First look: Ul­tra­light Con­cept SV4-RS

Prov­ing very pop­u­lar on the Con­ti­nent, the ul­tra­light Bel­gian-built SV4-RS im­i­tates the orig­i­nal Stampe but is not (of­fi­cially) aer­o­batic

Pilot - - CONTENTS - Words: Ste­fan De­graef Pho­tos: Ed­win Bor­re­mans

A 100 per cent size, Ro­tax­engined Stampe replica Euro­pean ul­tra­light that may yet make it to the UK

Af­ter WWII, the Bel­gian-de­signed but French-built sleek Stampe-ver­ton­gen SV.4C open-cock­pit bi­plane was used ex­ten­sively by the French armed forces as a train­ing air­craft. Built un­der li­cence by SNCAN (So­ciété Na­tionale de Con­struc­tions Aéro­nau­tiques du Nord) and the Al­ge­ria-based Ate­lier In­dus­triel de l’aéro­nau­tique d’al­ger, some 940 air­craft saw op­er­a­tional ser­vice within the ele­men­tary fly­ing schools of the French Ar­mée de l’air (Air Force), Aéron­avale (Navy) and Alat−avi­a­tion Légère de l’ar­mée de Terre, based in North Africa. Sim­i­lar to the PRE-WWII A-vari­ants, C-mod­els were equipped with a 140hp Re­nault 4-P en­gine.

The Ser­vice de la For­ma­tion Aéro­nau­tique de la Di­rec­tion Générale de l’avi­a­tion Civile (Civil Avi­a­tion Direc­torate) also used SV.4S in their var­i­ous train­ing cen­tres all over France (Cen­tres Na­tionaux de Vol à Mo­teur) for ini­tial aer­o­bat­ics and in­struc­tor train­ing.

The Stampe’s ex­cel­lent fly­ing and sim­ple main­te­nance char­ac­ter­is­tics inspired the French Ser­vice de l’avi­a­tion Légère et Sportive (Light and Sport Avi­a­tion Direc­torate) to of­fer the ubiq­ui­tous SV.4C to ae­ro­clubs at bar­gain prices. Its fu­ture as France’s ded­i­cated civil­ian pi­lot train­ing air­craft seemed set­tled well into the fu­ture... ex­cept for the un­for­tu­nate fact that the un­stop­pable quest for both tech­ni­cal and per­for­mance im­prove­ments, and the avail­abil­ity of more ad­vanced and bet­ter-equipped gen­eral avi­a­tion and train­ing air­craft, quickly made the old bi­plane ob­so­lete for train­ing pur­poses.

Luck­ily, a re­newed in­ter­est in vin­tage air­craft and nos­tal­gic com­pass-and-stop­watch fly­ing in France and across West­ern Europe made the then low­priced SV.4 vari­ants a soughtafte­r and de­sir­able col­lec­tor’s item for a new gen­er­a­tion of pri­vate and pro­fes­sional pi­lots.

To­day, the SV.4 is well-known on the Euro­pean vin­tage air­craft scene, with a large num­ber of air­craft still fly­ing. Ded­i­cated Stampe events for own­ers in Bel­gium and France are well at­tended, and air­craft go to a mul­ti­tude of lo­cal fly-ins, gen­er­at­ing keen in­ter­est from fans and other own­ers alike.

The in­creas­ing pop­u­lar­ity and cost of these old bi­planes (sim­i­lar to DH Tiger Moth and Bücker Jung­mann air­craft) have put them out of reach fi­nan­cially of the ‘av­er­age’ pi­lot and for train­ing, in terms of op­er­at­ing and main­te­nance ex­pense. To­day’s recre­ational pi­lots are in­creas­ingly look­ing for more cost ef­fec­tive al­ter­na­tives in the form of mod­ern and welle­quipped mi­cro- and ul­tra­light air­craft, which are be­com­ing more preva­lent in Europe’s skies.

