M20K stalling tendencies

[airbuspilot2436]

I've owned my 1980 M20K for a couple of months now and when she stalls, she has a tendency to bank very hard on one wing. Not always the same. 
 

As it will approach the stall it's stable, but as the stall comes in, it will usually want to bank pretty hard. On the approach to stall if I feel it banking left or right I'll compensate with rudder (not ailerons so I won't induce a spin) and then as it stalls I'll follow it in the bank and recover.

 

Is this just my airplane? Or something with Mooney airplanes in general? Thank you!

[carusoam]

Where are you at tonight ABP? Kind of late here on the East Coast.... you must be up really early in Switzerland.... 

Most Mooneys have pretty benign (non-scary) stall behaviors...  but they are different enough from planes that don’t have laminar type wings...

Much stall training in the US currently consists of identifying the stall and taking action to prevent it... 

Properly rigged Mooneys, with the ball centered, tend to stall straight ahead... out of rig, or missing stall strips can lead to variations in stall behaviors....

Falling off to one side or the other... not an experience that I have encountered... active centering of the ball... as the nose points higher, the forces change...

We have a few flight instructors here... the West Coast May still be awake...   inviting @donkaye to see if he may have an answer to get you started...

PP thoughts only, I am not a CFI...

Best regards,

-a-

[ArtVandelay]

. 
Properly rigged Mooneys, with the ball centered, tend to stall straight ahead... out of rig, or missing stall strips can lead to variations in stall behaviors....

I disagree with the generalization of Mooney stall behaviors.
The old short bodies were a nose heavy, so they tend to drop the nose when stalling. But when they extended the body, they didn’t change the wing position, so now they became less nose heavy, more balanced, the J being the most balanced. Somewhere they moved the battery from front to back as well. Starting with the K, because of the longer nose and little heavier engine, the balance started to move forward again. The long bodies have even bigger and heavier engines to balance the further extension of the body.
I’m not a Mooney CFI, but I would be shocked if they said all Mooneys handle the same. I don’t believe a Mooney CFI ever likes to fully stall the plane, and they usually like to gently approach the stall, feel the buffet and recover.
I think the abrupt loss of lift is a characteristic of laminar flow wings, some add vortex generators to disrupt the laminar flow to improve slow speed handling.
A year or two FAA has changed it’s requirements for demonstrating stalls. They no longer require a fully developed stall, and want to see recovery at first indication.


Tom

[carusoam]

Good morning Tom, @ArtVandelay

I think you may be misunderstanding what I wrote... (happens some times, my writing is still improving) 

 

 

the discussion is regarding one wing stalling before the other... are you seeing that?

Somewhat random to which side drops first...

My generalization is both the short and long body stall similarly... straight ahead...

ABP has a mid body... but that doesn’t make it stop flying on one side or the other either...

Beyond that knowledge... i’m Not a CFI so i’m Not really comfortable giving advice on the topic...

Looking forward to seeing if somebody can explain what causes the one wing to drop first...

As far as differences between the Mooneys... Adding torque can throw in a lot of difference... as can rigging or missing stall strips... but those are maintenance and procedure issues not related to the Mooney design.

hmmmm.....  ABP didn’t mention if these are power on, or power off stalls....   

I would say, I didn’t generalize anything... I gave very little advice at all... I did mention catching up with a CFI if he could find one awake at this time of day...

 

Best regards,

-a-

[aviatoreb]

3 hours ago, airbuspilot2436 said:

I've owned my 1980 M20K for a couple of months now and when she stalls, she has a tendency to bank very hard on one wing. Not always the same. 
 

As it will approach the stall it's stable, but as the stall comes in, it will usually want to bank pretty hard. On the approach to stall if I feel it banking left or right I'll compensate with rudder (not ailerons so I won't induce a spin) and then as it stalls I'll follow it in the bank and recover.

 

Is this just my airplane? Or something with Mooney airplanes in general? Thank you!

Maybe your airplane is out of rigging?  Are you stalling with the airplane coordinated/centered ball?

My m20k stalls straight ahead and balanced as long I keep the ball centered.

E

 

[airbuspilot2436]

15 minutes ago, aviatoreb said:

Maybe your airplane is out of rigging?  Are you stalling with the airplane coordinated/centered ball?

