AutoPilot Malfunction

Dynon AP74. The aircraft has electric pitch and roll trim and a 2 axis AP. IIRC, there are separate breakers for trim and AP. If a malfunction is suspected, how does one pull a breaker that's flush with the panel? Am I missing something?

RotorAndWing said:
Are we talking electric pitch trim or autopilot pitch servo?

What autopilot?
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GeorgeC said:
Dynon AP74. The aircraft has electric pitch and roll trim and a 2 axis AP. IIRC, there are separate breakers for trim and AP. If a malfunction is suspected, how does one pull a breaker that's flush with the panel? Am I missing something?
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Is that a certified AP? Don't think so. What aircraft were you flying? If it's experimental, then ask the builder why he used flush breakers.
 
Skip Miller said:
I can't quote the reg, but I believe that an autopilot without a breaker that can be pulled is not installed according to the regs.

The appropriate breaker does not sit flush when pushed in - it protrudes enough to grab and pull.

Like these: http://www.google.com/url?sa=i&rct=...gdTFz381lxI7--625JKuJouQ&ust=1386727010975315

-Skip
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Hmm. Interesting. The breaker in my panel is the flush/push to reset type. Its the original factory Cessna 200 Nav-o-matic. Nothing in the emergency procedures section says anything about pulling the breaker, either. It just says to turn the control wheel to overpower the servo or to turn the AP unit off.
 
GeorgeC said:
Dynon AP74. The aircraft has electric pitch and roll trim and a 2 axis AP. IIRC, there are separate breakers for trim and AP. If a malfunction is suspected, how does one pull a breaker that's flush with the panel? Am I missing something?
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I believe Dynon recommends install with a pullable breaker on the servos, and the AP74 is simply the AP head. In any case, experimental aircraft are a whole 'nuther kettle of fish - you are quite free to build something that can kill you if you want.

I don't have any breakers in my RV that can't be pulled, I've always hated those in production aircraft.
 
Fearless Tower said:
But, that said, thanks for reminding me that I need to practice identifying the CB in my Baron. I haven't gotten around to doing that yet.
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I can't say i'm the best about doing this either, I fly a bunch of club aircraft and the breaker is always in a different place.

There is a way around it. Just flip the master off.
 
I had a "malfunction" of the autopilot that more or less locked up the ailerons and forced me to do a rudder-only approach and landing back at the home field.

I basically did some maneuvering and forgot to disengage the autopilot, and the Century III doesn't have an auto disengage feature. The force on the yoke was strong - very strong. Strong enough that I was worried about breaking a cable if I tried to force it any further.

I didn't realize it was an autopilot issue at the time or I would have simply disengaged it. I thought some object managed to become stuck in the control rigging or aileron linkage someplace - that's what it felt like.

Total brain fart yes but it worked out and nothing got bent.
 
Century III servos have a slip clutch that allows the pilot to override pitch and roll inputs without excessive force. The clutches can become "sticky" over time but this can be repaired. Pilot's are supposed to verify the breakaway force is sufficiently low as part of their pre-flight checks.

On the C-III in my Baron IO can easily override the servos with one hand.

-lance

Sac Arrow said:
I had a "malfunction" of the autopilot that more or less locked up the ailerons and forced me to do a rudder-only approach and landing back at the home field.

I basically did some maneuvering and forgot to disengage the autopilot, and the Century III doesn't have an auto disengage feature. The force on the yoke was strong - very strong. Strong enough that I was worried about breaking a cable if I tried to force it any further.

I didn't realize it was an autopilot issue at the time or I would have simply disengaged it. I thought some object managed to become stuck in the control rigging or aileron linkage someplace - that's what it felt like.

Total brain fart yes but it worked out and nothing got bent.
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Come on guys, you know this is phony as a three dollar bill. VFR pilot at night in IFR and he can't turn off the A/P, in a 421 at that?! Are there any certified A/P's out there (that would be installed in as pressurized twin) that does not have at least three ways to disengage the servos? CWS, trim, breaker. I call BS on this one.
 
ronnieh said:
Come on guys, you know this is phony as a three dollar bill. VFR pilot at night in IFR and he can't turn off the A/P, in a 421 at that?! Are there any certified A/P's out there (that would be installed in as pressurized twin) that does not have at least three ways to disengage the servos? CWS, trim, breaker. I call BS on this one.
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I would agree with you on this.
 
All certificated autopilots for light aircraft are designed to be overridable. If the test to see if you can do so isn't explicitly required by the paperwork as your preflight check, you're an idiot to not do it. I've had autopilots try to kill me by rolling the plane upside down, but they've all responded to the red button and I could fight them anyhow.
 
