Forward Slips/Technique?

[airdale]

OK, this may be one of the posts where the OP gets skewered, roasted, and served for dinner, but I'll try it anyway:

I had an attack of good behavior today (I'm commercial/instrument rated but always a student.) and went out solo to work on forward slips and go-arounds. I've never really had trouble with forward slips and I use them, but they always feel a little awkward and tend to be one of the last choices in my toolbox for fixing a high approach. So don't do enough of them.

I was flying a left hand pattern, runway 15, wind 200 at maybe 15G20. What I discovered was that going into the slip as the base/final turn ended -- just leaving the bank in and adding opposite rudder with the nose down a little bit -- would integrate the slip into the approach very nicely. At base/final it's easy to see if you are high (I was deliberately 1000 AGL) and to initiate the slip as part of the pattern maneuver. The whole approach just felt better to me.

Two reasons I'm curious about other opinions on this:

1) I've always read and been taught that one slips on final, essentially that it is a completely separate event after lining up.

Maybe teaching the slip as I was doing it today is considered too risky because a student might push the wrong pedal?

2) I've also been taught to bank into the wind for the slip, which of course wasn't the case today. The argument being that the wings are then where you want them for crosswind correction on short final. But doing the slip at the end of the base/final turn got the airplane down long before this became a consideration. I just leveled into a crab, then kicked it out and added bank as usual when I got closer to landing.

So -- am I missing something here? Or is this so obvious that I should already have known it?

 

[dmccormack]

OK, this may be one of the posts where the OP gets skewered, roasted, and served for dinner, but I'll try it anyway:

I had an attack of good behavior today (I'm commercial/instrument rated but always a student.) and went out solo to work on forward slips and go-arounds. I've never really had trouble with forward slips and I use them, but they always feel a little awkward and tend to be one of the last choices in my toolbox for fixing a high approach. So don't do enough of them.

I was flying a left hand pattern, runway 15, wind 200 at maybe 15G20. What I discovered was that going into the slip as the base/final turn ended -- just leaving the bank in and adding opposite rudder with the nose down a little bit -- would integrate the slip into the approach very nicely. At base/final it's easy to see if you are high (I was deliberately 1000 AGL) and to initiate the slip as part of the pattern maneuver. The whole approach just felt better to me.

Two reasons I'm curious about other opinions on this:

1) I've always read and been taught that one slips on final, essentially that it is a completely separate event after lining up.

Maybe teaching the slip as I was doing it today is considered too risky because a student might push the wrong pedal?

2) I've also been taught to bank into the wind for the slip, which of course wasn't the case today. The argument being that the wings are then where you want them for crosswind correction on short final. But doing the slip at the end of the base/final turn got the airplane down long before this became a consideration. I just leveled into a crab, then kicked it out and added bank as usual when I got closer to landing.

So -- am I missing something here? Or is this so obvious that I should already have known it?

You just learned what pilots of old have known for a while -- the Spitfire Approach.

Basically, you don't square the base to final. You do a constant turn from downwind and transition to a slip -- that way, you can see where you're going to land (consider how long a Spitfire nose is).

So, you did fine! Now go find a tailwheel and do it for real!

 

[TMetzinger]

Seems reasonable to me. As long as you're slipping (keeping the nose down) you don't have to worry about the dreaded stall/spin. Direction of slip is all dependent on what problem you're trying to solve at the time.

 

[Areeda]

I don't have a problem with that technique and have used it myself. I see nothing wrong with starting the slip before the turn ends.

I tend to slip in the direction that gives the best visibility to the seat I'm in. If I'm in the left seat it's left aileron and right rudder.

To be honest if the cross winds are high enough to affect the direction of a slip, I'll go around and get it right.

Joe

 

[dmccormack]

Seems reasonable to me. As long as you're slipping (keeping the nose down) you don't have to worry about the dreaded stall/spin. Direction of slip is all dependent on what problem you're trying to solve at the time.

You bring up a good point, Tim.

A stall from a SLIP is essentially a non-event (go up a bit and try it). The outer, higher wing stalls and comes level or a bit below.

A stall from a SKID is a bit more exciting -- usually the bottom wing drops out and over the top you go.

 

[TMetzinger]

You bring up a good point, Tim.

