Autopilot confusion!

[BigAirHarper]

Hey all, so I'm in search of an M20J but I feel like there are a million different autopilots out there that people list from Century, King, Garmin, etc...my question is could someone help explain to me the functions of the common ones and ones to avoid? I'm wanting something that can at a minimum be slaved to a GPS and fly heading mode too with altitude hold. One that could do vertical components would be nice but not absolutely necessary. I've just been trying to do research on all the different types and it's confusing! Figured I would try with some of you experts! 

[Guest Mike261]

My 1998 J model has the King KAP 150 and the kln 94 GPS, and the king HSI all original equipment. if you move up to the KFC 150 you get a flight director with it.

i can at least give you the particulars on this setup. (KAP150)

I can fly autopilot and follow heading, a VOR or the GPS, maintaining a set altitude, all determined by settings on the autopilot and the Nav Selector switch.

there is no altitude pre select so you activate altitude hold when you arrive at your desired altitude.

you can initiate a climb or descent while in alt hold mode by holding the up or down button on the auto pilot. this will give you 500 feet per minute, when you release it will level out at your altitude.

you can hold a climb attitude by engaging altitude hold once you are settled into your climb I'm told, but I've never used it...so not sure.

in approach mode it captures the glide slope as long as I'm under it and flies it better than i ever could.

the kln 94 can only do the old style non precision gps approaches, for the new lpv's and such you'll need a new waas GPS.

overall this system functions well, and it hasnt given me any major headaches. i have found it to be easy to use, and dependable.

 

mike

 

[carusoam]

Mike's system above can also do two additional things...

- Set a climb or descent rate.  

Alt button off. 100fpm for each up or down button pressed.

Alt button on. 500fpm up or down depending on the button pressed.

- Hold the attitude by pressing the button.

The KAP combine with a GPSS can follow a flight plan automatically.

Check the details at PPI to make sure all these things work.  It is a highly integrated system.

my system has two shortcomings because of it's age.  It doesn't have altitude select so you need to pay attention while climbing.  It climbs so fast, you don't have to pay attention too long.  And, I don't have GPSS yet...

Best regards,

-a-

[Guest Mike261]

Mike's system above can also do two additional things...

- Set a climb or descent rate.  

Alt button off. 100fpm for each up or down button pressed.

Alt button on. 500fpm up or down depending on the button pressed.

- Hold the attitude by pressing the button.

The KAP combine with a GPSS can follow a flight plan automatically.

Check the details at PPI to make sure all these things work.  It is a highly integrated system.

my system has two shortcomings because of it's age.  It doesn't have altitude select so you need to pay attention while climbing.  It climbs so fast, you don't have to pay attention too long.  And, I don't have GPSS yet...

Best regards,

-a-

yes...but ive only used half of it...press and hold for descent with alt hold engaged, hold button you get 500 up or down. as i understand it from the manual if you have the alt button off each 1 second press of the button will increase or decrease pitch for a 100 FPM climb or descent. i havent had a flight with a situation i needed it, press and hold is usually enough, and it keeps my attention on the altitude, so i dont bust!

as far as the GPSS I dont have it, unless its built in to the 94 that i dont know about, but it follows the gps flight plans, you just have to make sure you move the pointer.

mike

 

[KSMooniac]

There aren't any Garmin autopilots in M20J's.  The earlier J's would likely have come with Century autopilots and King optionally.  Starting ~early 80's I'm not sure if there was anything but King autopilots.  The crown jewel would be the KFC-200 A/P system that was integrated with the King HSI system and flight director.  These are very capable, but also require quite a bit of upkeep.  There are also KAP-150 and KFC-150 systems as mentioned above.

If you find a plane that has been updated, you might run across an STEC A/P system.  The crown in that line is the 55x, which has a control head that fits in the avionics stack.  The 20 and 30 are much simpler and live in the turn coordinator gyro so it saves valuable panel space.  There are other STEC systems that have a separate control head in the panel.  These systems can be optioned with altitude hold, electric trim, etc.

