Fwd slip to stall

Jaybird180

Jaybird180

Final Approach
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Jaybird180
Yes, I know the airplane is supposed to spin, but for the sake of discussion, what if the stall recovery is initiated immediately and the airplane is something "benign" like my skyhawk? What can the pilot expect during and after recovery?
 
Depending on how your skyhawk is rigged, you might enter a crossover spin. Do you know how to recover from one.

(in his Mr. "T" mode:) You'd be a fool.
 
All depends how fast you are with the recovery. You can stop the spin before it fully develops in a Skyhawk if the entry was not accelerated. Hell it's even slow if accelerated.

It'll get incredibly mushy prior to that.

If it starts to roll, nose forward and power up NOW. You might bank only 60 degrees and be pointed nose down in the resulting turning dive, or you might go further over, bank-wise. Now you need time to level out and climb.

You're going to lose more altitude than you want to -- that low to terra firma. Recovery would be butt-puckeringly low if it could be done at all.

Some stall/spin accidents are a stall and an incipient spin entry (not fully developed) that are recovered and then the pilot starts pulling again as the ground comes up in the window and the second one is fatal. You need airspeed and time and you're likely out of both.

Better to recover at 10' AGL under control than to keep pulling and drop straight in.

The reflexes want to puuuuuuull though. Scary.
 
Before you listen to a lot of differing opinions about a SLIPPING turn, go to altitude and try it.

A lot of airplanes will not stall from a slip.

My Citabria and J3 will not stall from a POWER OFF slip. The Citabria will just mush into a high rate of descent and the Cub will just sit there nose up and turn into the direction that the pedal is held to the floor.

None of the above apply to a SKIDDING stall.
 
Take a CFI up and do a slipping stall vs a skidding stall. Never done it in a 172 but I figure from a slip, the wings will just level out and be a non event. a skid on the other hand... :rollercoaster:
 
dillardrg said:
Before you listen to a lot of differing opinions about a SLIPPING turn, go to altitude and try it.

A lot of airplanes will not stall from a slip.

My Citabria and J3 will not stall from a POWER OFF slip. The Citabria will just mush into a high rate of descent and the Cub will just sit there nose up and turn into the direction that the pedal is held to the floor.

None of the above apply to a SKIDDING stall.
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This x 10

:yesnod:
 
Jaybird180 said:
Yes, I know the airplane is supposed to spin,
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Why do you say it like that? A slip will not normally generate a spin. A stall while the nose is yawing, (skidding) is what is required for the aerodynamics of a spin to develop.

A slip is when you hold opposite rudder to prevent the nose from yawing, so no spin will develop from that.

However, if you stall while slipping(holding opposite rudder), and you continue to hold opposite rudder, the airplane's nose will yaw into that direction as the wings roll over into an incipient spin in the opposite direction. That would only be if you froze on the rudder and went over into a spin into the opposite direction.
Immediately relaxing the rudder you are holding in the slip, and using normal rudder pressures to keep the nose straight ahead as in any normal stall recovery.
 
What everyone else has said. You can certainly have something bad happen if you stall close to the ground. But a spin is not likely from a slip. Not impossible if you REALLY yank it, but not likely. I'd be more worried about not having enough altitude to recover from the stall and the very high sink rate (probably with wings level) that would likely result.
 
I have slipped a 172 with full rudder and then pointed the wing down toward the runway to lose altitude with aileron.

In this configuration, the airspeed indicator is not accurate, so I want to know what will happen if I go to altitude, slip and then pull into a stall on purpose. I want to know the IAS that this will happen.
 
Jaybird180 said:
I
In this configuration, the airspeed indicator is not accurate, so I want to know what will happen if I go to altitude, slip and then pull into a stall on purpose. I want to know the IAS that this will happen.
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"In this configuration, the airspeed indicator is not accurate"

You are correct.

"I want to know what will happen if I go to altitude, slip and then pull into a stall on purpose"

Probably nothing dramatic. If you are hesitant to try it on your own, get with an instructor and try it.

"I want to know the IAS that this will happen"

Look at the AI when you do it. Just remember that it will be innacurate, but it will be your INDICATED airspeed.
 
