No. 384 APRIL 2021 The magazine of the British Hang Gliding and Paragliding AssociationWe each kill the thing we love, as Oscar Wilde said. Could we be killing thermals? This chilling thought first occurred to me watching desperate pilots sniffing around the ridge on a typical Selsley Common light-wind day. One pilot would locate a promising waft of updraft, whereupon six other thermal sharks would immediately pile in. In the face of this onslaught the thermal appeared to give up. Young life is tender; maybe thermals are no different. A little parcel of slightly buoyant air rises and, sustained by a good lapse rate, gathers strength. Drawing more warmed air in below, the thermal grows. Maybe it becomes a towering vertiginous column, an elevator to the upper boundary layer; maybe it meets mixed air with lower buoyancy and loses coherence; maybe it dissipates laterally. Maybe its growing integrity is sliced to ribbons by the turbulence created by hungry pilots? And maybe their dead weight weighs it down? Let’s try and work it out. The idea of pilots weighing a thermal down bears scrutiny. I considered a few approaches here, and the one that made me sound most intellectual was an energy-budget approach. It takes energy to lift a pilot into the air, energy that originates from solar heating of the ground. Indeed, ‘Watts per m2’ is available as a metric on RASP, but there are a number of unanswerables here: • What’s the heating differential between the thermal source and the surrounding area? • How big is the area feeding the thermal? • What’s the transfer efficiency between the ground source heat and the airmass? Beyond this there is a more fundamental problem: the thermal gathers energy due to the lapse rate; the original thermal source is just a trigger to get it going. If we can’t calculate the energy budget of a thermal, let’s look at the outcome. Other approaches included considerations of change of momentum, mass and kinetic energy. These all start with the question – how much does a thermal weigh? Let’s start with three models – a Selsley waft, a Milk shaft and a Quixada tower. Assume cylindrical thermals and an air density of 1kg/m3. Model Height Diameter Temp diff Mass Selsley 100m 20m 2˚C 31 tonnes Milk 1000m 50m 3˚C 1,963 tonnes Quixada 3,000m 100m 5˚C 23,562 tonnes At first glance it appears that a few pilots are merely a pimple on the backside of even a Selsley waft – but wait! The thermal rises due to the differing density between itself and the surrounding air. The active part is the weight differential, not the total mass. If we assume the air pressure is the same as the surrounding air (it won’t be, quite – nothing’s ever simple) then we might brandish a bit of O-Level physics for adiabatic expansion. Boyle’s Law states P1 x V1/T1 = P2 x V2/T2, where V is volume, P is pressure (assume the same pressure inside and outside the thermal at a given height) and T is absolute temperature (i.e. Kelvin). Let’s make T 10 degrees C, or 283 Kelvin). By calculating the difference between V1 and V2, we can find the difference in volume for the same mass of air inside and outside the thermal. This gives us the density, which gives us the difference in mass for the same volume of air inside and outside the thermal. I am going to call this the thermal mass differential. Model Height Diameter Temp diff Thermic mass diff Selsley 100m 20m 2˚C 220kg Milk 1,000m 50m 3˚C 20,596kg Quixada 3,000m 100m 5˚C 40,9062kg I’ve had to change the mass scale from tonnes to kg to avoid decimal points. We now see that the incremental thermal mass of the Selsley waft is 220kg rather than 31 tonnes – equivalent to two fat paraglider pilots, or three thin ones. This is the most you could fit into such a waft at ridge level anyway. The Milk shaft is around 90 times bigger – around 200 pilots. A comp may have 100 pilots in such a thermal, amounting to half its incremental thermal mass. The Quixada tower would accommodate 400 pilots with just 10% of its thermal mass. What happens when the pilot mass equals the thermal mass? If we assume the pilots are fully entrained in the thermal, they are effectively increasing its density such that it matches the local air density and is no longer buoyant – but of course it’s more complicated than that. The buoyant air will keep rising past them, but they will undoubtably suppress the thermal if they benefit from it. At this point I would like to hand over to someone who knows what they are talking about. … Silence! Grim though these figures are for Selsley regulars, it could yet be worse. There are the turbulent disruption effects, which I really can’t quantify, and a further consideration, the non-cohesiveness of thermals. As mentioned earlier, the rising air draws buoyant air into the space it vacates as it rises. I’m calling this