The Mooney Pull & Take Off Trim ???

[DCarlton]

In another recent thread, there was a long discussion about "The Mooney Pull" when taking off.  I commented that I rarely change my trim setting from landing to takeoff.  If I trim for landing (typically with 3/4 flaps), experience suggests its set perfectly for takeoff.  Some folks seemed to think that shouldn't be the case.  Sooooo... today when taking off, I set my  trim indicator to the TAKE OFF position.  I was surprised by the result (not in a good way).  The plane pitched up very quickly when it reached flying speed and I found myself pressing against the yoke trimming down fast while managing airspeed, gear and flap retraction.  There was no Mooney Pull required whatsoever.  My plan is to go back to what seems to work very well (see attached pic).  Taking off with the same setting I use for landing works (plus I'm used to looking down and seeing the indicator below the take off position).  Wonder if my trim system or indicator might need adjustment or perhaps every plane is just a little different.  Wondering if other pilots have to move it much between landing and takeoff on the mid body F or J airplanes.  

[Shadrach]

I wonder if your trim indicator is adjusted differently than mine. The indication in the image is nose low for a typical landing in my plane.

[PT20J]

Takeoff trim setting should result in the trim assist bungees holding the elevators in trail with the horizontal stabilizer. If you adjust the trim for that condition, where does your trim indicator point?

[DCarlton]

8 minutes ago, PT20J said:

Takeoff trim setting should result in the trim assist bungees holding the elevators in trail with the horizontal stabilizer. If you adjust the trim for that condition, where does your trim indicator point?

If you mean the elevators and horizontal stabilizer are in the same flat plane, that’s close to the setting you see in the photo.  I’ll take a pic of the elevators like it’s trimmed now and a pic with it trimmed to the TAKE OFF position.  Sounds like my indicator may need adjustment.  TBD 

[Utah20Gflyer]

35 minutes ago, Shadrach said:

I wonder if your trim indicator is adjusted differently than mine. The indication in the image is nose low for a typical landing in my plane.

I was thinking the same thing.   When I have the plane trimmed for landing it's more nose up than takeoff ( above the takeoff mark).

Your plane seems to be the opposite, meaning that if the relationship between the settings is the same you would be extremely nose up at the takeoff trim setting.   I suspect something is out of adjustment. 

[Niko182]

Does the mooney pull change with year models? With my trim set at the top of the takeoff indicator, it rotates very smooth.

[DCarlton]

7 minutes ago, Niko182 said:

Does the mooney pull change with year models? With my trim set at the top of the takeoff indicator, it rotates very smooth.

My indicator is likely out of adjustment.  I’ve flown it this way for so many years it’s not an issue for me.  If needed though, I’ll get it adjusted in case someone else flies the plane.  

[tony]

10 hours ago, DCarlton said:

In another recent thread, there was a long discussion about "The Mooney Pull" when taking off.  I commented that I rarely change my trim setting from landing to takeoff.  If I trim for landing (typically with 3/4 flaps), experience suggests its set perfectly for takeoff.  Some folks seemed to think that shouldn't be the case.  Sooooo... today when taking off, I set my  trim indicator to the TAKE OFF position.  I was surprised by the result (not in a good way).  The plane pitched up very quickly when it reached flying speed and I found myself pressing against the yoke trimming down fast while managing airspeed, gear and flap retraction.  There was no Mooney Pull required whatsoever.  My plan is to go back to what seems to work very well (see attached pic).  Taking off with the same setting I use for landing works (plus I'm used to looking down and seeing the indicator below the take off position).  Wonder if my trim system or indicator might need adjustment or perhaps every plane is just a little different.  Wondering if other pilots have to move it much between landing and takeoff on the mid body F or J airplanes.  

My experiences are exactly as you describe.  I put a pencil mark where I want it to be for takeoff based on how the aircraft responds and feels and I find that I set my trim the same for take off as I do landing.  I have an F model as well.  I have never flown a c model or a long body but I would guess the airframe reacts differently.   

Edited November 12, 2022 by tony

[Pinecone]

If I tried to take off with the trim set for landing, it would be UGLY.  I am nearly full nose up trim when landing.

For my normal load (2 people, 1/2 - full tanks) I set the trim to be be at the nose up limit of the TO setting range (252).

[Shadrach]

6 hours ago, Niko182 said:

Does the mooney pull change with year models? With my trim set at the top of the takeoff indicator, it rotates very smooth.

