Mooney Stalls and Spins

[Rspencer612]

2 hours ago, mike_elliott said:

They might be in place, but are they placed correctly? Something is out of whack, and it can only be the rigging or stall strip placement, or your not as coordinated as you might think when it stalls. 

The last of that is the most likely!  Haha

[1980Mooney]

18 hours ago, Rspencer612 said:

Well I picked up my beloved Mooney M20J Missile today from its new Dynon panel install. Wow is it sweet!  The last thing needing calibrated was the AOA, which requires some stalls in the various configurations to be done. 

I began with a clean LOW power, power on stall at about 14” manifold pressure otherwise the plane just gets an insane deck angle. Even this angle was very nose high. As the plane got slow my slip indicator continued to go out right so I began to give the airplane gentle right rudder while holding the wings level. Well down right to about 58-60 kts indicated, the right wing aggressively dropped 90-100 degrees and the nose broke pointing down about 15 degrees. At that point the airplane began to wind into a spin. I smoothly but rapidly pushed, rolled left and applied heavy left rudder. The airplane was instantly reactive and recovery to straight and level was quick with about a 500-600 foot loss of altitude. 

this sure caught me off gaurd, but now I was prepared for what just caught me off gaurd. I did 2 more stalls in both landing config with full flaps and approach/departure with gear down and half flaps. Each stall attempted to react the exact same way with engine power around 10” manifold pressure. As I was prepared for these, the right wing only rolled off about 45 degrees each time instead of the big roll accelerating into a spin like the first one. Immediate left rudder and nose down corrected it. 
 

im very focused on keeping the airplane coordinated as the missile needs a lot of rudder input often with the 300Hp. So I wonder if keeping it coordinated applying the slight right rudder and wings level was creating the condition?  I didn’t try one uncoordinated with no rudder which may have answered my question on that. 
 

anyways, any Missile or Rocket owner’s experience this. Did I cause this or is this a symptom of the Mooney and the conversion?  While the first caught me off gaurd, I was never uncomfortable, nor was the airplane non reactive to proper recovery inputs, but it sure seems more prone to it then I expected. 

 

16 hours ago, Shadrach said:

Wouldn’t Torque cause a left break? My plane always rolls left performing power on stalls

 

1 hour ago, mike_elliott said:

They might be in place, but are they placed correctly? Something is out of whack, and it can only be the rigging or stall strip placement, or your not as coordinated as you might think when it stalls. 

My M20J was converted to a Missile in 2001. My plane always breaks to the left during power on stalls just as @Shadrach stated.   The break is always gentle.  And yes there is a lot of right rudder pedal in to keep it coordinated going into the stall.  Neither wing has ever broken aggressively in 21 years.  And the nose has never broken down.  The left wing just gently starts to drop a few degrees and slowly start to drift left.  More right rudder and it straightens out.  In one BFR I gave it a bit too much right rudder as the stall occurred and it started drifting slowly to the right.  That is the only time it ever went to the right.  My CFI got a bit panicky but I just eased up on the right rudder and it straightened out - and then I lowered the nose.  There has never been the severe snap that you experience.

I believe that THERE IS SOMETHING SERIOUSLY WRONG WITH YOUR RIGGING.

I have a standby vac system in the empennage which adds a little weight and helps with the CG - balance is just fine - very stable. You mention that you need a lot of right rudder - is that only in take-off and full power climbing?  When in cruise at full power wide open does your plane fly straight and level with hands off the yoke?  The trailing edge of my rudder is slightly bent to the left (like a trim tab) so that the rudder deflects just slightly to right to keep all the forces centered. 

[PT20J]

8 minutes ago, Shadrach said:

Did CAR3 cert require it be done at MGW?  300FPM does not require a lot of power on a standard day.  

Interestingly, it says ”appropriate weights”. I assume that would be interpreted as MGW. Here’s the complete section on stalls and spins including paragraph 3.85 referenced in the stall section.

[Rspencer612]

6 minutes ago, 1980Mooney said:

 

 

My M20J was converted to a Missile in 2001. My plane always breaks to the left during power on stalls just as @Shadrach stated.   The break is always gentle.  And yes there is a lot of right rudder pedal in to keep it coordinated going into the stall.  Neither wing has ever broken aggressively in 21 years.  And the nose has never broken down.  The left wing just gently starts to drop a few degrees and slowly start to drift left.  More right rudder and it straightens out.  In one BFR I gave it a bit too much right rudder as the stall occurred and it started drifting slowly to the right.  That is the only time it ever went to the right.  My CFI got a bit panicky but I just eased up on the right rudder and it straightened out - and then I lowered the nose.  There has never been the severe snap that you experience.

I believe that THERE IS SOMETHING SERIOUSLY WRONG WITH YOUR RIGGING.