When I built my panel...

I installed a power toggle 1" to the left of AP head. Also can hit red CWS button on the stick. Also electronically set my torque low enough to override without shearing off shear pins at servos.

My pitch trim is not connected to AP as some Experimentals. I am sure it is handy, but I like having that control. I have a pitch trim enable button near throttle that I must push in with thumb before bumping or holding rocker switch with forefinger to adjust trim. Otherwise, If we had a trim runaway over 125 kts, we would be in deep kimchi.
 
Sac Arrow said:
I had a "malfunction" of the autopilot that more or less locked up the ailerons and forced me to do a rudder-only approach and landing back at the home field.

I basically did some maneuvering and forgot to disengage the autopilot, and the Century III doesn't have an auto disengage feature. The force on the yoke was strong - very strong. Strong enough that I was worried about breaking a cable if I tried to force it any further.

I didn't realize it was an autopilot issue at the time or I would have simply disengaged it. I thought some object managed to become stuck in the control rigging or aileron linkage someplace - that's what it felt like.

Total brain fart yes but it worked out and nothing got bent.
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Also for future info, don't worry about breaking a cable, if it is sufficiently weakened that you can it was about to fail anyway.:wink2:
 
ronnieh said:
Come on guys, you know this is phony as a three dollar bill. VFR pilot at night in IFR and he can't turn off the A/P, in a 421 at that?! Are there any certified A/P's out there (that would be installed in as pressurized twin) that does not have at least three ways to disengage the servos? CWS, trim, breaker. I call BS on this one.
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Hey,

This is Not BS - I'm A Private Pilot with a "Multi-Engine" Rating. The Weather was VFR condition but it was overcast (I was avoiding clouds) and yes it was late night.

I was flying a Cessna 421B built in 1979 - When my friend bought the airplane we were told there is some issues with the Auto Pilot.

That night I tried the A/P (Big mistake, I know) But there is a A/P circuit breaker that I pulled and always keep it pulled when I fly.

I will be the first to tell you, that I need more training on the Airplane.

Don't call B.S. on something you don't understand.

Thanks
 
Chuckle, chuckle.

This thread sounds like a flight simmer trying to see if he can "fit in" with the real pilots. In addition to a number of errors, I find it interesting how he likes to eagerly throw extra knowledge in. Not just a pilot, a Private Pilot with a "Multi-Engine" rating. Not just a 421, a "Cessna 421B Twin Engine - 1979".

OP tried to link to an ad site in his first post. Maybe this was to drive traffic/links there. He botched the link anyway, though.
 
The key to an autopilot failure is to lean forward.
 
You are right on not calling BS on something I don't understand. However, I do understand this and I still call BS. 5446 I think you have it nailed.
 
F01LA said:
Chuckle, chuckle.

This thread sounds like a flight simmer trying to see if he can "fit in" with the real pilots. In addition to a number of errors, I find it interesting how he likes to eagerly throw extra knowledge in. Not just a pilot, a Private Pilot with a "Multi-Engine" rating. Not just a 421, a "Cessna 421B Twin Engine - 1979".

OP tried to link to an ad site in his first post. Maybe this was to drive traffic/links there. He botched the link anyway, though.
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He is trying just a little too hard.
 
We have a KAP-140 2 axis in our plane. Every aircraft that I've flown with an AP installed has a preflight procedure for the AP on the checklist.

I confess to never having run a ground check of our -140. Only possible explanation is that I would bet a crisp $5 bill (and I am not a betting man) that it's not on the checklist we keep in the airplane.

I've flown with three CFIs in this craft and neither mentioned it either. 2 of them I've flown in other aircraft before and have done APs checks in those aircraft.

My point is that there are times where following the checklist may not be all-inclusive and may not cover the important areas that one should check.

I've also flown a DA-40 that had a checklist that missed an important airframe check, that I discovered by reading the POH - but it's not on the checklist.

So, check your checklists!
 
I'll admit to not always checking the autopilot before each flight (I don't like waiting for it to initialize just to turn it back off). I do always verify it is hard off and the controls are free however.
 
GeorgeC said:
How does one pull a pushbutton reset-only breaker that is flush with the panel?
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You don't, but then those aren't installed on critical systems where one may need to pull the breaker either. There are also flush breakers that if you push them in further will pop them.
 
PilotNas said:
I will be the first to tell you, that I need more training on the Airplane.
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Then do yourself a huge favor and do not fly this plane again without a qualified instructor in the right seat. I can recommend a couple if you like (one in NJ and one in OH).
 
