Familiarize yourself!

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KC10Chief

Filing Flight Plan
Joined
Aug 9, 2011
Messages
25
Location
Anchorage, AK
Display Name
Display name:
Matt
The aero club I belong to just bought its 6th plane, another 172. They have a Piper Seneca, a 172 float plane, three other 172s and a 182. I usually fly the 182. Never fly the float plane or the Seneca. Anyways, the new 172 is pretty nice. Unlike the other two, this one has a two axis auto pilot.

I went out to fly it this morning, having only seen it from a distance before. Did my pre-flight, jumped in and was good to go. I took it out to a couple different airports for some soft field landings, and then to a bigger one, Birchwood (BCV) to do a few on a bigger paved runway. Birchwood is just north of the Anchorage area and it can be a very congested airspace.

The auto pilot on this plane trims the pitch for you as you lower the flaps. Pretty slick, or so I thought. I've never flown a plane that does this for you. I was doing my fourth touch and go, raised the flaps, pushed the power in and was quickly back in the air. However, the auto-pilot pitch trim alarm was screaming in my headset and the pitch trim was trimming uncontrollably into a nose down attitude. I had to physically hold the trim wheel to get it to stop. The auto pilot disconnect was having no effect on it. By the time I realized what was happening, it had already trimmed into a hard nose down trim and I was having to hold a LOT of back pressure to keep her climbing and having to hold the trim wheel at the same time to keep it from going nose down any further. It was now that I noticed that the circuit breaker labels were all about worn off. To reach a circuit breaker, I had to either let go of the yoke or the trim wheel. Letting go of the yoke would have put me right into a dive. Fortunately, I was able to pull the correct breaker after a couple of minutes and the alarm went away and it quit trimming. I was able to trim manually after that and the rest of the flight directly back home was uneventful.

I still have no idea what was wrong with it. Obviously, a malfunction or short somewhere in the auto pilot. Part of my problem, was that I didn't familiarize myself with everything in the cockpit, especially the circuit breakers. I could have got the situation under control a lot sooner if I had known right where it was. I was wondering how a student or a new pilot would have handled the same situation.
 
Sitting here on my couch my thought is that it would have been easier to hit the master, and then once safely in the air, work out which breaker was for the auto pilot. (of course it is always easy to second guess when not in the heat of the moment).

Good job dealing with the situation!
 
I wonder if you're supposed to disable the A/P during takeoff and landing....most planes I fly have included that as a checklist item.

Good job fighting it though. If it ever happens again, it might be beneficial to do like Tony suggested and just kill the master. You don't need the radios to fly!
 
Was going to say the same. Probably not supposed to be on during landings or takeoffs...
 
Apparently, this thing is supposed to be on. It's supposed to trim for you when you put the flaps down. Personally, in 15 years of flying, I haven't found it to be a problem to trim myself when landing. This is the first plane I've flown that is like this and there is absolutely nothing in the checklist about it.

I thought about killing the master and had it come down to it, I would have. The air traffic around Anchorage is very heavy and there were two other aircraft in the pattern with me, not to mention a bunch of others that were passing through the area. Anchorage has one of the most intense air spaces in the country. At the airport I was at, there is a restricted area to the south and west, and mountains to the east. Everybody flies through this two or three mile wide corridor to get in and out of Anchorage. When I started having this problem, I started turning back towards Anchorage. I didn't want to kill my radios as I was at least able to hold on to everything and keep it in the air.
 
Also, the 182 I fly most of the time, has an auto pilot as well. It's not like this one though. There is a switch to turn it on and off. On this 172, there is no switch. There is a disconnect switch on the yoke, but that's it. It didn't work at all today. Maybe I'm missing it. I went back out to the plane after I got back and searched for a switch. Could not find one anywhere. I won't be flying this one again until I am a lot more familiar with how the auto pilot works.
 
I've had a less dramatic but still eyebrow raising 172 autopilot moment. While in level flight, with plenty of altitude, the thing just error beeped and shut itself off. I'd imagine anyone who's flown a 172 has seen that happen at least a few times. What set this apart was that it didn't relinquish the controls. The trim and yoke were essentially locked into place.

Pulling the circuit breaker did the trick. Also explained why the breaker was pulled when I got into the plane. :rolleyes2:
 
Following a night flight with a skitterish first time pax and a wonky A/P is when I learned to remember where the CBs are for each system/instrument.
 
Sorry guys, I just don't know enough about it. I'll find out tomorrow what model of auto pilot it is. Again, it's kind of the point of this thread. I'm not familiar with it at all. I just assumed it was another 172, jumped in and off I went. Also, the auto-pilot itself wasn't engaged. I still had control of the yoke. This one, also adjusts the elevator trim for you when you lower the flaps. That's where the problem was. Tomorrow, the club manager and the maintenance guys will be in. I'll find out more.
 