I have a standby vac system in the empennage which adds a little weight and helps with the CG - balance is just fine - very stable. You mention that you need a lot of right rudder - is that only in take-off and full power climbing?  When in cruise at full power wide open does your plane fly straight and level with hands off the yoke?  The trailing edge of my rudder is slightly bent to the left (like a trim tab) so that the rudder deflects just slightly to right to keep all the forces centered. 

Yes, heavy right rudder in takeoff and climb. Cruise is pretty much centered, and high speed decent requires some left rudder. It flies hands off at high power cruise. Just a little adjusting of the pitch to hold altitude.

[Shadrach]

23 hours ago, 1980Mooney said:

 

 

My M20J was converted to a Missile in 2001. My plane always breaks to the left during power on stalls just as @Shadrach stated.   The break is always gentle.  And yes there is a lot of right rudder pedal in to keep it coordinated going into the stall.  Neither wing has ever broken aggressively in 21 years.  And the nose has never broken down.  The left wing just gently starts to drop a few degrees and slowly start to drift left.  More right rudder and it straightens out.  In one BFR I gave it a bit too much right rudder as the stall occurred and it started drifting slowly to the right.  That is the only time it ever went to the right.  My CFI got a bit panicky but I just eased up on the right rudder and it straightened out - and then I lowered the nose.  There has never been the severe snap that you experience.

I would say that my plane breaks gently during power off stalls with ample warning from the airframe. I would call it benign.   Departure stall is a "whole nother" thing.  Quite a bit more aggressive in every way...high deck angle, significant nose drop, wing drop can be caught early but requires aggressive rudder input. More dramatic in every way with less time between the onset of buffeting and the break.

[geoffb]

any chance the Dynon is giving erroneous slip indication at your high angle of attack leading to excessive right rudder input?

[haymak3r]

Hopefully I don't get blasted for this.

But my instructor showed me a technic that has worked for me in so far. As I would get fixated on the ball during stall practice. Instead he had me start keeping the wings level with rudder only, and not rely solely on the ball. To feel/see the plane to the horizon. If she is flying straight and level as the stall happens regardless of what the ball says, it has always broke straight. We had this discussion the last time we did a power on stall, and the right wing did break first on my a little more than he liked.. Perhaps this is the wrong way to think about it, but I am not so fixated on the turn coordinator as much. Of course, I do reference it, but try to visualize outside more now. 

[Fly Boomer]

3 hours ago, PT20J said:

According to CAR 3, all normal category airplanes had to be placarded against spins unless they are characteristically incapable of spinning. Nonetheless, CAR 3 required that they be shown to recover from a one turn spin in one and a half turns. Spins are not fully developed until 1.5 - 2 turns and a fully developed stall may be harder (or impossible) to recover from. But keep in mind that Mooney probably only tested this once per model and that would have been with a new, perfectly rigged airplane.

And an airplane with its stall strips precisely placed (which I could argue is part of "perfectly rigged"). 

[Pinecone]

7 hours ago, jaylw314 said:

A little OT but I recall reading an EAA article that I can no longer find.  An aerobatic instructor suggested that, for most GA planes, if you're in an unexpected spin and have the altitude, to simply aggressively pull the throttle to idle, aggressively center the controls, and wait until the rotation stops.  He had an eye-opening video of the standard technique of opposite rudder and pushing the yoke forwards flipping a plane from a well-developed spin into an inverted flat spin, and noted that most pilots have no experience or idea how to recover from an inverted spin.  He claimed the altitude loss during recovery was only a little more.

I wish I could find that article and video, but I couldn't find it.

Could be the Beggs-Mueller recovery.

Mueller published it in Flight Unlimited in the early 80s.

The recovery is:

Throttle Idle

Release stick/yoke

Rudder opposite spin direction

[Rspencer612]

17 hours ago, geoffb said:

any chance the Dynon is giving erroneous slip indication at your high angle of attack leading to excessive right rudder input?

Sure could be……..it’s brand new so. How would one test or verify that?  Dynon D10A standby was showing the same and they are independent of one another. 

[Shadrach]

17 hours ago, haymak3r said:

Hopefully I don't get blasted for this.

But my instructor showed me a technic that has worked for me in so far. As I would get fixated on the ball during stall practice. Instead he had me start keeping the wings level with rudder only, and not rely solely on the ball. To feel/see the plane to the horizon. If she is flying straight and level as the stall happens regardless of what the ball says, it has always broke straight. We had this discussion the last time we did a power on stall, and the right wing did break first on my a little more than he liked.. Perhaps this is the wrong way to think about it, but I am not so fixated on the turn coordinator as much. Of course, I do reference it, but try to visualize outside more now. 

I’ve never tested the strength of the rudder/aileron interconnect with the plane on jacks, so perhaps someone else can offer some insight. However, given the interconnect between rudder and ailerons, wouldn’t the plane you still be receiving some aileron input from your rudder input, albeit indirectly?

