AP Altitude Hold

gismo said:
How do you practice that? On my autopilot (C-III) operating the electric trim trips the autopilot offline and unless you disable the auto and electric trim you cannot move the trim manually.

One thought if there's an autotrim capability would be to surreptitiously pull back on the yoke while the autopilot rolls in down trim to compensate but then you'd have to release the pressure at just the right time and rate to provide the same effect as a real runaway.
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Well, as I said earlier - you either do it in a sim or CPT... OR you do it in the airplane without actually having it run away. On the ground, the instructor says "Trim In Motion" (which is a warning the GFC700 will give when the trim is running for a significant period of time and it's not commanded by the pilot using the MET switches), or the instructor says "Trim Runaway".

The pilot then works through the procedures for the problem. The "pretend" runaway may be all you can do in the airplane, since it may not be possible, or safe to have the trim actually runaway in flight.

It's sort of like the pretend blowout I had when I got my pressurization endorsement - we were in the sim at FL330, and the instructor whacked the side of the sim and triggered the pressurization warning system. We had to get our masks on in the appointed time, and then each of us did our respective jobs. Pilot flying pulled the throttle to idle, put out the spoilers to flight-extend, and pitched down until the clacker and then pulled up slightly. Pilot not flying hit the manual mask drop (just in case), and then worked with ATC, letting them know our problem on the way down to 10,000, then pulled the checklist to make sure we hadn't forgotten anything. We'd work any other emergencies as they arose on the way down.
 
TMetzinger said:
Except when it doesn't work, in which case you go on to the next step.
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Pull CB. another 2 seconds.

This is not rocket science nor should it be built into a complicated procedure requiring a checklist. It's just part of understanding the airplane. No need in making mountains out of molehills. This is just a simple oral question on the plane.

If you want to do training that has some meaning teach a student how to land a plane with a stuck trim tab. Most instructors never teach stuck trim.
 
That's one of the traps. The disengage (red) button does not disengage the trim (on some systems, such as the KFC 200) but is only an interrupt button. To disengage, you must hold the button down until you can use other measures (autopilot switch, CB, avionics master or airplane master) to stop the runaway. After some reported runaways, King ordered a recall on the 200's to modify a circuit board in the A/P.

Rotor&Wing said:
In all my years of flying I have never had a runaway trim situation, especially in a GA airplane. I've trained for it in large airplanes and airplanes with pure electric trim.

Since there is a "Disengage" switch by your left hand it's a non event anyway. Simply switch off and continue.
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And in some airplanes there's more than one CB for the autopilot and MET. And some pilots have no idea which ones / where they are. But they're not skygods (for whom practice would have little value).
 
TMetzinger said:
And in some airplanes there's more than one CB for the autopilot and MET. And some pilots have no idea which ones / where they are. But they're not skygods (for whom practice would have little value).
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CB's are marked, as per FAR, no secret there. So you are telling me there are pilots that are "checked out" in a model of airplane but can't tell you where the CB panel is? Or how a simple procedure such as autopilot/trim disconnect works? :nonod:

A typical GA airplane has 20 or so CB's usually situated on one panel. These are not highly complex airplanes, but some instructors try to turn them into one.
 
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wabower said:
That's one of the traps. The disengage (red) button does not disengage the trim (on some systems, such as the KFC 200) but is only an interrupt button. To disengage, you must hold the button down until you can use other measures (autopilot switch, CB, avionics master or airplane master) to stop the runaway. After some reported runaways, King ordered a recall on the 200's to modify a circuit board in the A/P.
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Interesting. I know the disengage button totally kills the AP as well as the flight director, but didn't know it doesn't kill a runaway trim. But, I'd just turn off the trim power switch, the white rocker right above the throttle.

http://mrpou.smugmug.com/Aviation/Trips/Outer-Banks-August-2007/4185305_FCcSm#244555997_A4jrX-L-LB
 
dmccormack said:
Wilco -- scheduled for this Monday.
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Any word?

Add me in as another "yes, I use it" and "yes, it should work a lot better than that" vote. We have the S-TEC 50 with GPSS hooked to a 430W in the 182. Awesome system.

We didn't have the GPSS at first - I noticed after adding it that it's a lot more accurate than nav tracking, and it is really slick to watch it fly a T approach on its own - It rolls out on final perfectly, way better than I can!

The altitude hold on ours works very well at first, but on a really long flight sometimes it'll get "tired" and start to wander ±20 feet with a period of 30 seconds to a minute.