Since mi­cro/ul­tra­light air­craft came along in the eight­ies, de­pen­dent on and

com­ply­ing with the var­i­ous na­tional reg­u­la­tions, a plethora of com­pa­nies have de­vel­oped, of­fer­ing a wide ar­ray of mod­ern, well-equipped and er­gonomic air­craft at bud­get-friendly and com­pet­i­tive prices (com­pared with stan­dard air­craft). In re­cent years the re­newed de­sire for vin­tage-like but much cheaper ul­tra­light air­craft has gen­er­ated var­i­ous start-up com­pa­nies on a mis­sion to de­velop ‘as close as pos­si­ble’ repli­cas of the ‘old masters’. One of these niche mar­ket ul­tra­light com­pa­nies is Bel­gium-based Ul­tra­light Con­cept, of­fer­ing the eye­catch­ing SV4-RS ul­tra­light, based on the orginal SV.4C trainer.

De­signed by a pi­lot

The Ul­tra­light Con­cept avi­a­tion com­pany and its SV4-RS ul­tra­light bi­plane are the brain­child of Raoul Sev­erin, a for­mer Bel­gian Army Avi­a­tion and Air Force he­li­copter and fixed-wing pi­lot. At the end of his ac­tive army ca­reer he cre­ated his own metal dis­tri­bu­tion com­pany, also spe­cial­is­ing in avi­a­tion ma­te­ri­als.

Raoul Sev­erin’s first step into the world of ul­tra­light avi­a­tion was the con­struc­tion of a Platzer Kieb­itz bi­plane, based on and us­ing the plans bought from Michael Platzer. Dis­tribut­ing welded steel tub­ing, us­able for Kieb­itz and other am­a­teur-build air­craft, he quickly be­came fa­mil­iar with the needs and de­sires of a large num­ber of (mostly Ger­man) ULM afi­ciona­dos.

Once pro­fi­cient at rel­a­tively easy self-build air­craft, some mem­bers of that self-builder com­mu­nity were mov­ing on to more re­al­is­tic repli­cas of ex­ist­ing vin­tage air­craft.

Sens­ing busi­ness op­por­tu­ni­ties, hav­ing good con­tacts within the Ger­man and French am­a­teur build­ing scene, and−above all− be­ing will­ing to de­sign and fly his own vin­tage-style ul­tra­light, Raoul started to con­ceive his own ULM (french mi­cro­light) de­sign. In or­der to achieve his busi­ness plan and ob­jec­tives, he had to choose as a ba­sis for this brain­child an easy-to-build, sleek and eye-catch­ing aero­plane that would be pop­u­lar in Ger­many and France. These neigh­bour­ing coun­tries, within driv­ing dis­tance of his eastern-bel­gium home­base, had wit­nessed an in­crease in home­build­ing ac­tiv­ity.

Meet­ing all pre­vail­ing mi­cro­light/ulm leg­is­la­tion and reg­u­la­tion would hugely boost the air­craft’s home-build ap­peal,

mak­ing it more eas­ily saleable and mar­ketable in other (more re­mote) coun­tries. The de­ci­sion to use the Bel­gian-de­signed vin­tage SV.4C bi­plane trainer as the model of choice was straight­for­ward since a large num­ber of orig­i­nal SV-4 mod­els were and are still fly­ing all over Europe.

Orig­i­nal draw­ings used

The am­bi­tious SV4-RS project started in 2007 with the pur­chase of Cd-rom-stored orig­i­nal man­u­fac­tur­ing draw­ings of the SNCAN SV.4C vari­ant from the Es­pace Air Pas­sion mu­seum. Based at Angers-loire air­port in west­ern France, this mu­seum houses one of France’s most im­por­tant col­lec­tions of air­craft man­u­als and tech­ni­cal archives of un­equalled im­por­tance within France’s vin­tage avi­a­tion com­mu­nity.

Grad­u­ally de­ci­pher­ing and con­firm­ing in de­tail all di­men­sions (over­all length, wing­span etc) of the orig­i­nal SV.4, Raoul quickly con­cluded that the widely available prewelded alu­minium tubes in his pos­ses­sion, used for Kieb­itz bi­planes, were of limited use for this. Since all Kieb­itz-like tubes have a stan­dard length of five me­tres and the orig­i­nal SV.4C mea­sures 5.15 me­tres, the only way to build and mar­ket a 100% ul­tra­light-replica was to ac­quire new metal tubes and con­sign the un­der­sized ones to the dust­bin.

