S-turns on final

[Molesworth 1]

Given that one needs at least 30 degrees of bank to accomplish this, is there not a danger of a spin-in?

My own reasoning is that if they are done at 20-25 knots above stall speed and in a steep descent (which is the reason for the S-turns) the angle of attack will not be high.

[mad_jock]

If the angle of attack according to your theory is not high you won't stall therefore you can't spin in.

It has been known for instructors on there tod to be doing 60deg banked S turns at approach speed. Wouldn't do it myself as I prefer to do a side slip if to much height. I would only use S turns to lengthen the approach if we required an extra few seconds to get a clear runway.

If your that far off profile you need to resort to S turn's or side slip go around and get it right the next time.

[Rod1]

S turns are discouraged in Gliding in favour of a 360. Less risk of spinning in.

Rod1

[bingofuel]

As long as the speed is appropriate for the angle of bank I see nothing wrong with a steep S turn, although I prefer sideslips myself if the aircraft allows it.
It can make all the diffference in a PFL, but if I was flying a normal approach and finding I needed an S turn, I might just be asking myself 'why?' and consider going around and flying a better approach,

Bottom line is fly the aeroplane, but try to set a good example as well. I would hate to see a student or inexperienced pilot try to emulate such a manoeuvre unless they were well aware of the pitfalls.

[englishal]

but if I was flying a normal approach and finding I needed an S turn, I might just be asking myself 'why?'
ATC spacing for example? I've been asked to make an S turn by the tower before.

The fact of the matter is that as long as the wings are unloaded, they cannot stall and without a stall a spin cannot happen. Try a decent wingover and you can have the ASI reading near enough zero at 60 degrees of bank and not even the chirp of a stall warner.

Something to remember if you need to do an S turn / get slow / have an EFATO...If you PULL on the other hand you might find yourself in trouble.

[Mark1234]

As others have opined, i'd be looking to sideslip, or quite likely go around unless there's a specific good reason for the S turn.

To the original question, in my opinion there is little danger - provided you don't fly the plane like a hamfisted moron - i.e. don't heave back on the stick, and do use the footrests for their intended purpose :)

1) A stall in a turn does not mean a spin. It means a stall. Recovered by unloading the wing. Spins require a stall and a rate of yaw.
2) the aircraft will not stall unless you heave back on the controls.

Stall speed doesn't actually increase with angle of bank, it increases with wing loading. If you hold level, at 60deg you'll be pulling 2G, that's why the stall speed goes up. If you don't try to hold the nose up, banking the aircraft makes no difference, as in englishal's example. Anyone here heard of stall stick position? Seems to be a rarely taught concept..

S turns are discouraged in Gliding in favour of a 360. Less risk of spinning in.

I find that quite interesting - I was taught (gliding) to always keep the field in sight, and never ever turn away. It takes more height than you think to do a 360, especially in any breeze, you loose height *AND* distance to the field. Would also question that there's less risk of a spin.

[Rod1]

Mark1234

Several pages in “Gliding” by DP on this. He makes the point that S- turns need as much turning as a 360 with more potential to get it wrong, and states that S-turns are discouraged. This message was also very firmly pushed by my instructors, but I may be out of date…

Rod1

[mad_jock]

Mind you how many instructors teach side sliping these days.

Or is it another tool in the box that has been forgotten.

[cats_five]

Mind you how many instructors teach side sliping these days.

Or is it another tool in the box that has been forgotten.

It's on the Bronze training card at my gliding club. Unfortunately a lot of glass single-seaters nose dive if you try combining airbrakes and a side-slip.

[mad_jock]

I wasn't on about gliding instruction.

The more I see of gliding instruction, the method of instructor training and upgrading the more I see how ****e the alleged professional powered instruction is.

[IO540]

I don't see a problem with S-turns - they are just normal left/right turns. Even the Space Shuttle does them to lose energy :)

But if somebody is flying the final approach at Vs + 0.01% then maybe not such a good idea...

A sideslip is also not a good idea in some types, I gather, due to disturbance of elevator airflow. So they would be type-specific, whereas any plane can do S-turns.

I would also not do S-turns on short final - too much risk of not ending up lined up with the runway (fairly obviously).

[robin]

S turns are perfectly acceptable depending on the layout of the site

At my gliding site between certain heights you would never make a 360, but a downwind then into-wind turn to land on the wide bit of the field is fine.

In gliding we are taught to be flexible and to plan ahead and use whatever safe landing areas are available.

Each site is different and you'll be briefed accordingly

[gpn01]

I find that quite interesting - I was taught (gliding) to always keep the field in sight, and never ever turn away. It takes more height than you think to do a 360, especially in any breeze, you loose height *AND* distance to the field. Would also question that there's less risk of a spin.

You've obviously benefited from quality instruction :-)

Going back to the original post, if you've been taught properly and your skills are considered by the instructor who signs you off as suitable for solo then there's no reason why an S-turn should increase the risk of spinning compared to a 360-turn. Admittedly it does require up to three manouvres (e.g. roll left, roll right, roll straight) that may need good co-ordination but that's not much different than, say roll left, maintain turn, roll straight. If you can't fly co-ordinated then I'm not sure if you should be solo.....

In gliding, as Mark1234 mentions, s-turns are preferred because you're able to keep the landing area in sight. As we don't have an engine this can be quite important when judging the circuit. Additionally 360-turns in the circuit significantly increase the risk of collision (do you really want to turn back to face opposite direction traffic?).

[dudduddud]

Well a 360 on approach is against the law where I'm from (and probably where you're from too!)