My m20k stalls straight ahead and balanced as long I keep the ball centered.

 

Yes it's rigged properly and it's centered. 

[aviatoreb]

56 minutes ago, airbuspilot2436 said:

Yes it's rigged properly and it's centered. 

I can’t think what it might be then.  My m20k stalls quite neutrally straight ahead.

[ArtVandelay]

My first stall in my J resulted in a severe left drop. I was used to 172s where I could man handle it and take it to a full stall. After that I was instructed to gently approach the stall (sneak up on it), recovering at first buffet. I was referring to a fully stalled condition, it was early morning so I read your comment about Mooneys stalls straight ahead as an indication they are benign.

172s are benign, I can yank the yoke back and end up in a falling leaf...I don’t think you can do that with the mid bodies and maybe with others.

If you go out and do a full stall (pull the yoke all the way back smoothly but not gently), I think you’ll get a wing drop. Isn’t there a instructor who wrote about this, I vaguely remember reading his account (donkaye maybe?)

 

 

Tom

 

[N201MKTurbo]

When I first got my J, I needed a BFR. The only time my CFI was available was after work so we did the BFR at night.

He asked me to do a departure stall, so I did. The plane almost snap rolled inverted. After I recovered in the dark I told him we weren’t doing any more stalls and he agreed.

After that I rerigged the flaps, ailerons and rudder. 

Now it stalls very gently and straight ahead.

[LANCECASPER]

4 hours ago, airbuspilot2436 said:

Yes it's rigged properly and it's centered. 

How do you know for sure that it's rigged properly? 

[ArtVandelay]

After that I rerigged the flaps, ailerons and rudder. 
Now it stalls very gently and straight ahead.

2 ?:
As long as the ball is centered, shouldn’t that compensate for mis-rigged rudder?
If plane flys straight with hands off, doesn’t that mean it’s rigged properly?


Tom

[Yetti]

The stall strips are small.   they may have been moved or painted over poorly.   Also if been repainted, where the surfaces balanced?

[N201MKTurbo]

24 minutes ago, ArtVandelay said:

2 ?:
As long as the ball is centered, shouldn’t that compensate for mis-rigged rudder?
If plane flys straight with hands off, doesn’t that mean it’s rigged properly?


Tom

You are correct, all I did to the rudder was trim it to center the ball in cruise.

The wing can be rigged with a less than optimal combination of aileron trim vs flap position and still fly wings level with the ball in the middle. The problem is the lift distribution across the wings. You want to have the flaps even and the ailerons even. You can make minor corrections by changing the flap stops, but if the flaps get too uneven (more than ~1 degree) it is better to trim the ailerons. A lot of people are opposed to trimming the ailerons, but if you do it gently  over the whole trailing edge you can't even tell it has been trimmed. Travel boards are a good starting point, but you have to test fly it to get it right. You have a choice to make, do you want it to fly straight and level with just you or you and a passenger? You know you have it right when it flys level hands off and stalls straight ahead and smooth.

BTW the ailerons and yokes should be even too.

Edited February 14, 2019 by N201MKTurbo

[Vance Harral]

I've seen too many reports of Mooneys dropping a wing during stalls to believe every airplane which exhibits that characteristic is severely mis-rigged, or flown by a ham-fisted pilot.  Rather, I think it's more likely a characteristic of an airfoil which is more sensitive in the post-critical-AOA region.

Remember that when the critical angle of attack is exceeded, lift does not instantly go to zero, but rather just reverses trend to a negative slope:

 

 

Some airfoils have a relatively shallow slope just past the critical AOA.  With these airfoils, a small difference in AOA between the left and right wings is not going to induce a significant rolling moment.  Other airfoils have a steeper slope past critical AOA, and are more prone to roll.  The steeper the post-AOA slope, the more "penalty" there is for a less-than-perfectly-coordinated stall.  This is true regardless of whether the imperfect coordination is imposed by a less-than-perfect pilot or less-than-perfect rigging (including placement of the stall strips).