Con­vinced a 97% scale replica would de­ter fu­ture cus­tomers and home-builders from buy­ing the kits, the de­ci­sion was quickly taken to fo­cus on a 100% replica and be the first to of­fer this type of ul­tra­light in a grow­ing leisure avi­a­tion seg­ment.

Since Raoul was still work­ing part-time as a mil­i­tary he­li­copter and HEMS pi­lot, as­signed to the Cen­tre de Se­cours Médi­cal­isé de Bra-sur-li­enne HEMSor­gan­i­sa­tion based at Bra in Bel­gium’s eastern Ar­den­nes­re­gion, the de­vel­op­ment of the SV4-RS pro­ceeded slowly. In 2013 he con­structed the fuse­lage, ailerons and tailplane for his pro­to­type. Soon af­ter­wards he was con­tacted by FH Aachen (Fach­hof­schule Aachen) to al­low stu­dents fol­low­ing the Uni­ver­sity’s

Luft-und Raum­fahrt­tech­nik - Ver­tiefungsri­ch­tung Flugzeug­bau (Aero­space) syl­labus to use var­i­ous tech­ni­cal as­pects of the SV4-RS as a sub­ject for their mas­ter-de­gree grad­u­a­tion pa­per. The tech­ni­cal in­put of these young mo­ti­vated engineerin­g stu­dents boosted the de­vel­op­ment process. The var­i­ous air­craft com­po­nents were de­signed by these stu­dents, cal­cu­lat­ing in ad­vance all tech­ni­cal and struc­tural char­ac­ter­is­tics and lim­its in an­tic­i­pa­tion of fu­ture of­fi­cial val­i­da­tion.

Fi­nally, in 2015, a bare, en­gine­less SV4-RS with wings, fuse­lage, ailerons and un­der­car­riage was ex­hib­ited at AEROFriedr­ichshafen (Ger­many) and Fes­ti­val In­ter­na­tional de l’avi­a­tion Ul­tra Légère in Blois (France). In the af­ter­math of these well-known ULM events, ten SV4-RS kits were sold at com­pet­i­tive launch prices to kick-start the of­fi­cial SV4-RS and gain in­ter­na­tional ex­po­sure within the mi­cro­light sphere. AERO2016 saw the pres­ence of a non-fly­able but com­plete Ro­tax 912-en­gined air­craft.

First flight and cer­ti­fi­ca­tion

Once all nec­es­sary ground tests had been suc­cess­fully con­ducted, the SV4-RS pro­to­type made its maiden flight on 28 De­cem­ber 2016 at Büllin­gen air­field (EBBN), close to the Bel­go­Ger­man bor­der. Its first flight suc­cess­fully com­pleted, Raoul and his team quickly ini­ti­ated the vi­tal process of gain­ing the rel­e­vant of­fi­cial air­craft cer­tifi­cates in the mar­kets of in­ter­est (Bel­gium, France, and Ger­many).

The first tar­get was Ger­man cer­ti­fi­ca­tion of the SV4-RS, pow­ered by the Ro­tax 912. Since this coun­try’s reg­u­la­tions, tests and ver­i­fi­ca­tion were the most elab­o­rate in num­ber and de­tail, achiev­ing this in Ger­many first would en­able Ul­tra­light Con­cept both to eval­u­ate its own de­sign and de­vel­op­ment skills in depth and also to use the Ger­man cer­ti­fi­ca­tion as the ba­sis for a sim­i­lar process in other coun­tries.

