MGL Avionics User Forum

I am using a Discovery Lite. The altimeter is always bouncing plus or minus 40 feet or so, even sitting still on the ground engine off. Is there a way to fix this? Turn down the sensitivity possibly?

I experience this same thing on my Challenger and Explorer iEFIS screens as well. Not just the Altimeter bouncing around but the VSI readout can jump from something like -500 to +500 fpm within less than 1 sec. It makes the readout useless.

It's like the display is showing raw data from the iBox pressure sensor without any dampening math applied.

Here is a link to a video from yesterday while in the air. But I also see this behavior while sitting in the hanger.

https://drive.google.com/file/d/1CtspVe ... sp=sharing

Totally agree with these post. We just purchased a plane that had a single 10 inch challenger. After much thought we decided to add a second screen (7.5 discovery), and for good measure we added the Aviogard backup power system.

Kinda vested and want to like the MGL system.

I am a student pilot and the extreme sensitivity on the altitude indication really makes it difficult to learn. Also have had two cfi’s mention the inaccuracy.

Any firmware update that could help would be very much appreciated.

You cannot typically test either VSI or altimeter in a hangar - you will get fluctuations. Even the slightest change in pressure that you cannot notice - the altimeter sensor will.
You can only do this if you seal the static port.

The firmware employs a dynamic, self adapting filter in order to get single foot resolution in flight. This is particularly tricky to do in flight due to the turbulence around an aircraft. Traditional filtering adds lag. Lag is the last thing we want as we need quick reaction in particular if you are using an autopilot to hold altitude. The filter employed here is pretty clever and we have been using it unchanged since about 1998 when it was first developed.

It is quite normal to see occasional excursions of the altitude when on the ground and not moving by +/-40ft or so. That goes away once the filter adapts itself - that it does once there is activity on the ambient pressure (i.e. you are flying).

Excursions of +/500 ft as reported above are certainly not normal and would indicate a faulty system in some way or another and definitely your altitude would not be accurate at all. Unless you are indeed in a hangar and the wind is causing significant pressure changes inside - then I would be worried if you do NOT see those fluctuations.

Just how good the altimeter is you will notice if you fly in calm air and let the internal autopilot take care of holding altitude - it will get down to single ft accuracy and the altitude is rock steady.

Thank you for the explanation. My observations were indeed in a hagar.