M20E Stall and leading edge question

[Petehdgs]

I have been using my '64 Super 21 to travel between Culpeper VA CJR and Dexter MI 2E8 several times last summer.  Because 2E8 is 2100 ft grass with displaced thresholds and has a down slope on RWY 6 in the center third of the runway, it has me working on my short field technique quite a lot.  I added a lift indicator and train with it to get better at slow flight and stay safe.  This training has helped me to identify a glitch that merits further investigation and I decided to ask you all for some advice.  

During slow flight practice at safe altitudes I noticed the wings fly well right up to the stall then break quickly and recover quickly causing the airplane to porpoise.  At altitude this is not a big deal except the break occurs without warning.  When this happens near the ground the results are a hard drop and perhaps a bounce.  I would like the stall to be softer with some feel to it, if that is possible without too much difficulty, and without loss of cruise performance and fuel economy.  

I reread Harry Ribletts book about GA airfoils and he suggests a leading edge modification (page 42) to the 64-212 (and similar 64 series airfoils) but makes no mention of a similar modification to the 63 series.  Since the Mooney uses the 63-215 airfoil, would a similar modification be of  any benefit?  It occurred to me that someone else may have had the same questions and may have done some research in this area.  So how about it? Do any of you have any ideas here?  

Before some comments on my lack of flying skills… I recognize that I can simply adjust my technique to not get so close to the stall during slow landings.  And I may be left with just that.  But admittedly that will leave some low speed performance on the table, not to mention the added safety margin attainable by softening the stall characteristics of the airplane.  So I am investigating to see if it is possible.  If you can help I am all ears.  
Petehdgs@yahoo.com 
 

[Niko182]

I spend a good chunk of my time flying into rather small strips. You might just want to flare maybe a tad bit lower. give or take half a foot. In my opinion however, if you're trying to get stopped quickly, planting the plane is better than greasing it. When it's planted on the ground, you can immediately apply the brakes without flat spotting your tires. Micro VG's are also an option. Most of the people here said that they don't affect cruise, and they reduce the stall speeds by 8%. However just remember that with VG's, the stall will be a bit harsher, since the wing doesn't go as gradually from flying to completely stalling.

https://microaero.com/vgkit/mooney-m20/

[takair]

Some F models were built with a different airfoil on the outboard wings.  They are very noticeable when side by side with the original wings.  I guess they helped with stalls, but I think they also slowed the plane down.  Not sure what the airfoil type was. 
 

I am curious of your description of the stall.  I get a notable buffet that builds until the plane stalls.  The horn is always there as a reminder too.   Even on a short field, I typically just get the horn at touch down, which seems to be about the right margin above stall (maybe 6mph). If you have the horn going off for an extended period, you may be cutting it close with any performance reserve.  I don’t really get it to the buffet, even on an 1800 foot strip.  I usually find that the sink rate gets excessive before the actual stall occurs, and to get the stall requires a good amount of pitch.....aggravating the sink rate.

  That said, your question was about airfoil.  Be sure your airplane has the stall strips on the wings, as this is where the buffet comes from.  Never saw them missing, except on a TKS wing, but your description of lack of warning makes me wonder.   Niko mentioned VGs, that is the only approved airfoil mod I am aware of.  As with everything, they are a compromise, but might help make short fields more comfortable.

[PT20J]

i’ve never flown a E, but I believe all the models have essentially the same wing. https://m-selig.ae.illinois.edu/ads/aircraft.html

Your stall description doesn’t match my experience with C and J models. However, stall behavior is part airplane and part pilot technique. In the planes I’ve flown, stalling it power off and trimmed for not less than 1.3 Vso, slow deceleration (1 knot/ sec), not pitched up excessively, ball centered, and not holding back pressure after the nose drops, yields a noticeable buffet before the stall. It may roll off one way or the other at the stall break, but not excessively. And, it recovers immediately when back pressure is released. If yours is different, I’d investigate why.

