TruTrak question - I think

I recently purchased an RV-9A with a Trutrak II AP that is supposed to be connected to a King KMD 150 VFR GPS. The builder told me that the AP used to do GPS NAV and got its signal from the KMD 150. I'm not exactly sure when the units quite communicating, however, they are not communicating now.

I've read both manuals and when I get back to the airport on Friday I want to verify the baud rate is set to 9600 on both units. I suppose its possible that it was inadvertently changed at some point. My question though is, the KMD 150 is giving me a message saying the internal battery is low. I've found a post here that explains how to change the battery. My questions are:

1. Would a low battery cause a problem maintaining internal settings or communicating with the AP?

2. Is there anything else that someone familiar with these units would suggest I look for in addition to the baud rate?

Thanks!

While I don't know for sure how the King works, it is possible it lost the baud rate settings when the battery died.

Start there and see what happens.

Yes the king will lose all its settings with the battery low, you can reset them when its on, but they will be lost as soon as you turn it off. I have a KMD150 and have seen this problem personally.

The KMD-150 has an internal battery that is well known to go dead after some period of time (as do almost all of them). There are instructions scattered around the web on replacing it at a very low cost, or you can pay a ridiculously high cost to have the factory do it. It's fairly likely that is your problem, as Walt said it is not uncommon witht he KMD's.

Also, it's not exactly "GPS NAV" as in steering the plane in anticipation of corners, vertical guidance, etc.. but it will follow a flightplan from point A to point B quite well. I flew this very combination many years ago in my older RV6.

Just my 2 cents as usual.

Cheers,
Stein

Hi Don, I fly a TruTrak AP coupled to a VFR GPS. If you get stuck, I'd be happy to have a debugging session with you. Let me know.

SteinAir said:

There are instructions scattered around the web on replacing it at a very low cost, or you can pay a ridiculously high cost to have the factory do it. Cheers,
Stein

Click to expand...

Or you can send it to me, I'll replace it for a ridulously low cost

Thanks for all the great replies. First, I'm going to turn everything on and reset the baud rate and see if that fixes the problem - until I turn the unit off and it looses the settings again. At least that will pinpoint the problem.

Stein - if I understand the TruTrak manual, GPS NAV follows a flight plan and over-shoots each turn because it doesn't anticipate the turn. If I upgrade the AP to include GPS Steering I'd get a GPSS indication instead of GPS NAV and the unit will anticipate turns. My issue is I'm not getting the GPS NAV mode when I press the MODE button. I think we're saying the same thing.

Glen - If I can't sort this out on my own pretty fast, I'll let you know. Two heads are always better than one.

Walt - I plan to take a look at what's involved in changing the battery. If it looks like more than I want to get involved with, I'll ship it off to you.

For turn anticipation/GPS Steering (GPSS), you need both an AP capable of using that information and a GPS capable of providing GPSS.

To get turn anticipation means an upgrade to the DigiFlight II VSGV but you need to also be sure that the KMD150 supports GPSS. Typically this is done over an ARINC 429 interface but there are a rare few that used an RS232 version of GPSS.

NMEA output only won't get you there. First glance at online specs seems to suggest that it does not have support for GPSS.

Stein or one of the people that have used this unit will be the definite answer on that however.