Ed Downham Flies 1017km in the Prototype JS1 Revelation

by admin - Posted on 2009-12-12

JS1 RevelationWhile the JS1 Revelation is designed to be a contest winner the performance is also a great for those long cross-country flights aimed at maximising OLC points.

For those still unaware of OLC, the On-Line Contest is a way to competitively share flights across the web, with flights scores optimised around up to five waypoints.Scores are based on handicapped performance and tasks do not have to be pre-declared. In the 2009 OLC season over 107,194 flights were posted by 13,424 competitors with a total of 28,691,130kms.

See Online Contest – Gliding

During early December 2009, Ed Downham flew the prototype JS1 Revelation “JS” for two weeks at New Tempe Airfield, Bloemfontein, South Africa . He describes his final flight on 12th of December:

I wasn’t quite sure what to try, as the day before I’d found conditions to the NE a bit showery and spread-out and going blue to the W & SW. In the end I declared a 750km O/R to the NW, hoping to be under cumulus without too much overdevelopment. I launched at 11am into a moist-looking sky full of clouds with rather ragged bases at around 7,000ft, supported climbs of 1-2kts.

About 50km down track, approaching Dealesville, conditions improved with base rising rapidly through 10,000ft with thermals of 4-5kts; by the time I went past Hertzogville it was 12,000ft with good cumulus and some nice energy lines.I caught up with Lars (Rune Bjornvik) in the Ventus-2c, who was on the same task and tried to pair fly for a bit, but the performance difference in the glides meant I was soon ahead on my own.

ed_mapFrom Christiana up to the Amalia area it was still looking good, with 6kt climbs about, then it went a bit ‘soft’ with decaying clouds until past Vryburg where normal climb rates resumed. I had a chat with Phil (Jeffery), attempting a 1000km O/R to the Botswana border along the same track, who said that although perfectly soarable, it wasn’t very high or strong so he was abandoning.

I turned near Ganyesa in moderate conditions, then came back SE a bit to the west of my outbound course, finding base up to 13,000ft and better climbs. South of Vryburg the sky looked more energetic and I was able to string lines of good air together; looking at the trace I had two glides of 90km at just under 200kph. An area about 150km North-South and 50Km East-West centred on Bloemhof seemed to contain the best conditions, with 14,000ft base under 2-3,000ft of tight cumulus. I ran this as far as Bultfontein on the way back to Bloem, then turned back NNW to see how far I could get on a three-waypoint flight.

The clouds were moving further apart on the way back out and after a good climb off the centre of Bloemhof, approaching 16:30, the LX8000 said I would complete about 850km if I went home from there. I checked the sunset time (about 19:10) and decided to carry on outbound until five or thereabouts.”I turned just before 17:00, 230km from home as by then it had gone rather blue, except for a few groups of working clouds in the area I had come from. And the LX was indicating >1,000km!”I was now consciously trying to stay high to remain in contact with the better lift and keep the TAS up; the last clouds were 130km out and put me on glide but I took some more on the way in for a decent margin.

Overall, it worked out as 1017km at around 135kph.”I found the best way to make progress was to fly steadily and use the JS1’s excellent performance in the 70-90kt range, while following any energy lines and being very critical about which thermals to use. The glides worked out at an amazing 95:1 at 170kph but the thermal average for the whole flight was around 4kts, which sort of proves the point.”A great flight to end a great two weeks in South Africa . Roll on next time!

A few interesting statistics from Ed’s flight (for the whole flight, not just on task):

– Average glide was 31.5km (19.6 miles) at L/D of 98.
– Only 18% circling time
– Five glides in excess of 70km (43.5 miles), the best probably being 88km (54.7 miles) at 196kph (122 mph) TAS and a glide angle of 211.

To check Ed’s flight, visit:

Edward Downham Flights 2010