royce (Deutschland) TAY650-15 engines.

Requirement:

1.    Unless accomplished previously, remove the normal maximum (second) detent for the reverse-thrust control in accordance with the instructions of Fokker Services Service Bulletin (SB) SBF100-76-014 at any revision status; and

2.    Concurrent with the modification as required by Requirement 1 of this AD, amend the Airplane Flight Manual (AFM) as specified in Fokker Services Manual Change Notification - Operational Documentation (MCNO) F100-032 Rev 1 dated 21 Sep 2007 or using AFM pages supplied by Fokker Services.

Note:  EASA AD No. 2008-0089 dated 13 May 2008 refers.

Compliance:

Requirement 1 and 2: Within 12 calendar months after the effective date of this AD.

This Airworthiness Directive becomes effective on 3 July 2008.

Background:

All F28 Mark 0100 aircraft with TAY650-15 engines were standard equipped with a normal maximum (second) detent on the reverse-thrust controls.  The second detent was intended to provide the flight crew with an easy reference position for the selection of normal maximum reverse thrust for daily use if more than idle reverse thrust was required.  Later, investigation revealed that stabilized operation in the N1 speed range of 57% to 75% in reverse thrust could lead to too high stresses on the fan blades of TAY650-15 engines, ultimately leading to structural damage of the fan blades.

Consequently, AD/F100/58 was issued in 2003 requiring amendment of AFM for F28 Mark 0100 aircraft fitted with TAY650-15 engines, prohibiting stabilized operation in the 57%-75% N1 speed range in reverse thrust.  Because selection of the second detent could result in stabilized operation in the prohibited speed range, a number of operators decided to remove the normal maximum (second) detent in accordance with (recommended) Fokker SBF100-76-014.

However, since the introduction of the operational limitation as required by AD/F100/58, occurrences have been reported of inadvertent selection of the second detent, still present on unmodified (pre-mod SBF100-76-014) aircraft.

For the reasons described above, this AD requires the removal of the normal maximum (second) detent and the introduction of related AFM changes on all TAY650 equipped F28 Mk0100 aircraft.

James Coyne
Delegate of the Civil Aviation Safety Authority

22 May 2008