AutoPilot Malfunction

PilotNas

PilotNas

Filing Flight Plan
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Nov 21, 2013
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Castro Valley, CA
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PilotNas
Hi Pilots,

I have a quick story to tell. Something that happened to me and some of my friends. I was flying a Cessna 420B and my Autopilot did not work. One night I took off around 10:30pm at night, I was grounded because of bad weather and was happy to be up in the air and I am a VFR Pilot with a multiengine rating.

After we took off, I was on flight following I decided to turn on the Auto Pilot. I noticed it didn't work so I tried to disengage it.

But I couldn't, it would not turn Off. I was still climbing passing through 8,000 feet. Flight following asked me if I had chosen an altitude but I didn't respond. I was fighting the plane to stay straight. I informed flight following that I had know control of the aircraft and their voice changed over the radio.

I started to tell my passengers that I do not have control of the plane and they started to freak out.

I have no control, Flying at 11:00pm and we have bad weather and I'm still climbing.

To make a long story short (Too Late)

Since I had no control and I was worried and the Auto Pilot wouldn't turn off; I pulled the circuit breaker for the Auto Pilot.

I had control again. I decided not to continue to fly, so I found the nearest FBO at Memphis International Airport.

After I secured the Plane I went inside and the people working their, told me that my passengers where all white and they were told of the story.

So I guess what I learned is, Never to Test things during flight, in Bad weather at Night and not knowing the system very well.


>>InformationOnFlying<<
 
PilotNas said:
So I guess what I learned is, Never to Test things during flight, in Bad weather at Night and not knowing the system very well.
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Your first lesson learned should have been to know where the A/P CB is without having to look for it. You did the right thing, but depending on how the A/P or elec trim failed, you may not have had time to go looking for it.

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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Cessna auto pilots have had the same problem. Cessna says that if you pull the breaker on an autopilot,it should not be reset,and autopilot engaged. If you are not getting the autopilot repaired it would probably be a good idea to lock out the circuit breaker. Glad it worked out for you.
 
I've read enough "never again" stories that started with "the autopilot was flying..." that when I started flying again last year and all the planes at the FBO had A/P, I made it part of my checklist to pull the breaker for A/P before turning on the master.

When I was doing hood time, I had a CFI keen to show me how to operate the A/P (probably because I was sweating buckets flying around under the hood in moderately turbulent air), and that's the only time I've used it. FWIW, it didn't do any better of a job at maintaining standard rate turns than I did. Did keep altitude a bit better, but I kept having to yank the throttle to stay under Va in some of the dives it used to maintain altitude in thermals.

I have a healthy (or more) skepticism of ole Otto.
 
BigSam said:
I've read enough "never again" stories that started with "the autopilot was flying..." that when I started flying again last year and all the planes at the FBO had A/P, I made it part of my checklist to pull the breaker for A/P before turning on the master.
Click to expand...

I don't know if I'd do that, AP is a useful device. Just know the various methods to cut the AP if something goes bad, including pulling the breaker if necessary.
 
BigSam said:
I've read enough "never again" stories that started with "the autopilot was flying..." that when I started flying again last year and all the planes at the FBO had A/P, I made it part of my checklist to pull the breaker for A/P before turning on the master.

When I was doing hood time, I had a CFI keen to show me how to operate the A/P (probably because I was sweating buckets flying around under the hood in moderately turbulent air), and that's the only time I've used it. FWIW, it didn't do any better of a job at maintaining standard rate turns than I did. Did keep altitude a bit better, but I kept having to yank the throttle to stay under Va in some of the dives it used to maintain altitude in thermals.

I have a healthy (or more) skepticism of ole Otto.
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A lot of folks killed by auto pilots. A lot of folks killed hand flying too. You should know and understand both.
 
Fearless Tower said:
A lot of folks killed by auto pilots. A lot of folks killed hand flying too. You should know and understand both.
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Understood. Right now, though, the A/P is the "devil I don't know". Maybe once I get serious about an IFR rating, I'll feel I need to buddy up with Otto. I don't yet feel the need to give the plane extra chances to kill me.
 
I love having an autopilot in the 172, and I know I'll enjoy the one in my RV as soon as I finish it and get it flying - but it's just one tool in the box. Just like a good sharp knife can be handy in the kitchen, it can kill you if misused. You should take the time to learn it, understand it, know how to make it do what you want, and how to turn it off if it doesn't.
 
Fearless Tower said:
He said the A/ P wouldn't disengage. Some can't be overpowered by the pilot
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How would such an autopilot get certified?
Sec. 23.1329

Automatic pilot system.

If an automatic pilot system is installed, it must meet the following:
(a) Each system must be designed so that the automatic pilot can--
(1) Be quickly and positively disengaged by the pilots to prevent it from interfering with their control of the airplane; or
(2) Be sufficiently overpowered by one pilot to let him control the airplane.
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If there's a lesson learned here, it's that one should never fly an airplane with an autopilot unless one knows how to disengage it under all reasonably foreseeable circumstances, and how to do all the preflight tests for operation, overpowering, and disengagement (which I'm guessing the OP didn't do).
 
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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.
 
rbridges said:
Don't feel bad. I didn't realize that APs couldn't be overpowered by the pilot. I know the one in my plan will, so I assumed they all could.
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They can, or they have a positive disconnect. See the regulation linked above. That's why I think the story is fishy, because I don't think there's an autopilot legal to put in a Cessna piston twin that can't be overpowered.
 