A stall from a SLIP is essentially a non-event (go up a bit and try it). The outer, higher wing stalls and comes level or a bit below.

A stall from a SKID is a bit more exciting -- usually the bottom wing drops out and over the top you go.

Yep, during my spin training Adam C basically proved it was a benign event. It's the skidding turn that kills. But in a forward slip, where the whole desire is to descend steeply, a stall shouldn't even be a possibility unless the pilot really yanks on the elevator.

 

[jesse]

I was flying a left hand pattern, runway 15, wind 200 at maybe 15G20. What I discovered was that going into the slip as the base/final turn ended -- just leaving the bank in and adding opposite rudder with the nose down a little bit -- would integrate the slip into the approach very nicely. At base/final it's easy to see if you are high (I was deliberately 1000 AGL) and to initiate the slip as part of the pattern maneuver. The whole approach just felt better to me.

Nothing wrong with slipping in a bank -- I do it all the time -- the main thing to remember is that you want to pick the nose up with the rudder. So if your left wing is down you want to add excess rudder with the right pedal. I find that explanation easiest for people to understand so that they can avoid skidding instead of the slipping.

1) I've always read and been taught that one slips on final, essentially that it is a completely separate event after lining up.

That is a big problem with a lot of teachings. It's all these "separate events" to attempt to get the airplane to one spot. In the real world it is a dynamic situation and often the use of multiple tricks at once will get the airplane in the spot you want it to go.

It is all about getting an airplane to go where you want it to go. How you got it there really isn't that important.

Maybe teaching the slip as I was doing it today is considered too risky because a student might push the wrong pedal?

Doubt it. Just teach them to push teh rudder pedal that is on the sky side..Picking the nose up. Don't pull on the yoke when you do this and you won't stall.

2) I've also been taught to bank into the wind for the slip, which of course wasn't the case today. The argument being that the wings are then where you want them for crosswind correction on short final. But doing the slip at the end of the base/final turn got the airplane down long before this became a consideration. I just leveled into a crab, then kicked it out and added bank as usual when I got closer to landing.

Once again -- if the airplane goes where you want it to go then that is all that mattered. In the end you want a low-energy touchdown, aligned with the runway, without side-load. How you accomplish that doesn't matter.

So -- am I missing something here? Or is this so obvious that I should already have known it?

You're not missing anything. You're just discovering how to fly it instead of driving it...which can be an enlightening moment.

 

[airdale]

Thanks, gents.

Basically, you don't square the base to final.

That's kind of a independent issue for what I was doing but I see what you mean. Basically what I was doing was ending the base/final turn with the rudder.

So, you did fine! Now go find a tailwheel and do it for real!

Yes, I need to get that done. I got a little "tourist dual" in a Tiger Moth in New Zealand a couple of years ago and it was fun to watch how the instructor handled the landing. Same issue with the nose.

As long as you're slipping (keeping the nose down) you don't have to worry about the dreaded stall/spin.

Well, that was my thinking. But I could see why it might not be a good idea/dangerous to teach this technique to a student.

Once again -- if the airplane goes where you want it to go then that is all that mattered. In the end you want a low-energy touchdown, aligned with the runway, without side-load. How you accomplish that doesn't matter.

Well, I have had the occasional landing that turned out that way but where I'm still glad there wasn't a video of the process!

 

[PilotAlan]

It sounds like you did fine, but here's what I do.

1 - I don't make uncoordinated turns close to the ground. Period. If I can't make the approach without coordinated turns, I go around.

2 - I roll out on final and get the right crab to offset the winds. That allows me to get a handle on the winds, then transition to a slip once there and stable.

That said, those are my limits. I'm not saying they should be yours.

 

[dmccormack]

It sounds like you did fine, but here's what I do.

1 - I don't make uncoordinated turns close to the ground. Period. If I can't make the approach without coordinated turns, I go around.

2 - I roll out on final and get the right crab to offset the winds. That allows me to get a handle on the winds, then transition to a slip once there and stable.

That said, those are my limits. I'm not saying they should be yours.

Hmmm...

A crosswind landing will require "uncordinated" flight (if its defined as ball not centered).

 

[TMetzinger]

Hmmm...

A crosswind landing will require "uncordinated" flight (if its defined as ball not centered).