That said, once you get your altitude hold fixed, I definitely recommend the GPSS module upgrade, especially since you're getting the 430W upgrade. That combo will fly procedure turns and holds for you in addition to all the other stuff. It's a VERY nice setup. :yes:
 
dmccormack said:
I work through the steps to disconnect and then run through it with eyes closed.

I have owners with A/P show me the disconnect procedures. Haven't had one yet that ended with "When all else fails, pull the breaker."

:rofl:
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pulling the breaker is the last step for my STEC 20 in my 140.

First is the disconnect switch on the yoke.
Second is the off switch on the STEC 20
Last is pulling the breaker.
 
Bob Noel said:
pulling the breaker is the last step for my STEC 20 in my 140.

First is the disconnect switch on the yoke.
Second is the off switch on the STEC 20
Last is pulling the breaker.
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The autopilot CB is hard to see and get to in my airplane, I might think about moving it to a better location someday.

Shutting down my autopilot and disabling automatic trim:

1. Depress the manual trim sw on the left horn of the yoke.
2. Depress the disconnect button on the right horn of the yoke.
3. Push the bottom of the right rocker switch on the autopilot console.
4. Switch the avionics master off.
5. Pull the autopilot CB
6. Switch the aircraft master off.

4-6 will also disable the pilot controlled electric trim as will flipping off the separate "Trim power" toggle switch near the autopilot console.
 
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gismo said:
4. Switch the avionics master off.
5. Pull the autopilot CB
6. Switch the aircraft master off.

4-6 will also disable the manual trim as will flipping off the separate "Trim power" toggle switch near the autopilot console.
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How can that happen that your manual trim get's disabled when shutting off electric trim and autopilot?
 
I think he means the "Manual electric trim", which in itself is grounds for shooting the writer who came up with the term.
 
Rotor&Wing said:
How can that happen that your manual trim get's disabled when shutting off electric trim and autopilot?
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I don't understand your question. Anything that turns the autopilot off also disables the automatic trim but the "manual electric trim" (split thumb rocker on the top of the yoke) works with the autopilot off even though they share the same power source. There's a separate switch that disables the both the manual and auto electric trim. With that switch off the trim wheel can be moved by hand whether or not the autopilot is engaged and the "manual electric trim" via the thumb rocker doesn't work either.

Edit: I finally saw that I left out the word "electric" in the last line of my prior post (corrected now) and now your confusion/question makes perfect sense. Somehow when I read "manual trim" in both my post and yours I saw "manual electric trim" which is what I intended to write.
 
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gismo said:
Edit: I finally saw that I left out the word "electric" in the last line of my prior post (corrected now) and now your confusion/question makes perfect sense. Somehow when I read "manual trim" in both my post and yours I saw "manual electric trim" which is what I intended to write.
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For "manual trim," you still have the big ole wheel under the panel, non?
 
The first time you fly an airplane without any means of manual trim it's a bit strange. The Aerostar is pure electric and so was the BE99 and the SA227 Metroliner. One of the things you learn to do in training is to land with stuck trim.

Back when I was teaching in both airplanes and helicopters I would fail the trim in cruise flight and have the student land without trim. It's something I feel they should experience.
 
Rotor&Wing said:
The first time you fly an airplane without any means of manual trim it's a bit strange. The Aerostar is pure electric and so was the BE99 and the SA227 Metroliner. One of the things you learn to do in training is to land with stuck trim.

Back when I was teaching in both airplanes and helicopters I would fail the trim in cruise flight and have the student land without trim. It's something I feel they should experience.
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Man, I think full up or down trim in my B55 would wear out my arms in about two minutes. But I suspect I could land it in cruise trim if I had to. Normal landing trim is 10-15 degrees nose up compared to cruise. That's the trim tab angle, not the aircraft's pitch attitude or AoA although IIRC the cruise AoA is 2-3 degrees up and landing is 10-13 degrees up.
 
I had an A/P without alt hold, and now have one with.. I use it all the time and would never consider going back.​
 
Rotor&Wing said:
How can that happen that your manual trim get's disabled when shutting off electric trim and autopilot?
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It is not likely, but possible. Say the wires to the trim servo get shorted to another system in the wire bundle and power is then provided to the servo. Obvioulsy it would be uncommanded.
 
John Collins said:
It is not likely, but possible. Say the wires to the trim servo get shorted to another system in the wire bundle and power is then provided to the servo. Obvioulsy it would be uncommanded.
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I was asking about normal operations such as outlined in his other post and he came back and corrected it by adding "manual electric trim".

Sure, lots of things could happen, wires short, actuators jam, meteors hit the tail in flight, etc.
 
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