Skip

[Shadrach]

7 hours ago, Petehdgs said:

I have been using my '64 Super 21 to travel between Culpeper VA CJR and Dexter MI 2E8 several times last summer.  Because 2E8 is 2100 ft grass with displaced thresholds and has a down slope on RWY 6 in the center third of the runway, it has me working on my short field technique quite a lot.  I added a lift indicator and train with it to get better at slow flight and stay safe.  This training has helped me to identify a glitch that merits further investigation and I decided to ask you all for some advice.  

During slow flight practice at safe altitudes I noticed the wings fly well right up to the stall then break quickly and recover quickly causing the airplane to porpoise.  At altitude this is not a big deal except the break occurs without warning.  When this happens near the ground the results are a hard drop and perhaps a bounce.  I would like the stall to be softer with some feel to it, if that is possible without too much difficulty, and without loss of cruise performance and fuel economy.  

I reread Harry Ribletts book about GA airfoils and he suggests a leading edge modification (page 42) to the 64-212 (and similar 64 series airfoils) but makes no mention of a similar modification to the 63 series.  Since the Mooney uses the 63-215 airfoil, would a similar modification be of  any benefit?  It occurred to me that someone else may have had the same questions and may have done some research in this area.  So how about it? Do any of you have any ideas here?  

Before some comments on my lack of flying skills… I recognize that I can simply adjust my technique to not get so close to the stall during slow landings.  And I may be left with just that.  But admittedly that will leave some low speed performance on the table, not to mention the added safety margin attainable by softening the stall characteristics of the airplane.  So I am investigating to see if it is possible.  If you can help I am all ears.  
Petehdgs@yahoo.com 
 

Stall speed is significantly lower in ground effect. When doing air work the break should definitely be preceded by a discernible buffet. My F almost gives the sensation of skipping before the break.
 

I routinely fly into <1800” strips, sometimes so slow that the yoke hits the aft stop in the flare. Never had a problem with hard landings during short field technique. My hard landings are almost always born out of ballooning from being too fast on a gusty day and not having enough energy to flare a second time. Can be mitigated with power.

Edited November 29, 2020 by Shadrach

[carusoam]

Summary of a few ideas around here...

1) Changing the wings characteristics is pretty challenging... but not impossible...

2) +1 for adding VGs...

3) There are some twisted wings that tried to address this situation...

4) But, in the end... Stalling is stalling... vertical speeds climb rapidly even when partially stalled... or stall occurs at a lower speed...

5) Study a few videos around here... the guys that like to perform precision landings... use really good speed control...

6) Their stall horn sounds just prior to wheels Chirping... a second or so...

7) If you let your stall horn come on, feet above the ground... or the horn is on for multiple seconds... a hard landing is nearly guaranteed...

8) one challenge that can occur... stall speed is variable with the ship’s weight... so knowing approach speeds can be memory intense...

9) To skip the memory challenges... the same people use an AOAi, for precision landings...

10) To improve speed control... Slow flight at altitude can be very helpful... After that, landing can be magical...

11) From slow flight, and near stalls... you can test the difference from the horn coming on, and buffeting occurs... compare to book values...

12) Recency... Recency is really helpful for good landings... mediocre landings today... perfect landings tomorrow... take a week off... first day back, mediocre landings... following day, nice and smooth again... 

13) Interesting to hear... Ross mentioned feeling buffet...  Pete mentioned stall cleanly, without any warning... there might be opportunity to review what the stall strips on the leading edge are doing? Is there a pair on each wing, or just one?

Sounds like Pete is pretty familiar with this list...

Might be time to get a really sharp pencil / Mooney specific CFI to go for a ride... 

You know there is one particular CFII around here that wrote the training for Mooney landings..? Website, video, details... 

PP thoughts only, not a CFI... or cog therapist...

Best regards,

-a-

[cliffy]

Changing the contour of the leading edge would be a big deal with the FAA   Not something to attempt without mucho FAA involvement and aero engineers

Checking the correct placement of leading edge stall strips might be a better endeavor

Adding VGs does work to lower stall speed and control at lower airspeeds.  

