'Run a mile if aircraft design not approved' - Francis Donaldson

One of the UK’s most respected light aviation experts has identified a key flaw in the ongoing attempt to have the TL Stream retrospectively approved by the UK CAA.

Francis Donaldson, former Chief Engineer of the LAA and now a freelance engineering consultant, says that a ready-to-fly microlight has to be built to an already approved design in an already approved factory.

The TL Stream bought by pilot Mike Clare met neither criteria at the time the aircraft was delivered in May 2021.

Francis Donaldson said, “A factory built microlight aircraft, to be issued a Permit to Fly, has to be built in an approved factory, and to an approved design, and supported by the manufacturer’s approved design organisation.

“Buying an aircraft of an unapproved type in the hope that the aircraft will be approved in due course is  a huge mistake. However well a foreign-registered demonstrator might appear to fly, not all non-compliances found during an approval programme can be dealt with by a ‘quick fix’.

“It’s not just a paperwork exercise – some might require for example that the airframe’s primary structure is made of a different material, if the designer hasn’t originally designed it to comply with some of the more stringent safety factors as required under BCAR Section S when compared to those in some of the design codes used abroad.

“The draft of the latest version of Section S, which was put out for consultation recently, has been harmonised with equivalent codes from abroad to a degree, but still contains some significant differences.

“But more fundamentally still, an individual aircraft that’s been built in a factory before the factory gains CAA design and manufacturing approval remains an unapproved aircraft even if the factory does later gain those approvals.

“In other words, the aircraft needs to have been built under CAA procedures in the CAA approved factory. Only under exceptional circumstances would retrospective approval be granted to a pre-existing tail number. Both the BMAA and LAA can achieve a great deal to help the process but as far as I know neither have yet found a way to turn back time!

“So if anyone suggests to you that you buy a factory-built aircraft that is of a design that hasn’t yet been CAA approved, or which was built in a factory when it was not CAA approved, you should run a mile.

“If the suppliers haven’t completed the work with the CAA and been granted their design and manufacturing approvals before it was manufactured, and been able to demonstrate that it meets the requirements for the type of aircraft to be type-approved, the aircraft will simply not be eligible for a UK Permit to Fly.

“Selling aircraft prematurely doesn’t help anyone – the inevitable resulting disenchantment and grief just detracts from the focus of the various parties working through the necessary process.”

Read the full story of Mike Clare’s TL Stream here.