News release: 6 Jan 2006, Highest tow yet

This was the test at Rivadavia. Yes, we did Everest 18 months ago but the tow line broke at around 28,000 ft. Aconcagua was a relatively low tow, the release was at around 23,500 ft, we did higher than that on one of our pre-Everest tests near Rome. My guess was the limiting factor would be Oxygen. Our third supplier (we had 7 big bottles by now) could provide it at 220 bar which meant that with a bit of judicious juggling of bottles we could fill our 10 litre lightweight spiral wound carbon fibre aluminium bottles lent by Paramina nearly full to around 110 bar but even that would give only around 2 to 2 1/2 hours, and we had to get down too. When you're planning these things you have to remember that one's "time of useful conciousness" at 30,000 ft without supplementary oxygen (and lots of it, at pressure) is less than one minute....

Our problem was the takeoff was low, around 2,300 ft and it was hot, very hot, 40 deg in the day and 25 at night, meaning that even with an early takeoff I wouldn't be able to really open the throttle for quite a while or risk overheating my nice engine, and it would be hell getting into all my high altitude kit. Still, it was worth giving it a blast, this is one of the World's great locations for high altitude wave which might give us a boost if we could find it; last year Terence Delore and Steve Fossett flew a glider no less than 2192.9 km in a day here in the lee of the Andes, an incredible distance, I suppose they must have been more or less in a steep dive for most of the flight. With a bit of luck we thought 10,000m (32,808 ft) might be on the cards.

As at Aconcagua, Beto turned up to help get everything ready which was really a great help. Up before dawn to assemble our kit. When it came to putting on my suit I decided to wait until Angelo starting putting on his, I wasn't going to sit around gently cooking whilst they got him into his torpedo which takes quite a while. The time eventually came, by now rather late, Beto and Nicky got me dressed, I taxied out onto the strip and we were off.

The first few minutes were a bit scary, just before takeoff the wind changed, it was a very fast downwind takeoff and once into the air it was very rough, Angelo did well to hang on in there there were a couple of very big 'slack line' moments and we both did our best to avoid a weak link break as the line came taught again. After a couple of thousand feet it settled down.

Engine temperatures rather high; CHT 123c and oil 110 but stable. Oil pressure still off the clock the same as the descent from Aconcagua. After a phone call to Nigel Beale at Skydrive and having tested all the wiring I'd come to the conclusion that the pressure sensor is probably defective. Nigel assured me that it isn't normally possible to get such pressures, the pressure relief valve won't allow it. The main consequence is that the FlyDat engine instrument now flashes "Service!" for ages every time I start the engine which is infuriating; it's just at the time when you want to know you have important things like there is at least some oil pressure. Nothing I can do about it though, something to be fixed when everything gets home.

At 18,000 ft, as on the Aconcagua flight, I thought my oxygen regulator started "wooshing" a bit lower than it should, I still hadn't trimmed my beard so I tightened my mask to save losing too much. Already cold outside, -20c, but my kit was working well, engine now at happier temperatures and running a bit more freely since I fined off the propeller 1/2 a degree since the Aconcagua flight.

Calm, no sign of wave, some nice lenticulars off to the south but we were restricted to a 6 Km zone around the airfield so couldn't go off to investigate. At these heights it's difficult to judge distances, really they were probably 50 miles or more away, too far anyway. Both Mendoza international airport and the Andes beyond now looked remarkably close. Aconcagua clearly the highest mountain, more or less straight to our west, and Tupangato, a dormant 'perfect volcano' also more than 6000m high and reputedly a harder climb to its south.

So on we climbed. I had decided that it would be a good idea to come down once my oxygen reached 50 bar, 1/4 full, especially as I wasn't sure quite how well the regulator would work for the last 20 or so before empty. On we climbed, now very cold, I'd had my electric gloves on since 15,000 ft and my hands were fine, but now it was time to turn on my electric suit a bit, I'm a bit wary of turning it on full as this gives a net discharge in the electrical system, it's vitally important the electric fuel pump still goes and I'd forgotten to reconnect the NelTec heater which keeps the machine's main battery warm, but my suit is so good that it only needed a low setting to keep me cosy.

After about 2 hours my oxygen got down to 50 bar and I waved Angelo off.

At the peak of our climb it was about -36c, as cold as I've ever had apart from in the FIAT wind tunnel, much colder than Everest. My engine was running beautifully all the time. At the top of the climb I was seeing -10c or so manifold temperature, the first time I've ever seen it below zero.

So: How high can my machine tow a hang glider? I think we were at something over 28,000 ft, higher than I've towed before, but the LCD on both my vario and my flight recorder had stopped working because of the low temperature. Quite how much over, or the exact time it took I'm not quite sure at the moment, my flight recorder will say exactly but right now I haven't got the cable to download it but the results will eventually be published on this site. What I do know is that the climb wasn't all that great by the time Angelo released, we certainly didn't find any of that magic wave, it was all rather stable.

Across the river, not far from Rivadavia aerodrome is a brick factory. To mix the clay they have a sort of giant gear wheel on a long arm fixed in the centre of a circular basin. A chap on a little green tractor drives round and round dragging the gear wheel through the clay. He gave me a wave just before I landed. Klaus the cameraman said he got a nice shot of me, Angelo and an airliner crossing paths. On the flight itself I though I had caught a glimpse of something but couldn't be sure. I haven't seen the shot for myself, but I hope he was a lot higher than us....

At the top my engine revs had dropped to about 5400 which suggests the prop was set about right. If one considers that the turbo is supposed to give a 15-18,000 ft advantage compared to a normally aspirated 912, and a normal 912 without a mixture control begins to struggle at 10-12,000 ft, but I've done a tow to 18,000ft with a 912 with a mixture control, then this might suggest that the 914 with a mixture control could be good for towing well over 30,000ft.

So there's potentially more yet, this will be the next mod, but difficult to test below 25,000ft or so...