Mooney tail

[Blue on Top]

10 minutes ago, MooneyMitch said:

With that said, I believe you can read all at http://specialcollections.wichita.edu/collections/ms/2016-01/2016-1-a.html#summary

Incidentally, Ken Harmon was in charge of the Mooney R&D Department while his father Ralph was running Mooney.  Under Ken, the Mustang and the "H" model were created among many other projects.

@MooneyMitch  Holy crap!  I recognize that web address; it's in town!  Thank you!

The files look super interesting!  For some reason box #3 is restricted … which are all the interviews with Beech, Cessna and Mooney.  I didn't know that he headed up the Cessna 620 design.  The 620 is basically a double 310 (hence the model number), basically a wood, 4-engine, King Air.  WOW!!!

Edited February 21, 2020 by Blue on Top

[MooneyMitch]

56 minutes ago, Blue on Top said:

@MooneyMitch  Holy crap!  I recognize that web address; it's in town!  Thank you!

The files look super interesting!  For some reason box #3 is restricted … which are all the interviews with Beech, Cessna and Mooney.  I didn't know that he headed up the Cessna 620 design.  The 620 is basically a double 310 (hence the model number), basically a wood, 4-engine, King Air.  WOW!!!

I hope you get to view all Ron !

[0TreeLemur]

On 2/20/2020 at 10:22 PM, Blue on Top said:

@MooneyMitch  Holy crap!  I recognize that web address; it's in town!  Thank you!

The files look super interesting!  For some reason box #3 is restricted … which are all the interviews with Beech, Cessna and Mooney.  I didn't know that he headed up the Cessna 620 design.  The 620 is basically a double 310 (hence the model number), basically a wood, 4-engine, King Air.  WOW!!!

It does sound like it might be a treasure of design info.  Please share with us all you can.  

[Blue on Top]

3 hours ago, 0TreeLemur said:

It does sound like it might be a treasure of design info.  Please share with us all you can.  

I will do so.  Sooooooooooo much data; sooooooooo little time.  I plan to be spending a lot more time at Wichita State's GoCreate facilities.  That will get me closer ... physically.

[0TreeLemur]

49 minutes ago, Blue on Top said:

I will do so.  Sooooooooooo much data; sooooooooo little time.  I plan to be spending a lot more time at Wichita State's GoCreate facilities.  That will get me closer ... physically.

There is a so-called "expert editor" that I'm having a disagreement with right now about the utility of minimizing spanwise flow with a forward swept rudder at high angle of attack.  Any data or especially a publication that supports this notion would be helpful.  No rush at all, this is a hobby project, but I would love to hear about anything you can find regarding the M20 tail.

Thanks,

Fred

[Blue on Top]

44 minutes ago, 0TreeLemur said:

... the utility of minimizing spanwise flow with a forward swept rudder at high angle of attack.  Any data or especially a publication that supports this notion would be helpful.  No rush at all, this is a hobby project, but I would love to hear about anything you can find regarding the M20 tail.  Thanks, Fred

@0TreeLemur  Fred:  There is probably not an easy to understand book to read that will talk about span-wise flow, but I'll give it a quick shot.  Before we start, flow direction does not determine pressures but is a result and indicator of pressures.  Let's talk with respect to just the forward swept Mooney tail and rudder.

(talking about the whole vertical surface) Aerodynamicists only care about the 25% chord line.  The Mooney vertical surface is swept slightly forward, even at higher angles of attack and made more forward swept locally by the wing downwash … especially with flaps.  The surface is more effective the closer the local airflow gets to perpendicular to the 25% chord line.  Simple, right?  Now lets look at the rudder and its hinge line.

Let's start with a hinge line that is perpendicular (90 degrees) to the airflow.  As the rudder is deflected (we'll say to the right), a higher pressure will form on the right side of the vertical surface.  Because the whole surface is (typically) tapered, a higher pressure will form at the base than at the tip, and flow will start to turn upward (an indication of where the relatively lower pressure is).  Even if the surface is not tapered this will still be the case because nothing is in the way of the airflow going off the tip (just like a wing tip vortex).  The further the rudder is deflected, the more this flow will turn upward.  Note: I haven't mentioned pressure changes … yet.