[A64Pilot]

6 minutes ago, Shadrach said:

I’ve never tested the strength of the rudder/aileron interconnect with the plane on jacks, so perhaps someone else can offer some insight. However, given the interconnect between rudder and ailerons, wouldn’t the plane you still be receiving some aileron input from your rudder input, albeit indirectly?

I don’t think he said to take his hands off of the yoke? Anyway I’ve not tested it either but it’s easily overridden or crosswind landings would be real interesting. Personally I don’t like the interconnect, I removed it from the Thrush H-80 aircraft, they are a crutch in more ways than one.

Maule had an intelligent well thought out interconnect in my opinion, the yoke had cables connected to a servo tab on the rudder so yoke deflection would add rudder, but rudder deflection didn’t feed back into the ailerons, Maule has a LOT of adverse yaw, so the interconnect is helpful

However I concur with his method, I just reference the ball myself, what’s important is wings level with the horizon, if that means the balls out, so be it.

There are aircraft that if you try to recover from a fully developed spin that an aggressive pitch down will put it on its back, but I’d think those are all aerobatic aircraft, but depending on aircraft if you push down, your going thru VNE, my 140 will and it can’t be alone in that, I’d suspect as slick as a Mooney is, it just might too, I don’t want to be past VNE looking at the ground at low altitude. That’s how I think you fail the elevator, and pull the wings off.

 

[brndiar]

On 12/1/2022 at 2:42 AM, PT20J said:

The right rudder counteracts the torque if you keep the ball centered. The decrease in wing lift at the stall doesn’t change that. But it takes increasing rudder as the airplane slows because the torque is (mostly) constant but the rudder becomes less effective. 

To be correct, the right rudder counteracts spiraling slipstream and P-Factor effects, but not torque.

Torque, in contrast to Slipstream, P-Factor and gyro effect does not "yaws" but "rolls" the airplane and "per se" is  corrected (in air) with aileron use.

LG,

m

[EricJ]

21 minutes ago, brndiar said:

To be correct, the right rudder counteracts spiraling slipstream and P-Factor effects, but not torque.

Torque, in contrast to Slipstream, P-Factor and gyro effect does not "yaws" but "rolls" the airplane and "per se" is  corrected (in air) with aileron use.

LG,

m

I think by "torque" usually what's referred to is the yawing torque due to asymmetric angle of attack of the propeller blades.

Edit:  To be a little more clear, P-factor is how engine torque gets translated to yawing torque. 

[PT20J]

1 minute ago, brndiar said:

To be correct, the right rudder counteracts spiraling slipstream and P-Factor effects, but not torque.

Torque, in contrast to Slipstream, P-Factor and gyro effect does not "yaws" but "rolls" the airplane and "per se" is  corrected (in air) with aileron use.

LG,

m

For simplicity, I just lumped all the effects into “torque.”  But you are correct that there are several forces at work. However, it is incorrect to say that rudder does not counteract torque. The aerodynamic center of the vertical tail is above the aircraft roll axis and so the force generated by rudder deflection does produce a rolling moment. 

Skip

[brndiar]

59 minutes ago, PT20J said:

For simplicity, I just lumped all the effects into “torque.”  But you are correct that there are several forces at work. However, it is incorrect to say that rudder does not counteract torque. The aerodynamic center of the vertical tail is above the aircraft roll axis and so the force generated by rudder deflection does produce a rolling moment. 

Skip

Hi,

.....we are flying behind Lycomings....  Engine& Prop. turns  Clockwise (as viewed from Cabin).....it causes "rolling force" that pushes LEFT wing (wheel) down.....(Newton)....

.... to correct that more lift at left wing is needed, it means right aileron (ev.  Aileron Trimming to the right)...

....The aerodynamic center of the vertical tail is above the aircraft roll axis and so the force generated by rudder deflection does produce a rolling moment...  correct,  BUT the right rudder that is needed in that situation produce rolling moment in the SAME DIRECTION as  ROLLING MOMENT CAUSED BY TORQUE (High power setting),  to the left (this force would be probably negligible).

.... NO.... right rudder, that is needed to counteract P-Factor and Slipstream in these situations DOES NOT COUNTERACTS TORQUE (in that case TO THE LEFT) (flying slow, high AoA)....

Torque is the only force that "rolls" and no "yaws" or ev. "pitches" the plane and is corrected by use of aileron (different lift).

...Of Course you can  cause "roll" moment to  the right by momentarily applying right pedal  and like this  momentarily increasing lift of the left wing....

 

LG,

M

P.S. PPL Only, Acro rating.

 

Edited December 3, 2022 by brndiar

[PT20J]

9 minutes ago, brndiar said:

Hi,

.....we are flying behind Lycomings....  Engine& Prop. turns  Clockwise (as viewed from Cabin).....it causes "rolling force" that pushes LEFT wing (wheel) down.....(Newton)....