The safest option obviously is to do a go-around and try again but if you are in a pinch and you want to get back to the apron before that clock ticks over, s-turns are the safest bet.

The reason for this is that, in my New Zealand cpl flight test pass, I was marked down for slipping on final. The problem is that if you were to get into an out-of-balance stall (just say) at the low altitudes of final approach, you will not recover. If you are flying in-balance s-turns and for some reason you stall, you may be able to recover.

If you find yourself with passengers in that situation and you have to use s-turns to get down...

Tell the passengers beforehand!!!!!

I can't imagine anything more terrifying as a non-pilot passenger than having the plane roll over to 60 degrees angle of bank left and right so close to the ground during a manouvre which is widely touted as the most dangerous of the whole flight!

[Genghis the Engineer]

The reason for this is that, in my New Zealand cpl flight test pass, I was marked down for slipping on final. The problem is that if you were to get into an out-of-balance stall (just say) at the low altitudes of final approach, you will not recover. If you are flying in-balance s-turns and for some reason you stall, you may be able to recover.

I've been similarly criticised for this flying with UK instructors when sideslipping a PFL.

Personally, I think it's cobblers. A low level stall will almost certainly kill you whatever sideslip you have on in all likelihood, but so long as airspeed as maintained at or above 1.3Vs and below Va the risk of stalling is no greater than in a normal approach. At the same time, a sideslipped approach is much better for maintaining runway centreline and touchdown point visibility than an S-turn. That and the bank angle of the S-turn increases stall speed, so you either have to increase speed or reduce safety margins. Additionally, a slowly approached stall with full sideslip is unlikely to actually turn into a spin, that usually comes with more rapid deceleration.

However, we will fly the way that makes our examiners happy of-course :}

Better still, if too high, take flaps early. Won't work on all aeroplanes, but on many it will.

G

[Piper.Classique]

However, we will fly the way that makes our examiners happy of-courseSideslipping-I asked my examiner about this, relative to the PFL, before flying my commercial GFT The reply was to the effect that if the flight manual didn't prohibit it then it was OK. So I did, and I passed. At the same time, a sideslipped approach is much better for maintaining runway centreline and touchdown point visibility than an S-turn. Yes, and it's fun. Mind you, so are the S turns....
I would argue for both in a forced landing, as being easy to vary, rather than flaps which tend to be a rather coarse and essentially one-way adjustment.

[Mark1234]

I've also been criticised for sideslipping. Personal theory is that it's so uncommon it scares people who might not be familiar and current. People fear what is out of the ordinary. Try landing a pitts without sideslipping :E

Now, caveat emptor: this is most likely entirely type, and possibly aeroplane specific, but I went out and deliberately stalled a decathlon in a full blooded, rudder on the stop sideslip. Guess what it did?

Stalled. That's it. No wing drop, cleanly and straight ahead. No drama. Who'd have thought it?

No guarantees that all a/c will behave in such a benign manner (and I am in very regular spin practice), but my take is that a rate of yaw is required for a spin. In a steady sideslip in a straight line both wingtips are travelling at exactly the same speed.

[It flies]

Mind you how many instructors teach side sliping these days.
Or is it another tool in the box that has been forgotten.I'm halfway through my PPL course and I just learned to sideslip. So it is still being taught.

Anyone here heard of stall stick position?Mark1234, can you please explain what you mean by this?

[BackPacker]

Stalled. That's it. No wing drop, cleanly and straight ahead. No drama. Who'd have thought it?

I've never flown a Decathlon but my gut feeling tells me that this is not entirely unexpected. Being a high-wing, the center of lift is above the center of gravity. Because of that, it doesn't need dihedral to remain stable. And from memory, it also doesn't have any sweep. It's basically a straight plank wing. That means that the lift and AoA, even in a severe sideslip, is more or less identical left/right. (There might be a little blanking from the fuselage though.)

With a low-wing aircraft you need dihedral to remain stable. In a sideslip, this causes a difference in AoA left/right, and this would induce, I think, a wing drop when stalling.

At least, that's what my gut feeling is telling me. Next time I'm up in the (low wing) R2160 I'll try a full-rudder stall and see what happens. (And yes, I'm current in spinning an R2160.)

Mark1234, can you please explain what you mean by this?

What Mark means is that a stall is not so much associated with speed, but with the AoA of the wings. And these have an almost 100% direct relationship with stick position. In other words: when you pull back at the stick, the aircraft will stall at the same stick position, regardless of speed, actual weight/balance, altitude and a number of other factors. As long as you keep the stick/yoke forward of this position, you will not stall or spin.

(Note that the stall stick position may vary slightly with the engine power setting though, since the propwash over the tailplane makes the tailplane more effective. In addition to this, the propwash also has an effect on the AoA of the wing portion that's in the propwash.)

[Gertrude the Wombat]

if I was flying a normal approach and finding I needed an S turn, I might just be asking myself 'why?' and consider going around and flying a better approach
There's another method which works with at least some Cessnas.

Full flap, just point the nose down. You lose height as fast as you like, and it doesn't speed up enough to bust the flap limiting speed. OK so you might end up a bit fast over the hedge, but it works if you've got 2km of tarmac runway.

[Say again s l o w l y]

Gertrude, I'm going to slap your legs for that one!

If you are in a normal powered aircraft such as a Cessna Spamcan and you find you need to s-turn or slip it in, then go around and do it again properly.

If you have had an engine failure and have no choice, then do whatever you need to get in. Read the flight manual as to whether sideslips are prohibited (For those who assume that Cessna 172's are prohibited, then RTFM. Not all 172's are.) and then go and practise the damn things at altitude until you can do it without screwing up.

