10 minute read
600KG: PART 2
BCAR Section S revision
Ben Syson explains the probable amendments to BCAR Section S to accommodate 600kg microlights…
ollowing Francis’ article describing the new
F600kg microlight category in September’s Light Aviation, I’ve been asked to write a short article on the changes being made to BCAR Section S, the CAA’s airworthiness requirements document for microlight aeroplanes, which is being updated to suit the expanded
Microlight defi nition. However, as a revised document has yet to be published – I fear I may have been stitched up!
To be fair though, I have been involved as LAA
Engineering’s representative in the CAA’s working group advising what should and should not go into the updated document, so I have a reasonable idea about what might appear. Above The Blackshape Prime is typical of a new genre of high performance 600kg aircraft. 45kt stall speed limits will allow many more higher performance aeroplanes into the microlight defi nition. Therefore, it has been decided to overhaul BCAR Section S to make it fully applicable to all aircraft in the new microlight category. It’s also been decided to realign BCAR Section S as much as possible with the Czech UL-2 and German LTF-UL documents.
Gust loads
BCAR Section S
BCAR Section S was introduced by the CAA in the mid-1980s as part of the regulation of the new, and previously unregulated, sport of microlight fl ying. Rather than starting from scratch, JAR-22, the then European airworthiness requirements document for powered sailplanes, was used as a starting point. The sailplane-specifi c requirements were removed, and the remaining requirements tweaked and toned down to suit the simple, lightweight, low-performance microlights of the day. An early version of BCAR Section S was used by the Czechs and Germans as the starting point for their ultralight airworthiness requirements, UL-2 and LTF-UL respectively. As time has gone on, the three documents, BCAR Section S, UL-2 and LTF-UL, have evolved independently, and grown apart to some extent.
Although BCAR Section S has evolved – mostly for the better – it is still only fully applicable to aeroplanes with a design maximum speed not exceeding 140kt. The few microlights in the current defi nition that are faster than that were approved by borrowing ‘high speed’ requirements from light aircraft airworthiness requirements. The expanded 600kg take-off weight and
The fi rst ‘high speed’ requirement currently missing from BCAR Section S are gust loads – the original BCAR Section S had the gust loading requirements of JAR-22 removed. This is a justifi able omission for low-speed aircraft, as fl ying relatively slowly through gusts doesn’t generate loads as large as the +4/-2g manoeuvre load limits. I’m expecting traditional light aeroplane gust load requirements to be introduced into BCAR Section S, which will align it with the Czechs and Germans, as well as the American Light Sport Aircraft (LSA) requirements.
Flutter
The other ‘high speed’ requirement that was signifi cantly toned down – although not entirely removed – in BCAR Section S, was fl utter. Although fl utter can occur at low speed, it becomes much more of a problem as airspeed increases. The German and Czech requirements are very hot on fl utter, as they have a number of universities that specialise in the subject for their glider and light aeroplane industries. Unfortunately, the UK is not well endowed with this particular expertise. I’m expecting the CAA to fi nd some middle ground for the new BCAR Section S, with some ground testing/analysis required prior to confi rmatory fl ight testing.
Increased payload
One of the criticisms of the 450kg microlight category is that it’s possible to squeeze a conventional-style light aircraft into it – think Eurostar or Flight Design CT – but only just.
Above A draft of the original BCAR Section S from the 1980s, a hand-amended page of the JAR-22 powered sailplane requirements showing the removal of the gust load requirements. Similar requirements are now being added back in!
Above The fl ight envelope – incorporating gust as well as manoeuvre loads – from EASA’s CS-VLA. I’m expecting the new BCAR Section S envelope to be similar to this, and the same as the envelope in the Czech and German requirements.
This has resulted in a lot of the fl eet being rather heavy and rather impractical as two-seaters. I’m expecting the new payload requirement will mean a 600kg microlight must have payload suffi cient to take two 100kg (220lb, or 15 stone 10lb) people, together with an hour’s fuel at the engine’s maximum continuous power. This is the same requirement as adopted by the Czechs and Germans for their 600kg ultralights.
