Autopilot S-Tec 50

[ChristianGodin]

Is the any ways to get altitude pre select if I have an S-Tec 50 autopilot. What would be the price approximatly.

Thank You

[Bob_Belville]

At SunNFun Aspen told us they were near having something to tie into their unit which now has an altitude alert field. The subject came up because there was a French(?) company offering a 3rd party, relatively inexpensive device. Mike Elliot (I think or maybe someone else) followed up at Oshkosh but if it is ready yet I have not heard about it. 

[mike_elliott]

I don't believe it has been released yet Bob. The system engages the altitude hold on your AP once the target altitude as set on your Aspen is reached. You still have to command pitch info via yanking and trim, unlike a true altitude pre-select system. Maybe they will change this, but I don't see how it would really be possible with an STEC, but I certainly could be wrong.

[Marauder]

I'm holding out hope they will get around to the Avidyne digital AP STC for our Mooneys. It is based on reusing the STEC servos but completely integrates AP control into the PFD, including vertical speed and altitude pre-select. I spoke with a Cirrus owner with it. Pretty awesome PIREP on it.

Then again, he spent $10k and would have told me he shot a 200 point buck during hunting season.

[Bob_Belville]

My avionics guru was skeptical that I would like the way an interface would abruptly level the plane out rather than trim into the reference pressure altitude. But I suppose that most of the time I'd be watching the altimeter as I got close and would be able to trim into level. And in the event I am not looking and the A/P stops descent abruptly at the pre-selected MDA I'd say good catch, George!

[Marauder]

My avionics guru was skeptical that I would like the way an interface would abruptly level the plane out rather than trim into the reference pressure altitude. But I suppose that most of the time I'd be watching the altimeter as I got close and would be able to trim into level. And in the event I am not looking and the A/P stops descent abruptly at the pre-selected MDA I'd say good catch, George!

I have the autotrim on my 60-2 and if I hit "ALT" at the top of a climb, it begins trimming immediately for level flight. Actually does a decent job. If I turn off the auto trim function, I get the idiot lights for me to start trimming. The AP does it much better than me. I would hope with altitude pre-select that it would have the intelligence to start trimming before the target altitude, but even if it didn't, the STEC auto trim is fast enough to get it trimmed quickly.

[Bob_Belville]

The manual for the STEC50 has:

 

"Should the pitch servo loading exceed a preset threshold for a period of three seconds, either the TRIM UP lamp or TRIM DN lamp will become illuminated, as a prompt to trim the aircraft in the indicated direction.  This is shown in Fig. 3-7. If no action is taken after four more seconds, then the lamp will flash.  Once the aircraft has been sufficiently trimmed, such that the pitch servo loading is below the preset threshold, the lamp will extinguish."

 

That sure sounds like the servo is holding elevator pressure, not moving the stabilizer (whole empennage)...

[Marauder]

Bob -- I am not too familiar with the STEC - 50. But I would imagine it performs in a similar manner to the 60–2. I have a trim motor that will move the entire empennage. If I have this trim motor shut off and the airplane is calling for trim, it recognizes that there is pressure on the elevator and behaves like you wrote. If I do not trim the airplane, then the altitude hold will drop offline. I fly most of the time with the auto trim turned on and never even have to do anything to trim the airplane when the autopilot is engaged.

[Bob_Belville]

Yeah, I have STEC power trim which moved the same worm as the wheel on the floor. In fact when using the yoke electric trim I often have my right hand touching the wheel for confirmation that the trim wheel is moving. That's obviously moving the empennage.  And like you when transitioning from climb or descent to level I would normally hold the altimeter steady with the elevator (yoke) while I trim of the pressure I'm putting on the yoke and then engage ALT HLD. Once the trim is about right the AP can handle the rest, even in pretty good up/down drafts.

 

Whwn I get my plane back it should not take long to see where the servo is.