Jaybird180 said:
I have slipped a 172 with full rudder and then pointed the wing down toward the runway to lose altitude with aileron.

In this configuration, the airspeed indicator is not accurate, so I want to know what will happen if I go to altitude, slip and then pull into a stall on purpose. I want to know the IAS that this will happen.
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Forget IAS. FEEL the yoke pressure and how close you are to the stall. Are you asking these questions out of pure curiosity, or so that you can go try it on your own? If you're going to go try it own your own without a CFI, you might as well just go do it and answer you own questions. If you're going up with a CFI, you'll be answering your own questions nonetheless.

In a power off slip to land configuration, most airplanes will not spin if you pull the yoke/stick fully aft, even with full rudder/aileron deflection. In the planes I've tried this in...sport and aerobatic types, I have not even been able to get a proper stall. This is pretty basic stuff. You never did this during PPL training? I think I am the only person at my large regional airport, including a large flight school that slips to land...the loss of altitude kind. I have been told that some pilots there think I'm crazy. :sigh:

Sorry if it came across this way, but I'm not attacking you at all, just disappointed with much of the flight training these days.
 
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Capt. Geoffrey Thorpe said:
No need to re-invent the wheel.

http://www.pilotsofamerica.com/forum/showpost.php?p=622872&postcount=4
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exactly what I was thinking, Jesse videotaped this before.

As said above, the danger of spinning comes more from a skid than a slip. In a slip, it has to come all the way over the top (you should be able to stop it before that happens in most trainers). I ran across a good illustrated video showing both events and the aerodynamics involved but have no idea where it is.

Jaybird, just being cross-controlled does not always introduce a spin.
 
It's interesting that in one configuration, I can't produce a spin with full rudder and full aft stick held. Anyone want to take a guess at how I can produce a spin (Pitts) with full aft stick and no rudder held? :)
 
whifferdill said:
It's interesting that in one configuration, I can't produce a spin with full rudder and full aft stick held. Anyone want to take a guess at how I can produce a spin (Pitts) with full aft stick and no rudder held? :)
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stall it then nail the throttle?
 
I think your best solution would be a check ride with the old curmudgeon that was my DPE. I put the nose down on my forward slip just like I had done a number of times with my instructor. It wasn't low enough for him, however, and he screamed
"keep that nose DOWN on a forward slip!" I mean he SCREAMED it.

After that I will NEVER forget to put my nose way down on a slip. In fact I slipped down this morning because I was too high coming in and I'm here to tell ya', I kept that nose DOWN! The yelling wasn't pleasant, but I won't ever forget to put the nose down deep when slipping.
 
dell30rb said:
stall it then nail the throttle?
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Plus full right aileron and you got it.

MBDiagMan said:
I think your best solution would be a check ride with the old curmudgeon that was my DPE. I put the nose down on my forward slip just like I had done a number of times with my instructor. It wasn't low enough for him, however, and he screamed
"keep that nose DOWN on a forward slip!" I mean he SCREAMED it.

After that I will NEVER forget to put my nose way down on a slip. In fact I slipped down this morning because I was too high coming in and I'm here to tell ya', I kept that nose DOWN! The yelling wasn't pleasant, but I won't ever forget to put the nose down deep when slipping.
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Sure, don't stall the airplane (as with any other non-slipping approach), but don't keep the nose down so far that you gain enough airspeed to defeat the purpose of slipping. No need to add airspeed during a slip. Have you tried stalling out of a slip in the 140? Curious how it behaves. In general you don't need to be any more concerned with nose attitude and stalling while slipping compared to not slipping. Many folks who aren't experienced (or comfortable) with slipping think it's some sort of extreme, risky, one-false-move-away-from-spinning-in sort of maneuver. It's not at all.
 
whifferdill said:
Sure, don't stall the airplane (as with any other non-slipping approach), but don't keep the nose down so far that you gain enough airspeed to defeat the purpose of slipping. No need to add airspeed during a slip. Have you tried stalling out of a slip in the 140? Curious how it behaves. In general you don't need to be any more concerned with nose attitude and stalling while slipping compared to not slipping. Many folks who aren't experienced (or comfortable) with slipping think it's some sort of extreme, risky, one-false-move-away-from-spinning-in sort of maneuver. It's not at all.
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Putting the nose down makes even more drag as you try to fly sideways fast. Makes for a real brick ride (not that you need a slip to do that in a Pitts :wink2:). The speed goes away fast if you let the nose back up before you kick straight.
 