Yep, but I think I see what he means. If the objective is to turn, do it coordinated. A slip is not by itself a turn, though I don't think there's anything wrong with a slipping turn.

 

[wby0nder]

One thing I teach that you may already be doing is when doing any kind of slip use ALL the rudder. It's either ON or OFF. Fewer variables to balance. Use the bank to adjust the flight path

 

[vontresc]

One thing I teach that you may already be doing is when doing any kind of slip use ALL the rudder. It's either ON or OFF. Fewer variables to balance. Use the bank to adjust the flight path

Yeah that technique is especially fun when you have a VERY effective rudder.

 

[MauleSkinner]

The turns from downwind to base and final are good places for a slip. In my mind, it also demonstrates the fact that you don't have to be on final to know that you're high.

I don't have a problem with that technique and have used it myself. I see nothing wrong with starting the slip before the turn ends.

I tend to slip in the direction that gives the best visibility to the seat I'm in. If I'm in the left seat it's left aileron and right rudder.

To be honest if the cross winds are high enough to affect the direction of a slip, I'll go around and get it right.

Joe

Everything else being equal, I tend to slip to the left (left wing low)...just the way my brain works, I guess.

I'll even make my forward slip to the left, and then transition to a right sideslip for landing in a right crosswind. Although there's a LOT of potential for a low-altitude, high-AOA skid in that operation. Like Joe said, maybe it's best to go around and get it right if you need to do that.

 

[PittsDriver]

One thing I teach that you may already be doing is when doing any kind of slip use ALL the rudder. It's either ON or OFF. Fewer variables to balance. Use the bank to adjust the flight path

Could you elaborate on that a little more? As someone pointed out, not every aircraft has the same rudder effectiveness and why wouldn't it be used like any other flight control surface to make the airplane do what you need it to.

If I'm slipping down to a spot landing, I'm trying to control my descent rate and keep my speed relatively constant. If I'm going to stay lined up on the centerline then I'm going to have to lay in varying amounts of yaw and bank to work it down on speed and target.

 

[brcase]

Could you elaborate on that a little more? As someone pointed out, not every aircraft has the same rudder effectiveness and why wouldn't it be used like any other flight control surface to make the airplane do what you need it to.

If I'm slipping down to a spot landing, I'm trying to control my descent rate and keep my speed relatively constant. If I'm going to stay lined up on the centerline then I'm going to have to lay in varying amounts of yaw and bank to work it down on speed and target.

In a C-150 there isn't much point in a forward slip without using full rudder simply because the rudder is so small. So use full rudder and use the ailerons to stay on the centerline of the runway.

This works in most airplane but in C-120 with lots of rudder it can result in some impressive descent angles.

Brian
CFIIG/ASEL

 

[SkyHog]

There was actually a debate on here a while back about whether a stalling slip would spin the aircraft. Jesse was awesome enough to go up and demonstrate it on video for everyone.

Turns out - slipping stalls are benign. Skidding stalls, on the other hand....

 

[wby0nder]

In a C-150 there isn't much point in a forward slip without using full rudder simply because the rudder is so small. So use full rudder and use the ailerons to stay on the centerline of the runway.

This works in most airplane but in C-120 with lots of rudder it can result in some impressive descent angles.

Brian
CFIIG/ASEL

Have you tried full rudder deflection in a K13? Feels like it's going to swap ends! Breathtaking the first time.

 

[airdale]

One thing I teach that you may already be doing is when doing any kind of slip use ALL the rudder. It's either ON or OFF. Fewer variables to balance. Use the bank to adjust the flight path.

Well, maybe for initial teaching, but I think the value of the slip is that its degree can be managed to be appropriate to the need. In other words, if I want to lose a couple of hundred feet, I don't have to slam the airplane sideways to do it.

This also depends on the airplane. I once flew a DA-40 to check out for some ferry work that didn't materialize and was surprised to find that a normal (to me) slip was kind of a non-event. I guess that waspish rear section is not too effective at adding drag. So for that one, the full-rudder approach may be the only useful option.

 

[Capt. Geoffrey Thorpe]

This works in most airplane but in C-120 with lots of rudder it can result in some impressive descent angles.

Yup. And if you slip to the left you can drive the indicated air speed to purd near zero...

And if you slip into a tank that is low on fuel...