Now, let's sweep the tail/rudder hinge line aft (jet, go-fast look).  We've now made it easier for the flow to travel up the rudder hinge line and off the tip.  Again, we're not losing pressure.  (note: it is less effective because the 25% chord line is swept).

Now, let's sweep the tail/rudder hinge line forward (Mooney, Lark, etc.).  We've now made it harder for flow to travel up the rudder hinge line and off the tip.  In fact, we're forcing the flow to travel down the hinge line (something it doesn't want to do).  In this case, the pressure does increase because we are forcing the flow to do something it doesn't want to do … travel INTO higher pressure.  In addition, the base of the vertical has a endplate called the fuselage and horizontal stabilizer, which makes it harder yet!  

I hope this helps.

BONUS, BONUS, BONUS (just in):  If you're going to Sun-N-Fun, I'll be giving a forum, "Demythifying Stall and AOA" on Wednesday and Saturday at 9AM.  I think they missed my "De-Tail - Mooney (and all other GA) Aerodynamics" application.  I'm "talking" with them now about doing the Mooney one on Thursday and Saturday at 1PM both days.  Either way, I'll be at SNF all week.

[cliffy]

2 hours ago, Blue on Top said:

@0TreeLemur  Fred:  There is probably not an easy to understand book to read that will talk about span-wise flow, but I'll give it a quick shot.  Before we start, flow direction does not determine pressures but is a result and indicator of pressures.  Let's talk with respect to just the forward swept Mooney tail and rudder.

(talking about the whole vertical surface) Aerodynamicists only care about the 25% chord line.  The Mooney vertical surface is swept slightly forward, even at higher angles of attack and made more forward swept locally by the wing downwash … especially with flaps.  The surface is more effective the closer the local airflow gets to perpendicular to the 25% chord line.  Simple, right?  Now lets look at the rudder and its hinge line.

Let's start with a hinge line that is perpendicular (90 degrees) to the airflow.  As the rudder is deflected (we'll say to the right), a higher pressure will form on the right side of the vertical surface.  Because the whole surface is (typically) tapered, a higher pressure will form at the base than at the tip, and flow will start to turn upward (an indication of where the relatively lower pressure is).  Even if the surface is not tapered this will still be the case because nothing is in the way of the airflow going off the tip (just like a wing tip vortex).  The further the rudder is deflected, the more this flow will turn upward.  Note: I haven't mentioned pressure changes … yet.

Now, let's sweep the tail/rudder hinge line aft (jet, go-fast look).  We've now made it easier for the flow to travel up the rudder hinge line and off the tip.  Again, we're not losing pressure.  (note: it is less effective because the 25% chord line is swept).

Now, let's sweep the tail/rudder hinge line forward (Mooney, Lark, etc.).  We've now made it harder for flow to travel up the rudder hinge line and off the tip.  In fact, we're forcing the flow to travel down the hinge line (something it doesn't want to do).  In this case, the pressure does increase because we are forcing the flow to do something it doesn't want to do … travel INTO higher pressure.  In addition, the base of the vertical has a endplate called the fuselage and horizontal stabilizer, which makes it harder yet!  

I hope this helps.

BONUS, BONUS, BONUS (just in):  If you're going to Sun-N-Fun, I'll be giving a forum, "Demythifying Stall and AOA" on Wednesday and Saturday at 9AM.  I think they missed my "De-Tail - Mooney (and all other GA) Aerodynamics" application.  I'm "talking" with them now about doing the Mooney one on Thursday and Saturday at 1PM both days.  Either way, I'll be at SNF all week.

OK interesting thoughts, somewhat "intuitive" if enough brain power was used in thinking about it. 

Now a question- with the "loss" of air "over the top" in a rear sweep rudder hinge (say later Cessnas)  what affect would a simple tip plate on the top of the rudder/vertical stabilizer have on controllability ?  Would it also increase "pressure" just as the inverse is true on Mooneys?

My guess is it would.

