“I’m looking for an aircraft to fly to New Zealand in 2018, I’ll need a range of 1300nm at 100 knots TAS, for it to be robust, reliable, good to fly and affordable.” Such was my initial question on meeting several kit aircraft agents in 2014. The general response was that they were happy to sell me a kit, but that I was then on my own. When I sat down with the third potential supplier, my opening line yielded a glance up at a sign which said, “the answer is yes, now what is the question?” Roger Cornwell’s reply was “let’s see what we can do.” An hour later Roger had found a section of wing structure to study, we’d worked out how to double the fuel capacity and preliminary design sketches were taking shape. After a flight in the then demonstrator, G-ZTUG, I knew we had our aircraft.
The Eurofox factory in Slovakia quickly got behind the project too. Stress analysis was conducted and submitted to the LAA. Ever helpful, Francis Donaldson quickly replied saying that he saw no show stoppers. Calculations showed that with the efficient 912 iS Sport engine 1300 nm was readily achievable and, with great attention to the mass of the aircraft and crew, almost full fuel could be carried with 2 crew.
Much has been written about building Eurofoxes in this magazine, so I’ll confine myself to the differences. Finding time for the build was a concern but Roger believed it was achievable in 6 disciplined weeks of leave from the RAF. He was right. The opportunity to occupy a build bay at the Eurofox microlight factory in Kent meant that all the tools, jigs and advice were immediately to hand. The build manual is excellent, but there is no substitute for a brief demonstration by example. For instance having watched me trying to fit the shoulder harness nut to the bolt (all Eurofox builders will know the one I am talking about!), I was shown that if you tape the nut to a spanner with about 5 degrees of tilt, it is achievable by those with normal size hands!
The LAA had recommended that the outboard tanks fed into the inboard tanks. While this would have been lighter and aerodynamically cleaner, after much debate we decided to have 4 separate feeds to the fuselage collector tank. Trapped unusable fuel is an oceanic flyer’s nightmare and this design meant that only ¼ of useable fuel would be trapped by a single failure; careful management would mean that land would always be in range in the event of a single wing tank blockage…and we’d have rudimentary trimming capability in roll!
Most mods add weight and, with the heavy 912iS, we expected a forward C of G on GBNZ. The partial remedy is carbon fibre cowlings, saving a few kg and moving the C of G aft. The aim, providing the long range proving trips show acceptable longitudinal stability for extended periods of hand flying, is to fly the trip with the C of G in the aft third of the allowable range, thus reducing parasitic trim drag and increasing cruising speed and range.
Encountering poor weather en route is obviously a concern. Whilst the Eurofox does not meet the LAA’s current minimum wing loading, flying one under simulated IF conditions showed me that it is a respectable instrument platform. GBNZ is equipped in accordance with the LAA’s guideline’s for IF approval, with a Kanardia Horis and 30 min battery backup as the primary horizon reference and an MGL Explorer lite as the secondary.
The first flight was an experience that will live with me forever. Having checked everything in a verymethodical manner, conducted a final ground run and leak check, smoothly advancing the throttle on a still, spring evening on a historic airfield in Wiltshire was the culmination, so far, of years of preparation and work. Climb to 3000’, a clean and full flaperon stall to confirm ASI readings and handling, a simulated circuit and go around at height then a circuit to land; it was all over very quickly. Another airframe and leak check, then off for a second flight before darkness set in to methodically check the remaining systems and expand the envelope further towards the airframe limits. A satisfying evening in the office!
The flight test schedule is now complete. As soon as the permit is received the preparation for the expedition will begin. Performance data gathering at varying altitudes, mass and C of G will be critical to understanding the capabilities and constraints of the aircraft as an oceanic cruiser. The performance of the 912iS at differing altitudes does not appear to be well documented, hopefully the ECU will give us an efficient cruise at FL100, achieving a higher TAS for the same IAS. Propeller efficiency is unlikely to degrade much between SL and FL100 at the low speeds we’ll be flying at, so provided the ECU controls the mixture effectively, there should be benefits to be had. The test programme will tell. Once the data is gathered 3 flights of 10 hours using representative profiles will be the final test, prior to departure from the UK on 28thOctober, from East Kirkby, with the Lancaster joining us for the first few hundred yards! We’ll be at the RAF 100 Cosford Air Show and the Royal International Air Tattoo; if you are there, do come and say hello. In the meantime there are more details at www.gb-nz.com.