It isn't hard and might just get you out of trouble one day.

S-turns are fine, but side slips at least keep you pointing in the right direction.

Am I right in thinking that people haven't been taught how to side slip whilst training for their PPL? If so, I'm going to shake my head in disbelief.

[Pace]

the aircraft will stall at the same stick position, regardless of speed, actual weight/balance, altitude and a number of other factors. As long as you keep the stick/yoke forward of this position, you will not stall or spin.

It is worth noting the control movements at differeing speeds. At slow speed ie in the flair you may pull the column back almost to the stops or some 9 inches.

The rudder is the same! At slow speeds almost full rudder is required for a given effect with a large movement on the rudder peddles.

Now at cruise speed measure the column movement to displace the aircraft to a given angle. You will be shocked that the 9 inch or so movement at slow speeds now reduces to maybe half an inch for a given displacement.

The control forces are high and there is no way in a high speed stall you could move the control column to the slow speed position to achieve a high speed stall.

There is nothing more wrong with an S turn on finals than a sideslip. All you are doing is increasing your track distance to touchdown and hence increasing your spacing to the aircraft in front.

Both require a certain amount of minimal skill the S turn with less danger as your glideslope remains the same as does the rate of descent as equally does your speed.

Pace

[Mark1234]

Oh good, I was hoping someone would bite! I might have guessed backpacker would get it, It is as he describes :ok:(let me know how the slipped stall in the robin goes - I have theories, but very interested in the outcome).

We're all familiar with the concept that you trim for a speed, and if you vary the power the a/c will climb/descend, but remain at the trim speed; the elevator is just a larger, more authoritative trim tab.

To be honest I'm not sure that weight and balance do not change the position, however, empirically they don't change it a noticable amount on anything I've flown. The simple fact remains that if the stick is forward of a certain point you're fat and happy, if it's back around that point you should be paying close attention.


Now at cruise speed measure the column movement to displace the aircraft to a given angle. You will be shocked that the 9 inch or so movement at slow speeds now reduces to maybe half an inch for a given displacement.

The control forces are high and there is no way in a high speed stall you could move the control column to the slow speed position to achieve a high speed stall.

Pace, I suspect you may be mixing deck/aircraft angle with AOA the angle of the wing to the relative airflow. At higher speed, wing DOES stall at the same stick position (as close as I can measure it), but at significantly more G loading (provided the wings don't drop off..) throw in a bit of rudder and its called a flick or a snap depending on where you're from. Not something to do in a PA28, but they fly by the same aerodynamics as the pitts, decathlon etc.

[It flies]

O.k., Mark1234 & BP.

let me know how the slipped stall in the robin goesMark1234, I suggest you have a go in the Pitts and report back? :ok:

[Flyingmac]

S-turns are handy when you've been cut up on final. Sideslips are handy when you've cut somebody else up on (long) final. Both should be taught a lot more than they are.

[Pace]

Pace, I suspect you may be mixing deck/aircraft angle with AOA the angle of the wing to the relative airflow. At higher speed, wing DOES stall at the same stick position (as close as I can measure it), but at significantly more G loading (provided the wings don't drop off..) throw in a bit of rudder and its called a flick or a snap depending on where you're from. Not something to do in a PA28, but they fly by the same aerodynamics as the pitts, decathlon etc.

Mark

If it was as simple as that it would be an easy task to make stall free aircraft right from 747s to 152 by limiting the stick movement to just before the stall.
Sadly it isnt that simple.

Aircraft manufacturers would not need to bother with all the expensive gizmos to prevent a stall in heavies but would have a simple stop before that AOA is reached .

Pace

[BackPacker]

If it was as simple as that it would be an easy task to make stall free aircraft right from 747s to 152 by limiting the stick movement to just before the stall.
Sadly it isnt that simple.

Aircraft manufacturers would not need to bother with all the expensive gizmos to prevent a stall in heavies but would have a simple stop before that AOA is reached .

Actually I recall from reading Langewiesches Stick and Rudder that it is that simple, and aircraft that were impossible to stall (and thus, spin) have been done in the past. Precisely by limiting elevator travel.

However, these aircraft were also a bitch to land, needed especially strengthened and long landing gear and such since they could not flare properly.

[Pace]

http://en.wikipedia.org/wiki/Stall_(flight)

Backpacker

This makes a good read see the list of anti stall devices you could make a fortune ;)

pace

[Mark1234]

Pace, I refer you to my previous comment:
To be honest I'm not sure that weight and balance do not change the position, however, empirically they don't change it a noticable amount on anything I've flown. The simple fact remains that if the stick is forward of a certain point you're fat and happy, if it's back around that point you should be paying close attention.

I'm sure there are reasons why it might not so simple - config changes (flaps will definitely change the position), weight and balance, perhaps regulatory requirements, in all of which the big tin has to accomodate much more variance. In any case, I believe you're still incorrect in as much as I quoted you.

However, it is but a useful tool in your armoury. I (for whatever my opinion may be worth) would recommend it is used two ways:
1) For pretty much 1G flight at slow speeds (i.e. approach), with respect to the configuration of the day - i.e. having previously stalled in that configuration at altitude to establish a datum.
2) As a gross error check. IF the stick is back in your guts you should be considering very carefully what you do next. If it is well forward you can be fairly comfortable.

I make no claims to know it all, I've just sought out interesting people to fly with, and done a lot of dual time, particularly aerobatic where you get to explore things a little more than those who get their PPL then avoid dual like the plauge.

@it flies - sure, I'll try to remember next time I'm up.