Start­ing in Fe­bru­ary 2017 some sixty struc­tural tests were ex­e­cuted−and val­i­dated by the in­spec­tors−on the air­frame and its var­i­ous com­po­nents (wing, ailerons, seats, sticks, har­nesses, un­der­car­riage etc). To pass Ger­man mi­cro­light weight lim­i­ta­tions the SV4-RS could not ex­ceed 297.5kg with a 472.5kg max­i­mum take­off weight. For the struc­tural tests, two com­plete spare fuse­lages and wings were man­u­fac­tured and tested to their lim­its. Ini­tially planned to be +4/-2g-ca­pa­ble, the air­craft lim­its were in­creased to +6/-3g. Planned to be +4/-2g ca­pa­ble, the air­craft lim­its were in­creased to +6/-3g

Ev­ery three to four weeks Ger­man in­spec­tors trav­elled to Ul­tra­light Con­cept’s home­base to check a pre­pared list of air­craft com­po­nents. To com­plete the ground cer­ti­fi­ca­tion tests, var­i­ous test­flights were flown by Raoul and a Ger­man uni­ver­sity stu­dent, recorded and mon­i­tored by Gopro cam­eras to cer­tify on­board in­stru­ments (e.g. air­speed indicators) and fly­ing char­ac­ter­is­tics (stall­test). An in­spec­tor would re-con­firm these re­sults dur­ing two test flights of the air­craft dur­ing the var­i­ous test­ing pro­files, as­sisted when needed by Raoul Sev­erin, fly­ing ‘P2’ in the front-cock­pit.

Dur­ing Aero2017 Ul­tra­light Con­cept’s SV4-RS replica re­ceived its Ger­man per­mit to fly, con­di­tional on com­plet­ing a min­i­mum of fifty hours’ over­all fly­ing time and suc­cess­fully pass­ing a noise test. Si­mul­ta­ne­ously, the process of ob­tain­ing Bel­gian and French type cer­ti­fi­ca­tions was ini­ti­ated, and the of­fi­cial per­mits for each were re­ceived in Novem­ber 2017.

Once fully as­sem­bled and ground-tested, the maiden flight will by made by a UC pi­lot

Fac­tory- or kit-build

In or­der to mar­ket its SV4-RS suc­cess­fully as the only ‘fullscale vin­tage bi­plane’ replica on the mar­ket, Ul­tra­light Con­cept (UC) can sup­ply the air­craft as a fac­tory-built item or as one of three kit op­tions for cus­tomers to choose from.

Kit 1 is for those fully able to build the mi­cro­light on their own, in­clud­ing all build­ing draw­ings, doc­u­men­ta­tion and ma­te­ri­als. It is sup­ple­mented by two four-day work­shops at UC’S hangar, dur­ing which clients will be helped to build their own fuse­lage, four in­di­vid­ual wings, wingspars and ailerons. Clients must pre­pare for the work­shops by build­ing var­i­ous com­po­nents at their home base be­fore head­ing to Kelmis for as­sis­tance and in­struc­tion if needed. A UC staff mem­ber will still need to in­spect the bare frame be­fore ap­ply­ing the fab­ric and, once fully as­sem­bled and groundtest­ed, the maiden flight will also be flown by a UC rep­re­sen­ta­tive.

The more elab­o­rate Kit 2 op­tion in­cludes ev­ery­thing in Kit 1, but comes with wings and fuse­lage ready built.

The more-en­com­pass­ing Kit 3 ver­sion de­liv­ers a fin­ished but un­cov­ered air­craft struc­ture, leav­ing the owner/cus­tomer in­stalling his own en­gine (gen­er­ally a Ro­tax 912), avion­ics and in­stru­ment-wir­ing. Whichever kit op­tion is cho­sen by the cus­tomer, all half­way-inspection­s must be per­formed and the maiden flight flown by a Ul­tra­light Con­cept staff mem­ber.

De­pend­ing on the pre­vi­ous tail­drag­ger ex­pe­ri­ence of the client, a short type-con­ver­sion in­struc­tion flight can be given by Ul­tra­light Con­cept to demon­strate the var­i­ous fly­ing and land­ing char­ac­ter­is­tics of the SV4-RS.

