Mooney tail aerodynamics - not backwards

[JohnB]

Ok, I thought of this and couldn't come up with an answer. Does anyone know why our tail design (straight leading edge) compared to a sloped leading edge on non-Mooney airplanes is more aerodynamic or efficient?  If it is more efficient, I wonder why havent airlines or other commercial carriers adopted it, because they think it would look funny to passengers or? If someone has a link or reference that someone has done wind tunnel tests to prove it that would be great, or is this just a signature mooney trademark? Not that Im complaining about our cool tail, but would like to know why, if anyone knows. Or if this is one of those "it's just better because someone did a test" with no physics explaination answers, I can go with that too.

[201er]

I suspect it's cause the straight vertical fin has less forward facing surface area than the sloped ones and thus less drag. However, it seems that it has more to do with the full trimming tail rather than aerodynamics. And the fact that it looks fricken cool. Everyone else has their tail on backwards.

[wiseng]

Ok I will bite.  I think i read somewhere that Al Mooney or someone said if you look at the nose up attitude when landing the tail is essentially straight in reference to the ground and supposedly provides better control. 

[MooneyMitch]

I'm sure someone on this forum will provide the information you are seeking, but I'm not going to give it away just yet!

 

With that said, you can see what our dear Mr.Bill Wheat says about why Al Mooney used this design, when you view our Mooney documentary Boots On The Ground.

 

Bill Wheat worked at Mooney over 50 years as a test pilot and engineer.  He was friends with Al and Art Mooney.  Bill knows pretty much everything there is to know about Mooney airplanes.

 

Boots On The Ground, The Men and Women that built Mooney DVD will be premiered at the MAPA Homecoming Convention in Kerrville, Texas, April 10-12, 2014.

[Bob_Belville]

I've understood that Al was such a fanatic about drag that he designed the rudder to be normal to the relative wind @ high AOA (landing mode, most importantly) so that the wetted area could be the smallest possible. ISTM Lopesti may have decades later calculated that it was not that big a difference.

[sreid]

Looking at the tail, I think it is much more simple. It looks like the h-stab and the v-stab are essentially the same parts. They appear to be the same length, leading edge radius, etc... Likewise, it looks like the rudder and the two elevators are all essentially the same parts with very very similar skins. Check it out the next time you are at your hangar.

Steve

[JohnB]

I'm sure someone on this forum will provide the information you are seeking, but I'm not going to give it away just yet!

 

With that said, you can see what our dear Mr.Bill Wheat says about why Al Mooney used this design, when you view our Mooney documentary Boots On The Ground.

 

Bill Wheat worked at Mooney over 50 years as a test pilot and engineer.  He was friends with Al and Art Mooney.  Bill knows pretty much everything there is to know about Mooney airplanes.

 

Boots On The Ground, The Men and Women that built Mooney DVD will be premiered at the MAPA Homecoming Convention in Kerrville, Texas, April 10-12, 2014.

Mitch, you mean you know the answer and are gonna make me wait until next year to find out? Be nice! Spill the beans!! heh eh

 

Ok I will bite.  I think i read somewhere that Al Mooney or someone said if you look at the nose up attitude when landing the tail is essentially straight in reference to the ground and supposedly provides better control. 

 

That actually makes sense, could it be better rudder control in landing and takeoff attitude?  As on a mooney airplane our usually forward sloped rudder rudder would be straight up and down at landing and takeoff attitude, whereas everyone elses rudder would be sloping backwards. i could go with this one.. are we getting close?

I suspect it's cause the straight vertical fin has less forward facing surface area than the sloped ones and thus less drag. However, it seems that it has more to do with the full trimming tail rather than aerodynamics. And the fact that it looks fricken cool. Everyone else has their tail on backwards.

It is way more cool no doubt! But wouldnt the drag be the same if the vertical fin's height and width are the same? I tried to involve a theory about less yaw as most of the anti yaw surface area would be in the front of the fin and a straight edge might have it more evenly distributed from the top to the bottom of the fin, but then realized that it would just be applied to a slightly more aft portion of the fin if the areas were similar.. and after that, it all got all swimmy...

[kmyfm20s]

Better rudder authority in a high angle of attack, stall situation to compliment the laminar flow wing.

[M20F-1968]

Ok, I'll bite on this one. 

 

First Ill speak about the angle of the trailing edge of the vertical stabilizer.  The rudder angle is set so that in a nose high attitude, and early stall configuration, the angle of the rudder to the oncoming wing is almost 90 degrees to the oncoming wind.  This will provide much more length of functional rudder and better rudder authority in a stall/start of spin situation when you need the rudder the most.  In a swept tail, the rudder has even less functional rudder length when nose high.

 

As for the leading edge of the vertical stabilizer, the straight upright leading edge is about 90 degrees to the oncoming wind in cruise configuration and the wind sweeps squarely over the remainder of the tail. 