.... to correct that more lift at left wing is needed, it means right aileron (ev.  Aileron Trimming to the right)...

....The aerodynamic center of the vertical tail is above the aircraft roll axis and so the force generated by rudder deflection does produce a rolling moment...  correct,  BUT the right rudder that is needed in that situation produce rolling moment in the SAME DIRECTION as  ROLLING MOMENT CAUSED BY TORQUE (High power setting),  to the left (this force would be probably negligible).

.... NO.... right rudder, that is needed to counteract P-Factor and Slipstream in these situations DOES NOT COUNTERACTS TORQUE (in that case TO THE LEFT) (flying slow, high AoA)....

Torque is the only force that "rolls" and no "yaws" or ev. "pitches" the plane and is corrected by use of aileron (different lift).

...Of Course you can  cause "roll" moment to  the right by momentarily applying right pedal  and like this  momentarily increasing lift of the left wing....

 

LG,

M

P.S. PPL Only, Acro rating.

 

I agree with your analysis -- I did neglect the sign. Thanks for pointing that out.

There are several roll effects that can be produced by rudder deflection:

Roll due to sideslip (dihedral effect)

Roll due to yaw rate (differential airspeed between wings)

Rolling moment due to rudder deflection (discussed above)

Aileron deflection due to rudder deflection (due to the interconnect springs)

Skip

 

[A64Pilot]

All you have to do is go out and fly the airplane, hold the yoke so that the aileron / rudder interconnect isn’t in play, add right rudder, the airplane will enter a right bank / turn, add left rudder the airplane will roll out of the right turn and enter a left turn / bank. I suspect this is due to dihedral, but don’t know, but I do know it works.

This is required by the FAA, the aircraft has to lift a low wing with rudder, the aileron / rudder interconnect guarantees it and became fashionable in the 60’s and 70’s, by fashionable the FAA gave you cudos if you had one in your design, that’s what I mean by crutch.

Crutch two is to some extent they help with adverse yaw, of course to turn left the right aileron goes down like a flap, this creates drag so if not corrected for left aileron causes the nose to yaw right. so we add rudder to correct that, the aileron / rudder interconnect adds some for you.

I dislike them because unless they are done like Maule did you are fighting the bungees in a cross wind landing because you’re cross controlled. But I really dislike them because the Thrush tailwheel lock was just like it is on a P-51, to unlock the tailwheel you let go of the stick and when it’s full forward the tailwheel is unlocked, so taxiing has the stick slamming back and forth with rudder inputs.

[PT20J]

Lets say I apply left rudder. The airplane will bank to the left because the rudder introduces a yaw rate which causes the right wing to have a greater airspeed (and thus more lift) than the left wing. However, the directional stability of the airplane will eventually cause the yaw rate (and thus the rolling moment) to decrease. There will however be a sideslip, and if the airplane has dihedral, the resulting yaw angle will cause a rolling moment to the right.  So, the ability to turn the airplane with the rudder is dependent on the interaction between the two moments. Reducing dihedral improves the ability to bank with the rudders, but decreases lateral stability and increases propensity to diverge in a spiral. So, rather than mess with the dihedral, the usual fix is to add a spring interconnect between the ailerons and rudder.

Skip

[rbp]

annoying helicopter pilot here.  you're forgetting gyroscopic precession. On a spinning disk (prop or rotor, or bicycle wheel), when the gyro is deflected, the effect is 90 degrees later. So when you bring the tail up on an airplane with a clockwise-spinning propeller, the tail will go (yaw) right. 

[Pinecone]

Technically nose goes left and tail is forced the other way.

[rbp]

1 hour ago, Pinecone said:

Technically nose goes left and tail is forced the other way.

the right hand rule says that the torque vector on a clockwise (from the pilot's POV) prop goes towards the tail. 

[rbp]

1 minute ago, rbp said:

the right hand rule says that the torque vector on a clockwise (from the pilot's POV) prop goes towards the tail. 

ok, here I am correcting myself. I was using my left hand. Torque vector goes towards the spinner. 

[Pinecone]

10 hours ago, rbp said:

the right hand rule says that the torque vector on a clockwise (from the pilot's POV) prop goes towards the tail. 

Yes, but being pedantic, the force is applied at the prop (spinning disk) to the crank through the engine mount.  So the NOSE is moved by the force, and the tail moves because it is rigidly attached to the nose.

[rbp]

1 hour ago, Pinecone said:

Yes, but being pedantic, the force is applied at the prop (spinning disk) to the crank through the engine mount.  So the NOSE is moved by the force, and the tail moves because it is rigidly attached to the nose.

did you not read my correction? 

anyway, it has nothing to do with the way the components are linked (prop, crank, mount), and everything to do with vector arithmetic