MGL Avionics User Forum

I have the Challenger Efis On the display the GPS has a big red x on it. I can't find out why. I thought it was because the plane was in the hanger but I took it outside today and the red x is still there. Still trying to get everything lined out. Help please.

Not sure if it will help but I have an explorer lite that the red X stays on the GPS button, even when it has a good lock, after I turn on the iEfis

Changing pages and back again fixes it every time though.

Mike

Tasmag

Ok I'll try that when I go to the airport. I'm new to this Glass screen stuff. How can I tell if I have a good lock or not. it does switch between raim and something else . Is there an indication for lock?

I'm not near the plane at the moment, but from memory you will get a lat lon when it gets a luck, and will show RAIM status.

Mike

It does show Lat and Long and the Raim flashes between Raim and Alt I think. Should the GPS be set to internal or what?

It will switch to internal anyway even if you have an external source selected if that source does not have a fix but the internal has.

It will show RAIM status and applicable category from En-Route to Approach based on the accuracy estimates of the RAIM system. Note these are worst case estimates - reality is in nearly all cases much more accurate. The GPS system used in these EFIS systems continues to operate if there are satellites detected that are considered failed - the failed satellites are removed from the solution. More than one can be removed.
The monitoring is based on the principle that a failed satellite will worsen the calculated position accuracy so this is done by removing any satellite from the solution and observing the effect on the position. If the effect exceeds certain bounds - the satellite is removed. As long as enough satellites remain that provide a consistent position the GPS will continue to provide both a position and RAIM status.

The same system is also used to detect spoofing (fake satellite signals intended to move the calculated position). In addition to this - the GPS is also pretty good at detecting jamming signals and eliminating the effect. This is actually quite noticeable as often "jamming" signals are things like your engines ignition system. Compared to older GPS systems we used 10-20 years ago newer systems and much more capable of handling this.

Rainier

I went and took a couple of pics of my screen. It says no GPS fix?

I'm thinking my GPS antenna must be bad? I mean there is only the cable to onto the Ibox, right. What could be wrong? Its not picking up any satellites. What else could it be. Is there a way to test the antenna?

I have an Explorer and a Discovery Lite, with the Explorer being the Master. I have had problems with GPS as well and sent Rainier screen shots similar to these posted here. Initial suggestion was the two GPS aerials should not be close. However significantly separating them did not resolve the problem. Turning on both systems together usually means the Explorer gets a GPS signal whilst the Discovery Lite doesn’t. Sometimes if the Discovery Lite is turned on later they both work fine, sometimes not. What is even worse the autopilot always craps out after about 55 mins and then the Explorer loses its GPS. I have also sent Rainier the crash.dat file but no response. It really is very frustrating so I put my trust in an iPad and SkyDemon for navigation. I am quite glad others are also having problems, maybe it will now be investigated.

drvale

I'm going to move the antenna and see if that's the problem. I don't think it is, but that will eliminate that. This is getting very frustrating trying to figure this thing out. Ok update. I moved the antenna outside the aircraft. No change. I put it back and made sure its grounded with the mounting nut, no change. Its not receiving any GPS signals at all. Just keep getting no fix. And in the log it says start up GPS error code 1. Anybody have any idea what is the problem. ??