entrainment. However, pilots attempting to climb out generally enter a thermal near the base. This could suppress the lower part of the thermal, allowing non-buoyant replacement air to be drawn in sideways, snapping the thermal off from its feed and liberating the leading bubble to sail skywards, unencumbered by ground-dwelling creatures. This may explain why I always seem to climb out better when I’m on my own. I don’t have to compromise on my line, or be lured by small gains indicated by other pilots – but the thermals may also simply have more energy. I would be keen to see development of these ideas by those with more knowledge of atmospheric dynamics, turbulence, hysteresis and other ghastly mathematics. Maybe we will never understand what is going on until somebody develops specs that enable us to see air density. Some claim that would take the fun out of paragliding; I say, ‘Would you be more inclined to take up kayaking if you couldn’t see water? … Would crossing the road be more fun if you were blind?’ Until then I will continue flying off to the unpopular end of the ridge, seeking my own private thermal. 2 SKYWINGS APRIL 2021 attitude Are we overloading our thermals? ALAN SPEY, PARAGLIDER PILOT AND DATA ANALYST Photo: Kate Pullin4 SKYWINGS APRIL 2021 regulars features THE BHPA LTD 8 Merus Court, Meridian Business Park, Leicester LE19 1RJ. Tel: 0116 289 4316. SKYWINGS MAGAZINE is published monthly by the British Hang Gliding and Paragliding Association Ltd to inform, educate and entertain those in the sports of Paragliding and Hang Gliding. The views expressed in this magazine are not necessarily those of the British Hang Gliding and Paragliding Association, their Council, Officers or Editor. The Editor and publisher accept no responsibility for any supposed defects in the goods, services and practices represented or advertised in this magazine. The Editor reserves the right to edit contributions. ISSN 0951-5712 SUBSCRIPTIONS AND DELIVERY ENQUIRIES Tel: 0116 289 4316, THE EDITOR Joe Schofield, 39 London Road, Harleston, Norfolk IP20 9BH. Tel: 01379 855021. E-mail: COVER PHOTO Ollie Chitty works out on Flow’s Yoti II 17m H&F mini-wing at Mount Tamborine, Queensland Photo: Ollie Chitty THIS PAGE Summit of the Dent de Crolles, Chartreuse mountains, France. Photo: Gareth Bird APRIL 2021 SKYWINGS 5 DESIGN & PRODUCTION Fargher Design Ltd. Killane House, Ballaugh, Isle of Man, IM7 5BD. PRINT & DISTRIBUTION Newman Thomson Ltd, One Jubilee Rd, Victoria Ind. Est, Burgess Hill, RH15 9TL. ADVERTISING Tel: 07624 413737 SKYWINGS ONLINE Go to For the April issue enter the username Apr_2021 and the case-sensitive password P7#95rl£ For the May issue enter the username May_2021 and the case-sensitive password BKc85$t4 DEADLINES News items and event/competition reports for the June issue must be submitted to the Skywings office by Monday May 3rd. Letters for the May Airmail pages should arrive no later than Friday April 16th. Advertisement bookings for the May edition must arrive by Friday April 9th. Copy and classified bookings no later than Friday April 16th.6 SKYWINGS APRIL 2021 news CAA EC rebate scheme extended The CAA EC Rebate scheme for Electronic Conspicuity devices has been extended until September 30th, 2021. There are still up to 4,000 rebates available; if funds run out before the deadline the CAA will notify a new closure date. The conditions are unchanged. There is a list of qualifying devices, and for us free flyers these mostly involve instruments with a FLARM element. Currently the manufacturers offering FLARM-enabled instruments are Naviter, Skytraxx and XC Tracer. A Google search for ‘CAA electronic conspicuity rebate’ will show the relevant CAA page, with further details and the application procedure. You will need to register for a CAA Portal account, then complete identity checks. Aafter the CAA have verified the checks you can complete the rebate form. You’ll get 50% of your expenditure back, up to a limit of £250. CIVL’s Zoom plenary CIVL’s annual plenary meeting went ahead in February on Zoom. Stephane Malbos, was re-elected President for a new two-year term and three bids for World Championships in 2023 were accepted: paragliding at Andradas, Brazil; accuracy at Sopot, Bulgaria; and hang gliding at Àger, Spain. It was also agreed that if any 2021 World Championship is cancelled due to the Covid-19 pandemic, the organiser will be offered the chance to organise the 2023 championships. If accepted the successful bids above will be cancelled. In these unusual times there were few proposals and even fewer that passed, mainly adjustments to current rules. Records of Annexes and Open meetings will be available soon Wolfi Lechner retires Wolfgang Lechner, one of the three original founders of Nova in 1989, is retiring at the age of 62. Starting out as head of sales, Wolfi worked his way through test pilot, warehouse worker, secretary and MD before handing over to new leader Sissi Eisl in 2018. Since then he has passed on his experience and knowledge to Sissi while remaining responsible for Nova’s Austria sales. He will of course continue as an unpaid on- call consultant and remains a shareholder. ‘It was a great privilege to be able to spend my working life doing something I loved,’ he says. ‘The younger generation is now taking over the reins at Nova and I’m happy to continue to play a small part in its future.’ He is looking forward to spending more time with his wife Carmen and on his hobbies: woodwork, maintaining his Tyrolean mountain hut, travelling, diving and paragliding. He is also deeply involved in Eisstockschiessen or Austrian curling; his team plays in the national league. A fond farewell to Wolfi can be viewed at BHPA subs increase A reminder that BHPA annual subscriptions increased on April 1st. The headline individual annual adult membership has gone up by by 7.75% to £139. Other annual memberships are: Family, £124; Concessionary (under 21/over 67), £119; and Non Flying, £51. One-day Introductory Membership is now £20 (under 21: £5); three months introductory Trial Membership £75; the Joining/Rejoining fee £25; and a Skywings subscription £50. The direct debit discount for all annual subscriptions remains at £7. Insurance supplements increased by an average of 4%: the Instructor Supplement to £85; the TI Supplement to £30; and the Paraglider Dual Pilot Supplement to £85. Retro rebuilds! Ever thought (some do!) that the Airwave Kiss was the best hang glider you ever flew? A Dutch company is offering ground-up rebuilds of out-of-production hang gliders, mentioning the Kiss in particular. Jakob van Dwaas of Zeilvliegen Dwaas invites pilots to ship their old hang gliders to his Dutch facility for a thorough inspection. An exacting schedule of work is drawn up, itemising the parts that need replacement. The interesting part is that Zeilvliegen Dwaas can replace all parts that Jakob has drawings for, and can and reverse-engineer others. Jakob also has facilities for sail repair, up to and including an entire new sail. Thus your Kiss, Rumour 1, Seedwings Spyder, OffPiste Discovery or La Mouette Top Secret can be brought back to 100% new condition and fly better than ever. The desire for older gliders isn’t pure nostalgia; weight, easy handling and forgiving landing are all parameters that have been recalibrated in recent years. It’s not clear how much a re-engineered Kiss 154 might cost, but there is a small coterie of pilots who regard that wing as ‘one of the last of the V-8 Interceptors’. Jakob is careful to stick to gliders whose manufacturers are long gone and, wisely, to those with existing BHPA/DHV/ HGMA certification. If anyone has the desire, and the wonga, to pursue this idea we’d be happy to write the process up. Jakob’s operation seems to be adjacent to Maastricht airport, and he’s offering a collection service from there. Contact him at Horsterweg 41, 6179 AC Maastricht, Netherlands, tel: ++31 43 358 7899, e-mail, jakobohyes@vliegendwaas.nl, or go to www.vliegendwaas.nl.Are you ready for the new flying season? My new website may be able to help. It is chock full of interesting stock, and is already working much better than was the old site. Improvements are being incorporated almost daily. We are getting there! There are several different payment methods available on the site, but if all else fails just call or email me, as you used to do in the past. We can sort it! New items have been coming in regularly throughout lockdown, and there is a positive flurry of deliveries expected after March 29th. This totally gorgeous Firebird Raven used to be my personal paraglider. It is in superb condition, has exceptional porosity readings and is stunningly attractive in unique Gulf Racing colours - no logos! I had a great time with this glider, so I am confident that the next owner will do the same. EN B, but could be flown by a talented new pilot, and it is only £695 - for a wing with years of life left! It is practically impossible to make an airbag harness look good on the ground and I certainly failed in this case, but don’t let that put you off! This reversible airbag Firebird Mowenpik in the medium/large size is a fine example of a brilliant paragliding harness at just £299. I still regard it as one of the best-ever designs, and have a lot of happy customers who still fly them. This Aeros Myth harness for the hangies should arrive before you read this, and will be priced somewhere around £550. It is a medium size, very aerodynamic and aimed at the competent club pilot. I have other harnesses listed in my stock selection, too, in a variety of sizes. Coming