I don't know anything about this installation, but what you had was a runaway trim - at a very inopportune time. Procedure would be to hold the pitch in a proper position until you could stop the trim motor somehow. You did this. It's a shame the cb / disconnect switch isn't labeled clearly. It should be, before further flight. Obviously the system must be fixed.

You DID write this up, right? And inform the club?
 
rotorhead1026 said:
I don't know anything about this installation, but what you had was a runaway trim - at a very inopportune time. Procedure would be to hold the pitch in a proper position until you could stop the trim motor somehow. You did this. It's a shame the cb / disconnect switch isn't labeled clearly. It should be, before further flight. Obviously the system must be fixed.

You DID write this up, right? And inform the club?
Click to expand...

Yes. The club I fly out of is owned by the Air Force. You have to dispatch the plane on a computer. When you return it, you have to option to write things up and ground the airplane if need be. I did that and also wrote it up in the aircraft forms. I informed the maintenance guy that was there doing a 100 hour on another plane. Anybody else who tried to check the plane out, wouldn't be able to. I was planning on calling tomorrow and suggest that they label the circuit breakers better. If I owned my own plane, and I plan to soon, I would make sure everything was labeled. I am a flight engineer on the E-3 AWACS. I have hundreds of circuit breakers and the labels are all worn off on them too. It sucks when I have to find one to pull. One of the situations we train for in the E-3, is a run away trim. The whole stab trims on the E-3. In my opinion, it's one of the most dangerous situations that you can have in the E-3. Not quite as serious in a Cessna, but still not good. I'm going to check into this further tomorrow. I'll ask some of the questions you guys have asked.
 
Circuit Breaker Caps.... Makes it easier to find what you need.

These color coded caps can easily be installed and removed from Klixon and similar type circuit breakers. Colored caps are used to "flag" designated circuit breakers for flight check and other purposes. In addition, they greatly improve grip. Won't shake loose and rattle like others can.
 

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While you're investigating, find out if there's a disconnect on the other yoke. Nice to know if there's a backup other than pulling the CB.
 
I don't see why you wouldn't disconnect during pre-landing checklist. The AP is wonderful for pitch trim, but I fail to see how it can help you trim for airspeed.
 
Here is from a 182 POH


"3. The autopilot must be off during all takeoff and landings.
4. Autopilot maximum engagement speed - 165 KIAS.
Autopilot minimum engagement speed - 70 KIAS.
Electric Trim maximum operating speed - 175 KIAS.
5. Maximum fuel imbalance with autopilot engaged - 90 pounds.
6. The autopilot must be disengaged below 200 feet AGL during
approach operations and below 800 feet AGL during all other
operations."

I suspect that the OP's autopilot is similar and he did not familiarize himself with proper operation.
 
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Well, I called the club manager today and he told me that there was definitely some sort of issue with the auto pilot. They haven't been able to figure it out yet. In the meantime, they have pulled and banded the auto pilot circuit breaker to get the plane flying again. They are working some other maintenance issues on a couple other planes. He didn't know for sure what type of auto pilot it has, either. Any way I can tell by looking?

So, the elevator trim was trimming for me when I was putting the flaps down and back up. All other aspects of the auto pilot were off. I never engaged the auto pilot at all. The 182 I fly most of the time, has an auto pilot. I never use it as I prefer to hand fly. Also, in this 172, there is only one auto pilot disconnect button and it's on the pilots side yoke. There are buttons for trimming the elevator on the yoke as well.
 
Matt, when I flew the P3 (predated the EP3) we had a string aoroung the trim breaker.....

As a result I fly ALL of my instrument FAF inbounds BY HAND. It's also good for recurrency. And I don't have to troubleshoot the thing, 400 feet away from breaking out and 700 feet above the obstacles......

"Son?"
"YesSIR?"
"Remember, everything in here is Lowest Bidder".

You need to go beyond "what type of AP it is", and to understand that particular Autopilots' mandatory preflight checkout. That sequence is in the real POH. A Cessna can just Barely Kill you compared to a 1250 x4 HP job powered by T-54s. :(

Thanks for posting. Sharing probably taught someone else!
 
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KC10Chief said:
Well, I called the club manager today and he told me that there was definitely some sort of issue with the auto pilot. They haven't been able to figure it out yet. In the meantime, they have pulled and banded the auto pilot circuit breaker to get the plane flying again. They are working some other maintenance issues on a couple other planes. He didn't know for sure what type of auto pilot it has, either. Any way I can tell by looking?

So, the elevator trim was trimming for me when I was putting the flaps down and back up. All other aspects of the auto pilot were off. I never engaged the auto pilot at all. The 182 I fly most of the time, has an auto pilot. I never use it as I prefer to hand fly. Also, in this 172, there is only one auto pilot disconnect button and it's on the pilots side yoke. There are buttons for trimming the elevator on the yoke as well.
Click to expand...

Any chance you were accidentally holding a nose down trim button?
 
KC10Chief said:
He didn't know for sure what type of auto pilot it has, either. Any way I can tell by looking?
Click to expand...

