Stalls and slow flight poll/discussion.

[201er]

Just now, teejayevans said:

How does Cloudahoy know your IAS?

I'm  pretty sure it's ground track. Or perhaps ground track corrected for forecast winds.

[201er]

3 hours ago, PTK said:

I strongly disagree on both.

The reason we teach stalls is not to fully stall the airplane and spin it. We teach stalls to help the student develop a feel and recognition for the airplane's slow flight and stall charactetistics. These are skills necessary to properly slow down and land the airplane. 

A stall can happen at any airpeed and from any attitude and it is a function of angle of attack. There are way too many stall/spin accidents in the traffic pattern every year. Most are a result of pilot's failure to maintain airspeed. I don't know of any airplanes that stalled and spun when sitting still on the ramp. No matter the slope of the ramp. Similarly not too many stall and spin in cruise. The overwhelming majority of these fatalities happen while maneuvering in slow flight in the pattern. 

And what airspeed is that? It's an arbitrary number that changes in all configurations, bank angles, weights, load factors, and density altitudes. The AOA which they failed to maintain is constant regardless of those differing speeds. It's alright, Peter, you go practice stalling your plane and I'll practice keeping mine from stalling ever.

Edited September 14, 2016 by 201er

[PTK]

22 minutes ago, 201er said:

And what airspeed is that? It's an arbitrary number that changes in all configurations, bank angles, weights, load factors, and density altitudes. The AOA which they failed to maintain is constant regardless of those differing speeds. It's alright, Peter, you go practice stalling your plane and I'll practice keeping mine from stalling ever.

It's not arbitrary at all. It is very predictable. It's in your POH. I will ask you again: how different is your Vso from what's in your POH?

[201er]

3 minutes ago, PTK said:

Arbitrary it's not. It's in your POH. I will ask you again: how different is your Vso from what's in your POH?

This is the entire stall related information from my entire POH. It does not compensate "stall speed" for altitude, above standard temperature, uncoordinated turns, above gross weight (just cause someone miscalculated and overloaded their plane, doesn't mean all passengers aboard deserve to die from an airspeed that would have normally been adequate but in that case creates an excessively high angle of attack), or additional g from pulling back more than standard. It does not give in between values. That is quite a range of stall speeds from 55-86 knots! How many pilots have that table posted on their dash? It still doesn't account for in between and other conditions. It does not compensate performance speeds (Vx, Vy, Best Glide) for weight, bank, or da. Angle of attack is always the same. Angle of attack is not just about stalls. It is about all operations at "low speed" (fine print: when compensated for flap/gear configuration, depending on weight, when charted for bank angle, without excessive loading, for coordinated turns, only at sea level at standard temperature, by a dentist pilot who is in bed with garmin and hates all american)

Edited September 14, 2016 by 201er

[carusoam]

Things I realize this far into this discussion...

1) Some people like stalls more than others.

2) Practicing power on stalls, light on an ordinary day,. Can be much different than hot and heavy.

3) flying AOA At max power, on a hot day, into rising terrain has got to leave a very empty feeling.

4) Stalls with poor rigging adds some variability into the stall and the recovery.

5) stalls in the dark = Thrill Seeker.

6) stalls in the dark with poor rigging = screaming prayer sayer.  

7) Some people have their stall charts memorized or a good handle on most of it.

8) the ball is centered in straight and level flight when the nose is kept on a target.  (?) sounds logical

8.5) Cloudahoy is using GPS derived speed, unless you can have it connected to an air data computer.

 

A couple of follow-up ideas...

9) Anyone doing steep turns while climbing out in the traffic pattern?

10) Anyone use maximum deflection of the controls in the traffic pattern?  ( full rudder/aerleron deflection)

 

Following along,

-a-

[N201MKTurbo]

21 minutes ago, carusoam said:

 

5) stalls in the dark = Thrill Seeker.

6) stalls in the dark with poor rigging = screaming prayer sayer.  

None of the above. Just the only time we were both available and I had a trip the next day.

I don't go out of my way to do stalls in the dark, but I'm not afraid of them either.

[ArtVandelay]

Regarding airspeed of stalls, I just use 99 number and not do any 60 degree turns. But there is a question how accurate is your air speed indicator at slower speeds and higher angle of attack. Ive glanced at my GPS speed vs ASI and the ASI reads higher in calm conditions, a good 7-8 knots IIRC.

I agree practicing stalls is unrealistic, especially the gentle increasing AOA while straight, a more realistic practice would be yanking of the yoke as if you were trying to avoid a bird or turn as in pattern. Pretty sure neither of those will be benign, probably best to just avoid them altogether.

