How do you feel about the Mooney tail?

[201er]

How do you feel about the Mooney tail? Did it attract you to Mooneys or was it a turn off? What have you learned about it and has it grown on you?

[A64Pilot]

I believe it’s shaped the way it is in order for it to be easier to manufacture back when it was wooden and since then it’s shape has been kept as it is unique and sets a Mooney apart, or maybe it’s to have a similar profile that the wings do.

I don’t think its shape has any real aerodynamic advantage or weakness.

However I do like the way it trims in pitch, ought to be slightly less drag than a trim tab.

It was fun during my Commercial check ride too, after being asked what happens when we trim the elevator the check pilot looked at me like I had a horn growing out of my head, this came soon after he asked me what was the voltage of the electrical system and I said 28 and he said 24, and I could explain my answers, his was well it has a 24V battery.

When we got to the airplane I had to demonstrate the pitch trim mechanism, I’m not sure he understood it 

Edited April 25, 2022 by A64Pilot

[Kmac]

I read that Al Mooney designed the vertical stabilizer that way so that it would have the most authority in low speed situations and in flare on landing.

Edited April 25, 2022 by Kmac

[Mooney Dog]

Next you're going to tell me the wings are on backwards on this plane...

 

[Greg Ellis]

Ron Blum who was an engineer at Mooney did a talk at Oshkosh last year about Mooney aerodynamics and the vertical stabilizer design does have a lot to do with aerodynamics.  @Ron Blum has not been around here in a while but maybe we can get him to drop by and speak briefly about it. 

[N201MKTurbo]

2 hours ago, Mooney Dog said:

Next you're going to tell me the wings are on backwards on this plane...

 

The wings are fine, the nose is on the wrong end!

[carusoam]

The tail is beautiful….

An engineering piece of art!

It isn’t a marketing jet aged triangle…..

It has seen a few upgrades over the years… but no required change…

Go Mooney…. Different by design!

Best regards,

-a-

[PT20J]

I believe there are two aerodynamic advantages to the forward-swept vertical stabilizer. First, the stabilizer will be more effective if all the airflow is normal to the quarter chord line as any spanwise flow component is not beneficial for generating an aerodynamic force. The most critical situation would be at low speeds where the dynamic pressure is lowest. At the higher deck angles for lower speed flight, the forward sweep will put the quarter chord line more perpendicular to the relative wind. This allows a smaller tail. The second advantage is that any spanwise flow will be away from the tip which will reduce the tip vortex and drag. This would be more important in cruise flight. I'm still learning and perhaps Ron @Blue on Top will come along and correct me if need be.

Skip

[cbarry]

The Mooney tail has enough authority in its design that others should question theirs.  For instance, when going from a low power setting to full tilt, most other big bore singles lack the rudder  authority in high AOA situations to avoid mushing to the left, not Mooney.

[A64Pilot]

The Mooney as most all more modern tricycle designs doesn’t have all that much rudder authority, most likely that’s why it’s not in Utility category as most modern designs aren’t. They don’t have enough rudder to recover quickly

Pretty sure the leading edge is essentially vertical, by fwd swept you guys are referring to the tapered trailing edge.

From an authority perspective, particularly at low speeds my C-140 as most tailwheel aircraft has way more authority, and as most all old designs it’s approved for spins, because with all that authority it can recover quickly.

Authority you guys are referencing is rudder authority, which honestly there isn’t a whole lot of, there’s plenty I’m not knocking it, but take an average tailwheel aircraft out and put it in a full slip, then you will see rudder authority.

Of course the tailwheel aircraft need more rudder authority to help prevent a ground loop, which isn’t a problem with tricycle aircraft.

The shape of a Mooney’s tail is about as effective as the wing tips on my J model.

[GeeBee]

It is iconic. No matter how many iterations of Mooneys there are, no body says, "Hey who makes that airplane".

 

[PT20J]

31 minutes ago, A64Pilot said:

Pretty sure the leading edge is essentially vertical, by fwd swept you guys are referring to the tapered trailing edge.

Sweep is defined by the angle of the quarter chord line relative to the plane of symmetry. A straight leading edge and swept forward trailing edge yields an effective forward sweep measured at the quarter chord line. Dating back to Max Munk's thin airfoil theory and Ludwig Prandtl's lifting line theory, aerodynamicists have referenced wing parameters to the quarter chord line because (to good approximation for most airfoils) that's where the pitching moment is invariant with angle of attack.