Pilot technique  and practice is easy and pays big dividends,

I try to do every 3rd landing as a short field landing every where. I easily get stopped in <1100'  (far end of the 1.000 ft big white blocks).  Of course Bill Wheat would bury any of us in this if he was still around!!!!!

[carusoam]

+1 for Mr. Wheat!

Who probably was involved with placing the stall strips on this M20E in the first place...

-a-

[Nukemzzz]

The stall on my 66’ E scares the pants off me. Breaks hard and snaps over nearly 90 degrees. Honestly, being ok with that is the biggest challenge I face getting my PPL in this thing. If the final test includes an uncoordinated power on stall I might just chicken out. LMAO. 

That said, it’s very obvious it’s coming. The buffet is pretty violent before it breaks. You can nearly hear it even...the sheet metal flapping. During that I’m focused like a laser beam trying to see which wing is going first to counter spin entry. It’s exhausting. Lol

My CFI says it’s no big deal “look at how fast it recovers when we let off the back pressure”. But I’m still there in shock at how we were just snapping into a spin like Art Scholl a second ago. Thankful that I didn’t use the wrong rudder and accelerate it.  

[Nukemzzz]

Idea that hasn’t been mentioned...is your W&B ok?  One reason my stall is so violent I think is because we are right in the nose heavy side of the envelop. My CFI is a big guy and I’m on the heavy side. I carry stuff in the luggage area to balance it out some. 

[carusoam]

Weight and balance are very important to this conversation...

Especially when the plane and/or the runway is new to you...

Best regards,

-a-

[RLCarter]

On 11/28/2020 at 8:48 PM, PT20J said:

i’ve never flown a E, but I believe all the models have essentially the same wing. https://m-selig.ae.illinois.edu/ads/aircraft.html

Your stall description doesn’t match my experience with C and J models. However, stall behavior is part airplane and part pilot technique. In the planes I’ve flown, stalling it power off and trimmed for not less than 1.3 Vso, slow deceleration (1 knot/ sec), not pitched up excessively, ball centered, and not holding back pressure after the nose drops, yields a noticeable buffet before the stall. It may roll off one way or the other at the stall break, but not excessively. And, it recovers immediately when back pressure is released. If yours is different, I’d investigate why.

Skip

My 65’ “E” is about the same, I was in the back seat of a buddies “C” and it was pretty much none eventful as well

[PT20J]

23 minutes ago, Nukemzzz said:

The stall on my 66’ E scares the pants off me. Breaks hard and snaps over nearly 90 degrees. Honestly, being ok with that is the biggest challenge I face getting my PPL in this thing. If the final test includes an uncoordinated power on stall I might just chicken out. LMAO. 

That said, it’s very obvious it’s coming. The buffet is pretty violent before it breaks. You can nearly hear it even...the sheet metal flapping. During that I’m focused like a laser beam trying to see which wing is going first to counter spin entry. It’s exhausting. Lol

My CFI says it’s no big deal “look at how fast it recovers when we let off the back pressure”. But I’m still there in shock at how we were just snapping into a spin like Art Scholl a second ago. Thankful that I didn’t use the wrong rudder and accelerate it.  

Getting comfortable with stalls is one of the hurdles to get over when learning to fly. It's natural to have the fear response kick in when you're way above the ground and feel the effect of going from 1G flight to less than one G while the nose drops and the airplane rolls. It just takes practice. It's not the Mooney -- a Cessna does pretty much the same thing. The gentlest stalling airplane I ever taught in was a Cherokee (which incidentally uses a laminar flow NACA 65-415 airfoil). 

I'll bet it didn't roll anything like 90-degrees (or your instructor would have been alarmed) -- it just seems like that. Since your instructor is comfortable stalling it, just practice them a lot straight and level, and in turns, and power on, and power off. I guarantee that after a while they will become a non-event.