[Crankshaft]

There is nothing more wrong with an S turn on finals than a sideslip. All you are doing is increasing your track distance to touchdown and hence increasing your spacing to the aircraft in front.

Both require a certain amount of minimal skill the S turn with less danger as your glideslope remains the same as does the rate of descent as equally does your speed.Generally I agree with you Pace. However I would consider a S turn to be somewhat more than just an increase in track distance. The bank itself increases the induced drag (especially at greater bank angles) and therefore also increases the rate of descent - steepens the glidepath.


It seems to be forgotten here that some aircrafts are not well suited for either of sideslip or S-turn. For example some modern aircraft with slim rounded composite fuselages do not increase its rate of descent as significantly as for example Piper Cubs or Decathlons in a sideslip. In many of those composite aircrafts it is much more efficient to use an S-turn. Similarly there are also some aircrafts that aer no good for S-turns depending on sluggish roll rate for example.

if I was flying a normal approach and finding I needed an S turn, I might just be asking myself 'why?' and consider going around and flying a better approachI think you missed the point in doing sideslips/S-turns. We practice this for being able to land following an enginge failure when a go-around obviously is not an option.Full flap, just point the nose down. You lose height as fast as you like, and it doesn't speed up enough to bust the flap limiting speed. OK so you might end up a bit fast over the hedge, but it works if you've got 2km of tarmac runway.The idea of making sideslips or S-turns is to be able to land even when you don't have that 2km tarmac, i.e to touch down at your aiming point rather than 500m after.

[generalspecific]

S turns on finals.... every time I do an ILS approach :E

[robin]

Side slips are also best when landing some of the 'long-nosed' types or bi-planes even when the wind is down the runway.......

Always good to keep in practice when flying tail-draggers

[UV]

S-turns are handy when you've been cut up on final. Sideslips are handy when you've cut somebody else up on (long) final. Both should be taught a lot more than they are.

....and how does that, and any of this S turn business, comply with the requirement for all turns in the circuit to be in the same direction as that set by other aircraft*? And surely good airmanship dictates that that if you cannot continue the approach safely you go around.

*Sorry, I do not sit here with volumes of the ANO in front of me ready to quote articles and sub articles, and sub sub articles!

UV

[Pace]

S turns on finals.... every time I do an ILS approach

Full deflection to the right then full to the left sounds good! General Specific is that intentional ? ;)

Actually know someone who did a barrel roll on the ILS and came out on the button :ugh:

Seriously though I am not suggesting you do 45 degree banked S turns but in VMC there is nothing wrong with gentle turns to adjust the spacing a bit.

You actually have increased vision good speed rather than dragging the speed back to just above the stall to get that spacing and done correctly a safer manouvre than a go around...... but what do I know :O

Frankly what is good airmanship???

Pace

[Gertrude the Wombat]

Gertrude, I'm going to slap your legs for that one!
I thought that would wind someone up!!

It works though. I did it once on a glide approach when I'd misjudged the wind, and the instructor was perfectly happy - I got onto the runway, if it had been a real forced landing in a field we'd have walked away which is all that matters.

No, I wasn't taught sideslipping near the ground on my PPL. It's on my list of things to ask for on my next hour-with-an-instructor.

[flybymike]

S-turns are handy when you've been cut up on final.

But sure confuse the hell out of the guy behind you who is rapidly catching up....;)

[Pace]

FlyByMike

Thats his problem! He can go round :E or even better he can do S turns too :cool:

Pace

[SNS3Guppy]

Given that one needs at least 30 degrees of bank to accomplish this, is there not a danger of a spin-in?

Why does one need 30 degrees to do S-turns on final approach? Is this a British regulatory or standards requirement? There's no such practical need. Practically speaking, one can do a steep turn on final without stalling or harm, or one can do very mild banking to do S-turns.

There's no reason to expect a spin simply from doing S-turns. The airplane won't spin unless you allow it to spin.

Actually I recall from reading Langewiesches Stick and Rudder that it is that simple, and aircraft that were impossible to stall (and thus, spin) have been done in the past. Precisely by limiting elevator travel.


Wolfgang's book is somewhat outdated, and while making for good reading, is not technically correct, and is not accurate. As a general picture, perhaps, but don't take it to heart.

Efforts have been made to create unspinnable aircraft. The Ercoupe was one such effort, albeit unsuccessful. Limiting elevator travel will NOT prevent a spin.

At higher speed, wing DOES stall at the same stick position (as close as I can measure it), but at significantly more G loading (provided the wings don't drop off..)

A stall has no bearing on stick position. Stall is a function of angle of attack, not stick position, not pitch angle, not power setting, not weight, not center of gravity...but of angle of attack for a given aircraft configuration.

I can demonstrate for you quite easily a stall in a variety of stick positions in the same aircraft; forward, aft, neutral, along with a variety of ways to stall the aircraft. I can also do the same thing in order to enter a spin. Divorce in your mind the concept of stick position and angle of attack; they are not related, and marrying the two concepts can simply confuse you...or get you killed. Relating stick position to a stall is a fallacy, and a dangerous misunderstanding of basic aerodynamics, and basic airmanship.

Furthermore, pilots have been killed stalling and or spinning an airplane with the control lock in. No aft travel at all, and pitch taking place as a consequence of power setting.

Given the extensive variety of aircraft available, one shouldn't attempt to make such broad, sweeping statements as the notion that an aircraft can't stall or spin if stick motion is limited. I've been able to fix the stick in position and move the airplane about simply by standing and leaning this way or that...I could just as easily stall the airplane, and subsequently spin it without any stick motion at all, if I desired.

