Limited Supplementary Type Certificates (LSTCs) work much like plain old STCs except that they are generally approvals for just one single aircraft. In Canada these are used when you wish to install a piece of equipment, such as an IFR GPS set, that requires integration with other equipment (such as an autopilot) and there is no STC for the installation.
Most people avoid having to go the LSTC route if they have a choice as it tends to be time consuming, cumbersome and expensive. The installer has to engineer the installation, write all the documentation on the installation, including the Instructions for Continuing Airworthiness (ICAs) and Flight Manual Supplements. They then have to submit all the paperwork to TC so that the TC engineering staff can confirm it is all correct. Then a TC test pilot will fly the aircraft to ensure it all works. In some cases the test flying can be delegated to a Delegated Airworthiness Representative (DAR). You have to pay for your own installer to do their work and also for the TC or DAR test flight as well.
While it can be done, it is much easier if the manufacturer of the equipment to be installed has done the work for you in advance and issued an STC.
Canada’s LSTC process is not as easy as the US 337 process, but it does ensure that the certification basis of the aircraft is protected and that the aircraft continues to be airworthy.
Installing parts on your certified plane is a subject that confuses a lot of people. What parts are you allowed to install and what paperwork is required for which parts?
The rules are contained in CAR 571.07 for new parts and CAR 571.08 for used
Let’s look at each class of parts in turn.
A new part manufactured in Canada by the holder of the type certificate (TC) or a
Supplemental Type Certificate (STC) can be installed, but requires a certification tag under Airworthiness Manual Chapter 561.
A new part manufactured by the holder of the TC or an STC in a country with
which Canada has a bilateral agreement to accept their export certification can be
installed without a certification tag as long as you have the export paperwork. Transport Canada no longer requires specific "export documents" for anything other than complete aircraft and this CAR is likely to be amended soon. In the meanwhile, CAR 571.07(2)(b)
COPA Guide to Certified Aircraft 42