Skip

[RLCarter]

My very first stall was in a C-150, I was on a north heading, pulled back, stalled and recovered. CFI asked how I thought I did, other than dropping a wing and loosing 6 or 700 ft I was happy, then he had me check my heading, almost due south, it had rolled on its back and I can out on the bottom..... never even knew it. Have your CFI stall your aircraft and see how bad the wing drops

[Nukemzzz]

9 hours ago, RLCarter said:

My very first stall was in a C-150, I was on a north heading, pulled back, stalled and recovered. CFI asked how I thought I did, other than dropping a wing and loosing 6 or 700 ft I was happy, then he had me check my heading, almost due south, it had rolled on its back and I can out on the bottom..... never even knew it. Have your CFI stall your aircraft and see how bad the wing drops

I like it even less when he stalls it.  He will force it to completely quit flying it seems.  It will buck and complain and try to wing over and he will keep it centered with the rudder and keep pulling back until it breaks hard.  When I do it, as soon as it starts to break I let it, and recover.  When he stalls it feels a lot like trying to break a bronco and he isn't getting off until it it submits or stops flying.  lol

[Nukemzzz]

10 hours ago, PT20J said:

Getting comfortable with stalls is one of the hurdles to get over when learning to fly. It's natural to have the fear response kick in when you're way above the ground and feel the effect of going from 1G flight to less than one G while the nose drops and the airplane rolls. It just takes practice. It's not the Mooney -- a Cessna does pretty much the same thing. The gentlest stalling airplane I ever taught in was a Cherokee (which incidentally uses a laminar flow NACA 65-415 airfoil). 

I'll bet it didn't roll anything like 90-degrees (or your instructor would have been alarmed) -- it just seems like that. Since your instructor is comfortable stalling it, just practice them a lot straight and level, and in turns, and power on, and power off. I guarantee that after a while they will become a non-event.

Skip

Thanks for the vote of confidence and hints that I'll be ok with it eventually.  

My CFI does say that the stall is more severe than the 172 that we also train in.  His eyes are a bit bigger after recovery.  But he includes with that the statement "but look how it recovers fast".  lol

He flies a Cardinal and I think they are similar so it's not as alarming to him.

I'm fairly certain it falls 90 degrees with the stalled wing down when it happens, but I plan on mounting my GoPro in the plane when we get flying again so I can confirm it's just a monster I'm seeing in the closet.  lol

[ArtVandelay]

i’ve never flown a E, but I believe all the models have essentially the same wing.

While true, when they extended the short bodies, they didn’t move the wing, they also have the batteries in the tail, not in the engine compartment. The result will be less nose heavy, less docile stalls everything else being equal. Starting with the K that has a long nose and heavier engine, they start to become nose heavy again.
If you want docile stalls, get passenger who is heavy and will cause the nose to drop early. ;-)

[carusoam]

Let’s see...

1) We don’t usually discuss stalls very much...

2) Mostly because modern training is all about identifying the signs of the stall...

3) It is most important to identify the signs of stalls, make corrections accordingly, Before it occurs...

4) The reasoning for this... stalls don’t occur in cruise flight.   (except for during extreme vertical gusts... while flying below maneuvering speed, intentional stall to avoid damaging the wings...)

5) Around here, stalls have occurred during slow flight...

• On departure 
• On final approach
• Engine out, trying to return to the airport after T/O...
• turn from base to final... (no examples that I recall around here, but very important to know and understand)

6) It is important to go through the effort of experiencing stalls, and accelerated stalls... as part of Transition and primary training...

7) A well rigged Mooney, with the ball centered, stalls comfortably straight ahead...

8) No, wing drops aren’t normal, no bucking Broncos... no changing directions... just stall, and the associated loss of altitude that comes with that...

9) focus on the important parts of recognition... the chance of recovery after a surprise stall at TPA is too much of a dice roll... the injuries are too great...

10) Stalls should be enjoyable... predictable... and easily recoverable...

