Tailplane and elevator in line in flight?

[garytex]

I notice that my elevator is always deflected slightly down from the tailplane in flight.  Is this a normal trim condition for solo flight?  On a recent trip I put 100 lbs. in the baggage, and another 50 lbs in the back seat, all same-same (although I may have been 2-3 mph faster, hard to tell).  Theoretically, wouldn't it generate less drag if streamlined?  How does the all moving tail figure in?

Thanks, Gary

[aerobat95]

I want to say mine is the same way.  Even if I have my wife and kid in the backseat....not sure when I have baggage also loaded......I find I like landing with a little more aft CG.....not sure about speed though....never really checked that.

[jetdriven]

Ours is the same way.  There are two other threads which discuss this, and no reason has been found.

[stevesm20b]

Mine is the same way. Looks like this is normal.

[Hank]

Mine makes five.

There was a thread about this with photos of several planes at various weights late last year. I posted pictures from solo flight and loaded for Thanksgiving, if that helps you with the time. Don't recall which forum exactly.

[Lood]

Same here - also no real difference whether I'm fully loaded or solo.

[KSMooniac]

That has always bugged me as being un-Mooneylike in temrs of drag.  My J is the same.  I wonder if the original, lightweight, short-fuselage M20A had the elevator "in trail" nicely with the horizontal stab, and as the weights and fuselage length increased the horizontal/elevator configuration was not updated.

[Parker_Woodruff]

My M20K has an elevator-up deflection.  Probably due to the heavier weight up front.

[MooneyMitch]

Quote: Parker_Woodruff

My M20K has an elevator-up deflection.  Probably due to the heavier weight up front.

[Hank]

Quote: KSMooniac

That has always bugged me as being un-Mooneylike in temrs of drag.  My J is the same.  I wonder if the original, lightweight, short-fuselage M20A had the elevator "in trail" nicely with the horizontal stab, and as the weights and fuselage length increased the horizontal/elevator configuration was not updated.

[KSMooniac]

My J is down elevator, which puts the horn slightly above the horizontal stab in cruise flight.

[Parker_Woodruff]

Quote: Mitch

Same with my M20R I believe.

[sleepingsquirrel]

Quote: KSMooniac

That has always bugged me as being un-Mooneylike in temrs of drag.  My J is the same.  I wonder if the original, lightweight, short-fuselage M20A had the elevator "in trail" nicely with the horizontal stab, and as the weights and fuselage length increased the horizontal/elevator configuration was not updated.

[takair]

Strange, my E has the elevator deflected up (to some degree) at all weights and CGs.  I would think at least the Bs adn Cs would be similar.  Must be related to the interaction between the tail rigging and the elevator bungee rigging/spring tension.  Will have to check out my rigging at some point.

[kerry]

Has anyone trimmed at lower speeds to see if it becomes even.  Maybe its designed for less drag in slow flight. Maneuvering speed.

[M016576]

Think about it this way:  rather than moving a trim tab into the wind to drive a control surface to equilibrium, you are actually changing the angle of incidence of the horizontal stabilizer.  The elevator is then fairing into equilibrium... Backwards of what you would traditionally think of for a light GA aircraft.

My theory on why the whole tail moves (please someone with more aerodynamics knowledge tighten me up!!): I'd say this decision probably reduces induced drag by changing CL of the elevator, at the expense of increased parasitic drag over a traditional horizontal stab/elevator/trim tab once in stabilized cruise.  At the speeds we operate in a mooney (less than 250kias), this is probably a worth while trade off.  

[garytex]

Thanks for all the input, guys.  I had serched for similar threads and came up empty before I bothered everyone.  It does seeem to be draggy, on the face of it, however, that trim condition is what one would see in a CPB brand plane with an aft CG and in its fastest trim condition.  I bet there is some method to the madness.  I sure can't complain about the design's speed.  Further, with a longer heavier engine on front in the Ks, we see the usual condition with the tail generating downforce.  This was not the original design however.  Another brain tickler is the design's tendancy to go flat in a spin. The tail is heavy.  Or was it lighter when wood?   I think the desigh may have been for something imitating an aft cg all the time for speed.  However these ideas could easily be wrong, as I frequently am.

[sleepingsquirrel]

It could be that the stabilizer is not big enough by itself to do the job and the deflection of the elevator was the trade off to keep flat plate area down.

here's another : geese fly in formation because it's more efficient, each one off the lead is riding on the vortices of the one in front. It could be that the vortex from the elevator (deflected to create lift instead of just streamlining) is actually making the Mooney go faster as the tail vortex interacts with the vortex off the wing.

I'm sure this is the answer until I make up something better! Hit submit crawl under a rock!

I'm going to play the part of the model maker who designed the "Phoenix" and use my model aircraft aerodynamics knowledge to justify my assertion.

 

[sleepingsquirrel]

Quote: M016576

.....I'd say this decision probably reduces induced drag by changing CL of the elevator, at the expense of increased parasitic drag over a traditional horizontal stab/elevator/trim tab once in stabilized cruise.  At the speeds we operate in a mooney (less than 250kias), this is probably a worth while trade off.  

[MooneyMitch]

I posed this question to Bill Wheat and just received the following information.

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

[Hank]

<dad gum! did it again . . .  at least this time it happened after "submit" gave an error message. "Refresh" and "retry" didn't work the first time, either.

[Hank]

< duplicate >

[Hank]

< duplicate, too >

[Hank]

Wow, Mitch! That's as close to "straight from the horse's mouth" as it's possible to get any more . . .

< why does this site sometimes act like it hates me?? >

[M016576]

Quote: Mitch

I posed this question to Bill Wheat and just received the following information.

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