The Use Of the Trim Wheel
Joined: Jul 2001
Posts: 486
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From: Belgium
When flying with a pilot new to the Bonanza, I ask them what they would do if they would have an electric trim runaway and how they would stop the runaway.
Depending on the aircraft there are six or seven ways to stop the runaway, I am sure they will remember one or two when it happens.
( A local PA32 crashed due to an electric trim runaway when I was a young pilot flying a similar PA32 many years ago. As a result the electric trim switches were modified to dual action)
Depending on the aircraft there are six or seven ways to stop the runaway, I am sure they will remember one or two when it happens.
( A local PA32 crashed due to an electric trim runaway when I was a young pilot flying a similar PA32 many years ago. As a result the electric trim switches were modified to dual action)
Joined: Dec 2011
Posts: 2,460
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The autopilot master switch should disconnect power to all servos.
The red autopilot disconnect button should do likewise - but only while it is being held down.
The avionics master switch...
The main electrics switch too
The red autopilot disconnect button should do likewise - but only while it is being held down.
The avionics master switch...
The main electrics switch too
Joined: May 2009
Posts: 348
Likes: 1
From: Hotels
The autopilot master switch should disconnect power to all servos.
The red autopilot disconnect button should do likewise - but only while it is being held down.
The avionics master switch...
The main electrics switch too
The red autopilot disconnect button should do likewise - but only while it is being held down.
The avionics master switch...
The main electrics switch too
FWIW, the aircraft type I fly for work has no trim wheels. It has 3 independent electric trim systems however, which move the variable incidence tail plane.
Joined: Jan 2004
Posts: 5,655
Likes: 500
From: Canada
Other ways to shut down the autopilot is to pull the autopilot circuit breaker or the electric trim circuit breaker, again for 2 axis systems
Joined: Apr 2010
Posts: 1,319
Likes: 100
From: IRS NAV ONLY
Originally Posted by Big Pistons Forever
On every auto pilot I have ever flown pushing the red autopilot disconnect button will immediately disengage the autopilot with no need to hold it down. Also moving the control wheel mounted electric pitch trim will also disengage the autopilot for 2 axis systems
Joined: Dec 2011
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On every auto pilot I have ever flown pushing the red autopilot disconnect button will immediately disengage the autopilot with no need to hold it down
In general terms (autopilots vary) the red button has several poles on it.
One is used to tell the autopilot software that you pressed it. If the autopilot software is running normally, and scanning that switch contact, it will then disconnect.
The other pole(s) are normally-closed contacts through which the power to the servo clutches passes. Pressing the switch immediately (barring the case of a defective switch) removes the power from all servo clutches which immediately (barring the case of stuck servo clutch(es) - if you get that then you are having a really bad day) removes the autopilot system from interfering with the controls. But this works only while you are pressing the button, obviously. In the unlikely case of a crashed autopilot and a non-functioning autopilot master switch (**) holding down the red button should enable to you regain control of the aircraft and fly it.
(**) The autopilot master switch also should have separate poles for the servo clutches, so disconnecting that should also "kill" the servos.
The above is based on the KFC225 but I think King autopilots are all similar in these respects.
holding the autopilot disconnect button (at least on KAP140) also disables the manual electric trim
Joined: Mar 2011
Posts: 19
Likes: 0
From: Edinburgh
I have another trim question. I am flying C-172s at our club. The one I fly most is a 1979 well used version that requires significant trim input for every change in attitude. Recently we have had a fairly new C-172 less than 10 yeasr old. It seems to require virtually no trim input, for instance set trim for climb, level out and throttle back and no trim change needed to maintain attitude with no force on the yoke. What trim adjustment is applied is minimal, one or two notches on the wheel.
Why are these two aircraft so different? is it likely to be to do with wear and tear on the older aircraft or is there a rigging problem with it?
Caber
Why are these two aircraft so different? is it likely to be to do with wear and tear on the older aircraft or is there a rigging problem with it?
Caber
Fleet Manager
Joined: Aug 2006
Aviation Qualifications: CPL
Posts: 7,082
Likes: 2,938
From: Ontario, Canada
If you're comparing a 1979 C172 to a 2001 C172, they should be very similar in trimming, as they are very similar airframes. There are possible rigging differences between any two 172's, particularly the wing angle of incidence. There is not, however, enough adjustment available in the wing cams, to change the flying characteristics of the plane that much. Other things like control system friction/free play, the direction you trimmed from, weight, and C of G may also have an affect, and each of these effects can be summed for a large total effect.
To get an accurate comparison between the two planes trimming characteristics, you should fly them under as similar conditions of loading, speeds, flap settings as so forth as possible. You'll probably find that the aircraft are closer to each other than they first seemed.
To get an accurate comparison between the two planes trimming characteristics, you should fly them under as similar conditions of loading, speeds, flap settings as so forth as possible. You'll probably find that the aircraft are closer to each other than they first seemed.