Grab some video, see if the ball isn’t centered, find out why the plane is behaving this way... or find out why the pilot is perceiving something different than what the video provides...

Have a discussion with the CfI... ask why we are doing stalls..? The rest of the world has moved on to recognition and avoidance...

For comparison... I enjoy roller coasters and stall training... can’t get enough... not something I do very often. 
 

I think something may be getting lost in translation.... could be me...

PP thoughts only, not a CFI...

Best regards,

-a-

[PT20J]

1 hour ago, ArtVandelay said:

While true, when they extended the short bodies, they didn’t move the wing, they also have the batteries in the tail, not in the engine compartment. The result will be less nose heavy, less docile stalls everything else being equal. Starting with the K that has a long nose and heavier engine, they start to become nose heavy again.
If you want docile stalls, get passenger who is heavy and will cause the nose to drop early. ;-)

I always thought that some of the 10 stretch between the E and F went ahead of the wing. The spar is in the same place under the rear seat, so to get more legroom it would seem necessary to move things forward. Anyone have a definitive reference on this? 

Skip

[RLCarter]

12 minutes ago, PT20J said:

I always thought that some of the 10 stretch between the E and F went ahead of the wing. The spar is in the same place under the rear seat, so to get more legroom it would seem necessary to move things forward. Anyone have a definitive reference on this? 

Skip

I think  5” was added in front and 5” in back (from the spar)

[Hank]

15 minutes ago, RLCarter said:

I think  5” was added in front and 5” in back (from the spar)

Yes, 5" more back seat legroom, 5" extra baggage space. But the Zero point for W&B also changed . . . .

Edited December 8, 2020 by Hank

[Hank]

3 hours ago, Nukemzzz said:

I'm fairly certain it falls 90 degrees with the stalled wing down when it happens, but I plan on mounting my GoPro in the plane when we get flying again so I can confirm it's just a monster I'm seeing in the closet.  lol

Please link the video here, I'd love to see it. Stalls aren't something I do often, but they aren't bad. But I was very, very careful [and recovered as early as possible] doing accelerated stalls on my Instrument check ride!

[Brian E.]

On 11/28/2020 at 5:16 PM, takair said:

  I get a notable buffet that builds until the plane stalls....I usually find that the sink rate gets excessive before the actual stall occurs, and to get the stall requires a good amount of pitch.....aggravating the sink rate.

My experience flying a couple of different C's and an E mirrors your experience--stalls are predictable, telegraphed and are a non-event if handled correctly.  I do tend to get reminded of the L/D profile when I go beyond the "normal landing pitch" due to an early round out and the sink rate gets aggressive...but again no stall.

[Pilot boy]

On 11/28/2020 at 1:12 PM, Petehdgs said:

I have been using my '64 Super 21 to travel between Culpeper VA CJR and Dexter MI 2E8 several times last summer.  Because 2E8 is 2100 ft grass with displaced thresholds and has a down slope on RWY 6 in the center third of the runway, it has me working on my short field technique quite a lot.  I added a lift indicator and train with it to get better at slow flight and stay safe.  This training has helped me to identify a glitch that merits further investigation and I decided to ask you all for some advice.  

During slow flight practice at safe altitudes I noticed the wings fly well right up to the stall then break quickly and recover quickly causing the airplane to porpoise.  At altitude this is not a big deal except the break occurs without warning.  When this happens near the ground the results are a hard drop and perhaps a bounce.  I would like the stall to be softer with some feel to it, if that is possible without too much difficulty, and without loss of cruise performance and fuel economy.  

I reread Harry Ribletts book about GA airfoils and he suggests a leading edge modification (page 42) to the 64-212 (and similar 64 series airfoils) but makes no mention of a similar modification to the 63 series.  Since the Mooney uses the 63-215 airfoil, would a similar modification be of  any benefit?  It occurred to me that someone else may have had the same questions and may have done some research in this area.  So how about it? Do any of you have any ideas here?  