 

[poadeleted20]

There was actually a debate on here a while back about whether a stalling slip would spin the aircraft. Jesse was awesome enough to go up and demonstrate it on video for everyone.

Turns out - slipping stalls are benign. Skidding stalls, on the other hand....

Don't underestimate the power of a stall in uncoordinated flight, slipped or skidded. Yes, it's easier to avoid a spin from a slipped condition in fairly benign light trainers, but there are planes where it's not so hard to turn a slipping stall into a spin. Nothing wrong with using slipping turns to lose altitude in the pattern as long as you control AOA properly, but don't negatively transfer what Jesse demo'd to other, less benign, airplanes.

 

[bullwinkle]

I did this technique on my checkride, and passed, so...I guess it's kosher.

 

[dmccormack]

I did this technique on my checkride, and passed, so...I guess it's kosher.

My PPL Checkride we were high (3500') coming to KLNS (417', IIRC).

The DEP growled, "We're a little high, dont ya think?"

He had put me through the wringer and I kinda didn't care what he thought of me anymore.

KLNS gave me straight in to 26. I turned that C152 sideways and we dropped like a rock. I kicked it out 20' above the runway and touched down on the top of the numbers. I really only did it to shut him up.

I passed.

 

[brcase]

Have you tried full rudder deflection in a K13? Feels like it's going to swap ends! Breathtaking the first time.

Haven't had the pleasure of flying a K-13. But I thought the L-13 feels about he same way.

Brian

 

[PittsDriver]

Don't underestimate the power of a stall in uncoordinated flight, slipped or skidded. Yes, it's easier to avoid a spin from a slipped condition in fairly benign light trainers, but there are planes where it's not so hard to turn a slipping stall into a spin. Nothing wrong with using slipping turns to lose altitude in the pattern as long as you control AOA properly, but don't negatively transfer what Jesse demo'd to other, less benign, airplanes.

Ron, do you know of any aircraft that can be spun from stalling in a slip? If so, what are they?

My experience in the Pitts is that, after many attempts, I cannot induce a spin from a slip. I can set up a slip and haul the stick hard back against the stop and fall like a stone in a full stall with no tendency to spin at all.

 

[jesse]

Ron, do you know of any aircraft that can be spun from stalling in a slip? If so, what are they?

My experience in the Pitts is that, after many attempts, I cannot induce a spin from a slip. I can set up a slip and haul the stick hard back against the stop and fall like a stone in a full stall with no tendency to spin at all.

Well you can't spin from a slip in anything. You can roll past wings level, into the other direction, and spin. I haven't flown an aircraft that'll even do that. I believe Chip said his Extra 300L would roll past wings level and into a spin..but you had plenty of time to see it coming and exit the slipping stall.

Needless to say..in most GA airplanes..it'll be obvious what is happening. I do slipping turns all the time..often nose up to drop a **** load of energy in a near instant.

 

[rottydaddy]

Ron, do you know of any aircraft that can be spun from stalling in a slip? If so, what are they?

My experience in the Pitts is that, after many attempts, I cannot induce a spin from a slip. I can set up a slip and haul the stick hard back against the stop and fall like a stone in a full stall with no tendency to spin at all.

Yeah, but that's still good enough to kill you when turning base to final...
I think the best reason to not stall when crossed-up, close to the ground, in any airplane, is that if you are coordinated at the outset, you will recover easier and faster.
Better, still, of course, to not stall, whatever you're doing.

Skidding base-to-final is something I have no interest in finding out about firsthand. Seems like an invitation for trouble.

 

[Capt. Geoffrey Thorpe]

Yeah, but that's still good enough to kill you when turning base to final...
I think the best reason to not stall when crossed-up, close to the ground, in any airplane, is that if you are coordinated at the outset, you will recover easier and faster.
Better, still, of course, to not stall, whatever you're doing.

Skidding base-to-final is something I have no interest in finding out about firsthand. Seems like an invitation for trouble.

Slipping does not make you stall.

Skidding does not make you stall.

Banking / turning does not make you stall.

Pulling on the yoke makes you stall.

 

[rottydaddy]

Slipping does not make you stall.

Skidding does not make you stall.

Banking / turning does not make you stall.

Pulling on the yoke makes you stall.

I know.
He said:

"...fall like a stone in a full stall with no tendency to spin at all."