[TheTurtle]

5 hours ago, bradp said:

At least they were practicing stalls over a lake.  Skip ahead to 2:56.  It looks like he may have stalled it, lowered the angle of attack and then increased it again.   The wing drop looks like it turned into a half turn of a spin (I couldn't tell if it was fully developed).   This is why I don't practice fully developed stalls in the Mooney  

 

pilot doesnt have his shoulder belt on it looks like.

[201er]

14 minutes ago, carusoam said:

9) Anyone doing steep turns while climbing out in the traffic pattern?

10) Anyone use maximum deflection of the controls in the traffic pattern?  ( full rudder/aerleron deflection)

Great summary Anthony. Good topic Cnoe. No matter how much we agree or disagree, it's still way better to have these topics on our minds and justify to ourselves (in the process of doing so to others) why we do things. In the course of discussion we may realize we do things right all along or realize ways to do it better. It is all more productive and beats looking at fat women and Hillary Clinton.

 

Anthony, to answer your 2 questions. NO. However, given a situation (that I can't imagine) that would necessitate it, yes. Here's why. A steep turn demands a lot of lift so it would substantially diminish my climb rate or perhaps even make the plane sink. In most cases, doing a shallower unpwind to crosswind turn will yield a greater gain in altitude. If there's a mountain perpendicular to the airport or rising terrain, a slower turn at Vx (Not published Vx speed but Vx AOA) should still maintain a fairly tight turn radius because the speed is slow while climbing.

 

If I found myself climbing into an airplane or bird, then yes. I might throw the nose down and turn steep. But in any case, if a steep turn is necessary during a climb, the nose is going to have to come down a good ways first.

[gsengle]

This is why AOA indicators are so valuable imho. Sure ok you memorized the stall speeds for *level flight* at every weight and bank angle combination, and throw in configuration too. How about a climbing turn? A descending turn? I want an AOA indicator for xmas.

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[201er]

Just now, gsengle said:

This is why AOA indicators are so valuable imho. Sure ok you memorized the stall speeds for *level flight* at every weight and bank angle combination, and throw in configuration too. How about a climbing turn? A descending turn? I want an AOA indicator for xmas.

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I think the Grinch, I mean dentist, didn't get one last xmas which left him so bitter

[Guest]

Once again a thread which is leading me to block some posters.

Clarence

[cnoe]

I still have questions. Two to be exact (though the 2nd is multi-part). I already asked one which went unanswered so I'll ask it again because being a novice pilot I want to make sure I'm not missing something.

#1. Isn't Vso based simply on IAS with density altitude and temperature having no direct bearing on the value?

If I'm wrong about this then I better hit the books and start adjusting my departure speeds when flying from high-elevation fields.

#2. (And I'm not trying to be a smart ass here...) What does the typical AOA indicator (in a Mooney) display when parked on the ramp idling (with little/no relative wind and a tail-low attitude)? Off? High AOA? Low AOA? Is there a come-alive speed for the indicator (based on airspeed)? I guess what I'm truly asking is how do you determine the rotation point using an AOA indicator in the absence of an airspeed indicator; just fly it off?

I don't recall exactly but I believe the Dynon unit (AOA indicator) I previously flew with (rental) required a certain airspeed before it was usable but that's just a guess.

Cnoe

P.S. Hang in there Doc. Something good HAS to come from this. I hope.

[Hank]

Cone, my understanding of Question #1 is Yes, stall happens at the same IAS regardless of conditions, for a particular weight and configuration.

Regarding stalls in my Mooney, imdomthem on BFRs and IPCs when requested, but only to buffet and recovery. On my Instrument checkride, the DPE had me reduce throttle to achieve a "realistic" deck angle for the accelerated stall, simulating what would happen by accident. But I can fly around for 5-10 minutes at MCA, turning in both directions, with the stall horn blaring.

In the pattern, Mike, I'm almost always at Flaps 15°/ Gear Down with bank angles < 20° until after I stabilize on final, giving a 2 mph variation at gross on your chart. I can remember that much. I account for weight in my "over the (imaginary) fence" speed by slowing down an additional 5 mph for every 300 lb I estimate below gross. Final speed = 85 mph, safely above stall; fence = 75 mph minus 5 as described if needed. No stall buffets in the last nine years; no steep banks in the last nine years; hand on the throttle if needed for the last nine years. Use your head a little, it works well. Nite that this keps me safely away from the edges of the performance envelope.

[cnoe]

Thanks for the response to question #1 Hank. I was pretty sure that was the case but then I read statements like:

 

"Next, on that day that you get yourself in a bind with a power on stall... most likely this won't be in winter either. Hot Day, higher DA, or actually the one time you go to a higher elevation field." 

and

 "Practicing power on stalls, light on an ordinary day,. Can be much different than hot and heavy."

 

I'm just trying to make sure that I (and others) get accurate info from these discussions. We have to keep it real. 

[Hank]

Stall speed will vary with aircraft weight and bank angle, and may vary slightly with CG.

