The engine development project is moving on fast...we’re learning new things about high altitude all the time and whilst the results are good so far, there are always going to be problems that have to be solved. With all the terrible flying weather we’ve had in the UK I’ve taken the opportunity to concentrate on getting more testing done inside the hypobaric chamber, rather than going for a test flight to high altitude as was planned this week. This has given us some new vital information about the problems associated with engines at high altitude.

The engine will currently only run on full power at 30,000ft plus, this is because it requires so much boost from the supercharger and the boost is only delivered when the engine is revving high. This is a problem because should we need to lower the revs in severe turbulence or gyroscopic induced oscillation, the engine will not have sufficient air to rev up again and then we will be forced to descend and land. Amongst other solutions to this issue I am considering applying a second supercharger to the engine, this will increase the boost pressure to the engine even at low revs therefore allowing us complete control of the engine all through the rev range.

I am extremely fortunate to be working with some of the world’s leading experts on high altitude aircraft and engine development, Andy Elson, Dave Boxall and Patrick Walker of Maxsym Ltd. How I’ve been lucky enough to have these guys on the team, I can’t imagine… their combined expertise, perseverance and enthusiasm gives this project the very best chances of success!!!

The engines ECU has now at last been fully mapped up to high altitude in the hypobaric chamber, the computer understands every altitude setting and can automatically adjust the fuel delivery. The next and most important test is to fly the engine to high altitude and see how it performs in fresh air…..the hypobaric chamber cannot simulate every aspect of out flight to 33,000ft. The low temperature at high altitude is an important factor which will help the engine and also the fresh air which is not available in the chamber may be a great advantage for the engine right the way through the rev range.

Hi Randy, and thank you for your support. The downside of the using a second supercharger is the extra heat it generates in the air. It means I will most likely have to make a small intercooler that fits before the engine inlet manifold otherwise the airtemp is just too high. Also it adds another 3.5 kg to the engine and more complication, more belt drives and generally things to go wrong..but we'll see..if I have to I have to!!!!

Hi Steve, the problem with nitrous is that it only works for fopr a short blast of power...yes you can inject smaller quantities for longer but we'd still need a very large cylinder to get an hours worth of flying at high altitude. Unless theirs something I'm missing, my research says that it's not an option for the amount of time we need but I'm willing to be worng so please enlighten me if you know of a really lightweight system (under 2.5kg) that will do the job. Thanks, Gilo

Hi John, with regards to your onfo about the waste-gate and bypass valve. I have a waste gate fitted but this is only to dump excess pressure when we're at lower altitude. Once we're above 25,000ft we need every bit of boost we can get. I'm using a centrifugal SC spinning up to 180,000 rpm which will achieve a 2.7 pressure ratio, this brings us to 0.8 bar absolute in the manifold at 30,000ft so the engine is still not working at sea level pressures and there is no more boost you can get unless you run a dual supercharger arrangement! Unless I'm missing something and you're on to something, I don't know how to achieve a 0.8 bar pressure in the manifold unless the super charger is running at 180,000rpm and it will only do this when the engine running at 8000rpm. lets say I drop to 4000 rpm, the SC then also drops to 90,000 rpm and is only capable of producing a 1.2 pressure ratio at this rpm. So I'm fascinated to hear if you can let me know something I've not worked out yet. Thanks very much and I look forward to hearing from you, Gilo

Hi Boyd, obviously we would love to have lots of other pilots on board, I think this a tough one though because we're only going to have two machines...they cost so much to build and they're not at all easy to make either. There is though a mission support trek that runs to the Everest base camp while we're ready and waiting for our weather window!! That could be fun!!!