My point was that you needn't spin to crash from the base-to-final turn, often just stalling is sufficient.

My other point (about not making uncoordinated turns in the pattern) was that in a turn, one is generally pulling on the yoke, especially if one is trying desperately to "buttonhook" back towards the runway after turning final too late....... and the load factor is increasing....... driving the "book" stall speed up... inviting a stall with rudder and ailerons uncoordinated.
Even when simply easing off that back pressure as a stall begins in a turn, you're better off being coordinated.

 

[PittsDriver]

He said:

"...fall like a stone in a full stall with no tendency to spin at all."

My point was that you needn't spin to crash from the base-to-final turn, often just stalling is sufficient.

Unless I want to fall like a stone on base to final. Being able to control your speed and descent rate with slips on approach is a life saving skill in an engine out emergency. If you practice engine out emergencies to a target spot on the runway, you already know exactly what I'm talking about. I think the old adage is mostly true - in an engine out emergency, landing long will hurt you; landing short will kill you. I fly a flapless aircraft that returns to earth pretty fast and so, I practice emergency landings nearly every time I go out to fly. My goal is to maintain a speed that makes my aircraft maneuverable and be high on short final in case the head wind is stronger than I anticipated. Then it's a matter of adding drag (slip/prop pitch) as necessary to hit the spot.

I agree that a stall on base to final, even one done under control, would not be something to flirt with. But that's not a reason to poo poo slips when descending in the pattern. The state of instruction is way too hung up on demonizing uncoordinated flight. It seems like our focus on spin awareness/avoidance vs. practicing spins, turned into that the mantra everyone now learns: that if you're don't let the ship get uncoordinated, you won't spin. So students get it in their head that a deflected ball is a dangerous thing. So what happens? Confusion sets in when it's time to learn slips to a landing.

So, if a turning base-to-final slip to a spot landing at minimum controllable airspeed seems like a lot to pull off, maybe that's a reason to practice them more.

 

[somorris]

I have mentioned this before, but Rich Stowell has an excellent, well-researched book out on this subject. It should be required reading for every pilot candidate. He very well summarized the history, old wives tales, research, etc. regarding stall and spin awareness. The book is interesting reading. He even included a training program to better equip pilots to handle stalls and spins.

 

[dmccormack]

I have mentioned this before, but Rich Stowell has an excellent, well-researched book out on this subject. It should be required reading for every pilot candidate. He very well summarized the history, old wives tales, research, etc. regarding stall and spin awareness. The book is interesting reading. He even included a training program to better equip pilots to handle stalls and spins.

Agreed -- http://www.richstowell.com/ssabook.htm

I have this book, but it doesn't seem to be in print any longer?

 

[poadeleted20]

Ron, do you know of any aircraft that can be spun from stalling in a slip? If so, what are they?

My experience in the Pitts is that, after many attempts, I cannot induce a spin from a slip. I can set up a slip and haul the stick hard back against the stop and fall like a stone in a full stall with no tendency to spin at all.

Never flown a Pitts, but I've been over-the-top in a fully cross-controlled C-150. Hold the controls that way, it it will spin. I suspect a Grumman will, too, given the amount of adverse yaw generated by the ailerons, which is enough to help you out of a spin if it flattens some and the rudder blanks -- ailerons full with the spin is a last-ditch technique in that case.

 

[John Baker]

My instructor is 74 and has been teaching me the forward slip. Yes, I did push the wrong pedal one time on a right base to final. The only thing that happened was a serious lecture from my instructor, it was about spins.

About a year ago, I was flying my Warrior with a friend out at Ramona and he did one of those famous "watch this" approaches to doing a slip. He lowered the wing close to 60 degrees and just dropped the whole plane in very short order to a few yards above the runway, then straightened it out for a beautiful landing.

Now I keep wanting to lower my wing to a very steep angle to slip it from base to final. My instructor has made it very clear to me that you never do that in the pattern, and it is completely unnecessary. He said, and has proved to me more than a few times, that all you need is about a twenty degree lowering of the wing.

Throttle back to idle, on the turn to final, keep the bank angle about twenty degrees and give full opposite rudder. The nose will already be lowered as you turn to final, then just let it sink. This gives you about a thousand foot per minute sink rate as you approach the threshold. Maintain your normal approach airspeed and keep it lined up with the centerline. My bird uses two notches of flaps in the slip, as per the POH.

