What it does
This instrument, Airworthiness Directive AD/CF6/68 (titled Compressor Discharge Pressure Spring), issued by the Civil Aviation Safety Authority and effective 22 November 2007, mandates inspection and replacement work on a discrete component of the main engine control (MEC) for a specified subset of General Electric (GEAE) CF6-series turbofan engines. Mechanically, the AD requires replacement of the compressor discharge pressure (CDP) restoring spring assembly with part number (P/N) 3018-248 (or an FAA-approved equivalent), and in specific circumstances requires re-marking of the MEC after the replacement, in accordance with manufacturer service bulletins. The AD identifies the affected engines by MEC part numbers listed in Table 1 and sets different compliance schedules for CF6-50A / -50C engines (Table 2) and CF6-45A / -50E engines (Table 3). It also prohibits installation of MECs that have not complied with the relevant service bulletin revisions or that have not had the CDP restoring spring replaced within the previous 10,000 hours of MEC operation.
The AD makes the replacement and re-marking mandatory and sets the effective date explicitly: "This Airworthiness Directive becomes effective on 22 November 2007." The background paragraph states the FAA reported five events of fractured CDP restoring spring assemblies and that the AD is intended "to prevent loss of engine thrust control that could lead to loss of control of the aeroplane." The AD requires compliance "from the effective date of this AD" (see "Compliance"). The primary compliance instructions point operators to Paragraph 3.A. of the Accomplishment Instructions of the relevant GEAE Service Bulletin: SB No. CF6-50 S/B 73-0119, Revision 02 (for CF6-50A and -50C engines), and SB No. CF6-50 S/B 73-0120 (for CF6-45A and -50E engines).
Concretely, the AD (a) lists the MEC Woodward and GEAE P/Ns that identify affected MECs (Table 1); (b) sets staged compliance triggers based on whether a replacement has already been done and the time-in-service (TIS) of the MEC or spring assembly (Tables 2 and 3); (c) defines "shop visit" for compliance timing as "induction of the engine or MEC into the shop for any cause"; and (d) forbids installation of MECs that do not meet the replacement and marking requirements. The AD also explicitly allows use of "FAA-approved equivalent spring assembly" as an alternative to P/N 3018-248 where that approval exists. The instrument is signed by David Punshon as a CASA delegate and references FAA AD 2007-19-06 as related authority.