Magneto calendar overhauls - the thin end of the wedge?

[Perspective]

Hi Progressive,
The question was,
"In any case AD ENG 4 applies to 'engine and components necessary for the operation of the engine', so does that not apply to magnetos??""

AD/Eng/4 states, under applicability,
"Piston engines and those components necessary for the operation of the engine, installed in aeroplanes maintained in accordance with Civil Aviation Regulation CAR 42B CASA Maintenance Schedule.",

Requirement A4,
"Note A2: AWB 85-4 “Aircraft Piston Engine Calendar Time Overhaul” provides guidelines for additional inspections related to the calendar time overhaul."

Within AWB 85-4,
"It is recommended that the following procedures are followed for engines that have exceeded the calendar time overhaul recommendations of the engine manufacturers. ALL PROCEDURES listed below, should be performed per approved data where applicable and IN CONJUNCTION with the condition checks per AD/ENG/4."
There are 10 procedures required in addition to those within AD/Eng4.

Procedure 4.5, Check electrical items such as magnetos, spark plugs and harnesses etc for corrosion and malfunction due to moisture ingress and deterioration.

So, AD/Eng/4 tells me carry out performance run on the engine, with additional procedures contained within AWB 85-004, and that all procedures listed, such as step (4.5) should be performed per approved Data IN CONJUNCTION with condition checks etc.

Approved Data relating to the Magnetos would be
TCM SB 643B, and as example S20/S-200 service manual X42002-3 Which notes,
"Magnetos are electro-mechanical devices that use rotating parts and are subject to the same service treatment, environmental conditions and wear as the engine."
Then goes on to state about the 4 yearly inspection etc.

AD/Eng/4 and on to AWB 85-004, including SB 643B specifically talk about environmental conditions being a factor in continued service.

AWB 74-005 also states,
4. Recommendations
Follow manufacturers approved data for maintenance of magnetos. Magnetos operating in harsh environments or operating conditions should be overhauled more frequently than the recommended maintenance intervals....

So, in a nutshell,
AD/Eng/4, note A2 AWB 85-004
AWB 85-004 following procedures to be per approved Data.
4.5 check of electrical items such as magnetos for malfunction, moisture ingress and deterioration.
Approved data is SB643B and x42002-3 S-20 service manual amongst others.
Approved Data states 4 year's etc.