Just head work here as I'm only a layman not an aero guy. Although I did design and build lots of model airplanes in my youth and I stayed at a Holiday Inn last year :-)

Would love to hear you in FLA BUT I'll be  9000 miles west at that time. 

[Blue on Top]

5 minutes ago, cliffy said:

Now a question- with the "loss" of air "over the top" in a rear sweep rudder hinge (say later Cessnas)  what affect would a simple tip plate on the top of the rudder/vertical stabilizer have on controllability ?  Would it also increase "pressure" just as the inverse is true on Mooneys?

My guess is it would.

Just head work here as I'm only a layman not an aero guy. Although I did design and build lots of model airplanes in my youth and I stayed at a Holiday Inn last year :-)

@cliffy  Yes, your intuition is correct, but an end plate would have very little effect.  The flow would just "plan ahead" and go there more directly/straightly, leaving a vortex at the inside corner of the end plate.  Remember the fuselage and horizontal surfaces are pretty big.  Similar to winglets, end plates have to be fairly large (and laying them flat -extending the wing- is much more efficient).  On a wing , the higher and lower pressure sides are known … yes, unless flying inverted .  Thanks!

[0TreeLemur]

9 hours ago, Blue on Top said:

@0TreeLemur  Fred:  There is probably not an easy to understand book to read that will talk about span-wise flow, but I'll give it a quick shot.  Before we start, flow direction does not determine pressures but is a result and indicator of pressures.  Let's talk with respect to just the forward swept Mooney tail and rudder.

(talking about the whole vertical surface) Aerodynamicists only care about the 25% chord line.  The Mooney vertical surface is swept slightly forward, even at higher angles of attack and made more forward swept locally by the wing downwash … especially with flaps.  The surface is more effective the closer the local airflow gets to perpendicular to the 25% chord line.  Simple, right?  Now lets look at the rudder and its hinge line.

Let's start with a hinge line that is perpendicular (90 degrees) to the airflow.  As the rudder is deflected (we'll say to the right), a higher pressure will form on the right side of the vertical surface.  Because the whole surface is (typically) tapered, a higher pressure will form at the base than at the tip, and flow will start to turn upward (an indication of where the relatively lower pressure is).  Even if the surface is not tapered this will still be the case because nothing is in the way of the airflow going off the tip (just like a wing tip vortex).  The further the rudder is deflected, the more this flow will turn upward.  Note: I haven't mentioned pressure changes … yet.

Now, let's sweep the tail/rudder hinge line aft (jet, go-fast look).  We've now made it easier for the flow to travel up the rudder hinge line and off the tip.  Again, we're not losing pressure.  (note: it is less effective because the 25% chord line is swept).

Now, let's sweep the tail/rudder hinge line forward (Mooney, Lark, etc.).  We've now made it harder for flow to travel up the rudder hinge line and off the tip.  In fact, we're forcing the flow to travel down the hinge line (something it doesn't want to do).  In this case, the pressure does increase because we are forcing the flow to do something it doesn't want to do … travel INTO higher pressure.  In addition, the base of the vertical has a endplate called the fuselage and horizontal stabilizer, which makes it harder yet!  

I hope this helps.

BONUS, BONUS, BONUS (just in):  If you're going to Sun-N-Fun, I'll be giving a forum, "Demythifying Stall and AOA" on Wednesday and Saturday at 9AM.  I think they missed my "De-Tail - Mooney (and all other GA) Aerodynamics" application.  I'm "talking" with them now about doing the Mooney one on Thursday and Saturday at 1PM both days.  Either way, I'll be at SNF all week.

Sorry to have you waste so many words.  My understanding is not the issue.   My problem is that I have a troll editor who is resisting my attempts to incorporate this little gem of knowledge regarding the swept forward Mooney rudder into the M20 article on Wikipedia.   He insists on a good 3rd party reference.  The 1996 article from Flying by Garrison (?) that Skip referenced at the beginning of this thread is insufficient for this troll editor because Garrison wrote both that it matters, and that it maybe doesn't.  That is the problem with requiring 3rd party verification from the lay press.    What is needed is a good reference report or article saying that a forward swept rudder has more effectiveness at high angle of attack than a normally aft-swept rudder, using itty-bitty words, with no uncertainty.   I could write dot products with fancy sketches all day, and that won't matter.