In other words: when you pull back at the stick, the aircraft will stall at the same stick position, regardless of speed, actual weight/balance, altitude and a number of other factors. As long as you keep the stick/yoke forward of this position, you will not stall or spin.


This is 100% untrue. The aircraft will stall at the same angle of attack for a given configuration, but not the same stick position. Given more experience in aircraft, or a variety of aircraft, you'll realize this. An aircraft can be stalled with the stick forward or aft, and CG will have a significant bearing on the position of the stick, as will power setting, etc. The aircraft can be stalled slow or fast, pointing skyward or at the ground, light or heavy...and the stick position will vary throughout those regimes.

Now...as far as sideslips and forward slips go...

When I was younger and inexperienced, I was a big user, and a big proponent of the slip. Much easier than reconfiguring the aircraft, it's really just "free" drag...and unlike lowering flaps or doing something else to alter the aircraft configuration, the slip can be instantly disposed, with an instant performance recovery.

This comes at a price, however, and one that's seldom advertised. I've seen it on big aircraft and small, and I've personally handled the broken parts and seen the trends. One seldom hears it mentioned, but a slip puts an enormous air load, even at low airspeeds, on the vertical stabilizer. In many aircraft, including most light airplanes, one might be shocked to find out just how little is holding that vertical stab in place...usually two brackets or bolts.

I maintained a fleet of 30 single engine Cessna's years ago, that were used for mountain flying, tours, sightseeing, and a lot of canyon work. Slips were used a lot to get into some of the strips we used, and regularly used for landings, and other types of flying that we did. I found a trend among many of the airplanes; cracked vertical stab attach brackets...meaning complete failure of the part. As a result of the findings, the parts were changed from an aluminum alloy, to steel. Never the less, we found more cracks.

I've found them on large four engine airplanes (which we also aggressively slipped into canyons in exactly the same way we do it in light airplanes) during inspections. We've learned in recent years, with fortunately more publicity, that airplanes can be broken at speeds considerably less than Va...something that many didn't believe would happen, just a few years ago. Slips are hard on the airframe.

Now, I've done a lot of flying in airplanes without flaps, and slips are often used in such airplanes. I don't do slips as a rule, any more, regardless of what I'm flying, because I know the cost and the stress on the airframe.

[Flyingmac]

Since when was an S-turn against circuit direction? That would be a U-turn according to my recollection of the alphabet, and since when was a side-slip a component of an unsafe approach? I've flown into many a tight strip where the safest option was slipping in for obstacle clearance.

There appears to be two types of flyer on this forum. Pilots and aeroplane drivers. Eventually some of the latter will become the former. Some never will.

[Mark1234]

I can demonstrate for you quite easily a stall in a variety of stick positions in the same aircraft; forward, aft, neutral, along with a variety of ways to stall the aircraft. I can also do the same thing in order to enter a spin. Divorce in your mind the concept of stick position and angle of attack; they are not related, and marrying the two concepts can simply confuse you...or get you killed. Relating stick position to a stall is a fallacy, and a dangerous misunderstanding of basic aerodynamics, and basic airmanship.

Ok, I'm sceptical I admit - I think I understand pretty well, so please, explain - I'm always happy to learn. Taking away pod mounted engines with big power/pitch couples, and also disallowing establishing an unsustainable climb angle then centering the stick, which is, even to the meanest intelligence obviously going to lead to a stall, just how DO you demonstrate a stall with a forward stick position?

As far as I understand it's just basic aerodynamics: (most) aircraft are speed stable - you increase power you climb at the same speed, decrease to descend at that speed. Trim (or more coarsely stick position) sets speed.

[BackPacker]

Taking away pod mounted engines with big power/pitch couples, and also disallowing establishing an unsustainable climb angle then centering the stick, which is, even to the meanest intelligence obviously going to lead to a stall, just how DO you demonstrate a stall with a forward stick position?

I was thinking the same thing. Very interested to learn where my understanding of aerodynamics and aircraft behaviour fails.

And no, flying inverted with full forward stick, leading to an inverted stall disqualifies also. As do out-of-limits CofG positions.

[SNS3Guppy]

An aft center of gravity may result in a stall with a forward stick, and no...one needn't exceed CG limits.

When losing half or more of one's weight quickly, common in certain general aviation aircraft...one can have the stick buried against the forward stops and still climb without any ability to arrest the climb. I've experienced that hundreds of times. A number of pilots have died in such a situation. The stick position is irrelevant; angle of attack is the consideration in the stall.

I said nothing about pod mounted engines, nor establishing unsustainable climbs and then centering the stick.

With a student, I prefer to demonstrate stalls with the airplane level on the horizon, and prefer to demonstrate a stall recovery with nearly imperceptible movement of the stick and a very, very slight decrease in angle of attack...this tends to show the student that a stall isn't something to be feared. Too many students have been shown violent stalls, have been floated in their seats, and scared by inexperienced instructors who felt that a big, dramatic recovery was a necessity.

Stick position during the recovery may be aft, may be neutral. The rapidity with which one causes a stall to occur, and the acceleration of the stall itself, play some part in stick position, but to suggest that stick position remains the same for a high speed stall as with a low speed stall is utterly ridiculous. It doesn't, nor does stick position have any bearing. One doesn't teach stall recovery by instructing a student to put the stick to a "safe" position, but to decrease angle of attack.

