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Trim out and cruise observations


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Hello,

Today I was fortunate to be able to fly my "new" 1975 M20F on my first cross country (in this plane).  It was uneventful.   

Once I got to cruise the altitude of 7500 and trimmed the plane out I set the altitude hold on the S-Tec 30.  That was real nice!  First time I've ever had a autopilot.  

At some point, I looked back at the tail and saw that the elevator was in a slightly down position, as noted by the outboard part that is fore of the hinge point (that was up).

Later when I cancelled the ALT Hold, there was no significant pitch up or down.

Shouldn't the full pivoting tail section have the elevator perfectly lined up with the horizontal stabilizer?  Seems in the configuration it was in, it would have a lot of drag.   

 

Thanks,

Philip 

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There was a thread about this three or four years ago, with tail photos from many of us in level cruise. Seems like the elevator counterweight is always about halfway above the horizontal stab. Seems to be that way in my Mooney every time I've looked.

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There was a thread about this three or four years ago, with tail photos from many of us in level cruise. Seems like the elevator counterweight is always about halfway above the horizontal stab. Seems to be that way in my Mooney every time I've looked.

Ditto, this would be a good question for Don Maxwell, given his rigging experience he might have some insight.
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Welcome to the Mooney club, Phillip.

What you are seeing is the effect of the center of gravity and airplane construction.  Adjust your cog and that variation will change.

The whole moving tail thing is a bit simplified for the general population, possibly by the Mooney marketing team in 1968... :)

When you are on the ground, adjust the trim from front to back to see how everything works in sync.

Long Bodies might be different, the elevators want to hang low while not moving.

Best regards,

-a-

Edited by carusoam
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Here is some insight to the initial question regarding the slightly down deflection issue.   The below information is what I would say is directly from the horses mouth, so to speak...... the late Mooney guru, Bill Wheat.  
 
Someone asked me the same question several years ago, about the down deflection.  I then asked Bill Wheat to provide some insight on this subject, which he so graciously did.  Below is a direct copy of Bill's reply to me.
 
If you would like more insight on Mooney facts and history from the late great and dear Mr. Terrible himself, maybe pick up a copy of the DVD "Boots on the Ground, The Men and Women made Mooney".  Bill is the star of that video and has further great insight to some wonderful Mooney history.
 
Here's the question:
 
"I notice that my elevator is always deflected slightly down from the tailplane in flight.  Is this a normal trim condition for solo flight?"
 
And here's Bill's reply:
 
Mitch,
 
This condition is quite normal and is better aerodynamically than it being up. This would cause the angle of atack of the wing to be slightly nose up thereby causing drag.
 
The lower the atack angle of the wing means higher performance.
 
Since every Mooney built was basically a custom equiped aircraft and the equipment installed at customer request causes a considerable variation in the empty weight cg of each aircraft and the flight loading will be different for many flights depending on the number of passengers and fuel loading plus the amount of baggage requiring different trim settings.
 
With most aircraft, the elevator alone is deflected by a tab to compensate for these variations tn cg where the Mooney does most of the trimming with stabilizer angle setting and allowing for far less deflection of the elevators keeping them closer to the sme angle as the stabilizer thereby reducing drag.
 
I always hear comments that the Mooney tail is backwards and why isn't it swept back?  There is a very good reason for that.  The straight leading edge has more lift than a swept surface so therefor 'acording to Al Mooney' the empenage is 20 % smaller than it would have to be and therefor lighter and les drag than a swept surface.
 
I get the idea that the question comes from someone who generally flies his aircraft in basically the same loading configuration, but if flown with a considerably different loading he would see a different empenage configuration in normal cruise.
 
I hope this helps. I spen considerablel time With Al Mooney asking why he did certain things in his designs. He was always willing to take time to explain his reasons to us Peons.
 
Bill Wheat
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