[Marauder]

Yeah, I have STEC power trim which moved the same worm as the wheel on the floor. In fact when using the yoke electric trim I often have my right hand touching the wheel for confirmation that the trim wheel is moving. That's obviously moving the empennage. And like you when transitioning from climb or descent to level I would normally hold the altimeter steady with the elevator (yoke) while I trim of the pressure I'm putting on the yoke and then engage ALT HLD. Once the trim is about right the AP can handle the rest, even in pretty good up/down drafts.

Whwn I get my plane back it should not take long to see where the servo is.

Bob - it sounds like you have manual electric trim but not the autotrim, is that right? I don't think I have ever seen the trim indicators come on because I have it do all the trimming. Is that what you use as a clue to tell if the trim is within limits?

[Bob_Belville]

yes and yes

 

I think I'll have to play with it a little to see if the Alt Hld disengages if I ignore the trim or run it out of trim intentionally.

[mike_elliott]

yes and yes

 

I think I'll have to play with it a little to see if the Alt Hld disengages if I ignore the trim or run it out of trim intentionally.

[ArtVandelay]

I'm used to an AP where you set the altitude and adjust the rate of climb/descent, can this function be added easily (relatively inexpensively)?  For a AP with alt hold, I assume that doesn't prevent it from doing couple approaches (both ILS and GPS)?

[Marauder]

I'm used to an AP where you set the altitude and adjust the rate of climb/descent, can this function be added easily (relatively inexpensively)? For a AP with alt hold, I assume that doesn't prevent it from doing couple approaches (both ILS and GPS)?

Tell us more... What AP are we talking about? The STEC I own has altitude hold, but not altitude pre-select. It has a vertical speed hold, but not a vertical speed digital pre-select. In other words, I set pitch for climb, hit VS and it will hold that climb rate. When airspeed decays, I hit the DN button to lower the rate of climb at the desired airspeed. Other autopilots can hold a desired speed. Each autopilot has their own features and how they do it. Some are built into the base box price, others can be added as add ons. Sent from my iPad using Tapatalk

[ArtVandelay]

Tell us more... What AP are we talking about? The STEC I own has altitude hold, but not altitude pre-select. It has a vertical speed hold, but not a vertical speed digital pre-select. In other words, I set pitch for climb, hit VS and it will hold that climb rate. When airspeed decays, I hit the DN button to lower the rate of climb at the desired airspeed. Other autopilots can hold a desired speed.

Each autopilot has their own features and how they do it. Some are built into the base box price, others can be added as add ons.

Sent from my iPad using Tapatalk

KAP 140 Two-axis Autopilot with Altitude Preselect

[Marauder]

So, does this AP have an electric trim capability? With an altitude pre-select, do you set the altitude and then manually trim the plane for climb?

Sent from my iPad using Tapatalk

[ArtVandelay]

So, does this AP have an electric trim capability? With an altitude pre-select, do you set the altitude and then manually trim the plane for climb?

Sent from my iPad using Tapatalk

It autotrim if necessary, it was great for shooting shotgun approaches, once on heading for the MAP, I could set the altitude and start briefing the next approach, when it got close (~100') , it would level out, which I would feel even if I wasn't looking. Nice feature to have, I wouldn't pay a lot for it, which is why I ask the questions.

It sounds like atl-hold can do the same thing except it won't level out at the selected alt.

[Marauder]

I guess I am a little confused. Are you trying to upgrade the KAP 140 in your plane to have this feature? I found the manual for it and they show three flavors of the 140. For both the two axis and two axis with altitude pre-select, the only options are auto trim or manual electric trim.

If you have a single axis, it does not look like a straightforward upgrade path exists.

Sent from my iPad using Tapatalk

[ArtVandelay]

I guess I am a little confused. Are you trying to upgrade the KAP 140 in your plane to have this feature? I found the manual for it and they show three flavors of the 140. For both the two axis and two axis with altitude pre-select, the only options are auto trim or manual electric trim.

 

No, I was referring to STEC and found the answer, the STEC 60 (using SA-200 or ST-360) can do it but not the 50.