With moderate back pressure, my F breaks ground cleanly with take-off trim and take-off flaps. Trim will need to be adjusted after the plane is reconfigured for climb.

[Shadrach]

14 minutes ago, tony said:

My experiences are exactly as you describe.  I put a pencil mark where I want it to be for takeoff based on how the aircraft responds and feels and I find that I set my trim the same for take off as I do landing.  I have an F model as well.  I have never flown a c model but I would guess the airframe reacts differently.   

How do you configure for landing? 
Generally speaking, the F model is not a CG sensitive aircraft. Trim position will vary but not a huge amount. On final I’m trimmed nose high. The lighter I am the closer I get to the nose up stop.  The factory performed a great deal of flight testing from which they derived flap and trim “take off” positions.  It’s interesting to me that some pilots find that their personal experiences and preferences are so different from the majority who use the settings derived from flight testing.  I wonder if it is maintenance or technique related.

 

[skykrawler]

I think a lot of these airplanes have maladjusted trim indicator systems.  In order to correct it the trim shaft must be disconnected somewhere and the indicator set to the correct position.  PT20J had a good suggestion for when maintenance was being performed to run the trim to a stop and mark the stab position - then make sure it goes back together just like that.     The difference in the OPs picture could be one full turn of the jackscrew.    There is a procedure in the maint manual that calls for leveling the airplane and using  board on the stabilizer.    I found raising the airplane on jacks high enough to make the avionics bay opening level to be uncomfortably high.

The thing to worry about is if the indicator hits the nose down stop, it prevents further nose down trim.  If you've loaded an aft CG you can run out of trim at a high airspeed.  This is sort of self correcting - but probably uncomfortable.

[tony]

18 minutes ago, Shadrach said:

How do you configure for landing? 
Generally speaking, the F model is not a CG sensitive aircraft. Trim position will vary but not a huge amount. On final I’m trimmed nose high. The lighter I am the closer I get to the nose up stop.  The factory performed a great deal of flight testing from which they derived flap and trim “take off” positions.  It’s interesting to me that some pilots find that their personal experiences and preferences are so different from the majority who use the settings derived from flight testing.  I wonder if it is maintenance or technique related.

 

Well that's true to Ross.  I hadn't thought of that.  I was just sharing my experiences with the author.  I usually fly alone, not a lot of stuff in the airplane but me.  I put in two pumps of flaps for both take off and landing.  My landing config is the same as my take off config.  It simplifies a go around, just my personal preference.  

[Niko182]

2 hours ago, Pinecone said:

If I tried to take off with the trim set for landing, it would be UGLY.  I am nearly full nose up trim when landing.

For my normal load (2 people, 1/2 - full tanks) I set the trim to be be at the nose up limit of the TO setting range (252).

This is the same for the long body too, or at least my eagle. I took off once with the trim set for landing, which is usually full nose up trim (accidently) and it was an exciting takeoff to say the least.

[Guest]

2 hours ago, skykrawler said:

I think a lot of these airplanes have maladjusted trim indicator systems.  In order to correct it the trim shaft must be disconnected somewhere and the indicator set to the correct position.  PT20J had a good suggestion for when maintenance was being performed to run the trim to a stop and mark the stab position - then make sure it goes back together just like that.     The difference in the OPs picture could be one full turn of the jackscrew.    There is a procedure in the maint manual that calls for leveling the airplane and using  board on the stabilizer.    I found raising the airplane on jacks high enough to make the avionics bay opening level to be uncomfortably high.

The thing to worry about is if the indicator hits the nose down stop, it prevents further nose down trim.  If you've loaded an aft CG you can run out of trim at a high airspeed.  This is sort of self correcting - but probably uncomfortable.

Disconnecting the trim shaft is not required to adjust the trim indicator.  Take the airplane to someone with the correct tools and knowledge.

[Stetson20]

Related question- should my horizontal elevator be level during preflight? Another Mooney owner on my field noticed that my elevator was sitting in the full nose up position when the plane was at rest. He showed me his, and the elevator was spring loaded to neutral position. He has a J, mine's a K. I didn't even notice at the MAPA PPP looking at the other planes.

[Niko182]

I think the later models hang down. I went flying once in a J and his elevator was level. Mine has never been. Mine always hangs down. 

