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Successful Winch Trials in Bogota, Colombia
Here a cross posting from some info I posted yesterday on the Yahoo
winchdesign group for those of you who are interested in winch launching. It might be that we managed to successfully establish the highest winch launch operation in the world here in Bogota, Colombia, at an altitude of 8478 feet (2584 meters) with density altitudes commonly around 11,000 feet sometimes approaching 12,000 feet (3350/3660 meters). This might be of interest especially to glider operations in the Western US since high density altitudes are very common out there. Markus Graeber Aeroclub de Colombia/Albuquerque Soaring Club ------------------------------------------------------------------------ I am pleased to announce that over the last 8 days we have successfully completed our winch trials and initial winch driver training here in Bogota. The first 6 launches were done on Sunday, Jan 27th, with the club's IS-28B2 Twin Lark on a great soaring day with density altitudes approaching 11,000 feet. Over the week we accumulated some more launches culminating in the official winch inauguration on this past Sunday, Feb. 3rd. During the festivities which were attended by some 200 members & guests we managed to put in 24 launches mostly on Sunday afternoon launching our Blanik L-13 and IS-28B2 as well as a member's Janus CM with guests in the second seat. We used about 1800m (5900 feet) on the initial launches leading to launch heights in excess of 2000 feet even with relatively inexperienced winch drivers (trainees) and pilots. Later we shortened the run to about 1400 meters (4600 feet) to allow the gliders to roll up directly to the launch point for higher launch frequencies and commonly achieved launch heights in excess of 1600 feet. Density altitude was probably in excess of 11,000 feet during Sunday's hot afternoon. All launches were done in almost nil wind conditions which sometimes increased to about 5 knots max headwind component. Our setup is a single drum Skylaunch 3 winch with 2500 meters of 5mm Dyneema cable and a Chevy 502HO big block engine with a Holley 870 cfm four barrel carburetor rated at 450 HP at sea level delivering some 315 HP (estimated) at 11,000 feet density altitude. Transmission is a Hughes Performance Heavy Duty TH400 without reverse gear using all 3 forward gears with their Tow Master 2000 RPM stall converter. Even launching the Janus CM 2 up with a launch weight near 650 kg was no problem at all, gear changes to 3rd gear during the initial ground acceleration are not noticeable at all. Revs at rotation for the relatively fast Janus CM are in the mid 4000s, since the engine has a rev limit of 5500 rpm it gives us a nice reserve should it be needed in case of an unexpected emergency. I will collect some more hard data with the help of our telemetry system and GPS traces over the next few weeks and report back with more details. Initial experience suggests that at our density altitude with inexperienced pilots and winch drivers you can expect about .35 launch heights (in relation to the cable run) which are probably around .40 once everybody is tuned in. In comparison, at sea level the Skylaunch winches routinely reach .45 with experienced pilots and winch drivers sometimes reaching .5 with the right glider/pilot/winch driver combination in near nil wind conditions. Thanks for all the input and feedback I have received during the course of the last 1.5 years while bringing this project to a successful conclusion, Markus Graeber Aeroclub de Colombia |
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