Ron Levy said:
They can, or they have a positive disconnect. See the regulation linked above. That's why I think the story is fishy, because I don't think there's an autopilot legal to put in a Cessna piston twin that can't be overpowered.
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Don't assume. He may have weak arms.

:D
 
Ron Levy said:
They can, or they have a positive disconnect. See the regulation linked above. That's why I think the story is fishy, because I don't think there's an autopilot legal to put in a Cessna piston twin that can't be overpowered.
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Yes, there is supposed to be a disconnect, but if the A/P is not responding to pilot input (ie securing the disconnect switch), who is to say that the other designed disrupting mechanism is working as well?

I've never physically tried to 'overpower' an active autopilot for fear of breaking it, but the few occasions where I've attempted to manipulate the control with the A/P enaged, the resistance was pretty substantial, at least on Pipers and Beech airplanes....come to think of it, I honestly have never been in a Cessna with with an autopilot that was not placarded INOP.
 
Fearless Tower said:
Yes, there is supposed to be a disconnect, but if the A/P is not responding to pilot input (ie securing the disconnect switch), who is to say that the other designed disrupting mechanism is working as well?

I've never physically tried to 'overpower' an active autopilot for fear of breaking it, but the few occasions where I've attempted to manipulate the control with the A/P enaged, the resistance was pretty substantial, at least on Pipers and Beech airplanes....come to think of it, I honestly have never been in a Cessna with with an autopilot that was not placarded INOP.
Click to expand...

Most autopilots use either a clutch or shear pin type mechanism for over riding the servo. Then there is a disconnect switch to shut off electric power as well.

Research the type autopilot you have and become familiar with it. An avionics shop can show you how to test it to insure its working properly.

The OP's tale is a bit suspect. There's a few holes in it that don't add up. Perhaps he would share with us the type of autopilot in his airplane.
 
Part of the pre flight checks in the newer stuff has you engage the AP on the ground and manually overpower it to verify that you can.
 
How does one pull a pushbutton reset-only breaker that is flush with the panel?
 
PilotNas said:
Hi Pilots,

I have a quick story to tell. Something that happened to me and some of my friends. I was flying a Cessna 420B and my Autopilot did not work. One night I took off around 10:30pm at night, I was grounded because of bad weather and was happy to be up in the air and I am a VFR Pilot with a multiengine rating.

After we took off, I was on flight following I decided to turn on the Auto Pilot. I noticed it didn't work so I tried to disengage it.

But I couldn't, it would not turn Off. I was still climbing passing through 8,000 feet. Flight following asked me if I had chosen an altitude but I didn't respond. I was fighting the plane to stay straight. I informed flight following that I had know control of the aircraft and their voice changed over the radio.

I started to tell my passengers that I do not have control of the plane and they started to freak out.

I have no control, Flying at 11:00pm and we have bad weather and I'm still climbing.

To make a long story short (Too Late)

Since I had no control and I was worried and the Auto Pilot wouldn't turn off; I pulled the circuit breaker for the Auto Pilot.

I had control again. I decided not to continue to fly, so I found the nearest FBO at Memphis International Airport.

After I secured the Plane I went inside and the people working their, told me that my passengers where all white and they were told of the story.

So I guess what I learned is, Never to Test things during flight, in Bad weather at Night and not knowing the system very well.


>>InformationOnFlying<<
Click to expand...

Why are you flying bad weather at night VFR? Assuming that, by bad weather, you mean you took off under an overcast, why did it take you 30 minutes to pull the circuit breaker?

Part of a proper aircraft checkout is understanding the autopilot's operation, testing procedures, failure modes, and multiple methods of disconnect. Most have at least three ways of disconnecting...autopilot disconnect, the on/off switch, and pulling the breaker.
 
The other lesson is be careful what and HOW you day things to you passengers. It hadn't escalated to a true emergency yet (by our standards...you were still going UP not DOWN)...but you poor Px are thinking they are gonna die!

I have leaned that even the simple verbal innocent "oops" or "whoops" by a pilot can make a nervous passenger think we are going straight down!
 
Fearless Tower said:
That's what he said....although FWIW, we have another member here who owns an Aeostar and doesn't have his IR yet.
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True. Nothing wrong with that, but I guess where I'm going with this is who provided the training? Understanding the autopilot and its limitations is a fairly important piece of information in a plane like this.

From the OP it doesn't sound like he really knew what he was doing.
 
RotorAndWing said:
True. Nothing wrong with that, but I guess where I'm going with this is who provided the training? Understanding the autopilot and its limitations is a fairly important piece of information in a plane like this.



From the OP it doesn't sound like he really knew what he was doing.
Click to expand...

Yes, something does seem odd. Almost sounds a bit that that case a few years ago involving some kids joyriding in a Citation.
 
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Sorry, it was just a pic of Other People's Panels :) The one I fly has an AP CB. The point remains; what if the trim ran away, how would you pull the breaker? Turn off the master?

TMetzinger said:
And none of them are labelled "autopilot".
Click to expand...
 
GeorgeC said:
Sorry, it was just a pic of Other People's Panels :) The one I fly has an AP CB. The point remains; what if the trim ran away, how would you pull the breaker? Turn off the master?
Click to expand...

My electric trim has it's own switch on the panel. It's the right most rocker along the bottom. AP is King KFC200, a good unit.
 

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