Stec 30 AP Question

[Steve Marcozzi]

I've got an Stec 30 with a AP DG, and have been using the heading bug to steer forever. The unit won't nav on direct signals from the GPS or VOR/LOC (mini toggle switch to select them) on low or hi sens. Owned the plane for 6 yrs and have never went after it....getting more picky now and want to make it work. Is there something I could check out, or is this a "call the radio guy" problem? Note: The radios are old.... KLN89B and Narco MK12D. All the radios work fine.

Thnx,

Steve

[9089P]

Hi Steve,

In order to use the GPS for A/P guidance I believe you need a GPSS unit. STEC has one($1500?) which is what I had installed. There are other stand alone units out there and I think the Aspen units have one built in(?).

I had the stec 30 w/ gpss installed and hooked up to the 430W. A great investment. It will fly the approaches(not glideslope) including holds if I wish. It anticipates the turns on the flight plan so they are seamless. I use it almost exclusively over the bug. It is worth the price in my opinion.

Don

[Mark Anderson]

Steve,

I too have the S TEC system 30 with GPSS and an HSI. I think you have to have a heading system such as an HSI, Aspen or G500 that has a built in VOR needle for the AP to track. I am not familair with a AP DG. Does it only have a HDG bug? GPSS definitely makes the AP track the GPS signal more precisely, no drifting or hunting. I don't think the GPSS has anything to do with the tracking of a VOR or localizer signal. When tracking the VOR or localizer the GPSS switch stays in HDG mode. I often stay in HDG mode and fly the Localzer with the HDG bug because in my opinion the AP doesn't do Avery good job of making wind corrections. If you get in set up perfectly and not much wind it will track it pretty good. There are some tricks you can do by flying the localizer in GPS mode. The GPSS is definitely worth the money. Depending on how low the weather, I often prefer a GPS approach to the ILS because the GPSS makes it so easy.

Mark

[Steve Marcozzi]

I don't have GPSS, but do have a hdg bug. I thought that if you intercepted a course manually or with heading bug, whether it's in GPS or VOR/LOC mode it would at least track the course? I mean.....before GPS, even the most basic AP's would track a straight line off a nav signal wouldn't they? I have a dedicated CDI for the GPS so I don't have to switch the CDI between radios.....just have the annunciators.

For some strange reason, I thought GPSS was for more pronounced turn commands like you mentioned having it track RNAV apch segments, etc.

......Time to get out the log books and see if the manual says anything more about it. When in doubt, read the directions right?

Steve

[Mark Anderson]

Steve,

You are correct, you should be able to track the VLOC and the GPS course without the GPSS. GPSS just make it track the GPS signal more precisely and has nothing to do with VLOC.I think it makes it track digital data instead of analog. When you are in GPS or VLOC mode does the heading bug still steer the plane if you move the heading bug around?

Mark

[Steve Marcozzi]

Mark,

Right. I got the book out too.... If you select Lo trak mode (for enroute) and manuver the a/c within +/- one needle width on the CDI or 10 degrees of the desired course and it should track it. Hi trak mode is for approaches (loc or gps apch legs). On gps approaches, after entering a segment of the approach, I've been leaving it on the heading bug (HD mode) or hand flying the approach. It would seem distracting to set up the trak mode for such short legs. Same for a loc approach where there's a procedure turn.....it's just seems easier to use the hdg bug. ST mode is just the basic wing leveler with roll commands off the mode switch.

To answer your question..."no" if you're in trak mode, the hdg bug won't make roll commands, at least not on my plane. Probably shouldn't....it's not in heading mode right?

My pitot static / xpdr is due this August, so I'll see if he'll take a look at this too. I'll look at the stupid stuff first to see if there's something disconnected, etc.
GPSS would definitely be nice, but I'll probably put the $1,500 in the gas tank.

Thanks,

Steve

[Mark Anderson]

Steve, it may be that your sensitivity needs to be adjusted on the AP. After my install the shop had to go back and adjust mine because the high and low sensitivity was too slow to react. Also as you said, the AP as I understand it will not intercept the VLOC coarse; you must be within in plus or minus 10 degrees. But the GPSS all but turns your 430/530 into a FMS( flight management system). Once you put in a flight plan you are done! Very useful for flying arrival or departure procedures, holding patterns and missed approaches.

Good Luck!

Mark

[Steve Marcozzi]

While on this subject....I remember the article on your plane. Did you know Ron Collins shop just went Chapter 7? Just heard about it Wednesday.
Real shame as they did a lot of good work. We had our state planes / 'copters on a contract for radio work with them.

Steve

[Mark Anderson]

Steve,

Wow! I did not know. Great group of guys, I hate to here that. Definitely tough times for any business. I hope they all land on their feet. Thanks for the info.

Mark