For a while we been interested on testing the performance of the engine at altitude, specially finding out how would it respond to a restart with the engine cold when above 14,000ft.
So, we packed our shades, glide computer, water, oxygen bottle and started a climb from sea level to 16,000 ft.
Our climb was uneventful. The engine at 4800 rpm, speed 70kts. Climb rate was steady at about 500+ fpm, but after 15 minutes the oil temperature reached the end of the green line at 110C so we increased airspeed to 80kts while reducing power to 4300 rpm. With this new settings the engine oil slowly started cooling down. (the climb rate went town to 200 fpm) Curious thing, everything else; water temp, oil pressure, EGT and CHT temps where all normal at all times.
I have to say that the oil temperature surprised me a bit. I've never seen the temperature go up like that on any other 912 equipped ultralights. Usually it is almost impossible to get those engines to heat up!
I am guessing that on the sinus, the oil radiator has been shrunk to its minimum effective area for weight and space reasons. Still it was not much of a problem on a few minutes we resumed climb where outside temperatures help reduce further the heating issue. At 10'000 feet and above, the issue was pretty much gone.
I am guessing that on the sinus, the oil radiator has been shrunk to its minimum effective area for weight and space reasons. Still it was not much of a problem on a few minutes we resumed climb where outside temperatures help reduce further the heating issue. At 10'000 feet and above, the issue was pretty much gone.
Eventually we reached 16'000 ft so, we slowed airspeed to 50kts and toured a little to let the engine cool down before turning it off. A few minutes latter, engine idle, magnetos off, un-necessary electrics off, feathered propeller, trim to 55kts and enjoy the quiet woosh of the air along with spectacular views of the Andes below.
In general the air was stable with great visibility, very few thermals of weak lift. To the East we could clearly see snow caps on top of the 20,000+ ft Nevados topped by a thick layer of clouds another thousand feet above.
At this altitude our glide computer showed we needed 10:1 to reach our home base airport 40km to the West (at sea level) so we circled around looking for lift (with not much luck) on the regular places..
When we reached 14'000 feet we turned back on the Dynon engine computer which showed oil temperature had gone down to 20C. It was not as cold as we wished, but decided to test the restart anyway.
Un-feather prop, magnetos on, no choke, throttle idle and... it started flawlessly! it did not take a 1 second push on the starter to get it purring again. I just love that trusty Rotax 912 engine.
In general the air was stable with great visibility, very few thermals of weak lift. To the East we could clearly see snow caps on top of the 20,000+ ft Nevados topped by a thick layer of clouds another thousand feet above.
At this altitude our glide computer showed we needed 10:1 to reach our home base airport 40km to the West (at sea level) so we circled around looking for lift (with not much luck) on the regular places..
When we reached 14'000 feet we turned back on the Dynon engine computer which showed oil temperature had gone down to 20C. It was not as cold as we wished, but decided to test the restart anyway.
Un-feather prop, magnetos on, no choke, throttle idle and... it started flawlessly! it did not take a 1 second push on the starter to get it purring again. I just love that trusty Rotax 912 engine.
With that test over, still over 13'800 feet, we decided to just shut down again and glide our way back home. The tricycle sinus L/D is listed at 27:1 , Our glide computer consistently showed above 24:1 at speeds higher than best glide so we toured around the area again, looking for good lift areas and enjoying the dramatic terrain below us.
A new piece of equipment for the flight was XCSoar gliding computer software running on a Google Nexus 5 android phone. It is really superb, at all times we could see terrain, L/D required, distances, speeds, times everything!
The terrain feature is fantastic, showing a thick surrounding line on the map indicating "reachable" areas for our current speed and L/D. It also has a nice speed to fly feature, a vario with audio (The Nexus 5 has a barograph sensor) and all sorts of navigation aids for competition flying. The actual device s my regular phone, it has great battery life (we had a spare charger) and the array of sensors is impressive. To top it all, up there at over 3000 meters there was great signal reception, so I kept Tati posted of our progress via whatsup chat messenger!
To resume XCSoar in few words: All in all a wonderful piece of software.
Next test, getting further East while climbing to 18'000 ft and return gliding,
I will keep you posted!
Alx.
