Engines Without Calendar Time Limits
There are still some engines where the manufacturer does not specify a calendar time limitation on its overhaul life. Most notable of these is the Gipsy series. Already the CAA has floated a draft Mandatory Permit Directive to impose a caledar backstop (of ten years) on all jet engines used in Permit to Fly aircraft.
They are also working on doing the same for those piston engines where the manufacturer has not seen fit to make any calendar limitation. This will be imposed by amendment of GR 24. Watch out for any consultation document and if you are affected, make your views known.
The CAA line will be that they are out to catch those engines fitted to aircraft which are operated for the purposes of public transport. Those engines operated for the purposes of private flight will be allowed to continue under the 'on condition' assessment stated in GR 24.