Capt. Geoffrey Thorpe said:
Putting the nose down makes even more drag as you try to fly sideways fast. Makes for a real brick ride (not that you need a slip to do that in a Pitts :wink2:). The speed goes away fast if you let the nose back up before you kick straight.
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Yep, there's a happy pitch attitude in most planes that will maximize the slip potential, yet not cause airspeed to increase to the point where the value of the slip significantly diminishes.

In the Clipped Cub, I'll normally fly a power-off approach at 50 indicated when solo. If I try to put in a full deflection slip with the nose up to 50 indicated, it doesn't come down very fast. But if I let the nose to drop to a 55mph attitude, it's much more effective at losing altitude. If you fly this full deflection slip all the way to runway and slowly remove it while rounding it, it will bleed speed quickly enough to make the extra 5mph of airspeed on final to be fairly insignificant. But since 55 (in the Clipped Cub) is more like 1.3Vso, it wouldn't say I'm actually nosing down any if we're talking about normal approach speeds. The 50 I normally use is on the slow side, and I'll bump that up to 55 if it's gusty/turbulent.

But the Pitts has higher wing loading and doesn't bleed speed as quickly as the kite-like Cub, so I generally slip at my normal approach speed without pitching the nose down any more. Even a half-rudder slip in the Pitts is much more effective than a full deflection slip in most other airplanes, so getting max slip out of the Pitts is pretty unnecessary....but pretty dern fun. :)
 
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FWIW I've never been able to get a 172 to spin out of a slipping turn. They just kind of bob around. If it were to spin keep in mind that it's going to have to go the other direction, roll through wings level, and into the spin. You have a lot of time to stop that.

Here is a video I made years ago doing a full slip in a turn holding the elevator back to the stops in a C172:
 
jesse said:
FWIW I've never been able to get a 172 to spin out of a slipping turn. They just kind of bob around. If it were to spin keep in mind that it's going to have to go the other direction, roll through wings level, and into the spin. You have a lot of time to stop that.

Here is a video I made years ago doing a full slip in a turn holding the elevator back to the stops in a C172:
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Won't work in my iPad. How can I search for it?
 
Love the video. It shows the bobbing Cessna slip-stall steady state real well.

Now add full power without taking the control inputs out. Like someone panicking on base to final.

I think the panic power up and unwillingness to take the control pressures out lead to the most of the actual Cessna stall-spin accidents in the pattern. There's almost always a witness who says "we heard the engine racing"...

Nose pitches way up... Pilot doesn't relax elevator back pressure... Pilot leaves the up-side rudder locked to the floor... Pilot tries to roll wings level with nearly full up-wing aileron... Inside wing stalls and around they go.
 
denverpilot said:
Love the video. It shows the bobbing Cessna slip-stall steady state real well.

Now add full power without taking the control inputs out. Like someone panicking on base to final.

I think the panic power up and unwillingness to take the control pressures out lead to the most of the actual Cessna stall-spin accidents in the pattern. There's almost always a witness who says "we heard the engine racing"...

Nose pitches way up... Pilot doesn't relax elevator back pressure... Pilot leaves the up-side rudder locked to the floor... Pilot tries to roll wings level with nearly full up-wing aileron... Inside wing stalls and around they go.
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It'll do it no problem from a skid - and a skid is what people end up doing in the pattern when they spin in.

That was a slip which is a bunch of anti-skid rudder.
 
Apparently the iPad doesn't see the embedded video, I had to use my PC and there it was.

So why didn't it spin since the "great sin" of an uncoordinated stall had been committed?
 
Jaybird180 said:
I don't get what difference it would make.
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Yaw/roll vs. not.

As I understand it:

In a skid, the aircraft is yawing; the inside wing is moving slower and has a higher angle of attack so it stalls first - adding more yaw (due to drag) and roll which sets up the whole spin thing.

In a slip, both wings are at the same airspeed and same angle of attack. The difference between them is pretty much just the direction of the span-wise flow. That will have some effect on the stalling behavior of the individual wings, but not as much as the difference in speed / angle of attack when yaw is present.

