rwarederek

Hey all Our turbo was just overhauled but looks like we'll also need a replacement compressor discharge pipe (it was previously patched - but not very well). Does anyone know where one can find parts or recommend a place to have the part manufactured? Thanks! Derek

Not a problem - I can say that this forum has been a wealth of knowledge for myself. Happy to contribute

Seems like the issue has been resolved! Found a bad crimp on the output side of the alternator. New end fitting is in there now and everything is working. Amazing that the GPS exhibited symptoms months before any actual alternator issues popped up. The signals must be that sensitive. Derek

Hey all - starter is in and we were able to test it out a bit more. This whole time we've been flying we've been seeing ~13.8 to 14v Pulling the CB for the alternator allows the GPS to re-acquire a signal!! However... since we pulled the CB (and subsequently put it back in) for the alternator, we are seeing <12v! Took it to our mechanic and now it would seem that there is something wrong with the wiring to/from the alternator and/or voltage regulator. Alternator seems to be putting out power - regulator seems good too. We just pulled/tugged on wires, started her up and it showed 13+v. Starting it up a second time and it's back down to 11 ish volts... Hmmmm

Thanks all for the added input - our starter decided to die so until that gets replaced I won't have an update. Should be able to test out the GTN within the next couple weeks

Thanks all for the input - I think the next step is to get another antenna (a verified working one!) to rule that out.

When the unit loses the satellites, it enters LOI mode and does not display anything in gray. The unit sometimes will start to re-acquire satellites and will display them in gray - at this point the unit enters DR (Dead-reckoning) mode and will provide some nav guidance. The unit will typically remain in either LOI or DR mode until we turn off the runway on the ground. A couple words about DR mode for those that may not have experienced it during an in-flight failure of the GPS. If you read the Garmin manual, it states that under DR mode, navigational guidance is only recommended as a last resort (meaning, if you have other nav available, use them instead!). According to the manual, any changes in true airspeed, altitude, winds aloft, etc will produce significant variances in the level of accuracy. I can tell you from experience that this is absolutely true and that you probably don't want to rely on DR mode very long as it will produce extremely misleading information. For example, one of our partners was on a flight to the Los Angeles area and experienced a LOI. After some time without any satellites, the unit switched into DR mode and for a period of about 15 minutes, all Track information seemed correct. After a small altitude change of ~1000 feet and some more time in level, unaccelerated flight, the Track information became extremely inaccurate (> 30 degrees off).

Hey all Thanks for the all the comments, I'll try to address as many as I can here and update you all on the progress as well: - New stuff to the airplane: Nothing new in the panel except a new USB cigarette adapter to replace an older one (it's been in the plane for quite a while now though). This was removed during a failure in flight with no positive results (thinking about it, I may to fly with this off from startup to shutdown to test it again). The only airplane related thing was a new battery within a couple months before the GPS started exhibiting issues. - New stuff in the airplane: We have iPhone 6's and I guess those are relatively new. We all have iPads that we velcro to the yoke when we fly (has been that way for years) and all maintain the same hardware since the GPS was first installed. We tried flying with the phones and all peripherals completely off with no positive results. - GTN software: Updated by the avionics shop to the latest release - Turning the unit on and off: That was tried as well when the signal was lost in flight - power cycling had no effect - Playing with the antenna on the ground: The shop said they covered the antenna to induce a failure but every time they uncovered it, it re-acquired signals...on the ground Attached is a screenshot of an inflight failure with the GPS status page. Note it shows the satellite constellation but no satellites at all. I have seen this exact problem myself and have also seen the satellite bars (predominantly in grey during a failure). Does anyone have any ideas why the 650 will acquire signals on the ground but not at altitude? That's the part that bugs me the most since there really should be no change in configuration to the airplane environment aside from the landing gear. Thanks all! Derek

Hey all I'm a part of a partnership in a '68 M20F. We had a GTN 650 installed about two and a half years ago and from install time till about last March, the unit has been rock solid. We're having serious LOI issues with the unit and can't seem to figure out what the heck is going on. When the GPS unit is turned on on the ground, it captures satellite signals and everything is golden; however, the GPS unit will fail at seemingly random times and never re-acquire satellites until we're on the ground. Usually what happens is after takeoff, and after some random time (sometimes after a couple minutes while still climbing, sometimes during cruise) the GPS unit displays that big red "X", indicates a LOI and does not acquire satellite signals until on the ground (usually about when we we're about ready to talk to the ground controllers). The issue has been presenting itself on almost every single flight since March. Our avionics shop is stumped and is convinced the issue is unrelated to the install or the equipment. They have performed the following with no effect: - Antenna swapped out - Coax ends re-crimped - All connections verified and tested - Ground tested with the engine running and not running - GTN 650 replaced with a refurbished unit Also maybe relevant to note is that ALL on-board GPS receivers (iPad, iPhone) continue to receive GPS signals and track the airplane without any issue - even when the 650 has failed. We have also tried to fly with all on-board devices disabled (iPhone, iPad, etc) with no effect. The avionics show has been unable to re-create the issue on the ground which obviously has made this whole process much harder. At this point I'm at my wits end with the unit and am reaching out to see if anyone out there has any clue as to what may be going on or what we should instruct another shop to check. Thanks in advance!!! Derek