Certainly various kinds of stall recoveries are possible, depending on the stall condition. Also depending on the airplane, and on the altitude and circumstance in which the stall occurs. Some aircraft will tolerate nearly any kind of recovery, others won't. Some won't recover well at all. Some take very long distances. A deep stall in a Learjet, despite the substantial power available, can take nine thousand feet of recovery, and will continue or occur with full forward stick...and indeed many business class aircraft are recovered in climbing stalls by rolling to a steep bank, unloading the wings, and letting the nose fall through the horizon while adding power...one doesn't push the nose forward...which is a poor habit that one "gets away with" in light aircraft. Again, different techniques for different circumstances...but to suggest that stick position has any bearing on stall, or the inability to stall, is ridiculous.

Certainly one may need to have the stick buried in one's abdomen to induce a stall in a given airplane under some circumstances, but may find it stalls quite admirably with the stick in the center of it's range of movement, under another circumstance. In my present assignment, I can induce a stall by banking at altitude without any need to move the control column aft...go too steep, no movement will be evident or necessary, but an accelerated stall will occur.

Some airplanes, when flown at a high angle of attack, will require significant forward stick to prevent stalling. The airplane may then be stalled while holding forward stick, proving again that stick position has no bearing on when the aircraft stalls...that is, one can never say that the airplane always stalls at the same stick position, because this is patently untrue.

[BackPacker]

When losing half or more of one's weight quickly, common in certain general aviation aircraft...one can have the stick buried against the forward stops and still climb without any ability to arrest the climb. I've experienced that hundreds of times. A number of pilots have died in such a situation. The stick position is irrelevant; angle of attack is the consideration in the stall.

Okay, I think I get what you're trying to say here. I know you have extensive experience with aerial fire fighting and possibly meat bombing and for-real bombing too. Most of us here in "private flying" don't do that sort of stuff. So our frames of reference may be different.

But more importantly, what I think is the case here is that these types of aircraft have a trim that moves the whole tailplane, and a stick which independently moves the elevators attached to that tailplane. In that case, yes, stick position on its own is not directly related to the AoA/stall. If you have trimmed too far forward you can bury the stick in your abdomen and not stall, and if you have trimmed too far aft you can push the stick all the way forward and still not prevent a stall. What we probably should have said is something along the lines of "pitch position largely determines the AoA (and thus the stall), where pitch position is the result of trim position plus stick position".

And of course losing half the aircrafts weight may lead to a massive CofG shift and a massive out-of-trim situation. Which may not be correctable by stick alone. Which may lead to a stall with full forward stick.

So, good point. Thanks.

but may find it stalls quite admirably with the stick in the center of it's range of movement, under another circumstance. In my present assignment, I can induce a stall by banking at altitude without any need to move the control column aft...go too steep, no movement will be evident or necessary, but an accelerated stall will occur.

What I think you're talking about here is the coffin corner. High altitude meaning that your Mach limiting number (or whatever it's called) creeps down while your stall speed creeps up. Go a little too fast and you get into the transonic regime with all its associated dangers, go a little too slow, or load the wings just a little too much, and you get into a stall.

Again, good point. But I do wonder what the trim position is in that kind of flight regime, and what the resulting speed of that same trim position would be much lower down.

Certainly various kinds of stall recoveries are possible, depending on the stall condition. Also depending on the airplane, and on the altitude and circumstance in which the stall occurs. Some aircraft will tolerate nearly any kind of recovery, others won't. Some won't recover well at all. Some take very long distances. A deep stall in a Learjet, despite the substantial power available, can take nine thousand feet of recovery, and will continue or occur with full forward stick...and indeed many business class aircraft are recovered in climbing stalls by rolling to a steep bank, unloading the wings, and letting the nose fall through the horizon while adding power...one doesn't push the nose forward...which is a poor habit that one "gets away with" in light aircraft. Again, different techniques for different circumstances...but to suggest that stick position has any bearing on stall, or the inability to stall, is ridiculous.

You've subtly moved the discussion here from stall onset to stall recovery. And I fully agree that deep stalls, particularly in aircraft with T-tails, may require some very unusual stall recovery techniques. I think the same is true for aircraft with significant wing sweep.

And I need to smile at the picture of the CEO of BigBucks Inc., cruising along at FL410 in his private jet, fat, dumb and happy sipping his champagne, and all of a sudden there's some turbulence, a buffet and the next moment the aircraft is doing a 90-degree wingover.:ok:

[Mark1234]

Have to confess I also hadn't considered swept wings and high altitudes - rather outside my experience, as is throwing most of the payload overboard :)

I do ponder this though
In my present assignment, I can induce a stall by banking at altitude without any need to move the control column aft...go too steep, no movement will be evident or necessary, but an accelerated stall will occur.If you don't move the stick (or have the trim move? going along with backpacker's thinking), then banking the a/c will result in the nose dropping and entry to a descending turn, still at 1G right? How is an accelerated stall possible under those circumstances?

[It flies]

these types of aircraft have a trim that moves the whole tailplaneQuite a few GA aeroplanes have this as well. The Piper Super Cub and the Fleet 7 spring to mind.

[SNS3Guppy]

But more importantly, what I think is the case here is that these types of aircraft have a trim that moves the whole tailplane, and a stick which independently moves the elevators attached to that tailplane.

Most don't have a movable tailplane, though some do. I hadn't really thought about skydivers, but I've seen that happen, too. I've been nearly full forward on the stick as jumpers reposition. I wouldn't include that in the same group, because it's very possible for the jumpers to move the CG outside the CG limits, and that's something you specifically excluded from consideration. None the less, even with the CG remaining in limits, it can certainly be a situation in which one is trimmed far forward or holding significant forward stick when arriving at a stall. I've seen airplanes stalled and rolled over, during jump operations, and I've seen it done when holding full rudders against the assymetric drag of a number of jumpers hanging onto the outside of the airplane.