in soon is this amazing Litespeed RX 3.5 which has had just a couple of flights! It has all the sensible options, and cost around £8500 when new. Not now, though! I’d like to think this might become my personal glider, but it may be too heavy for my post- cancer body. Perhaps I will let Jezzer fly it for a while - until somebody rolls up with the money…. This Airwave Scenic 2 tandem paraglider is already here. Condition is excellent - just a few slightly muddy marks on the top surface and the porosity readings average around 300 seconds, so there is a lot of life left in it! As you know, tandem gliders are rather rare, and this one is only £550 - grab it before it is gone! Early in April I am taking delivery of a very tidy Moyes Malibu 188 which should fetch £2750, but I will set the price when I have checked the glider over. Malibus are probably the easiest hang glider to fly, and are also really easy to live with once you have stumped up the purchase price. That is why I always keep this green one in the hangar as my personal glider, and why they often sell before they get advertised. So, I have lots of interesting stock, most of which you will find on the website. With summer coming fast, I can’t honestly pretend that I will be sitting by the phone 24/7 waiting for your call. In good weather I plan to be out flying, karting or motorbiking. But the system is in place for you to leave messages on my phones, emails, telegram or via the website, so you should get a quick response to any questions or orders. Give me a try! Lockdown Run away with the Flying Circus! Luppitt, Honiton, Devon, EX14 4SA tel: 01404 891685 Forty years in the business - my extensive range allows you to choose what best suits your needs. Find lots more on the Zoot headsets: Four models for open- and full-face helmets and various radios. Prices from £34.45. Zoot Radio outfits: A great radio and a choice of Zoot headsets for just £77! I stock various speaker/mics and antenna, too! Lots of instruments - all prices reduced to clear Charly Quickout Karabiners for tandem pilots. Weighs 200 gm with a breaking load of 4000kg. £60each The Austrialpin Tropos Steel karabiner for hang gliding, weighs 215gm and is rated to 32Kn. £24 each Charly Pinlock alloy Karabiners: Weighs 80gm, certified to 25 Kn. £27.50 each. The new Charly Snaplock alloy Karabiner, weighs 75gm and certified to 30Kn. £23 each. Tow releases from £48. Hang glider wheels from £51.10 a pair. Zoot Camera Mounts £29.50. Zoot Pip-pins, three lengths from £10.75, and Zoot Caps at £2.75. SMFC Speedarms reduced to clear - £25 Accessories Simon Murphy’s Flying Circus Summer is Coming!news 8 SKYWINGS APRIL 2021 No TMZ for Oxford In February the CAA refused London Oxford Airport’s bid for a Transponder Mandatory Zone in the area. The CAA decided the proposal had not made a compelling case for a TMZ, nor had it engaged in adequate consultation with other affected air users. Nor had the proposal adequately addressed co-ordination with nearby RAF Brize Norton. Yet again a regional airfield (formerly Kidlington), in seeking to reinvent itself as a business aviation hub, has attempted to play fast and loose with the airspace change mechanism to the detriment of other air users. RAF Brize Norton itself had sought increased controlled airspace; their case too was refused by the CAA as poorly designed and executed. Small victories for common sense, helped in part by pressure from GA organisations. But they’ll be back … CANP contact change Despite having changed only last January, the contact for the new Military Airspace Management Cell (MAMC) has changed yet again. With immediate effect, the contact e- mail is The contact phone number is still 01489 443100 and the Freephone number 0800 515544 remains active. On March 15th MAMC working hours reverted to 0700-2000 Mon–Thurs (ie up to 1959 hrs) and 0700- 1500 on Fridays. The best way to submit a CANP request remains via the online system at The prime mechanism to keep our pilots out of the way of RAF and other low flying aircraft has now changed its e-mail address six times in the last five years and twice this year already. For those with a keen eye on the date, this is not an April Fool! Paragliding Worlds cancelled Despite valiant efforts to ensure that this closed-door event would start on time on May 23rd, the evolution of the global Covid- 19 pandemic proved too problematic. With too many uncertainties unresolved, a decision was taken on March 12th to cancel the event. The organisers write, ‘We thank the many people who worked on this project and the teams who shared their worries and their support. We leave the 2021 event behind with regret but, we believe, with wisdom, and are ready to run the next World Championship in 2023.’ Top marks to the organising team for really trying hard to make the ’21 Worlds a goer! Kössen testival The 10th edition of Kössen’s Super Paragliding Testival is confidently scheduled for May 31st - Jun 3rd. Now sponsored by the Tyrolean Government, local government and AXA Insurance, and partnered by XC Mag and Thermik, the event anticipates 50 manufacturers and other exhibitors and over 3,000 pilots attending. Last year over 7,500 flights were logged, boosting the organisers’ claim that it’s become the one of the biggest air sports events in the world. Book accommodation at Skyway Code v3 In March the CAA published version 3 of the Skyway Code, designed to provide GA pilots with quick and easy access to key information relevant to their flying. Version 3 brings the publication up to date; changes reflect the UK’s departure from the EU, the latest regulatory requirements and ‘best practice’ from the CAA. Also new is enhanced guidance for using moving map devices and avoiding infringements, an updated introduction to EC reflecting recent developments, and new sections on Unmanned Aerial Systems and ‘Just Culture’. It would be easy to think that the Skyway Code is not relevant for our kind of flying. This is far from the case; it contains pretty much everything we need to know for the legal aspects of flying, plus a lot of common sense, even if the reader has to filter out a lot of more mainstream stuff. And you can access it on your phone! If there is a drawback to the latest edition it is that it has become rather bloated, hindering navigation of the document and almost burying the key information under a thicket of other stuff. Rest assured – what you need to know is still there, and the other stuff is not without interest. The Code is available online with easy internal navigation for on- screen use, or as as a PDF download for easy printing. Go In brief Return to flying. On March 2nd we received DfT confirmation of the ‘roadmap’ by which General Aviation can resume in England. In essence solo leisure flying in England was to have commenced on March 29th, with training resuming on April 12th. However regulations published on March 5th allow an interpretation that hang gliding and paragliding are legal forms of outdoor open air recreation. Therefore, where there is no landowner objection, flying could have legally resumed from March 8th. The BHPA was continuing to liaise with the DfT over the date for the re-opening of schools. Details, and the current rules for Scotland, Wales and Northern Ireland, are at date information check the BHPA website and Facebook page. We owe it to ourselves to play this return to the air safely and sensibly – see Safety Matters on page 14 Skywings online. The online version of this issue of the magazine can be found at username Apr_2021 and the case-sensitive password P7#95rl£. For the May issue ? enter the username May_2021 and the case-sensitive password ?????? These details can also be found on the contents page of each issue. Issues with a cover date over six months old can be viewed online/downloaded with no need to log in. Speedflying in France. Sunsoar are running a speed flying trip to Grand Bornand in the French Alps from August 7th - 15th. Mont Lachat offers the opportunity of long descents in the mornings before paragliding in the afternoon along the spectacular Aravis. Annecy, a short drive away, will be an alternative flying area during the week. If you have BHPA speed flying and paragliding qualifications, book now at very limited. More online tutorials. Leavesley Aviation has begun producing an extended series of paragliding tutorials. Filmed to a high standard using Røde remote mics, these will eventually cover ground handling, launches, side landings, top landings, losing height, stress-free flying and more. Mark Leavesley’s first tutorial covers rigging in the wind; others will follow quickly as the weather improves. Find them on Mark’s YouTube platform at Bollington news. For the foreseeable future the Bollington Paragliding School, operating at Barton airfield in Manchester, will not be accepting any new trainees, or tow conversion courses. However for existing members the club will continue to operate as usual. Lakes Classic put back. As a result of the lockdown only being fully relaxed the week after the original planned dates of the June 18th - 20th, the Lakes Charity Classic has been put back a month to July 16th – 18th. Details are at BHPA 500 Club WIN CASH PRIZES AND HELP THE ASSOCIATION! February winners Michael Carter £132.20 David Forty £66.10 John Mills £33.05 Andrew Burton £19.83 Charles Blount £16.53 Richard Clark £16.53 Tanya Ephgrave £13.22 David Ebbs £13.22 Jonathan Down £9.92 Jason Harper £9.92 BHPA £330.48 If by the time you read this you have not received your cheque, please contact me on 07802 525099. Marc AsquithNext >