What high temps and high DA does is make your true speed higher, so that nice and low in the pattern with eyes outside, you may think you are fast and slow down, then a steeper-than-normal bank may kill you . . . Just like you will be moving much faster when you flare at 70 MPHI when DA is 6000' than when it is 50'--that's the whole reason runways are longer in the intermountain west, to give you room to accelerate on takeoff and decelerate after landing because real flying speed is much higher.

Slowing down increases angle of attack if your descent rate doesn't change; banking steeper increases your angle of attack if you don't increase your descent rate; banking steeper increases your stall speed, because the lift vector is no longer perpendicular to gravity. This is a bad combination. 

[201er]

1 hour ago, cnoe said:

Thanks for the response to question #1 Hank. I was pretty sure that was the case but then I read statements like:

 

"Next, on that day that you get yourself in a bind with a power on stall... most likely this won't be in winter either. Hot Day, higher DA, or actually the one time you go to a higher elevation field." 

and

 "Practicing power on stalls, light on an ordinary day,. Can be much different than hot and heavy."

 

I'm just trying to make sure that I (and others) get accurate info from these discussions. We have to keep it real. 

Yes, DA affects true airspeed of stalls and not indicated. However, ground affect and air compression do affect indicated airspeed of stall.

 

1) Implication of True Airspeed on Stalls - At higher temperature and/or altitude (higher DA), stalls will occur at a higher true airspeed (yet same indicated airspeed). The issue here is that those pilots that prefer to "rely on their eyes" and not bother "looking at the airspeed indicator in the pattern," even with wind aside (or perhaps they are factoring in the wind), the stall will occur at a faster apparent groundspeed. The stall will happen at a lower pitch attitude. In a departure stall, the stall will happen at a lower pitch attitude.

 

2)  "Practicing power on stalls, light on an ordinary day,. Can be much different than hot and heavy."

Yes. The pitch attitude, ground speed, and amount of sweat pouring down your back will be different. The plane will be climbing much worse than when you load it light or in the winter. The higher DA will be a double whammy for NA guys. Higher TAS and lower engine power output. Add being heavy to that, and this still looks nothing like the one you practice with instructor.

 

3) Ground effect - Stall speed decreases in ground effect. There's no published number or formula (that I know of) for this phenomena. You can potentially takeoff and fly in ground effect below "stall speed" but as you pull up out of ground effect at a constant airspeed, it turns into a stall. Hot and heavy will play a drastic role here because the rate of acceleration to "flying speed" will be much slower and the plane won't catch up to you going from rotation to climb like it would light/cold.

 

4) Performance speeds are affected by both weight and DA. If these are not properly compensated to account for being "hot and heavy" beyond sea level at standard temp, your climb will be much worse on the induced drag side of the curve. Slowing down will only make it climb worse and put you perilously close to stall.

[bradp]

Ok guys let's not let this thread spin out of control.  

[HRM]

10 hours ago, 201er said:

Better yet learn how to fly so you would never stall unintentionally. Be aware of angle of attack in all phases of slow flight. Even without an angle of attack indicator, it is possible to be more aware and think in terms of angle of attack rather than airspeed.

Well said.

...easy on the dentists, please. They are still reeling from the latest research on flossing.

[jonhop]

Haven't read the discussion thread--I intend to--but demo'd a stall to a non-pilot friend who asked for it. He was thankful to know that planes just don't fall out of the sky on a whim and is now seriously considering getting his PPL. Had I never experienced a full stall in training, I would've been very uncomfortable demonstrating/performing one. I did it a 5500 feet, so there was plenty of room to recover. My J's stall was so benign, that even I was surprised... 

Good timing for this discussion, as this article hit me today... http://www.avweb.com/avwebflash/news/FAA-Revises-Slow-Flight-Advice-226939-1.html

Regards... Jon

Edited September 15, 2016 by jonhop

[Guitarmaster]

10 hours ago, bradp said:

At least they were practicing stalls over a lake.  Skip ahead to 2:56.  It looks like he may have stalled it, lowered the angle of attack and then increased it again.   The wing drop looks like it turned into a half turn of a spin (I couldn't tell if it was fully developed).   This is why I don't practice fully developed stalls in the Mooney  

 

I have seen this video before.  The first stall breaks clean and straight forward.  It looks like he held it and got the secondary.  It also looks like the plane yaws just before so maybe he was trying to intentionally spin.

I will admit to not fully stalling Riley.  I used to fly a "C" around years ago.  I was a young, indestructible instructor then and was teaching in the owners airplane.  I was demonstrating stalls.  The power off were not a problem.  It was predictable albeit more abrupt than your average Cessna.  The takeoff/departure stall however...  Full power, nose pointed to the sky, little burble and BAM!  Looking at the world upside down!  I guess we will practice spin recovery techniques now.  Honestly it spooked me and I need to just go do it. 