Well... Process of elimination:

1) Is this a new 172 with a G1000 glass cockpit?
A) If so, do you activate it using buttons on the G1000 bezel? If so, it's a GFC700.
B) If it has a G1000 but the autopilot is in a separate box with an amber screen, it's a KAP140.

2) If it's a 1997 or later model without the G1000, it's almost certainly a KAP140 unless it was added aftermarket. (Again: KAP140 uses an amber display.)

3) If it's an older (pre-1985 or so) model... Well jeez, could be anything.
 
bbchien said:
Matt, when I flew the P3 (predated the EP3) we had a string aoroung the trim breaker.....

As a result I fly ALL of my instrument FAF inbounds BY HAND. It's also good for recurrency. And I don't have to troubleshoot the thing, 400 feet away from breaking out and 700 feet above the obstacles......

"Son?"
"YesSIR?"
"Remember, everything in here is Lowest Bidder".

You need to go beyond "what type of AP it is", and to understand that particular Autopilots' mandatory preflight checkout. That sequence is in the real POH. A Cessna can just Barely Kill you compared to a 1250 x4 HP job powered by T-54s. :(

Thanks for posting. Sharing probably taught someone else!
Click to expand...

I'm familiar with the P3. I've never actually been on one. A buddy of mine is a comm guy on the P3 at Whidbey Island. I am a flight engineer on the E-3 AWACS in the Air Force. It's an old plane, but it has all the kinks worked out of it! I have to go to Oklahoma City once or twice a year to fly the simulator down there. Of all the emergency situations we practice from fires, to losing one or two engines, total hydraulic loss, etc., one of the most dangerous situations I think you could have, is a runaway trim. If you don't catch it and stop it soon enough in the E-3, you're in serious trouble. The chances of it happening are extremely remote. It can still be trimmed by hand with a LOT of work by me, it can be shut off with the stab trim switches, and there is a stab brake. A lot of things would have to fail in order for it to get out of hand. I also know exactly where those breakers are. Of course, a Cessna isn't as serious. Even if I had allowed it to trim to a full nose down trim, I could have still flown the plane with enough back pressure on the yoke.

ajstoner21 said:
Any chance you were accidentally holding a nose down trim button?
Click to expand...

No. The auto pilot cutout is right there as well. I tried to use the trim buttons in the opposite direction as well. No effect. I spoke to the club manager and he said that there was definitely some sort of issue with it. They just haven't had time to get to the bottom of it. In the meantime, the auto pilot is completely disabled.

flyingcheesehead said:
Well... Process of elimination:

1) Is this a new 172 with a G1000 glass cockpit?
A) If so, do you activate it using buttons on the G1000 bezel? If so, it's a GFC700.
B) If it has a G1000 but the autopilot is in a separate box with an amber screen, it's a KAP140.

2) If it's a 1997 or later model without the G1000, it's almost certainly a KAP140 unless it was added aftermarket. (Again: KAP140 uses an amber display.)

3) If it's an older (pre-1985 or so) model... Well jeez, could be anything.
Click to expand...

I wouldn't know what to do with a G1000 cockpit! HA! This is a standard, analog gauge cockpit. However, when I spoke to the club manager, he did mention that he thought the auto pilot was a 140. That means nothing to me as I'm not real familiar with the different types. He just said that he thought it was a 140. Apparently, at our next safety meeting (held monthly with mandatory attendance), they are going to discuss it further as nobody is really familiar with it.
 
KC10Chief said:
I wouldn't know what to do with a G1000 cockpit! HA! This is a standard, analog gauge cockpit. However, when I spoke to the club manager, he did mention that he thought the auto pilot was a 140. That means nothing to me as I'm not real familiar with the different types. He just said that he thought it was a 140. Apparently, at our next safety meeting (held monthly with mandatory attendance), they are going to discuss it further as nobody is really familiar with it.
Click to expand...

Do you know what year the plane is? If not, what's the tail #? If it's analog gauges and 1997 or newer, it's almost certainly a 140.

Does it look like this?

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Kent's next post will say, "See that 'ARM' button in the upper right corner...?"

;)

The suspense is killing me! :D
 
I suppose now is not the time to interject that the E-2 Hawkeye (my old home office) performed with a crew of 5, what the E-3 Sentry does with a crew of 21? (except land on a carrier, that is... maybe that's a plus to the Sentry?)

:D

oops, I just did ... :rofl:
 
It's good to know I'm not the only one that's been nearly killed by a malfunctioning autopilot. I was with a friend on a casual lunchtime flight in a rented 172 one day when the AP decided we needed to make a right turn... as soon as we left the runway.

Now, mind you, this was before I had even my current grand total of 1.8 hours dual received time in my log book, so I can't give you all the details with any degree of accuracy. But I don't want to repeat that, ever.

I'm not going to repeat the whole thing here, but I did write it up in a blog post -- names changed to protect the semi-innocent, though in hindsight complacent and over-confident PIC.

My blog post about it...
 
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