The CAA has announced that for various G- registered ‘Annex 2’ aircraft, mainly vintage types still operating on a Certificate of Airworthiness, mods covered by a Supplemental Type Certificate (STC) will no longer have to be validated by CAA if they have been approved by a state with which the UK holds a bilateral agreement, such as the US or Canada. The owner/operator can simply have the STC’ed mod carried out and then get their maintenance organisation to certify its installation in the aircraft’s log-book.

Supporting the change, Francis Donaldson, LAA Chief Engineer, said: “We welcome this initiative to simplify the fitting of STC’ed modifications to vintage aircraft operating on a C of A, allowing owners similar access to STC’ed mods as is already enjoyed by those with aircraft operating on an LAA Permit. We hope this change will also help maintenance providers and businesses supplying STC’ed parts.”

“The new CAA decision mirrors long-established LAA policy insofar as we do not re-investigate the design of STCs that have already been formally approved by competent authorities overseas. All we do with these at LAA HQ is to check that the STC is genuine, that the application onto the aeroplane concerned is appropriate (no compatibility issues with other mods already in place) and that the instructions contained in the STC are properly complied with, using the local LAA inspector to verify quality and conformity”.

Asked why LAA permit aircraft owners have to contact LAA Engineering at all over STC’ed mods, and why they can’t all be dealt with by the LAA inspector, Francis replied:

"While the mutual acceptance of modifications from reputable countries is fairly straightforward where current certificated ICAO-compliant aircraft are being preserved to an ICAO compliant standard, it’s more complicated where aircraft are not ICAO compliant, because of the different standards applied by different countries and the different kinds of category/regulatory regimes in which sub-ICAO aircraft operate. Also, many ex-type certificated LAA aircraft have been so heavily modified over the years that STCs approved on the standard model wouldn’t be compatible - the nature of the Permit world is that each Permit aircraft is to an extent unique.”

“Many STCs call for alterations to aircraft’s operating limitations, cockpit placards, or both, and for C of A aircraft these changes are instigated by changes to the approved Flight Manual. Most LAA aircraft aren’t provided with approved Flight Manuals so instead the limitations and placard requirements are shown on the limitations sheet that forms part of the Permit to Fly, so amendments created by an STC have to be issued by HQ”.

“Finally, we need to keep tabs on what owners have fitted to their aircraft to carry out our continued airworthiness role effectively, so if snags come up with an STC we can let owners know.”

Spurred on by the CAA’s move, LAA Engineering are now setting up a new and more streamlined process for notifying HQ of an intention to fit an STC’ed mod, using a new application form to distinguish it from other kinds of mods needing in-depth technical investigation and a new technical leaflet to give both specific and general guidance. LAA’s management team are also reviewing the LAA’s pricing arrangements for this and other kinds of mod.