The air­craft has proved pop­u­lar. By mid-2017 fifty-two SV4-RS kits had been sold to clients in Bel­gium, Ger­many, France, Poland, Czech Repub­lic and Lithua­nia. The fu­ture SV4-RS pi­lot and ac­tive builder is typ­i­cally in their early/mid-six­ties. With the planned build likely to take around 1,000 man hours (de­pend­ing on the kit se­lected), the first cus­tomer­built SV4-RS may well take to the air in 2019. Fu­ture mod­i­fi­ca­tions or op­tions in­clude an ‘SV-4B’ model with closed canopy, and a glider tow­ing con­nec­tion un­der­neath the air­craft. In fu­ture, two ad­di­tional en­gines will be cer­ti­fied for the SV4-RS.

Aer­o­bat­ics a grey area

So what about aer­o­bat­ics, for which Stampe air­craft are well known, and many have been used as mounts for aer­o­batic cham­pi­onship com­pe­ti­tions? The air­craft is ca­pa­ble of aer­o­bat­ics, but the en­gine isn’t cleared for them and, in any event, ul­tra­lights are not au­tho­rised to per­form aer­o­batic flights. Only in France is there a grey area where aer­o­bat­ics in an ul­tra­light are not for­bid­den. How­ever, if cus­tomers reg­is­ter the air­craft as ‘Ex­per­i­men­tal’, then aer­o­bat­ics are au­tho­rised…

The cur­rent (and in­creas­ing) cost of PPL and GA fly­ing, and new more strin­gent na­tional reg­u­la­tions (es­pe­cially med­i­cal re­quire­ments), may well see a shift by cur­rent and fu­ture ‘week­end fly­ers’ to the mi­cro­light seg­ment. Time will tell if the Ul­tra­light Con­cept of­fer­ing of a 100% scale vin­tage air­craft replica, aimed at ‘young pen­sion­ers with a bud­get and some abil­ity’, will be an over­all suc­cess in this mar­ket. How­ever, the sales to date of fifty-seven SV4-RS may well hint at that ultimate an­swer.

LEFT: new Stam­pes on a pro­duc­tion line in 2018 – only these U-C SV4-RS mod­els have wire­braced steel tube fuse­lages with bonded-on foam for­m­ers and tube stringers

ABOVE: this could al­most be a shot from Pi­lot forty or fifty years ago – pro­trud­ing Ro­tax 912 cylin­der heads are the only give-away that ‘Uniform Char­lie’ is a 2017/18 SV4-RS and not a 1940s or 50s SV.4C

TOP TO BOT­TOM: not only look­ing right and be­ing beau­ti­fully fin­ished, the 1:1 Stampe SV.4 ul­tra­light replica fea­tures some clever de­tail de­sign: a tail­wheel that can be linked to the rud­der for take­off or man­u­ally dis­con­nected for ground ma­noeu­vring; nicely triangulat­ed en­gine mount and (just vis­i­ble, lower left in im­age) a se­cure ratchet strap for the bat­tery; and the liq­uid-cooled Ro­tax’s ra­di­a­tor lurk­ing be­hind the orig­i­nal pat­tern air scoop. The Her­cules pro­pel­ler is one sig­nif­i­cant Bri­tish item

CLOCK­WISE FROM ABOVE: Ny­lon pul­leys re­place the Pax­olin orig­i­nals; braided ca­bles are used, rather than stream­line wires. The struts – tubu­lar stream­line sec­tions with riv­et­ted-in end fit­tings – are iden­ti­cal to the orig­i­nals. Fi­nally, turn­buck­les al­low pre­cise rig­ging in time-hon­oured man­ner

Up front ‘P2’ has limited in­stru­men­ta­tion and flight con­trols but no brakes

TOP TO BOT­TOM: The pro­to­type seen here is kit­ted out in ba­sic VFR fash­ion for the rear-seated pi­lot in com­mand (aer­o­batic pi­lots will note the lack of a g-me­ter); sim­ple stick sport­ing a cy­cle brake lever and con­trol levers we’d pre­fer to see shaped and colour-coded (note that changes have been made to the pro­duc­tion ver­sion); and, fi­nally – mir­ror­ing the photo op­po­site – a replica that re­ally looks spot-on

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