My '77 J originally came with a Century II (I believe) and was replaced by the previous owner with an STEC-30 with GPSS.  I believe it to be a perfect fit for this class of plane as it will couple to GPS or VOR/localizer, fly the entire lateral flight plan and instrument procedure via GPSS, or use the heading bug.  It has altitude hold but does not do glideslope capture, altitude-preselect, etc.  That part is easy enough to manage manually though.

I wouldn't get hung up on *which* autopilot a candidate plane might have, but would make very sure it is 100% functional!

[KSMooniac]

GPSS is the best bang-for-the-buck upgrade out there.  It is amazing if coupled to a WAAS GPS as it will fly procedure turns, holds, course changes, etc. completely hands-off.  Truly amazing.

[Guest Mike261]

here is an article i find useful...not comprehensive but some good info.

http://www.avionicslist.com/articles/autopilots.php

 

 

[Jerry 5TJ]

Some KFC150 systems have the auxiliary KAS297 permitting altitude pre-select and vertical speed setting for flight director and autopilot guidance. 

 

 

[bonal]

We have an STEC 40 in our C its single axis I can fly the heading or the Nav and it works great very reliable I'm sure the 2 axis models would be as well.

[M20F]

I am an S-Tec fan personally.  They are fairly simple to use, generally bullet proof, and comparably cheap.  The King auto-pilots especially the ones the feed a flight director seem to break a lot from reading these forums and are in general expensive. 

[Guest Mike261]

I am an S-Tec fan personally.  They are fairly simple to use, generally bullet proof, and comparably cheap.  The King auto-pilots especially the ones the feed a flight director seem to break a lot from reading these forums and are in general expensive. 

should have mentioned that..i read that the king units with flight directors were prone to problems before i bought my plane. it actually had some weight in passing on a plane with it installed.

[cnoe]

Mine came with the Century IIB and had an STEC PSS60 altitude hold system added on later. In good working order it will:

Hold the wings level (or your preferred bank angle).

Follow a heading bug.

Follow a GPS track or VOR radial (keeps your indicator needle centered).

Track in LOC mode on approaches (keeps needle centered with greater precision).

Track a LOC back course approach (reverse sensing).

... and with the altitude hold it will also:

Hold an altitude within ~20 feet in good weather.

Hold an ascent or descent rate to <100 fpm in good weather.

Intercept and lock onto a glideslope on an ILS or LPV approach (keeps your GS needle centered on indicator). I will admit that it will fly a precision approach to minimums better than I can, though I still practice hands-on.

What it WILL NOT do is follow a procedure turn or hold automatically (use your heading bug for that).

Also, you have to turn the heading bug to match your GPS/VOR course changes.

And I don't have auto-trim so if I get out of trim it flashes a light telling me to trim up or down if necessary (easy enough to do).

Sure, I'd love to have a newer system with GNSS (roll steering functionality) but until the FAA gets the Part 23 rewrite completed I'm not paying $20K-$30K to replace my perfectly functional A/P.

Hope this helps.

 

[KSMooniac]

I believe some of the aftermarket GPSS systems are compatible with the Century autopilots.  Some of them even appear on the used market as folks upgrade to Aspen too.

[cnoe]

Hmmm. I wasn't aware you could get roll steering out of an old Century. Are you referring to mating with new systems like the Aspen, Avidyne, or similar? I'm comfortable with my GNS530WAAS for now but would consider an upgrade if we ever get pricing inline with experimental guys' equipment.

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[cnoe]

On second thought I guess I understood that the vital element to roll steering is what the GPS outputs rather than what the A/P inputs. If my GPS weren't WAAS capable it would be a bigger concern to me considering ADS-B requirements. In the meantime holds and procedure turns still require a bit of thought, which might not be a bad thing.

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[KSMooniac]

Yes, I believe there is an aftermarket GPSS system that will work with the Century. Maybe DAC. An Aspen PFD would do it also, but not required.

