The Plot Thickens...
Yes, you can engage the entire system on the ground and do not need to be moving.
Hi Andrew and Bob,
I think I may have found the culprit. Long story so you get all the facts:
I climbed into "Super Tweety" my RV7A this morning, went through my normal checklists. Started the engine, turned on all of the avionics including the GNS430W, The TT A/P, the SL40 (COM2), GTX327, EFIS, EIS, Uavionix Echo. Programmed a short flight from KFHU to TOMBS Intersection to E95 into the 430W and activated it checking to make sure it transferred to the EFIS. It did. The 430W also attained 3D Differential Navigation with several satellites. Taxied to the runway, did my runup and mag/prop checks. Departed and with a right turn out, I turned to my initial course of 022 degrees. As I was climbing, I pushed the center knob on the TT to activate it, then pressed the Mode button to have it track the course via GPSS. It did. As I reached my cruise altitude of 6500' I leveled and trimmed the aircraft and activated the Alt Hold function. It was now tracking the GPSS course and holding altitude. I'm thinking SWEET! It flew over TOMBS and then turned left to pickup the new course to E95 while maintaining altitude. All is well. Within 10 miles of E95, I disengage the autopilot's Altitude Hold to begin my descent and I make my first call to E95 traffic, providing all pertinent info. Within less than probably 30 seconds, my 430W displays a warning that it has lost GPS and to begin Dead Reckoning. DAMNIT!
I turn off the TT A/P at it's toggle switch. Nothing happens as far as the GNS430W reacquiring satellites. I turn my attention to making a safe approach and land at E95 and taxi to the run up area while I cycle the 430W. No Change, will not re-acquire the satellites. I shut everything down, and turn off the engine. Restart the 430W, no change, still will not re-acquire any satellite. Turn it off.
Decide to return to home base at KFHU. Go through my normal cockpit procedures as I restart the engine and turn all avionics back on, GNS430W will not acquire satellites.
Return to KFHU and land uneventfully. Taxi to my hangar and shut the a/c down with normal shutdown procedure, all avionics off, fuel pump off, avionics master switch off, master switch off, etc etc.
Sitting on the ramp, I turn everything back on with standard checklist procedures. The GNS430W RE-ACQUIRES all satellites and attains 3D differential position!!!! I program a flight plan in and activate it. Flight plan is active on 430W and EFIS. Engage the autopilot and initially have it fly the heading the airplane is sitting on. Then select GPSS Mode and it actuates the appropriate a/p servos to turn to GPSS course, GNS430W maintains satellites. Turn on the A/P Altitude Hold, GNS 430 maintains satellites and flight plan! Push the autopilot deactivate button on my control stick and then turn it back on to maintain current course, 070 degrees. Put the 430W on a COM Frequency not in the local area so as not to cause any problems with other pilots in the area and key the mike for several seconds, nothing happens to the GNS430w's flight plan or hold on satellites. Do it again and this time I notice on the TT A/P the course heading begins fluctuating upward and continues upward, increasing 16-17 degrees (to 86-87 degrees) from where it was initially, before I started keying the mike. Release the mike and the course heading returns to where it was, 70 degrees. Do it again, same outcome. Do it again, same outcome. Do it again, same outcome. All the time, the GNS430W flight plan and the satellites stay full acquired, green, no issues!
It seems now that I piece it together that as I was making my approach to E95 after turning off A/P Alt Hold but still allowing the TT A/P to follow the GPSS course, and making the traffic call, the transmitted power caused interference with the TT A/P (I didnt see any deviation on the display on the TT at that time) and somehow that appears to have also caused the GNS-430 to lose the satellites and as a result the flight plan course.
I have no idea why the GNS430W wouldn't reacquire the satellites at E95 (totally clear 360 degree view of the sky) but it did reacquire when I shut down and restarted everything again back at KFHU.
Thats the story! Obviously, I need to look at the antenna cable on the 430W and trace it to see if it is beleaguered in any way (Connectors, kinks, cuts, etc) and how close it is to any A/P servo or signalling line.
What else would you suggest? One thing which has come to mind is to program and fly a flight plan in the 430W and not allow the TT A/P to ever take control and see if keying the mike on it causes it to lose the satellite signals and drop the flight plan as a result.
Thanks for your continuing help Gentlemen.
Dan