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Michael Moe

Trim cutout on Control Stand

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Hi,

 

I am reading the FCOM2 9.10.6 section about the Trim cut out for the trim switches but when would you do such a thing like cutting them off (from the yoke i guess ? ) and the Autopilot ?

 

Just trying to imagin a scenario to learn from with no luck (lack of knowledge)

 

Also it seems like the OVERRIDE on the AFT panel goes the otherway around and restores you mistake ? :-)

 

Maybe i should search the QRH also ...

 

 

Thanks

 

Michael Moe

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Maybe i should search the QRH also ...

 

Sounds like a good place to start  :wink:

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Off the top of my head, maybe trim runaway?  Dump the electrics and use manual trim.

 

Let's see what QRH has: pg 9.2 Runaway Stabilizer step one is A/P off and if that doesn't work then trim cut-off... hey, called it.  This one you'd want to do from memory, right? Is that what the Quick Action table of contents is?

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This one you'd want to do from memory, right? Is that what the Quick Action table of contents is?

 

The quick action index permit the crew to immediately locate checklists that require immediate attention. Basically, instead of flipping through 300 pages of checklists for the SMOKE, FIRE OR FUMES checklist, they can go to that index and see that it is on page X.X.

 

 

 


Off the top of my head, maybe trim runaway? 

 

There are a few checklists in the QRH that may be applicable to using the STAB CUTOUT switches.

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Hi Michael
 
The STAB TRIM CUTOUT switches on the control stand, as you quite rightly said, disconnect both the autopilot and the electrically operated stab trim switches on the control column.
 
 

Just trying to imagin a scenario to learn from with no luck (lack of knowledge)

 
 
Two likely scenarios with which the QRH would action you to move these switches would be STABILIZER TRIM INOPERATIVE or as someone has already mentioned, you're experiencing a RUNAWAY STABILISER.

 

Also it seems like the OVERRIDE on the AFT panel goes the otherway around and restores you mistake ? :-)

 

 

The STAB TRIM OVERRIDE SWITCH bypasses the STAB TRIM CUTOUT switches if they both fail and allows you to operate the electric trim regardless of the position of the control column.

 

In a nutshell any problems with the stabiliser action the appropriate checklist and you'll in most situations end up having to trim manually. In the aircraft you would then extend the manual trim wheel handles and treat it like a big Cessna.

 

In the real aircraft before extending the manual trim wheels you want to ensure that both stabilizer trim cutout switches are in CUTOUT, There is nothing more painful than that trim wheel spinning inadvertently and smashing you in the knee and/or shin!

 

Hope I helped answer your question

 

Sam Breese.

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Hi Michael

 

The STAB TRIM CUTOUT switches on the control stand, as you quite rightly said, disconnect both the autopilot and the electrically operated stab trim switches on the control column.

 

 

 

 

Two likely scenarios with which the QRH would action you to move these switches would be STABILIZER TRIM INOPERATIVE or as someone has already mentioned, you're experiencing a RUNAWAY STABILISER.

 

 

 

The STAB TRIM OVERRIDE SWITCH bypasses the STAB TRIM CUTOUT switches if they both fail and allows you to operate the electric trim regardless of the position of the control column.

 

In a nutshell any problems with the stabiliser action the appropriate checklist and you'll in most situations end up having to trim manually. In the aircraft you would then extend the manual trim wheel handles and treat it like a big Cessna.

 

In the real aircraft before extending the manual trim wheels you want to ensure that both stabilizer trim cutout switches are in CUTOUT, There is nothing more painful than that trim wheel spinning inadvertently and smashing you in the knee and/or shin!

 

Hope I helped answer your question

 

Sam Breese.

 

 

Thanks for creating events/ scenarios to backup the FCOM2/QRH and my learning curve

 

 

One more Q from your response . "bypasses the STAB TRIM CUTOUT switches if they both fail "

 

Do you meen if they fail to cutout or ? I meen if they fail to cutout i would still have trim on my control Coloumn so why an "OVERRIDE" option ?

 

 

Thanks again

Michael Moe

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The STAB TRIM OVERRIDE SWITCH bypasses the STAB TRIM CUTOUT switches if they both fail and allows you to operate the electric trim regardless of the position of the control column

 

 

 


Do you meen if they fail to cutout or ? I meen if they fail to cutout i would still have trim on my control Coloumn so why an "OVERRIDE" option ?

 

I'll have to dig through a MX manual for schematics, but here's what I think happens:

 

The Override switch doesn't do anything to the Cutout switches on the control quandrant. If they're off, there's no power to the trim motors.

 

There are switches in the base of the control column that you don't see. If you're pushing against what the auto-trim is trying to do, it'll stop the trim motors. Good if you are trying to push nose down and the plane is trying to trim nose up. If those fail and stop the trim motors from working, then you have no trim unless you use the OVERRIDE switch.

 

The override switch restores power if the cutout switches at the base of the control column malfunction and erroneously cut out trim.

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I'll have to dig through a MX manual for schematics, but here's what I think happens:

 

The Override switch doesn't do anything to the Cutout switches on the control quandrant. If they're off, there's no power to the trim motors.

 

There are switches in the base of the control column that you don't see. If you're pushing against what the auto-trim is trying to do, it'll stop the trim motors. Good if you are trying to push nose down and the plane is trying to trim nose up. If those fail and stop the trim motors from working, then you have no trim unless you use the OVERRIDE switch.

 

The override switch restores power if the cutout switches at the base of the control column malfunction and erroneously cut out trim.

 

 

Thanks

 

Appreciate your time and explanation  B)  Technical stuff but really nice to know this . All these double switches/systems . If on system fail we need another system to work around. 

 

Its a priority . No backups for landing lights  :lol:

 

Thanks

Michael Moe

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Its a priority . No backups for landing lights

 

I was taught to land with a failed landing light in basic private pilot training.  Not really an issue.

Now, no runway edge lights...., that is an issue.

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