It is pretty darn easy once you get past the "watch this" stage.

John

 

[dmccormack]

My instructor has made it very clear to me that you never do that in the pattern, and it is completely unnecessary. He said, and has proved to me more than a few times, that all you need is about a twenty degree lowering of the wing.

Throttle back to idle, on the turn to final, keep the bank angle about twenty degrees and give full opposite rudder. The nose will already be lowered as you turn to final, then just let it sink. This gives you about a thousand foot per minute sink rate as you approach the threshold. Maintain your normal approach airspeed and keep it lined up with the centerline. My bird uses two notches of flaps in the slip, as per the POH.

It may have FELT like 60 degrees -- especially if you haven't slipped before.

The Warrior's rudder isn't capable of countering 60 degrees of bank. That's actually the limiting factor in a slip -- amount of rudder travel. If you bank 60 degrees, and put in every last inch of rudder. you'll still drift to the direction of the bank in most airplanes.

As far as the numbers game, that's a good way to bound the problem and help you know what to expect. But quite frankly if I am slipping I am NOT looking at the panel! (and I don't want students looking at the panel). The sink rate is high and the objective is to lose altitude to some pre-determined point while not straying off the lateral limit.

Toss in some wind, and what matters is what's happening outside.

It sounds like your instructor is helping you set up and understand what is happening in a slip, which is great! You can glance at the panel to assure yourself of what's happening to descent rate, perhaps, but airspeed may or may not be accurate, depending on the airplane and the direction of slip -- so how do you know you're still flying?

You feel it. You hear it. You sense it through the yoke, your seat, and your head tells you there's still plenty of lift in the wings.

There's plenty of interesting discussion on this topic on this thread (as in nearly all threads on here), but forget formula (X airspeed, Y descent rate, G bank). Practice slips until they become a tool in your toolbox, then use the information and skill your acquiring when you judge you need it, at the intensity you need it, given the current conditions.

And that will come with experience. A slip is a fun, effective, safe manuever when done well and appropriately.

 

[N1347B]

Unless I want to fall like a stone on base to final. Being able to control your speed and descent rate with slips on approach is a life saving skill in an engine out emergency. If you practice engine out emergencies to a target spot on the runway, you already know exactly what I'm talking about. I think the old adage is mostly true - in an engine out emergency, landing long will hurt you; landing short will kill you. I fly a flapless aircraft that returns to earth pretty fast and so, I practice emergency landings nearly every time I go out to fly. My goal is to maintain a speed that makes my aircraft maneuverable and be high on short final in case the head wind is stronger than I anticipated. Then it's a matter of adding drag (slip/prop pitch) as necessary to hit the spot.

I agree that a stall on base to final, even one done under control, would not be something to flirt with. But that's not a reason to poo poo slips when descending in the pattern. The state of instruction is way too hung up on demonizing uncoordinated flight. It seems like our focus on spin awareness/avoidance vs. practicing spins, turned into that the mantra everyone now learns: that if you're don't let the ship get uncoordinated, you won't spin. So students get it in their head that a deflected ball is a dangerous thing. So what happens? Confusion sets in when it's time to learn slips to a landing.

So, if a turning base-to-final slip to a spot landing at minimum controllable airspeed seems like a lot to pull off, maybe that's a reason to practice them more.

+1.

This mirrors my experience in the Luscombe.

Deb

 

[dmccormack]

The state of instruction is way too hung up on demonizing uncoordinated flight. It seems like our focus on spin awareness/avoidance vs. practicing spins, turned into that the mantra everyone now learns: that if you're don't let the ship get uncoordinated, you won't spin. So students get it in their head that a deflected ball is a dangerous thing. So what happens? Confusion sets in when it's time to learn slips to a landing.

Exactly!!! Well said.

During my PPL training and stage tests "Ball Centered!" was a constant refrain.

Then we learned slips.

"But -- the ball's not centered...?"

"Well, keep it centered always -- except in slips."

"Oh."

I learned to slip pretty well during my PPL training, but I'll admit it wasn't until my commercial training that I really learned about true "coordinated" flight, which wasn't necessarily about the ball.

It shouldn't require that rating to get that knowledge.