Before some comments on my lack of flying skills… I recognize that I can simply adjust my technique to not get so close to the stall during slow landings.  And I may be left with just that.  But admittedly that will leave some low speed performance on the table, not to mention the added safety margin attainable by softening the stall characteristics of the airplane.  So I am investigating to see if it is possible.  If you can help I am all ears.  
Petehdgs@yahoo.com 
 

I have been working on my accuracy landings in my 1964 M20E lately and practice makes perfect.  As carusoam mentioned we generally focus on speed and that makes all the difference.  With full flaps I do tend to come down more firmly than with half (2 pump) flaps.  I would focus on your speed and weight of the plane.  Practicing for short field landings to commercial standards I have added ballast weight to the plane to always be at or near full gross.  Otherwise the plane will act differently if I’m lighter etc.  I come in at 80 mph in low wind conditions, then lower it to 75 mph as I get over the runway, pull power right past the numbers and I can hit first centerline stripe.  I usually add a little power to make it to 2nd stripe as that’s my aiming point for commercial PTS.  I’m surprised by your comment that the stall happens with no warnings...you should be hearing the stall horn around 68 mph.  (10 mph above Vso in the E.). 
Again, you should land with full flaps for a short field but if you want a gentler landing 2 pumps works better to make it not as abrupt of a drop.  However that’s not really the proper procedure as others have mentioned.  
if you have room....I come in quite low toward the runway threshold...probably less than 50 ft.  This shortens the ground effect and flare.  
one last caution,  be careful departing that short field grass strip in summer with only 2100ft.  If you increase the weight at all or to a high temp high DA day you might have trouble departing a 2000 ft strip.  I personally won’t use less than 3000 if within 100 lbs of full gross above 90 degrees.  I did a takeoff this summer on asphalt that took about 1900 ft when I was close to max gross and 95 out.  The strip was 3000 ft fortunately.    It looked a bit close toward the end....

[Ragsf15e]

14 hours ago, Nukemzzz said:

Thanks for the vote of confidence and hints that I'll be ok with it eventually.  

My CFI does say that the stall is more severe than the 172 that we also train in.  His eyes are a bit bigger after recovery.  But he includes with that the statement "but look how it recovers fast".  lol

He flies a Cardinal and I think they are similar so it's not as alarming to him.

I'm fairly certain it falls 90 degrees with the stalled wing down when it happens, but I plan on mounting my GoPro in the plane when we get flying again so I can confirm it's just a monster I'm seeing in the closet.  lol

I have been doing this flying thing for ~35 years, but I remember being afraid of stalls too.  I also remember being about 5 and sitting in the back of a C-172, terrified, while my dad practiced for his PPL with his CFI.  Since then, I flew a lot of high performance airplanes upside down, vertical up/down, and twice backwards (one time was on purpose).  The only way to get comfortable with some of this stuff is learning and practicing.  Keep doing it (safely) and you’ll eventually be comfortable with it, but remember the feeling because your non pilot passengers probably feel like you once did.

Now, my Mooney buffets plenty that the stall is definitely not a surprise.  Accelerated stalls can be forced right into the break though if you pull real quick through the buffet and that’s more exciting.  When coordinated, mine rolls relatively slowly left in general and is easily controlled/recovered by releasing the back pressure.

I have purposely stalled at close to full power in a climb with my feet on the floor (no right rudder) because I wanted to know what to expect if I really screwed up.  It did quickly roll toward a 60-90 degree left bank spin entry but recovered very quickly with slightly forward elevator (and idle power and right rudder, but the elevator broke the stall).

I have heard that the stall characteristics are very sensitive to the exact position of the leading edge stall strip on the wings, and those are removable/moveable.  If the airplane is painted maybe they are put back close?  Moved in the last 50 years?  Supposedly, Bill W. And the other test pilots would test fly them and then come back with a recommended adjustment for that stall strip.  Anyone know if that’s true?  And how would we adjust them now if your aircraft stall was “unconventional”?

Edited December 9, 2020 by Ragsf15e