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Skylane81E said:
Got your endorsement for the 421 twin engine?
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There is no FAA endorsement required specifically for the 421. Obviously, the PIC will need the high altitude, complex, and high performance endorsements, but at least from an FAA perspective, you could get those in other (or even a flight simulation training device) and then go fly a 421 without further FAA ado. Whoever's insuring the plane may want more, and may require some sort of training completion certificate from Simcom, RTC, or the like, but there's no other FAA "endorsement" required.
 
PIC Malfunction

PilotNas said:
That night I tried the A/P (Big mistake, I know) But there is a A/P circuit breaker that I pulled and always keep it pulled when I fly.

I will be the first to tell you, that I need more training on the Airplane.
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See. He didn't do the a/p preflight which is called out in the POH....
He did this VFR but at night.
Learned where the breaker was afterward (or at least how to trip it).

Well, that's one low time move at least that one pilot won't do again.....
 
Jaybird180 said:
I confess to never having run a ground check of our -140. Only possible explanation is that I would bet a crisp $5 bill (and I am not a betting man) that it's not on the checklist we keep in the airplane.
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Is this a Cessna 172? It may be that they created the checklist from the POH checklist but forgot to check the autopilot supplement in the back of the Cessna POH for the KAP-140 which has additional checklist items.

Either way, I would always add autopilot ground checks to any preflight runup.

And, yes, check all checklists that aren't straight from the POH, I've seen many errors or poor checklists in even my short time.
 
I became suspect when the OP was talking to "flight following".

If this story IS true then it's even more scary. At the very least, I would encourage the OP to stop flying with passengers. They don't know how much you don't know, and can't be blamed for assuming that a "Multi Engine" pilot would know what he's doing with something so basic as autopilot disconnect options and workarounds.

Also, if the story is true, maybe liveatc.net has the radio archive. Which airport did you depart and roughly when was it?
 
I was viewing the Chat Stream regarding an autopilot failure and wondered if anyone out there has ever experienced an issue like this with a Century 41 autopilot with altitude pre-select.
I have recently upgraded my later serial number Duke A-60 to go from steam gauges to a G600, a GTN 750 and 650, ADS-B via a GDL 88 and an Avidyne EX600 for my color radar display. In addition, I replaced the old, non-functional Century III autopilot with a Century 41 with altitude pre-select and replaced the old yaw damper with a newer Century 41 compatible version. Needless to say, my banker loves me for the upgrade.

Shorly after getting the plane out of the avionics shop, I noticed in the ground test of the Trim system that it would only trim up using the yolk electric trim switch but not down. This required sending the computer to Century for a replacement of the trim circuit board. Got it back and it worked fine. Flew it several times and was impressed with its ability to hold altitude even in mountain wave activity over the cascades. A week later, while flying a backcourse and holding at 7000 ft, I noted the trim wheel to be gradually trimming up and disconnected the autopilot via the yolk disconnect switch only to have the yolk "slap" back into my hands and requiring a hand trim correction of the wheel to regain level flight. Discussions with the avionics shop and Century resulted in a test flight in which the AP preflight test revealed an "auto trim malfunction" flashing light and a subsequent second and third trip for the autopilot computer (not my airplane) across the US to Century for a "test table negative test sequence" and then a subsequent replacement of several circuit boards as well as a prolonged discussion with the avionics shop and Century's techs. Got it back and it flew well for several weeks then, once again, it trims up with the altitude pre-select after reaching the desired altitude and holding it for several minutes until I initiate an "autopilot directed" heading change and then it begins to slowly trim up. When I engage the altitude hold button directly, it holds altitude fairly well and will even fly a coupled ILS and an RNAV GPS approach to the LPV minimums without issues.
Needless to say, while I am extremely happy with the system, it is most disconcerting about the altitude hold feature and the pre-select. Has anyone else had a similar problem or have anyone they consider an autopilot guru that may have a line on a possible fix for this issue?
Thanks
:dunno:
 
RotorAndWing said:
Most Cessna autopilots have a shear pin installed in the pitch servo. Apply enough pressure in the opposite direction and the shear pin breaks and the pitch servo is now free.

If this didn't happen a qualified avionics shop needs to look over the servo.
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Yes, the servos should release if you pull hard enough if designed with a shear-pin mechanism. Pulling the breaker was smart though. Glad you got control back...
 
Fighterdoc18 said:
or have anyone they consider an autopilot guru that may have a line on a possible fix for this issue?
Thanks
:dunno:
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Bob Ferguson at Autopilots Central retired and Barry Sparks is now the guy there. Worth a call.
 
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