I won't get into the are they Mandatory or not argument, IMHO they are warranted and under Schedule 5 required as per the previous posts of Tridac and Perspective.
The FAA did direct all of the TC Holders to develop Supplemental Inspection programs and few did this, what will happen to those types long term that do not have SI programs is anyones guess.
SIDs will not be cheap and $6,500 for the Dr's 1966 Cessna 172 does seem a little light for the work involved unless the labour rate is ten bucks an hour. For example the first task on Operation One of the SID for 100 SERIES (1963 - 1968) states
Inspect aircraft records to verify that all applicable Cessna Service Information Letters, Cessna Service Bulletins and Supplier Service Bulletins are complied with
Researching SB's etc back to 1966 and cross referencing against AD's, old Rex drawings as well as preparation and final certification of the work package alone will take days of work before a panel is even removed. So already the best part of $3,000 has been spent before we even start looking at the aircraft ....
Some suggest the compliance date has changed, for the 100 SERIES (1963 - 1968) the compliance time is ...
If an airplane has exceeded the inspection limits given, the inspection must be done before June 30, 2014. Inspections in subsequent revisions to the SID shall be accomplished in accordance with the requirements of the revised inspection.
All SIDS would be therefore due on this date except the Engine Mount MPI as the SID document states ...
This is a complex and involved inspection. It is recommended that the inspection be coordinated with an engine overhaul, even if the time does not exactly agree with inspection hours. Recurring inspections will be satisfied by inspections at engine overhaul. The initial inspection must be completed by June 30, 2015.
ref
https://support.cessna.com/custsupt/...df?as_id=37390
Avgas, Cessna do not
put out AD's these are the responsibility of the governing NAA, in the case of Cessna Aircraft the FAA. The SID's I am sure will be amended in time to reflect the findings and address additional areas of concern, some may be added, removed or the compliance times changed.
Yes Oracle the U bolts on the older spring leg aircraft are not the best design and do often fail NDT but remember in 1955 they were probably high tech! Would you rather a SB mandating the fitment of a better designed UC leg as per the later models? Such a mod I would hazard to guess would be tens of thousands of dollars. Remember Cessna improved the design here in all new models from the late 60's.
So many times I have heard the owner tell me his 1980 172 is nearly new as he tries to justify not spending a cent more than he has to on it, bear in mind if it was a car it would be something like an XD Falcon and you would just have it towed for scrap. The same owner screams when you do the first 100 hourly and find more has 20% of every leading edge rib has corroded away and he needs his wings rebuilt.
Then you have the "just do a little this time" owner, you fall for his sob story genuinely believing he is doing it tough and that he will do the right thing and return to progressively bring his aircraft up to speed. You know its safe enough and do a bare minimum schedule 5 inspection to help the poor bugger out. The next week the aircraft has another owner and at the next 100 hourly CASA are knocking on your door asking for a please explain.
For the sake of keeping flying affordable I would very much be in favour of an owner signed waiver for items such as SB's and SID's. A copy in the log book and a copy to CASA to be kept on the aircraft file, this would show that you as the owner are aware of and choose to ignore the requirement and indemnify the LAME. The aircraft could also be placarded much the same way as experimental aircraft are. You could then maintain your biodegradable spam can to the standard you desired in Private Category only and incur the reduction in value.