Even standing still in hangar, ASI jumps between zero (---) and about 21 kts but corrects itself to --- after about 25 minutes (presumably when something has warmed up?). Backup analogue ASI plumbed into same pitot/status holds zero. Any help appreciated... Thanks
ASI fluctuates wildly
- Thread starter skyboy999
- Start date
- Joined
- Mar 23, 2005
- Messages
- 13,226
You need to run a zero airspeed calibration as described in the install manual.
20 knots is about 0.01 PSI, which is really small and does sometimes require a re-calibration.
20 knots is about 0.01 PSI, which is really small and does sometimes require a re-calibration.
That's odd. If you go all the way back into the zero airspeed calibration menu again, does it have a RESET button next to the acquire button? I just want to make sure that it actually did perform and store the calibration successfully. If so, we should probably take a look at your ADARHS, and you should give us a call at 425-402-0433 or email at support at dynonavionics dot com to talk to our support team directly.
El_Zopilote
I also love flying!
- Joined
- Jun 22, 2017
- Messages
- 7
Hello Dynon people !
As per the request of the board rules I think that I have some issues related to this topic and this is the reason why I put my question(s) here polluting a little bit Steve-D's topic instead of starting a new one. If the starter of the topic or someone else think that my post landed in the wrong place please remove it.
The story begins with upgrading the software to the new 15.2.0 version on my dual SV1000 system. I've had some problems with the upgrade itself, but it seems that I solved 'em on my own after reading a lot on this forum. So after the software upgrade, playing with the screen layout in the closed hangar and with the pitot cover on the tube, I've noticed that my ASI tape indicates (and continuously jumps) in the range of 19-20-21 knots and the needle also jumps up and down too. To a similar problem the Dynon Support recommend to run a Zero Airspeed Calibration described in the Dynon installation manual.
I've already see this bad indication before on the runway, but I've think at that moment that it was from the wind blowing (my RWY is at 3000 ft AMSL in a windy enough area) or maybe from the rotating propeller somehow blowing the air against the pitot tube.
My question is : if I'll do the above mentioned calibration my speed indications on the higher ranges will be affected or not ? My fear is that after the calibration the actual reading of the 20 knots will become zero, then accordingly the reading of say the 60 kt will be 40 kt... Which is by any means not at all desirable (specially on the short final). If I'm wrong in my supposition(s) please tell me what is the logic behind this Zero Airspeed Calibration and how it works.
Any answers/solutions will be greatly appreciated,
Alex.
As per the request of the board rules I think that I have some issues related to this topic and this is the reason why I put my question(s) here polluting a little bit Steve-D's topic instead of starting a new one. If the starter of the topic or someone else think that my post landed in the wrong place please remove it.
The story begins with upgrading the software to the new 15.2.0 version on my dual SV1000 system. I've had some problems with the upgrade itself, but it seems that I solved 'em on my own after reading a lot on this forum. So after the software upgrade, playing with the screen layout in the closed hangar and with the pitot cover on the tube, I've noticed that my ASI tape indicates (and continuously jumps) in the range of 19-20-21 knots and the needle also jumps up and down too. To a similar problem the Dynon Support recommend to run a Zero Airspeed Calibration described in the Dynon installation manual.
I've already see this bad indication before on the runway, but I've think at that moment that it was from the wind blowing (my RWY is at 3000 ft AMSL in a windy enough area) or maybe from the rotating propeller somehow blowing the air against the pitot tube.
My question is : if I'll do the above mentioned calibration my speed indications on the higher ranges will be affected or not ? My fear is that after the calibration the actual reading of the 20 knots will become zero, then accordingly the reading of say the 60 kt will be 40 kt... Which is by any means not at all desirable (specially on the short final). If I'm wrong in my supposition(s) please tell me what is the logic behind this Zero Airspeed Calibration and how it works.
Any answers/solutions will be greatly appreciated,
Alex.
The zero-pressure calibration ONLY affects the zero airspeed calibration setting, and that will in turn help with very low airspeed readings as well because of the way that calibration works at very low pressures. IAS pressures aren't linear, and so once you're above a few dozen knots, nothing you do in that calibration will affect IAS accuracy adversely.
Put another way - the zero IAS calibration can only help your situtation, not hurt it (assuming it's done in still air, as required). And it won't affect your higher airspeed readings.
Definitely do the zero pressure calibration for what you're describing.
Put another way - the zero IAS calibration can only help your situtation, not hurt it (assuming it's done in still air, as required). And it won't affect your higher airspeed readings.
Definitely do the zero pressure calibration for what you're describing.
swatson999
Well-Known Member
- Joined
- Oct 6, 2010
- Messages
- 1,528
Related to my similar issue reported here?
http://dynonavionics.com/cgi-bin/yabb2/YaBB.pl?num=1489547186/20#20
http://dynonavionics.com/cgi-bin/yabb2/YaBB.pl?num=1489547186/20#20
El_Zopilote
I also love flying!
- Joined
- Jun 22, 2017
- Messages
- 7
Yes, as I answered in your topic... But anyhow I'm (kind of) happy that there is a logical explanation for the problem. At least now I know my program for the week-end. 
Regards and thank you for the link,
Alex.
Regards and thank you for the link,
Alex.
El_Zopilote
I also love flying!
- Joined
- Jun 22, 2017
- Messages
- 7
You guys are good !!! Thanks alot for your quick and pertinent answer ! I'll report here the results ASAP...
Alex.
El_Zopilote
I also love flying!
- Joined
- Jun 22, 2017
- Messages
- 7
The before bouncing ASI tape after doing the Zero Airspeed Calibration now indicates a steady "---" (zero). Exactly as should be and the upper speeds are not affected by this calibration procedure. Problem solved.
Regards,
Alex.
Regards,
Alex.