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[Marauder]

On second thought I guess I understood that the vital element to roll steering is what the GPS outputs rather than what the A/P inputs. If my GPS weren't WAAS capable it would be a bigger concern to me considering ADS-B requirements. In the meantime holds and procedure turns still require a bit of thought, which might not be a bad thing.

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I installed my STEC 60-2 in 1998. It has altitude hold & auto trim. For years I flew it VOR only. When I added the GTN in 2012 and the Aspen in 2012, it turned my autopilot from an autopilot to a flight management system. Having GPSS and autoslewing of the course is not just nice, it is friggin awesome. Once you load up the flight plan and then the approach, you are managing the flight.

I still hand fly everything on shorter flights and will hand fly half of the approaches, but on longer flights, "George" takes on a bigger role. If you have the funds, I highly recommend jumping up to something that provides these functions. Really helps with the workload.

For Mr. Harper, I have been extremely happy with my STEC 60-2. The 55X adds altitude pre-select and you can also select your rate of climb. If you are able to look at planes with various APs, I would look for something that has an interface with a GPS and can do altitude hold. Adding stuff later on is really expensive.

Here is my Aspen setup to follow the GPSS signal and is doing the auto slew of the course. The "A" is a menu selectable feature where you can let the Aspen do the auto slew of the course line or you can let the Aspen do it for you.

The red circle on the right shows the Aspen is in GPSS for heading mode. In other words, it is following the GPS course.

The picture is also a good example of the capabilities of the system. I am showing a 39 knot cornering tail wind from 311°. The GPS course is 186° and the autopilot is flying a 198° heading to stay on course. You can get the sense of how much correction by looking at the course line below.

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[Bob_Belville]

I have an STEC50. It is very capable. In the plan view I suppose it does everything that Marauder's STEC60-2 does. But it has only altitude hold but otherwise does not manage vertical. No altitude pre-select, no rate of climb/descent or speed lock on, no glide slope lock. 

GPSS is pretty special. With a compatible A/P in hdg mode it will follow a GPS flight plan from take off to landing. My Aspen/GTN750/STEC50 combo will fly procedure turns, automatically switch to localizer from GPS and fly the published missed approach including a charted hold.    

 

[Marauder]

I have an STEC50. It is very capable. In the plan view I suppose it does everything that Marauder's STEC60-2 does. But it has only altitude hold but otherwise does not manage vertical. No altitude pre-select, no rate of climb/descent or speed lock on, no glide slope lock. 

GPSS is pretty special. With a compatible A/P in hdg mode it will follow a GPS flight plan from take off to landing. My Aspen/GTN750/STEC50 combo will fly procedure turns, automatically switch to localizer from GPS and fly the published missed approach including a charted hold.    

 

I should have provided more detail on the altitude functions on the 60-2. I do have the ability to set a vertical climb and descent profile. Unlike the 55X, when I hit the "VS" button, I then push the up or down button to set the climb or descent FPM. Each second of hold will product 160 FPM of climb or descent. So, counting off 3 seconds will produce a 480 FPM climb or descent. On the 55X, you can select the FPM as a number. What you do need to be aware of is the fact these are rate based climbs or descents. If you set it for 640 FPM rate of climb, it will allow the airspeed to continue to erode to meet the climb rate. Some autopilots are capable of constant airspeed climb or descents.

As for a coupled approaches, unlike Bob's 50, mine will provide vertical guidance for an ILS or LPV approach. Typically you select the precision approach and at a point before the glideslope intercept, you put the AP in "approach" mode by engaging the "NAV" button. On an ILS, this is done about 2 miles out and below the glideslope. On an LPV, I have found that it will couple further out.

One other thing I didn't see mentioned in the thread is about flight directors. My plane has a single cue flight director. This can be engaged with the autopilot flying the plane or with the autopilot servos turned off but with the AP engaged. When the flight director is on and the AP servos are off, you can follow the flight director commands by tucking the AI's ARS (Aircraft Reference Symbol) underneath the Steering Command Bars. By following them, you can fly the profile for the flight.