That's not too far removed from typical general aviation operations, given that many jump operations involve commonly used airplanes such as Cessna 182's and 206's.

The trim on many ag type light general aviation airplanes doesn't move the stab, but a trim tab on the stab. A common example is the Cessna A188B AgTruck. This airplane is little more than a Cessna 185 with the wing on the bottom, instead of the top...and a slightly longer nose to hold a 300 gallon hopper. It's got the same tail and horizontal stab and elevator, and works the same way.

A difference that many ag type airplanes have in trim is that they trim roughly...rather than giving fine trim such as we see in a Cessna 172, where the trim is moved by small degrees by repeatedly spinning a trim wheel, the ag aircraft use a single lever..push it forward a few inches and you have full forward trim, pull it aft and you have full aft trim. One doesn't really trim ag airplanes out that much. When punching off a load, I find if it's a downhill run I will often put in full forward trim or put my hand on the trim as I get set to push the button, then push it forward as the load goes out. Then throttle. I've seen myself pointing at the sky on a few occasions with the stick fully forward against the stops.

With the heavy tankers, trim systems vary considerably; the P2 has a variable camber horizontal stab rather than a moving stab, whereas the 4Y utilized a trim tab on the elevators with a conventionally fixed horizontal stab. Systems varied with each airplane, but aren't particularly relevant here. Point is that the all-flying tail or trimmable tail isn't really a consideration here. In fact, the full flying tail or stabilator is more common in light airplanes, and fully trimmable stabilizers are also common, especially in older light general aviation airplanes.

What I think you're talking about here is the coffin corner. High altitude meaning that your Mach limiting number (or whatever it's called) creeps down while your stall speed creeps up. Go a little too fast and you get into the transonic regime with all its associated dangers, go a little too slow, or load the wings just a little too much, and you get into a stall.


Very few aircraft have the ability to get close to "coffin corner." Typically most aircraft have a 30+ knot window at altitude, which isn't at all in coffin corner...so I'm not talking about coffin corner. A large airplane operated at altitude may stall in a steep bank, and not simply maintain a 1 G loading and descend. Typically, performance is calculated to provide a stall and buffet margin for turning, and altitude is limited in large airplanes in part by buffet margins, as well as climb and cruise performance. These things aren't particularly relevant either, in the private pilot arena, but may be of interest.

And I need to smile at the picture of the CEO of BigBucks Inc., cruising along at FL410 in his private jet, fat, dumb and happy sipping his champagne, and all of a sudden there's some turbulence, a buffet and the next moment the aircraft is doing a 90-degree wingover.


I haven't seen that picture, but I've been in that situation, without a CEO on board, mind you. An upset condition isn't common, but in my case we were doing atmospheric research and went looking for it in and around thunderstorms at night. We found it, too, violently...and got stick shaker, pusher, and past a 90 degree roll out of it, as well as a very pronounced stall buffet. That was also in a Lear 35. It was pronounced enough that it broke the headset of one of our operators sitting in back, and stripped the guts out of my computer, which was in a padded case.

The reason, incidentally, that one rolls the wings and lets the nose fall through the horizon during a climbing recovery is to protect the airplane. Simply pushing forward can overstress an airplane, and in a turbojet, with climb rates that can range from two thousand feet a minute to twelve thousand feet a minute (ala LR24), one can wrinkle the wings pushing forward. Rolling and letting the nose fall through the horizon accomplishes two things; it unloads the airplane and lets gravity and aerodynamics protect the airframe as one recovers, and it automatically reduces angle of attack as the nose falls through and the flight path changes. Simple stall recovery in a large jet is a little different, too...typically one powers out of the stall without movement of the control column, or very slight movement.

This, of course, does little to help the private pilot who is considering S turns on final.

S turns will not cause a stall. S turns will not cause a spin. S turns don't need to be steep or shallow, particularly...they're just there to cause the airplane to cover more distance by turning back and forth, while making less progress forward toward the runway. They may be performed for traffic delays, or to allow more time to get down from altitude. I've done S turns at the Aspen airport in the US...where one crosses the VOR at 14,000' and reaches the runway at 7,800'. The S turns are mild, and allow the descent without an excessive rate or rush...and sometimes may be necessary due to aircraft limitations. I've done them in the traffic pattern at local airports at times, and I've been requested to give an S turn at busy commercial airports, too. It's another technique a pilot can do, commercial or private, to put the airplane on the runway and adjust timing and altitude in the process.

Stalls should be thoroughly understood, including the mechanism, and mechanics of the stall. Pilots need to understand what causes a spin, how to prevent a spin, how to recognize a spin, and how to the fly the airplane and not spin...and of course, how to recover from a spin. Pilots should not be taught that a stall occurs at the same stick position, because it most certainly does not. Pilots should not be taught that the stall occurs aft or forward of a certain stick position, either...because this simply is not true.

Operate an airplane in slow flight. Approach the crossover on the power curve where more and more power is required to fly slower and slower. Note the trim note the stick position. The airplane can be trimmed off to fly just above a stall, with power on, and the stick position, or trim position will be decidedly different than where it's trimmed for cruise, or for another circumstance in which the airplane may be stalled. In some cases, the stick may be full aft to cause a stall, and in others it may be in a more neutral, or even forward position (and this doesn't consider tailplane stalls in icing, another subject entirely, but a stall none the less...proponents of limiting aft stick movement would be in a world of hurt in a tailplane stall, where aft stick is used to recover).