Any written independent article that says exactly what we know will be most appreciated, so that I can edit the M20 wikipedia page to say this.  I added it, including the reference to the 1996 Flying article, and he deleted it, because he is "experter" than me.   Well, I'm not gonna give up that easy.  Any help you can provide, ideally written in not too many big words or high level mathematical notation will be appreciated.  

Someone on the MooneyPilots.org or some such place said that there was an interview of Al Mooney from years ago where Al discussed all this.  Anyone have a reference to that?

Thanks.

[Blue on Top]

@0TreeLemur  Fred: I feel for you.  I have heard of that Al Mooney referenced article, too, but I have never seen it.

Somewhere I have a Mooney advertisement that has a lady sitting on the tail (it's a black and white drawing), and it explains the tail, too.  If it helps at all, I have a degree in Aeronautical/Astronautical Engineering from a major university, and I have formed, managed and supervised Aerodynamics and Flight Test department from coast to coast and border to border, literally   I was also a Chief Engineer for Mooney (on the M10), if that helps your case ,  Sorry, yes I know that it won't.  Keep up the good fight.  he truth will win!

[0TreeLemur]

39 minutes ago, Blue on Top said:

@0TreeLemur  Fred: I feel for you.  I have heard of that Al Mooney referenced article, too, but I have never seen it.

Somewhere I have a Mooney advertisement that has a lady sitting on the tail (it's a black and white drawing), and it explains the tail, too.  If it helps at all, I have a degree in Aeronautical/Astronautical Engineering from a major university, and I have formed, managed and supervised Aerodynamics and Flight Test department from coast to coast and border to border, literally   I was also a Chief Engineer for Mooney (on the M10), if that helps your case ,  Sorry, yes I know that it won't.  Keep up the good fight.  he truth will win!

Thanks for the encouragement.   I was inspired by Garrison's article to improve the "Design" aspect of the M20 page.  With your help maybe we can get it done.  If you can find that advertisement, that would be really cool to see and another bit of evidence.  Oh- some interesting quotes, including at least one attributed to Al Mooney here:    http://www.mooneyevents.com/quotes.htm

Edited February 25, 2020 by 0TreeLemur
detail.

[carusoam]

O’tree,

do you have a copy of the Larry Ball Mooney book?

To go with your copy of Gordon Baxter’s book?

Those two resources may have a shade of what you are looking for...

Best regards,

 -a-

[0TreeLemur]

8 hours ago, carusoam said:

do you have a copy of the Larry Ball Mooney book?

To go with your copy of Gordon Baxter’s book?

No, I don't have Larry Ball's "Those Remarkable Mooneys", nor do I have Garrison's 1980 "The Complete Guide to Single Engine Mooneys".   Garrison's article is unfortunately not definitive about the Mooney tail, so I suspect that his book isn't either.   Do you know if Larry Ball talk about the tail design and the advantage of a swept-forward rudder at high angle of attack?

 

[cliffy]

OTL   You realize no amount of "evidence" you provide will appease your nemesis. That's the crux of a troll  

[carusoam]

7 hours ago, 0TreeLemur said:

No, I don't have Larry Ball's "Those Remarkable Mooneys", nor do I have Garrison's 1980 "The Complete Guide to Single Engine Mooneys".   Garrison's article is unfortunately not definitive about the Mooney tail, so I suspect that his book isn't either.   Do you know if Larry Ball talk about the tail design and the advantage of a swept-forward rudder at high angle of attack?

 

I don’t have a copy, and my memory isn’t that good... 

But, Larry’s daughter is a registered MSer...

Best regards,

-a-

[amillet]

E

[Andy95W]

⬆️⬆️⬆️⬆️

That's the quotation I've been looking for.  Fred, if that doesn't convince your troll, I doubt there is anything out there that will.

[0TreeLemur]

25 minutes ago, Andy95W said:

⬆️⬆️⬆️⬆️

That's the quotation I've been looking for.  Fred, if that doesn't convince your troll, I doubt there is anything out there that will.