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[PaulB]

I have an STEC 55x and saw the benefit of a rate based AP 2 weeks ago flying back from Florida.  With about 4 hours to go the vacuum pump went out.  Instead of having to hand fly the remainder of the trip and plane didn't even notice.  I like knowing that if I loose the vacuum pump that it just keeps on going.  An attitude based AP has two modes of failure: electrical and vacuum.

[Bob_Belville]

 

I should have provided more detail on the altitude functions on the 60-2. I do have the ability to set a vertical climb and descent profile. Unlike the 55X, when I hit the "VS" button, I then push the up or down button to set the climb or descent FPM. Each second of hold will product 160 FPM of climb or descent. So, counting off 3 seconds will produce a 480 FPM climb or descent. On the 55X, you can select the FPM as a number. What you do need to be aware of is the fact these are rate based climbs or descents. If you set it for 640 FPM rate of climb, it will allow the airspeed to continue to erode to meet the climb rate. Some autopilots are capable of constant airspeed climb or descents.

 

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You don't miss what you've never had. For climb and descent I simply trim the pitch to an airspeed: initially Vy, usually 120+ kts for en route climb, and Vne minus ~5 kts for en route descent. The rate of descent is controlled by throttle if necessary. (Assuming not in moderate turbulence, ATC cooperation, etc..) I find the pitch trim is quite capable of holding IAS.

Pre-select altitude and GL lock features would be nice but not having them is does not create a major workload. FWIW, Aspen told us a couple of years ago that they were going to offer altitude pre-select using their present altitude alert feature but I have not heard anything recently. ISTM, for my current A/P all the Aspen could do would be to engage ALTHLD as the selected altitude is reached so pitch trim would be up to the pilot and the pitch transition might be abrupt if you're attention is elsewhere. (My A/P does alert the pilot that trim is needed.) OTOH, abrupt would be better than overshooting. 

[Marauder]

You don't miss what you've never had. For climb and descent I simply trim the pitch to an airspeed: initially Vy, usually 120+ kts for en route climb, and Vne minus ~5 kts for en route descent. The rate of descent is controlled by throttle if necessary. (Assuming not in moderate turbulence, ATC cooperation, etc..) I find the pitch trim is quite capable of holding IAS.

Pre-select altitude and GL lock features would be nice but not having them is does not create a major workload. FWIW, Aspen told us a couple of years ago that they were going to offer altitude pre-select using their present altitude alert feature but I have not heard anything recently. ISTM, for my current A/P all the Aspen could do would be to engage ALTHLD as the selected altitude is reached so pitch trim would be up to the pilot and the pitch transition might be abrupt if you're attention is elsewhere. (My A/P does alert the pilot that trim is needed.) OTOH, abrupt would be better than overshooting. 

They offer an altitude pre-select for the KFC offered through a German company called Avionik Straubing. What I am holding out for is the DFC 90 integration. Hopefully at some point they will offer it to us. In addition to digital control, it offers constant airspeed climbs and the nice safety feature of "upset recovery"

http://www.avidyne.com/landing/dfc90/index.asp

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[Mooneymite]

 

 

.... and the nice safety feature of "upset recovery"

Wasn't that the original intent of the original PC?

Let go of the button and the wings level.

[Bob_Belville]

 

They offer an altitude pre-select for the KFC offered through a German company called Avionix Straubing. What I am holding out for is the DFC 90 integration. Hopefully at some point they will offer it to us. In addition to digital control, it offers constant airspeed climbs and the nice safety feature of "upset recovery"

 

http://www.avidyne.com/landing/dfc90/index.asp

 

 

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Yeah, the German company's add on was the reason I asked Aspen about that feature at SnF a couple of years ago. They suggested I wait for their version... 

You would swap out your STEC 60-2 for the Avidyne?

[Marauder]

Wasn't that the original intent of the original PC?

Let go of the button and the wings level.

In theory. I think the big difference is how deep you are into the upset. From what I read about the Cirrus version, it will handle some pretty extreme upsets.

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