When someone suggests that S turns on final will cause a stall or spin, they're really suggesting a lack of understanding of stall and spin dynamics; this is an alert that additional study and training is required. The same can be said for an assertion that stalls always occur at the same stick position.

[englishal]

There is a very important phrase I once read...

"An aircraft can stall at any airspeed, any altitude and any attitude".....

In some aeroplanes applying full power too early during a stall recovery has the effect of increasing nose up pitch so the aeroplane could remain stalled with the stick fully forward...to answer the one about forwards stick stalls.

[SNS3Guppy]

Quite right.

[Mark1234]

There is a very important phrase I once read...

"An aircraft can stall at any airspeed, any altitude and any attitude".....

In some aeroplanes applying full power too early during a stall recovery has the effect of increasing nose up pitch so the aeroplane could remain stalled with the stick fully forward...to answer the one about forwards stick stalls.


Other than ones with low slung pod engines? Completely agree with airspeed, altitude, attitude quote, would never suggest otherwise.

@it_flies: Did as you suggested. 1 up, S2A - left wing down, right rudder, no noticable break, just settled into a nose high, high descent rate mush. Slight tendency to roll out of the slip, held with aileron (so they weren't stalled). Full back and out stick, full in rudder. Other way around, right wing down it eventually over several seconds rolled into the left wing and began a slow, steep spiraling turn (which I didn't wish to explore). Not drawing any conclusions as to whether it was a spin or spiral, but it initiated very slowly - effectively I ran out of aileron to counteract the rolling tendency.

I suspect that the rolling tendency is due to a combination of the slightly swept upper plane, and fuselage blanking of the lower. No particular conclusions to be drawn, a different CG might result in a more determined behaviour, the aileron application might be sufficient to trip the outer wing into a stall, etc..

@Guppy
"A large airplane operated at altitude may stall in a steep bank, and not simply maintain a 1 G loading and descend. "

I'm still struggling to get my head around this. We all agree (I think) that a wing stalls because of an increased angle of attack. Now, rolling into a turn does not intrinsically increase the angle of attack - that's set by the aerodynamics - speed, tailfeathers, etc.. - it simply re-orients the lift vector, and as gravity doesn't re-orient, the nose should fall. If you want to maintain your vertical trajectory, you must increase the AOA to compensate for the lift vector, which is clasically what causes the turning stall. In order to increase the AOA, you must apply some moment around the wing to 'rotate' it and increase the AOA - typically by use of aft stick/trim/etc. What did I miss?

[Say again s l o w l y]

Oh dear Mark. Before you get shredded by the aerodynamicists amongst us, may I suggest a quick reread of a basics aerodynamics book.

I'm just rushing out so haven't got time for an indepth post, but you might want to read about how the angle of attack changes when rolling.

[Mark1234]

No need to shred (!) I'm thinking you mean that there will be an increase in the AOA of the downgoing wing, and a decrease of the upgoing? I'd expect that to be significant at large rates of roll, but largely insignificant at the sorts of roll rates used by bizjets and airliners - there I may be wrong.

I confess I'd assumed that the stall was in the turn, not due to the roll effects.

[It flies]

Thanks Mark1234. I appreciate your effort. But from reading your description it's unclear to me whether you tried a stall from a sideslip or a slipped/skidded level turn?

My last lesson got cancelled thanks to the volcanic fiasco, but next time I will try to ask my instructor about this.

[Mark1234]

A sideslip. Originally did this in the decathlon after being admonished on a checkride for sidesliping a PA28. "If you get slow you'll spin and die in a smoking hole" (from an instructor). On the other hand, one of my aeros instructors taught slips all over the place as an approach technique. Being as I wasn't worried about spinning the decathlon, I thought about it a bit, then went nice and high to see what happened.

No effort. The comments from you and BackPacker lead me to more thinking, and more experimenting. Always good to learn.

[It flies]

Always good to learn. I certainly agree with you there.

A sideslip.That's what I thought you had tried. I meant to suggest setting up a constant coordinated turn and then try to stall the plane either by throttling back and trying to hold the nose up, or by pulling G and accelerate into a stall.

Then repeat with skidded and slipped turns. I wondered whether the behaviour would be as written here (from the stalling in a turn thread):

If the airplane is slipping toward the inside of the turn at
the time the stall occurs, it tends to roll rapidly toward
the outside of the turn as the nose pitches down
because the outside wing stalls before the inside wing.
If the airplane is skidding toward the outside of the
turn, it will have a tendency to roll to the inside of the
turn because the inside wing stalls first. According to John Farley power and type are more important than general rules so it is probably fruitless to try to come to any firm conclusion here. Nevertheless, it's interesting to read about other people's experiences with stalls and spins.

[Final 3 Greens]

Originally did this in the decathlon after being admonished on a checkride for sidesliping a PA28. "If you get slow you'll spin and die in a smoking hole"

I wouldn't disagree with the instructor's comments.

If you get too slow in a slip at low altitude, you will spin and die.

However, you can choose to keep the speed safe.

I used to be a big fan of slipping as a way of losing altitude quickly, but having read SNS3Guppy's comments about the impact on the vertical fins am having second thoughts.

To return to the original question, I see no problems with using S-turns to increase the track distance to touchdown, so long as airmanship says it is appropriate under the circumstances.

I've done it many times, when joining straight in under ATC control and making room for circuit traffic.

Like most things in flying, you have bear in mind the 'law of the situation' and make the best choice; you may be able to slow down and you can always go around.

Can't say I like the idea of doing a 360 on final and would be likely to decline and go around, but equally that probably is reflective on my ability to fly and others may be perfectly comfortable with that.