I'm sure someone will come along to point out where I am wrong.
 
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Jaybird180 said:
I don't get what difference it would make.
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In that video, to make it skid, I'd had needed full left rudder (into the turn) versus full right rudder. Had I stomped the rudder pedal to the left instead of the right in that left turn and stalled it would have snapped into a spin in a heartbeat.

A moderate to steep bank, with lots of skid, into a stall, will spin in an instant. That's what kills people. They're turning base to final, in a left bank, and start to stomp left rudder to cheat the corner and they pull to cheat the corner..suddenly they stall in a skid and it's good night.
 
jesse said:
In that video, to make it skid, I'd had needed full left rudder (into the turn) versus full right rudder. Had I stomped the rudder pedal to the left instead of the right in that left turn and stalled it would have snapped into a spin in a heartbeat.

A moderate to steep bank, with lots of skid, into a stall, will spin in an instant. That's what kills people. They're turning base to final, in a left bank, and start to stomp left rudder to cheat the corner and they pull to cheat the corner..suddenly they stall in a skid and it's good night.
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So that means my ball to inside turns in the pattern acts as a safety buffer:rofl:
 
Jaybird180 said:
Why didn't Jesse snap roll?
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Because he was holding a lot of left aileron, against the right rudder (slip) and pulled the yoke back progressively, so that by the time he reached near or at stall AoA, the airplane had very little acceleration (g-load). A snap roll is done from significantly accelerated flight at higher airspeeds than what Jesse ended up with when the yoke was eventually pulled completely aft. But there's more -

The Cirrus in the video had a steep left turn going toward the runway, at high AoA (but not stalled), and started overbanking to the left. It is not clear if this was simple overbanking or an actual incipient spin. I would tend to believe simple overbank, because it seems unlikely the pilot would have responded that quickly to an incipient spin to the left, even if he overdid the recovery and reproduced one to the right.

So there the Cirrus pilot is overbanking to the left at high AoA, and decides to do something about it by trying to roll to the right with a lot of right rudder, right aileron, but without unloading the stick. This is now a skid, and in accelerated flight, lots of rudder will produce a snap roll. The Cirrus pilot basically snapped the airplane to the right into the ground.
 
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Capt. Geoffrey Thorpe said:
Yaw/roll vs. not.

As I understand it:

In a skid, the aircraft is yawing; the inside wing is moving slower and has a higher angle of attack so it stalls first - adding more yaw (due to drag) and roll which sets up the whole spin thing.

In a slip, both wings are at the same airspeed and same angle of attack. The difference between them is pretty much just the direction of the span-wise flow. That will have some effect on the stalling behavior of the individual wings, but not as much as the difference in speed / angle of attack when yaw is present.

I'm sure someone will come along to point out where I am wrong.
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Yup. But you're not much wrong.

In a descending turn the inside wing is at a higher AoA than the outside wing. This has to do with the radii of the two helices decribed by the wings. Slipping in a descending turn actually reduces the difference in AoA between the wings (making the turn safer) and skidding increases the difference, making the turn deadly.

In a level turn the AoAs are the same, but as the turn gets steeper the overbanking tendency demands some opposite aileron. That down aileron on the inside wing increases the AoA (because the chord line is changed) and we'll have a tendency to stall that wing first.

In a coordinated climbing turn things get silly. The outside wing will stall first and the airplane will roll away from the turn and want to spin. This is often called a departure stall and I used to teach it. Quite exciting at full power. Don't even need much turn, maybe ten degrees of bank. Just keep the nose getting higher and higher and keep the ball centered.

A while back I posted some pictures of an AoA demonstrator I built to make it easier for students to see the effects. Go to this page and scroll about two-thirds of the way down: http://www.pilotsofamerica.com/forum/showthread.php?t=40070&highlight=AoA+table&page=4

Dan
 
We did a slipping stall in the Super Decathlon this morning. Power off, stick all the way back, full left rudder, and right aileron to hold the ground track in order to simulate a stall on approach in a forward slip. Held this way in the stall for several seconds, descending at almost 2000 ft/min, it was completely stable with absolutely no tendency to spin.
 
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