AD/F100/82 Piccolo Tube Peri-Seals (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/F100/82 Piccolo Tube Peri-Seals 12/2006

Applicability:

Fokker Aircraft B.V. Model F28 Mark 0070 and Mark 0100 aircraft, all serial numbers, unless modified per Fokker Service Bulletin SBFI00-30-022.

Requirement:

Unless previously accomplished, inspect the Piccolo Tubes and their surrounding area and replace the Peri-seals in accordance with Part 3 Accomplishment Instructions of Fokker Service Bulletin SBF100-30-028 dated 18 May 2006 or a later EASA-approved revision.

Note:  CAA-NL AD NL-2006-011 (EASA Approval 2006-0231 dated 31 July 2006) refers.

Compliance:

Within the next 4,000 flight hours or 24 calendar months after the effective date of this AD, whichever occurs first.

This Airworthiness Directive becomes effective on 23 November 2006.

Background:

In 1997, Fokker introduced a new type of Peri-seal (SBF100-30-022).  The old type was known to be subject to deterioration, which, in combination with improper installation, can cause leakage of hot wing anti-icing air from the Peri-seal housing.  This results in an uncontrolled flow of high-pressure hot air to enter the forward (anti-icing) plenum chamber of the wing leading edge, potentially damaging the anti-icing barrier webs.  Subsequently, the wing auxiliary spar can also be damaged by high-pressure hot air.  Analysis at the time showed that any resulting damage (known to occur at inboard positions only) would not affect the wing load capability.  For this reason, the modification was not classified as MANDATORY and no AD action was warranted.  However, through a recent occurrence, it was discovered that deterioration of the Peri-seals enables the piccolo tubes to vibrate, resulting in a broken piccolo tube.  In this case, the location of the failure was more outboard than previous occurrences.  This condition, if not corrected, may cause heat damage to the front spar that potentially affects the wing’s load capability.

Since an unsafe condition has been identified that is likely to exist or develop on aircraft of this type design, this Airworthiness Directive requires inspection of the Piccolo Tubes and the surrounding structure to establish correct installation, as well as the replacement of the 460-series Peri-seals by the improved 600-series, which have a higher temperature limit.  A new MRB task will be introduced to require the repetitive replacement (life limit) of the new Pen-seals to prevent long-term degradation.

James Coyne
Delegate of the Civil Aviation Safety Authority

12 October 2006