I put much thought into the "why" of the violent power-on stall.  With power-off, there is very little to no rudder to stay coordinated.  Not so with power-on.  If you watch, you will be almost full rudder to keep the ball centered.  Well... we now have a cross-controlled stall and, predictably, resulting spin.  

It seems you are kind of "damned if you do and damned if you don't" since centering the rudder will have the ball WAY out of center.

I think it is important to know how the plane feels just prior to the break.  Regardless, recovery is ALWAYS the same.  Lower AOA BEFORE adding power.  Of course, if you want to find out if the plane is rigged properly, stall away.  

[gsxrpilot]

5 hours ago, cnoe said:

#2. (And I'm not trying to be a smart ass here...) What does the typical AOA indicator (in a Mooney) display when parked on the ramp idling (with little/no relative wind and a tail-low attitude)? Off? High AOA? Low AOA? Is there a come-alive speed for the indicator (based on airspeed)? I guess what I'm truly asking is how do you determine the rotation point using an AOA indicator in the absence of an airspeed indicator; just fly it off?

I had an AOA in my previous Mooney. It's indication was all over the place from red to green and everything in-between while taxiing around the ramp. But it would straighten up and fly right as soon as I was moving down the runway. It actually probably became accurate at about 40 kts.

On the other note, I don't use either the AOA or the ASI to determine take-off speed. I just wait until the airplane is ready to fly. That seems to work at all weights and all DA numbers. We did quite a bit of gross weight, high DA airports, on our summer trip just before selling the plane. In the C at gross weight and 8000+ ft DA, it takes awhile before it want's to fly, and even then, it's fairly reluctant. ;-)

[cnoe]

Thanks for the reply Paul. I was just curious if the indicator would tell you when it's time to fly.

You fly more seat-of-pants than I do but I assume on a high DA departure you transfer to the ASI fairly quickly (in the absence of an AOA indicator)? It's really hard for me to judge Vx or Vy at 8,000' just looking out the window. Probably not so much in the 252!

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[cnoe]

1 hour ago, cnoe said: Thanks for the response to question #1 Hank. I was pretty sure that was the case but then I read statements like:

 

"Next, on that day that you get yourself in a bind with a power on stall... most likely this won't be in winter either. Hot Day, higher DA, or actually the one time you go to a higher elevation field." 

and

 "Practicing power on stalls, light on an ordinary day,. Can be much different than hot and heavy."

 

I'm just trying to make sure that I (and others) get accurate info from these discussions. We have to keep it real. 

Yes, DA affects true airspeed of stalls and not indicated. However, ground affect and air compression do affect indicated airspeed of stall.

 

1) Implication of True Airspeed on Stalls - At higher temperature and/or altitude (higher DA), stalls will occur at a higher true airspeed (yet same indicated airspeed). The issue here is that those pilots that prefer to "rely on their eyes" and not bother "looking at the airspeed indicator in the pattern," even with wind aside (or perhaps they are factoring in the wind), the stall will occur at a faster apparent groundspeed. The stall will happen at a lower pitch attitude. In a departure stall, the stall will happen at a lower pitch attitude.

 

2)  "Practicing power on stalls, light on an ordinary day,. Can be much different than hot and heavy."

Yes. The pitch attitude, ground speed, and amount of sweat pouring down your back will be different. The plane will be climbing much worse than when you load it light or in the winter. The higher DA will be a double whammy for NA guys. Higher TAS and lower engine power output. Add being heavy to that, and this still looks nothing like the one you practice with instructor.

 

3) Ground effect - Stall speed decreases in ground effect. There's no published number or formula (that I know of) for this phenomena. You can potentially takeoff and fly in ground effect below "stall speed" but as you pull up out of ground effect at a constant airspeed, it turns into a stall. Hot and heavy will play a drastic role here because the rate of acceleration to "flying speed" will be much slower and the plane won't catch up to you going from rotation to climb like it would light/cold.

 

4) Performance speeds are affected by both weight and DA. If these are not properly compensated to account for being "hot and heavy" beyond sea level at standard temp, your climb will be much worse on the induced drag side of the curve. Slowing down will only make it climb worse and put you perilously close to stall.

Fair enough. High DA has many negatives.

I just wanted to confirm that for those of us without an AOA indicator the ASI provides vital info that will allow us to avoid a departure stall no matter what the DA or temperature is.

These discussions do indeed force us to think outside our comfort zone. I believe that's a good thing.

Sent from my iPad using Tapatalk

[N201MKTurbo]

I don't think the plane stalls any different on a high and hot day, but you are much more likely to get yourself into a departure stall situation on a high and hot day. 

And remember it is much better to crash with the plane under control at MCA then from a stall.

Edited September 15, 2016 by N201MKTurbo