[A64Pilot]

A lot of people accept this definition as “forward swept” wing

https://en.wikipedia.org/wiki/Forward-swept_wing

Here’s a list of forward swept aircraft, 

https://en.wikipedia.org/wiki/Category:Forward-swept-wing_aircraft

Google forward swept wing see what pops up

Edited April 26, 2022 by A64Pilot

[carusoam]

Speaking of rudder authority…

The short body Mooneys with a short rudder… 65 (?) and older….

You can easily run out of rudder doing a slip…  maximum tail braking….

(use caution near the ground… this can be a bad idea…)

PP thoughts only, not a CFI…

Best regards,

 -a-

 

[A64Pilot]

In a full slip your going to run out of something, either rudder or aileron. In my 140 a slip is full rudder to the stops, aileron as necessary to level the wings, if it ran out of aileron, that would be upsetting, who likes a roll you can’t stop. I assume the bigger rudder on newer Mooney’s were the result of higher engine power?

I slip my J the same way, for a Modern design I think the J anyway slips really well, many more modern design don’t have enough rudder authority to slip well.

[Shadrach]

4 hours ago, A64Pilot said:

In a full slip your going to run out of something, either rudder or aileron. In my 140 a slip is full rudder to the stops, aileron as necessary to level the wings, if it ran out of aileron, that would be upsetting, who likes a roll you can’t stop. I assume the bigger rudder on newer Mooney’s were the result of higher engine power?

I slip my J the same way, for a Modern design I think the J anyway slips really well, many more modern design don’t have enough rudder authority to slip well.

The full length rudder was introduced with the F model in 66. I’m not aware of any other dimensional changes to the rudder, are you? I have no time in C140s but I’ve never felt that my Mooney lacked yaw authority at any speed. As you said it slips quite well.  I think a better demonstration of rudder authority can be demonstrated during slow flight at high AOA. My sense is that there is a change in control harmony at low speeds (<60KIAS) where the rudder feels more effective than ailerons. This is likely due to the orientation rudder and it’s hinge line axis being near perpendicular to the relative wind at high AOA. A rear swept rudder (trailing edge and hinge axis) obviously moves closer parallel to the relative wind. I suspect that the Mooney airframe does not meet the utility certification requirement for spin recovery which mandates that the aircraft demonstrate recovery in no more than three rotations WITHOUT control inputs. Once beyond the incipient stage it can take   at least two rotation to recover with inputs (according to @donkaye’s experience). 

[carusoam]

Two early changes to the Mooney rudder… and a later change…

1) Short rudder, above the tail cone… became longer and included the tail cone in the motion…

2) M20B, had the short rudder… and a short rudder throw…. Really short on rudder effectiveness…. Often upgraded to M20C status…

3) Later Mooneys have different sheet metal… large corrugations in place of the nice smooth looking sheet metal… 

 

PP thoughts only,

-a-

[A64Pilot]

I don’t think you guys are as nose high as you think you are, yes I know if feels like your pointing at the sky, but for instance for a Certification I had to take an 800 HP turbine out at min weight and record it’s nose up attitude at full power as it broke into a stall, purpose was to prove our fuel system could deliver in excess of the engines demand under worst  conditions, of course that was proved in the test flight as it didn’t flame out, but we needed to prove it on the ground for the FAA.

Tests don’t have to be as sophisticated as people want to believe, for instance to get the nose up attitude I dug a trench in a ditch to put the tailwheel in and put the mains on ramps, only relevance was to get the correct attitude

But this is the attitude where an empty Ag plane stalls with min fuel and empty hopper with full 800 HP applied, and we can’t get near that in our Mooney’s. Max gross for this airplane is 10,500 lbs and test weight was just above 5,000, so it was very light.

 

Edited April 27, 2022 by A64Pilot

[0TreeLemur]

10 minutes ago, A64Pilot said:

I don’t think you guys are as nose high as you think you are, yes I know if feels like your pointing at the sky, but for instance for a Certification I had to take an 800 HP turbine out at min weight and record it’s nose up attitude at full power as it broke into a stall, purpose was to prove our fuel system could deliver in excess of the engines demand under worst  conditions, of course that was proved in the test flight as it didn’t flame out, but we needed to prove it on the ground for the FAA.