Yes, I know of that quote.   The problem is this: If Al Mooney or I said it, it is opinion.   If an independent "expert" confirms it in writing in widely available popular literature, it becomes fact.   I kind of get it.  I really thought that Garrison's article in Flying sealed it- but the "expert editor" seized on the statement by Garrison that aft sweep is bad.  Therefore, forward sweep is good.  Eh?  Here's what Peter Garrison wrote in Flying in the April edition of 1995:

"The loss of stabilizing authority of a swept tail is slightly offset by the increase in tail moment arm -- that is, the tail, by virtue of being swept, is slightly farther away from the center of gravity and so slightly more effective.  But the increase in tail moment arm is proportionally very small and its benefit disappears beyond about 15 degrees of sweep.  (Lift curve slope can be regained by increase the aspect  ratio of the vertical surface, as Cessna did when it swept fins in 1960.

Sweeping the tail is also detrimental to spin recovery.   In a spin, air flows across the fin and rudder at a steep angle; with a strongly swept fin- the fins of single-engine Cessnas have 40 degrees of leading edge sweep, worthy of a transonic fighter-- the hinge line about which the rudder pivots is more nearly aligned with the flow, and the effectiveness of the rudder drops sharply.  In fact, the swept forward fin that is a hallmark of Mooneys was originally intended to enhance the spine-recovery characteristics of Al Mooney's single-place Mite (which was to be an aerobatic airplane) by setting the rudder hinge line at something closer to a right angle to the airflow in a spin.   What eventually became a styling feature began as a rather ingenious technical innovation."

Who can read this and not confirm the assertion that forward sweep is good for rudder authority at high angle of attack?   Anybody else on here ever edit Wikipedia?   Anybody else want to insert or cite this quotation into the "Design" section of the M20 Wikipedia page and reassert the point? 

[0TreeLemur]

6 hours ago, cliffy said:

OTL   You realize no amount of "evidence" you provide will appease your nemesis. That's the crux of a troll  

Yes, this is an issue.  It is why I stopped donating to Wikipedia- their editors can be maddeningly inflexible.  If someone else who likes a good fight wants to "tag in" and carry on with this battle, I'd welcome it.   Ideally, if I could find a perfect, irrefutable published source confirming that Big Al Mooney was correct, I'd put it in there and dare the troll to show is true colors or shut up.  I thought I had done it with the Garrison article.   Grrrr. 

[Blue on Top]

22 hours ago, 0TreeLemur said:

Thanks for the encouragement.   I was inspired by Garrison's article to improve the "Design" aspect of the M20 page.  With your help maybe we can get it done.  If you can find that advertisement, that would be really cool to see and another bit of evidence.  Oh- some interesting quotes, including at least one attributed to Al Mooney here:    http://www.mooneyevents.com/quotes.htm

If anyone has Peter Garrison's contact information, I would appreciate it.  He has a lot of great information, and I want him to personalize one of his books that I own.  Great guy.

I WILL find the ad.  It's somewhere in a box in the basement … made more confusing by the moves from Chino, CA to Kerrville, TX for 6 weeks and now in Wichita.

[Blue on Top]

4 hours ago, 0TreeLemur said:

Yes, this is an issue.  It is why I stopped donating to Wikipedia- their editors can be maddeningly inflexible.  If someone else who likes a good fight wants to "tag in" and carry on with this battle, I'd welcome it.   Ideally, if I could find a perfect, irrefutable published source confirming that Big Al Mooney was correct, I'd put it in there and dare the troll to show is true colors or shut up.  I thought I had done it with the Garrison article.   Grrrr. 

I'd be happy to join the fight.  And, yes, even modestly, I know my sh** (aerodynamics).

Will you post the offending material?  Or a link to it?  Thanks!

I know I don't count, but I have given talks across the nation on the Mooney tail and why it is designed as such.  Send the wiki editor to Oshkosh or SNF, I'll teach him/her a thing or two!  LOL LOL Isn't it amazing how tough I sound on the internet  

[Blue on Top]

@0TreeLemur and all.  These aerodynamics are actually a complicated subject (especially when talking about spin aerodynamics … it is not as easy as the books (so far) have stated, but we are getting closer with CFD … what one can trust of them.

