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Elevator take off trim position


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Corporate pilot does my training with me. Right before rolling on to the runway we do a FATS CHECK:

Flaps to takeoff setting

Altimeter set and showing field elevation

Trim to take off settings

Speeds posted (abort, rotate, climb,)

 

I once started takeoff roll with down trim instead of up trim and when I tried to rotate she would not come off the ground. Immediately aborted. Very scary, stopped maybe 40 ft from the end of the runway. 

He also calls them the killer items. 

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Had the same problem until I redid the W&B.  Plane is 100lbs heavier than the original Factory weight.  The T/O trim position (markings) are for a balanced plane at 1570 LBS but mine is nose heavy due to all the electronics over the ages.  I use a slight nose up trim setting on Takeoff which I have worked out over the years.   Remember most of the weight added or subtracted in our Mooney's is in front of the pilot which shifts the CG forward.  I also fly SOLO with 80 Lbs in the aft Baggage to keep the CG in the proper range.  Flying an "old" C model.

 

Duck

 

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On 3/7/2018 at 9:16 PM, Immelman said:

Look at it this way... should you be trimming immediately after takeoff? 100' AGL? 200' AGL? (Basically from liftoff until the wheels are stowed and you're climbing away, before any flap changes).

My answer to that is 'NO'. Trim should be set such that you get the gear stowed and the airplane pitches for your desired initial climb speed with no pilot intervention on the elevator control. What ever trim setting that is... that is what you use, making estimated adjustments for CG changes due to pax/cargo.

I found the spot in my airplane that corresponds to this and set it accordingly before takeoff. Trial and error. It is slightly off from the takeoff 'spot' on the trim indicator.

That’s what you use as a guide for what you want your takeoff trim setting to be... and it’s completely reasonable.

 

id be interested to see what the Mooney test pilot’s guidance is regarding take off trim position (what mooney’s Intent is/was regarding takeoff trim).  I’ve flown some airplanes that have a hands off takeoff trim setting that achieves optimal (or thereabouts) rotation automatically at nosewheel liftoff speed, but the second you leave ground effect, trim is required to maintain the tech ordered climb attitude. 

Ive never really put too much thought into the “why’s” in regards to trim setting for takeoff, but in this case it would be a fun little piece of trivia to know.

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  • 2 weeks later...

The J trim indicator and its related cable connection to the trim wheel assembly is not as repeatable as you might expect.  I 

like to have a tighter reference on the trim indicator than the grey "Take Off" zone graphically displayed.  Thus I have set and flown the airplane using the upper edge of the "Take Off" grey zone as my initial reference and got to know how the plane flies at that set point.  

I need to go back and reference this position with a travel board just for information, but the point here is that setting the trim with a defined line on the indicator seems to provide a much more predictable starting point.  What that means relative to a travel board measurement can be determined, but you will only know when cross referencing with a known travel board (as they too show variations from one to another).  

John Breda

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Cliffy, Great advice, older Boeing’s did not have takeoff warning systems until several accidents occurred then they were all retrofitted. On all Boeing aircraft if the trim is not in the green band on the trim indicator the warning will sound when the thrust levers are advanced for takeoff.

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At every airline I was at if the T/O warning sounded at throttles up an abort was immediate and mandatory. Many times it was just that the speed boards were not selected all the way down but still an abort and taxi back. No investigating the problem while rolling down the runway. And yes, the early years didn't have all the warnings in use today. 

IIRC there was a Stratoliner out of La Garbage that went into the bay with the cowl flaps extended fully blanking out the wing airflow and increased drag, on T/O. No warnings back then either.  

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On 3/7/2018 at 8:51 PM, Gary0747 said:

Thanks that was exactly what I was looking for.  I have been trying to figure out why I am getting a shimmy only at rotation speeds on take off. 

 

Try tapping the brakes after takeoff before the shimmy and see if this prevents it. As a cfi I fly a lot of planes and see this commonly. 

-Robert

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On 3/9/2018 at 7:47 AM, M016576 said:

id be interested to see what the Mooney test pilot’s guidance is regarding take off trim position (what mooney’s Intent is/was regarding takeoff trim).  I’ve flown some airplanes that have a hands off takeoff trim setting that achieves optimal (or thereabouts) rotation automatically at nosewheel liftoff speed, but the second you leave ground effect, trim is required to maintain the tech ordered climb attitude. 

 

Based on CG (rear seats full or not) usually. In a fancier world the trim would be set by CG for takeoff but a single position is good enough for govt work  

-Robert

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