Tests don’t have to be as sophisticated as people want to believe, for instance to get the nose up attitude I dug a trench in a ditch to put the tailwheel in and put the mains on ramps, only relevance was to get the correct attitude

But this is the attitude where an empty Ag plane stalls with min fuel and empty hopper with full 800 HP applied, and we can’t get near that in our Mooney’s. Max gross for this airplane is 10,500 lbs and test weight was just above 5,000, so it was very light.

 

I wish that guy would move.  I'd love to see how that thing was held down....

[A64Pilot]

Gravity.

Thrush carries a lot of weight on the tail, it was originally a North American Rockwell airplane and they carried over the same tailwheel locking mechanism used on their T-6, P-51 etc. To unlock the tailwheel, you release the stick so that it goes to full forward, nose down. A cable pulls the unlock pin on the tailwheel, so you taxi with the stick full nose down, so you need to carry a lot of weight on the tail so that you don’t get a nose over when you hit the brakes etc.

Most tailwheel aircraft taxi with the stick back to prevent a nose over

It’s done that way because it’s impossible to take off with the tailwheel unlocked, high power aircraft would most likely run off the runway from P factor if the tailwheel was unlocked, and if landed unlocked it can shimmy, breaking and of causing a loss of control, so they made it so you couldn’t forget.

But any tailwheel aircraft wouldn’t need to be held down

[0TreeLemur]

7 minutes ago, A64Pilot said:

Gravity.

Thrush carries a lot of weight on the tail, it was originally a North American Rockwell airplane and they carried over the same tailwheel locking mechanism used on their T-6, P-51 etc. To unlock the tailwheel, you release the stick so that it goes to full forward, nose down. A cable pulls the unlock pin on the tailwheel, so you taxi with the stick full nose down, so you need to carry a lot of weight on the tail so that you don’t get a nose over when you hit the brakes etc.

Most tailwheel aircraft taxi with the stick back to prevent a nose over

It’s done that way because it’s impossible to take off with the tailwheel unlocked, high power aircraft would most likely run off the runway from P factor if the tailwheel was unlocked, and if landed unlocked it can shimmy, breaking and of causing a loss of control, so they made it so you couldn’t forget.

But any tailwheel aircraft wouldn’t need to be held down

Thanks for your reply.  My question was more about resisting the static thrust.  I'd guess that 800 HP with a four blade prop must be capable of producing at least 3500-4500 lb of static thrust.  What resists that?  I'd love to see a video of that test... 

[A64Pilot]

17 minutes ago, 0TreeLemur said:

Thanks for your reply.  My question was more about resisting the static thrust.  I'd guess that 800 HP with a four blade prop must be capable of producing at least 3500-4500 lb of static thrust.  What resists that?  I'd love to see a video of that test... 

We didn’t run the engine. The fuel pump is electric, GE supplies a number that is the max fuel flow the engine is possible to consume and a min pressure the fuel needs to be, so we simply disconnected the fuel at the fuel control, installed a ball valve and using the MVP 50T’s pressure and fuel flow transducers and simply adjusted the ball valve to get the min pressure and ensured fuel flow was in excess of what the engine could use. Simple test, the work is in writing the test plan and getting it accepted of course. 

Which is the way for all tests, you already know your going to pass as you conducted them in the Company flight tests. Unless your FUBAR FAA tests are a formality, unless  your airplane is marginal, which you shouldn’t be but some are.

111 GPH sticks in my head, I think that’s the number we got, not what he engine can burn, I think that’s closer to 100 GPH maybe?

Edited April 27, 2022 by A64Pilot

[T. Peterson]

On 4/25/2022 at 4:01 PM, N201MKTurbo said:

The wings are fine, the nose is on the wrong end!

[Blue on Top]

On 4/25/2022 at 3:01 PM, N201MKTurbo said:

The wings are fine, the nose is on the wrong end!

Although I laughed at that comment, leave that fuselage alone . The fuselage is an F-5 fuselage ... and that's my mistress.

Edited April 27, 2022 by Blue on Top

[N201MKTurbo]

2 minutes ago, Blue on Top said:

Although I laughed at that comment, leave that fuselage alone . The fuselage is an F-5 fuselage ... and that's my mistress.

You like em backwards eh? Can't hold that against ya.