I did my CFI training in our M20F, including the full stall series of trim stalls, cross-controlled stalls, and so on.  I won't speak for short- and long-body airplanes, as I agree with @ArtVandelay that the different airframes likely have different characteristics.  I won't even speak for airplanes other than our particular specimen.  But based on experience in that airplane with a multi-thousand-hour "Gray Eagle" "CFI (not Don Kaye, but similar), I don't think it's a significant risk to fly a mid-body Mooney completely into the stall break for training purposes, even in the dreaded skidding turn.  Yes, a skidding stall does cause the airplane to roll significantly in the direction of the low wing, and it felt like an E-ticket ride the first time.  But a prompt push on the yoke and application of top rudder resulted in a normal recovery, and no more than about 60 degrees of bank (it feels like you've gone completely knife edge the first time, but not really).

Based on this, I don't feel any need to "ease up on the stall" or "recover at the first indication of buffet" when training.  Note in particular that the current FAA Private Pilot ACS tasks on stalls call  for the applicant to "recover promptly after a full stall occurs".  It's true the FAA has been refining the language in the ACS recently, but the current version most certainly calls for a full stall.  Don't conflate this with the slow flight task, which the FAA currently wants to involve absolutely no indication of an impending stall.

Finally, don't confuse flying the airplane into a full stall and promptly recovering, with flying the airplane into a full stall and holding it there to perform a "falling leaf" or otherwise just see what happens.  I'll let Don tell his own stories, but my recollection is his keep-you-awake-at-night incident involved the latter.  I would not teach or even experiment with that in a Mooney.

Edited February 14, 2019 by Vance Harral

[bradp]

Also recall that each airframe is born from the factory a little different. They leading edge stall strips are placed by hand and may vary in placement between wings.  

[Ragsf15e]

There is definitely a difference in my M20F when I stall it power on (~60%+) vs power off.  If the ball is centered it’s relatively straightforward either way and relatively straight ahead, but much quicker and more sensitive to small yaw with the power on.  I have purposely stalled it with power on and feet off the rudders just so I’d know how quickly it would turn bad.  It was quick.  Very much like a half snap roll.  It got my attention and I was flying a fully aerobatic airplane at work at the time.  It did recover very nicely with power reduction (just to help me get rid of yaw)  slight push on the controls and a coordinated roll to wings level. 

One great thing about the mooney is that it really talks to you before stalling.  Stall horn screaming, buffet, forces me to pull back very hard to get it to actually stall.

So to the OP... how certain were you that it’s really well coordinated and rigged?

Edited February 14, 2019 by Ragsf15e

[Danb]

I’ve had two J models and currently have an M model. My 1988 J purchased new by me occasionally had entered a violent stall much different than either of my two other planes. During a BFR back when they were called that at 4000 feet  we went into a spin to the right, about two revolutions. I’ve been more aware to respond quicker at the first sign of a stall. My M never seemed to be as violent. 

[LANCECASPER]

10 hours ago, bradp said:

Also recall that each airframe is born from the factory a little different. They leading edge stall strips are placed by hand and may vary in placement between wings.  

Exactly . . . when Mooney test pilots would get back from a test flight adjustments would be made. No two ever left the factory exactly alike. When Mike Miles, Mooney test pilot, checked me out in a new Bravo that I bought back in '96, he told me that they all fly a little differently.

Fast forward a fews years and let's says it's been painted and control surfaces have been removed and maybe balanced by someone that doesn't know Mooneys well. The ball could be centered but due to stall strip locations or other things, one wing could stall before the other, etc, etc.

[PT20J]

Hmmm. Lots of interesting comments. Let's see if we can sort this out...

 Mooneys are hand built and it is true that they are all a little different. Back around 1992, Rob McDonnell (VP of Engineering at the time) told me that they flight tested each airplane with the stall strips duct taped on and moved them around until the wing drop was "about" equal at stall and then riveted them in place. So, some are probably better than others, but none should roll off greatly.

Assuming a wings level, ball centered entry, the stall characteristics will vary with power on or power off, and also the rate of deceleration. To avoid dynamic effects, a power off deceleration in level flight of about 1 knot per second is a good target. Pull up more than that and it will get more exciting.

If it still falls off, the first thing to check is that the airplane is rigged correctly, of course. Here's an excellent article on flight checking the rigging. Don't forget the flaps! http://www.knr-inc.com/shoptalk-articles/25-shoptalk/75-201407-control-rigging.

