With an aircraft which has an ICAO CofA, any modification which is determined to fall outside the Minor or Major mod regime renders it unairworthy and thus illegal to fly.
With no ICAO CofA, however, there is no apparent concept of “airworthiness”.
So how far can you modify a design and still have valid insurance?
I know that on a G-reg one, the LAA inspector won’t sign off the Annual check if he doesn’t like something, and I guess there is a written regime for that.
Peter wrote:
So how far can you modify a design and still have valid insurance?
The insurance company insures an experiment. The experiment is conducted in accordance with regulations that apply to that particular experimental aircraft. I think it’s as simple as that, and doesn’t include the concept of operating within an approved type certificate.
Obviously as long as the insurance companies can make money at it, they don’t care what they insure and time has apparently proven they can make money insuring (lots of) experimental category homebuilt aircraft.
Peter wrote:
With no ICAO CofA, however, there is no apparent concept of “airworthiness”.
It certainly is. Each individual needs to be airworthy, and this is accomplished through inspections during the built and when finished, and through the test program. Each country has some differences here, but the basic concept is more or less the same. ICAO compliance does not equal airworthiness. Certification is not the same as airworthiness. Airworthiness is whatever some aviation authority say it is essentially.
Peter wrote:
So how far can you modify a design and still have valid insurance?
It’s up to the insurance company essentially, and they usually follow the regulations. Here in Norway, a larger modification places the aircraft back in the test phase. This means the CofA is not valid, or limited, until the modification is tested and the handbook is corrected (after a successful test phase).
The UK permit to fly, as administered by the LAA, is much closer to an airworthiness regime. For most kit and plans types there is a type acceptance data sheet (TADS) that forms the basis for approval. Any addition or deviation from the TADS requires a mod approval apart from some basic mods that can be signed off by an approved inspector e.g. instrument panel mods etc.
I don’t think an approved mod, such as autopilot or LED lighting etc, would have any insurance implications unless it affects any of the disclosures in the policy.
