Hi LML gang,

does somebody know the answers to those questions ?

1° I would like to install a Trutrak autopilot on my LNC2.I am seeking informations about the GPSS fonction. Do I need to have ARINC format signal or is a serial RS 232 signal enough to use the GPSS fonction ?  When reading the Trutrak documents it is not clear and Trutrak does not answer to my questions.

2° I have a King KLN 89B GPS in my plane . I would like to transmit navigation datas to a KMD 250,as a moving map,and to the Trutrak autopilot . If I use the KLN 89B ,P 891 #2 pin (labelled " General RS 232 Output") for datas to the KMD 250,can I use the # 6 pin (labelled "Spare RS 232 Out") for nav datas to the A/P ?I asked BendixKing about that problem but I am till waiting for the reply....!

Many thanks for your help and best regards.

Alain NOIREAUX   L 320

Alain,

 

In general, AutoPilot guidance takes the following forms:

 

1. Left/Right course deviation.  This is the same type of signal that drives the CD indicator and either a VOR, Localizer or GPS may provide such a signal to an A/P circuit that will try to keep the needle centered.  Does a Tru-Trak interface to a Localizer signal or can it only fly GPS approaches? 

 

2. GPS RS 232 data is usually output in the NMEA Text format and may contain sentences that include Lat/Long, GS, and track deviation information.  This information is the type that is interpreted by moving map computer programs and some autopilots that may use the track deviation data. Note that this is only present position information.  The Tru-Trak understands this as it is the same data produced by the simple Garmin (35? see Garmin.com) that can used with the Tru-Trak. 

 

3. ARINC data is far more sophicated in its format.  Especially since it can send steering data, both horizontally and vertically.  The S-Tec GPSS interface is to take ARINC data and change it into the same autopilot input as that from the DG and the bug on the DG.  That is, the GPSS device converts ARINC data and either sends that or the DG information to the autopilot based on a switch setting.  The ARINC data can be computed by the GPS unit to lead a turn (direct future movement) based on your speed and ground track to the turn waypoint.  You would need to know if your GPS produces the ARINC data, I think that the Tru-Trak can understand it.