Thanks Mike, food for thought. I won't make any decision for a few months, and look forward to news of the Dynamis. All the best, Paul.
From: [email protected] [mailto:[email protected]] On Behalf Of Mike Borgelt Sent: Tuesday, 31 March 2015 12:39 PM To: Discussion of issues relating to Soaring in Australia. Subject: Re: [Aus-soaring] Clear Nav VARIO and Multi Function Display At 09:37 AM 31/03/2015, you wrote: Is it able to compensate electronically? The Zander goes wild when I connect to TE probe, presumably due to the two Winters that are on that line. And its electronic compensation is crap. All the best, Paul Easy fix is to run a second TE line to back behind the back seat and put the T piece there. This isolates the electronic system from the pneumatic one. Better still, ditch the Winters and put in a modern standby vario with its own batteries for emergencies like a B700 or B900 (B400 also still in production). Electronic TE using the pitot - static is one of those things that sounds like a good idea but in practice is very difficult to make work well. Peter Zander says that in his manual I think. There are several problems with it. One is that the static and pitot are more sensitive to off axis (yaw and pitch) airflow than is a TE probe. There are errors which depend on the fore and aft location of these when the aircraft pitches and position error on the static or pitot will cause problems as the real airspeed isn't the same as what is being indicated and an especially severe problem when the error changes with airspeed (bad on the certified statics on most Schempp gliders and the nose pitot on the ASW20). You can run from a pitot static probe on the fin but this gets you the G sensitivity problems of the normal TE probe and then you still have the problem of getting the signals to the vario at the same time as the tubing has distributed capacity and resistance which causes delays in the signals which are unlikely to be the same. The signals can be large (5000 feet/min) and are subtracted so small timing errors cause large transients in the vario reading. The timing errors are magnified if you hang any kind of instrument with a capacity on the same line (ASI, altimeter and they have capsules that vary in size inside). Generally not worth the grief and support calls which is why we don't do it. The whole gust sensitivity problem is caused by all current TE systems measuring airspeed using the pitot static - TE probes do the same thing but subtract the dynamic pressure from the static pressure by design of the probe. There have been attempts to compensate for the gust effects but none have exactly taken the world by storm and I have report of unsatisfactory performance from some users of recent systems with difficulty in getting calibration. In the next couple of weeks at least one and maybe 2 Dynamis systems will be tested by customers. Dynamis is an electronic TE system which ignores horizontal gusts and works on principles unlike those of any other variometer system. It is an add on to our B600/B800 vario systems as the displays, audios (including the thermal centering two speaker system) etc of these instruments are well proven and I cannot think of what else to do, so no point in designing a whole new vario for this. Dynamis also provides real time (several times a second - will need averaging to be sensible) wind speed and direction information and will soon also do "Natural Netto" so the netto doesn't depend on knowledge of the glider polar but is provided from the Dynamis sensors as you fly. Bugs are automatically compensated for and even the engine running on a motor glider. There is one innovative new pilot interface that will also be an option. This has been a 30 year project which needed the right sensors to become available (I remember discussing this with Peter Zander at the 1985 San Diego SSA convention) and I think will be a game changer. No more will you be fooled by the vario showing good lift only to find that no matter which way you turned, there wasn't any worthwhile lift, just a longish period horizontal gust lasting several seconds. Remember, every wasted circle cost 30 to 60 seconds. Having done the research and testing , I strongly suspect the "inertial gust filtering" isn't going to solve that problem but the Dynamis sensor suite does. Mike Borgelt Instruments - design & manufacture of quality soaring instrumentation since 1978 www.borgeltinstruments.com <http://www.borgeltinstruments.com/> tel: 07 4635 5784 overseas: int+61-7-4635 5784 mob: 042835 5784 : int+61-42835 5784 P O Box 4607, Toowoomba East, QLD 4350, Australia
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