[DCarlton]

1 hour ago, M20Doc said:

Disconnecting the trim shaft is not required to adjust the trim indicator.  Take the airplane to someone with the correct tools and knowledge.

That's what I was guessing.  Seems like I remember a clamp holding the outer sheath to the cable at the back of the trim indicator.  Wondering if the cable slipped in the clamp.  Something simple like that.  Will find somebody that knows before anything is done.  

[PeteMc]

1 hour ago, Stetson20 said:

should my horizontal elevator be level during preflight?

No, what you show in the picture is correct.

The Rocket is a modified K, not a J.   The K has weights added for better control and trim up at higher altitudes. 

 

Edited November 12, 2022 by PeteMc

[DCarlton]

4 hours ago, Shadrach said:

How do you configure for landing? 
Generally speaking, the F model is not a CG sensitive aircraft. Trim position will vary but not a huge amount. On final I’m trimmed nose high. The lighter I am the closer I get to the nose up stop.  The factory performed a great deal of flight testing from which they derived flap and trim “take off” positions.  It’s interesting to me that some pilots find that their personal experiences and preferences are so different from the majority who use the settings derived from flight testing.  I wonder if it is maintenance or technique related.

 

I don't think it's technique in this case.  I think the trim indicator is out of adjustment and we're flying the airplane correctly.  With takeoff flaps set, and when operating near sea level, with a typical load, I don't think there's much that can vary in this case.  If you read my original post, I tried the TAKE OFF position yesterday to see if I had a technique issue and the plane did not perform like you would expect at all.  It pitched up way too rapidly without any force on the yoke.  It required a significant push to stabilize.  Based on everyones comments though, it looks like the planes with the longer noses do require more adjustment than the F between landing and takeoff.   

[PT20J]

2 hours ago, Stetson20 said:

Related question- should my horizontal elevator be level during preflight? Another Mooney owner on my field noticed that my elevator was sitting in the full nose up position when the plane was at rest. He showed me his, and the elevator was spring loaded to neutral position. He has a J, mine's a K. I didn't even notice at the MAPA PPP looking at the other planes.

The J and earlier models have trim assist bungees and sit with the elevator level. Starting with the K and after, the trim has a variable down spring and the elevator controls include a bob weight so the elevator hangs down on the ground. 

[Guest]

4 hours ago, DCarlton said:

I don't think it's technique in this case.  I think the trim indicator is out of adjustment and we're flying the airplane correctly.  With takeoff flaps set, and when operating near sea level, with a typical load, I don't think there's much that can vary in this case.  If you read my original post, I tried the TAKE OFF position yesterday to see if I had a technique issue and the plane did not perform like you would expect at all.  It pitched up way too rapidly without any force on the yoke.  It required a significant push to stabilize.  Based on everyones comments though, it looks like the planes with the longer noses do require more adjustment than the F between landing and takeoff.   

From the IPC, here is the trim indicator wire.  If the stabilator rigging and travel are correct(confirmed with travel board) then the trim position indicator requires adjustment.

[skykrawler]

20 hours ago, M20Doc said:

Disconnecting the trim shaft is not required to adjust the trim indicator.  Take the airplane to someone with the correct tools and knowledge.

Sound advice.  It gets harder to do every single day.

On your first point...it may depend on the model.   The procedure  in the M20J service manual does say disconnect the shaft.

This particular section also references the stepped nuts that are supposed to help prevent a jammed condition if one runs the electric trim into the stop (a previous post incorrectly identified this as a run away trim)

 

[Guest]

6 hours ago, skykrawler said:

Sound advice.  It gets harder to do every single day.

On your first point...it may depend on the model.   The procedure  in the M20J service manual does say disconnect the shaft.

This particular section also references the stepped nuts that are supposed to help prevent a jammed condition if one runs the electric trim into the stop (a previous post incorrectly identified this as a run away trim)

 

Yes, but the first thing to do is verify that total travel is correct before doing anything, then determine if the travels require adjustment or just the indicator.

[skykrawler]

18 hours ago, PT20J said:

The J and earlier models have trim assist bungees and sit with the elevator level. Starting with the K and after, the trim has a variable down spring and the elevator controls include a bob weight so the elevator hangs down on the ground. 

Correct, a significant design change to the longitudinal control system.   That down spring design seems similar to the C182, King Air and other aircraft.  Used to add stability for the widest possible CG range.  Stability in the sense that the nose down tendency is retained with an aft CG condition when a nose up pitch is applied.