|How high can my machine tow a hang glider?
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
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...