Also, you can check if any wing repairs may have altered one wing slightly.

Even so... My '78 J always rolled at stall. There was no damage history, but the stall strips were in noticeably different positions on the "nose" of the wing, one being quite a bit higher than the other.  My '94 J stalls without noticeable roll, the stall strips are about even, and the right wingtip had a rib and skin replaced due to a hangar door incident by the previous owner (Maxwell did a very nice repair) and there is some bondo on the leading edge from an earlier ding. 

So, I wouldn't lose sleep over some roll off. Every one is going to be different. If you are uncomfortable with it, go up with an instructor and do stalls until it's second nature so you aren't afraid of it and then focus on stall avoidance. That's important because good landings in Mooneys come at slow speeds.

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[ArtVandelay]

FWiW, my stall strips are screwed on and equal size and position.
I have to wonder the benefits of doing stalls under ideal conditions:
1. You get warning before you even start
2. You approach with the ball centered
3. speed falling off no more than 1 knot/sec.

I would think in real life scenarios, none of the above is going to be the case. You’ve already unintentionally stalled the plane?

Stall avoidance and slow flight to recognize the characteristics of a pending stall seems more valuable.


Tom

[PT20J]

2 minutes ago, ArtVandelay said:

I have to wonder the benefits of doing stalls under ideal conditions:

Stall avoidance training is better for real life situations. Lot's of people are afraid of full stalls though, and the value of doing them is to lose the fear. Even if it rolls off, you still have plenty of control authority to recover - it just seems scary at first.

[aviatoreb]

Could the difference between what I think my airplane is a mild coordinated stall and others are finding a severe snap roll wig dropping stall not be the difference between coordinate/uncoordinated or  ball centered/not, but instead be the difference between what ai am doing which is pretty much a mild stall then relatively early recovery vs a much deeper stall than some of you are doing?  Maybe it is more standard a snap roll, wing drop situation for our airplanes if we let the stall get pretty deep?  I don't really know from experience.  Who here can speak to this question?

[Ragsf15e]

44 minutes ago, aviatoreb said:

Could the difference between what I think my airplane is a mild coordinated stall and others are finding a severe snap roll wig dropping stall not be the difference between coordinate/uncoordinated or  ball centered/not, but instead be the difference between what ai am doing which is pretty much a mild stall then relatively early recovery vs a much deeper stall than some of you are doing?  Maybe it is more standard a snap roll, wing drop situation for our airplanes if we let the stall get pretty deep?  I don't really know from experience.  Who here can speak to this question?

Yep, potentially that’s true.  Mine buffets pretty good before the nose really falls off.  Much easier recovery if you do it at the first big buffet.  Who’s to say what was the last big buffet or full stall.  Tough to put in words on a post too.  We may just be describing differently.

[aviatoreb]

2 minutes ago, Ragsf15e said:

Yep, potentially that’s true.  Mine buffets pretty good before the nose really falls off.  Much easier recovery if you do it at the first big buffet.  Who’s to say what was the last big buffet or full stall.  Tough to put in words on a post too.  We may just be describing differently.

Exactly what may be the difference here.  I am a "regular ol' pilot" so maybe I whimp out earlier than you a real legit aerobatic pilot.  So what I am experience is different from what you are getting as the "full" effect.

[gsxrpilot]

With Geneva Switzerland as the location feel free to ignore this post. But for anyone else experiencing the same... here's my $0.02

1. The problem could be with the airplane - When it comes to rigging and other delicate adjustments, until Don Maxwell tells me it's not the plane, I would be suspect about it.
2. The problem could be with the pilot - In which case I'd want a very experienced Mooney instructor such as @donkaye or @mike_elliott to verify it's not the pilot.

Virtually every A&P claims to be able to follow the instructions and rig a Mooney, but Don has rigged hundreds and flown them all. I once had a C that I was told was rigged correctly, then Don got.ahold of it. And it was a whole different airplane, and several knots faster as well.

I've also had a few CFI's in my Mooney who would tell me about how "Mooneys are just like this" then later I learn better. There is a handful of instructors who have enough hours in enough different Mooneys to know better.