 

There is logic here which is then carried to the fully trimmed empennage.

 

John Breda

 

John Breda

[yvesg]

My guess is that it was easier to build it this way....

Yves

[Bob_Belville]

My guess is that it was easier to build it this way....

Yves

You need to read up on Al Mooney! It's an M20...you do know what that means, right?

[Ned Gravel]

Not going to spoil it here, because Mitch and Jolie have something in mind, but the common understanding was one (or all) of the three following reasons: 

 

1. The increase in rudder authority at higher angle of attack
2. The smaller wetted area needed for it to serve our airframes, and
3. (this is the one that has been hinted at here and will not surprise you when you hear/see/read it).

[MooneyMitch]

 

[captainglen]

_{Drag is related only to the total whetted surface area of the tail not the angle of the leading edge and the Mooney tail is relatively small for the airframe size. What is critical in the mooney is that the entire tail is hinged at the bottom for pitch trim, therfore the upper sliding seal has the most potential for parasitic drag and also for wear. The tail moves verry little at the bottom during trim but the top moves a lot more and the vertical angle of the leading edge means there is better seal with less stress on the seal. One thing to note is the tail is vertical when the trim is in the landing position but it actually slopes back a bit when the airplane is trimmed for cruise flight. On the ramp trim your airplane to half way between the takeoff mark and full nose dawn and take another look!}

[jetdriven]

My airplane was built without the seal between the vertical stab and the dorsal fin, but we are rectifying that.  Also, the vertical stab and horizontal stabs look similar but they are really not anywhere close to the same part number.

[kmyfm20s]

I thought this already mentioned but the pitch trim moving the entire tail. When trimmed for level flight the leading edge is sweeped back and the trailing edge is almost vertical and trimmed for slow flight or landings it has the forward trailing edge to give it better rudder authirity.  This is why when discussing landings with people that refuse to trim a Mooney bugs me, they dont understand the design.

[Bob_Belville]

I thought this already mentioned but the pitch trim moving the entire tail. When trimmed for level flight the leading edge is sweeped back and the trailing edge is almost vertical and trimmed for slow flight or landings it has the forward trailing edge to give it better rudder authirity.  This is why when discussing landings with people that refuse to trim a Mooney bugs me, they dont understand the design.

I think you're overstating how much the tail moves. A Mooney tail looks like a Mooney tail whether at red line descent or at full flaps touch down.

[David Mazer]

Noone seems to be answering the obvious remaining question.  In this high cost fuel environment, if the Mooney tail is more efficient, why haven't other manufacturers copied it.  If it is a safety benefit (better rudder control at high AOA), why haven't others copied it?

[Bob_Belville]

Noone seems to be answering the obvious remaining question.  In this high cost fuel environment, if the Mooney tail is more efficient, why haven't other manufacturers copied it.  If it is a safety benefit (better rudder control at high AOA), why haven't others copied it?

If you go back to my first post I answer that point. I may be  mis-remembering but I think I read/heard that Roy Lopresti did the calculations and determined there was not much advantage. Check out the promo video on the 301 (which had a conventional tail) that has been posted on one of our FB sites and elsewhere recently. 

[kmyfm20s]

I think you're overstating how much the tail moves. A Mooney tail looks like a Mooney tail whether at red line descent or at full flaps touch down.

I agree the tail will always look like a Mooney tail but it also changes position. Take a look at this article and look at the tail with this plane only 90 kts. I didn't intend to overstate the sweep portion of the tail but those slight changes have a impact on the aerodynamics. http://www.mooney.org.au/files/Up_to_Speed_Mooney.pdf

[PMcClure]

Hey, where can I buy one of those 301's? That looks nice!! 

[Marauder]

It is a real shame the factors played out the way they did and Mooney is in the state they are in today.

[DAVIDWH]

The tail design is an Al Mooney Steve Jobs thing. ie. We didn't know we needed it until Al manufactured it.

 

But to quote Al, " The Mooney is the only aircraft in general aviation today whereby a wing can be lifted with a rudder".

 

Can't get much better than that.

[jetdriven]

Noone seems to be answering the obvious remaining question.  In this high cost fuel environment, if the Mooney tail is more efficient, why haven't other manufacturers copied it.  If it is a safety benefit (better rudder control at high AOA), why haven't others copied it?

Its not more efficient from a drag standpoint, but it is more effective at high alpha and low speed.  All the other manufafturers, such as Cessna, used to have vertical tails that were square, but in the 1960s swept them because they looked cool. Aerodynamically they fly worse.

[Alan Fox]

Hey, where can I buy one of those 301's? That looks nice!! 

You can buy the 301 from Socata , the 301 was sold to Socata and produced as the TBM700 .... True story...