On the simplest portion, the vertical flying with attached airflow, the most effective surface will be the one with the 25% chord most perpendicular to the airflow.

Spin characteristics and airflow are a completely different animal and depends on many, many other factors, such as: the horizontal surface - shape and location, the aft fuselage - shape, location, edges, etc., horizontal/rudder interface, fuselage/rudder interface, etc., etc, (meaning there's a lot more!  We have proven that the NASA formula for spin recovery is incorrect … or at least not complete.  This is why we are still required to spin the airplanes in all configurations.  We just don't know enough yet.

[PT20J]

I think I understand that at Mooney speeds, the most efficient vertical stabilizer in cruise would be straight (measured at the quarter-chord line). Sweeping back looks jet-age cool, but is less efficient which means more wetted surface (and thus more drag) to achieve the same aerodynamic result. Sweeping forward slightly might be a small penalty in cruise but would improve the efficiency at higher angels of attack which occur (unaccelerated flight) at low speeds and thus low dynamic pressure.

But.. in an earlier post, I compared the tail feathers of the Mooney to the Comanche (which is interesting because the airplane planforms are so similar) and found that the the Mooney vertical stab is actually slightly larger than the swept back Comanche vertical stab. So, before we crawl too far out on the Wikipedia limb, it might be good to compare a bunch of designs and figure out if the advantages are real or theoretical. Maybe I made a mistake.

On 1/7/2020 at 7:33 PM, PT20J said:

This is interesting. I ran down the specs on the PA24-250 at https://www.skytamer.com/Piper_PA-24-250.html.

Since the dimensions of the M20J and the PA24-250 are almost identical except for the tail feathers, it is interesting to compare.

The Mooney horizontal tail is 2 ft² larger than the Comanche (Mooney 34.5 ft², Comanche 32.5 ft²)

The Mooney vertical stabilizer + rudder is slightly larger than the Comanche (Mooney 14.15 ft², Comanche 13.4 ft²)

So, the Mooney's empennage design (swept forward surfaces and trimmable stabilizer with trim assist bungees) didn't end up smaller (less drag) than the Comanche's empennage (stabilator and swept-back fin). 

Skip

 

[Blue on Top]

@PT20J  Skip: You are not mistaken!  You are correct.  But, no one said that all tails are created equally or have exactly the same stability, which also includes factors for wing area, wing chord and dihedral.  Many, many factors play with many, many other factors … especially when dealing with lateral AND directional issues that are coupled.  It's not simple, cut and dried.

For example, yaw/roll coupling is very wing sweep dependent, whether it be rearward or forward sweep.  We typically think of sweep as stabilizing (yaw and roll in the same direction), but forward sweep (X-29, Moonies, Blanik sailplane, etc.) is destabilizing (yaw and roll in opposite directions).

[PT20J]

34 minutes ago, Blue on Top said:

@PT20J  Skip: You are not mistaken!  You are correct.  But, no one said that all tails are created equally or have exactly the same stability, which also includes factors for wing area, wing chord and dihedral.  Many, many factors play with many, many other factors … especially when dealing with lateral AND directional issues that are coupled.  It's not simple, cut and dried.

I understand, but that's why I compared the Mooney and Comanche -- because they are about as similar as two different airplanes can be. Similar airfoils, almost the same wing area, same MAC, same wingspan, dihedral within 1/2 degree, same forward sweep, essentially the same fuselage length.

44 minutes ago, Blue on Top said:

For example, yaw/roll coupling is very wing sweep dependent, whether it be rearward or forward sweep.  We typically think of sweep as stabilizing (yaw and roll in the same direction), but forward sweep (X-29, Moonies, Blanik sailplane, etc.) is destabilizing (yaw and roll in opposite directions).

Hmmm. I hadn't thought of that. Maybe that's one reason for adding the aileron rudder interconnect. I wonder if the Comanche has one?

Skip