Undercarriage strength
The current BCAR Section S has simplifi ed undercarriage strength requirements, compared to the traditional undercarriage requirements for light aeroplanes. Again, these were aimed at the simple microlights of the 1980s and 1990s, many of which didn’t have conventional springs or other energy absorbing components in the undercarriage, but relied on the fl exibility of the airframe to absorb the landing impact energy. Although the BCAR Section S requirements are easy to test, they are quite conservative when applied to a more conventional undercarriage system. I’m expecting traditional light aeroplane ground load requirements to be introduced into BCAR Section S, which will align it with the Czechs – but not the Germans – as well as the American LSA requirements.
Unintentional spin recovery
There has been some discussion about whether it should be removed from BCAR Section S to help align with UL-2 and LTF-UL. However, there are some contemporary European ultralight types with poor stall/spin accident records, so it has therefore been decided to keep a spin recovery requirement in BCAR Section S. It’s also worth noting that Germany, for example, has possibly justifi ed not having any spin recovery requirements for ultralights Light on the basis that it has a requirement for a mandatory, functioning ballistic parachute. By contrast, the UK doesn’t require a ballistic chute and, if one is aircraft ground fi tted, our requirements don’t require the installation’s effectiveness to be verifi ed. load requirements The current spin recovery requirement in BCAR Section S is essentially the same requirement as for certifi ed introduced into aeroplanes. This requirement requires that the aircraft can’t get into an unrecoverable spin, however hamfi sted and perverse the pilot. Although well intended, proving this BCAR Section S, will align it with the defi nitively requires the test pilot to plough through an enormous number of spins to check all possible combinations of Czechs entry conditions and recovery actions – both right and wrong. There has been a lot of discussion about whether this can be simplifi ed for microlights, to concentrate on those spins that are most likely to be problematic. I’m looking forward to seeing what the CAA proposes in this respect.
Although not in the initial BCAR Section S, a requirement to ensure that an aircraft can be recovered in case it gets into an unintentional spin, was introduced into BCAR Section S about 20 years ago. The Czechs and Germans haven’t introduced this into their ultralight requirements.
When?
The CAA has promised to release a draft of the new BCAR Section S any time now for a public consultation, with the fi nal document being published around year-end. ■
Chrislea Super Ace fl ies again…
Rupert Clark relates the news that his uniquely controlled vintage machine is back in the air…
fter just over four years in storage since
Aher last fl ight, Chrislea Super Ace G-AKUW has once again been airborne in the skies of Lincolnshire. The 74-yearold aircraft had been stored in a dry and well-ventilated environment (a hangar with a number of holes in the roof!) and needed servicing and a roof!) and needed servicing and a full inspection before a Permit
Flight Release Certifi cate could be Flight Release Certifi cate could be issued. With everything in place, the test fl ight took place in calm conditions late in the day at the beginning of August. Mark Sharp, beginning of August. Mark Sharp, an LAA Coach and Shuttleworth
Trust pilot, amongst his many qualifi cations, fl ew the aircraft for 40 minutes and seemed pleased that everything was in order, as I did that everything was in order, as I did not have a current Medical.
With its distinctive and unique-toWith its distinctive and unique-toAbove Owner Rupert Clark with Chrislea Super Ace G-AKUW.
Below Mark Sharp after a successful test fl ight. fl ight. type fl ying control system, where pitch is controlled by moving the control wheel up and down, the Chrislea Super Ace is certainly a quirky aircraft. However, once airborne she climbed well and seemed to enjoy being back in her natural environment. After landing, she drew the usual small crowd of interested onlookers along with many comments on the design, cockpit layout and blue velvet-lined interior décor. Many comment on the ‘windy’ generator on the starboard wing, and these days I can describe it as a ‘Green’ feature, making use of ‘renewable energy’ to charge the battery; although most will fi nd the idea of a ‘Green’ Gipsy Major powered aircraft a bit far fetched! With her new Permit to Fly in hand I look forward to a few more adventures with her. My thanks go to Rick Hand, LAE and LAA Inspector, for his guidance and advice on the return to fl ight process, to Al Weir for assisting me with the work, and to Mark for doing the test fl ight. ■
