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Avoiding spins from base to finals
After reading the 'instructors who refuse to spin' thread on the instructors forums:
What is the best way to ensure that you DON'T inadvertently spin the aircraft on turn from base to finals? Understand about not lifing nose, or letting airspeed bleed off with flaps extended, but is there a way to really ensure that you don't enter one? (This has always been a thorn in my side) Also, should you be unfortunate enough to spin at this point, is there ANYTHING at all you can do, being so close to the ground? <apologies if this is in the wrong forum> |
Airspeed and Bank Angle. Choose the right numbers for your aeroplane and Bob's your uncle.
If you enter a genuine spin at or below 1000 AGL, you can forget any real hope of recovery. |
As they drum into you during the PPL
" Airspeed Airspeed Airspeed" Nail your airspeed and bank angle & you should always be ok. If you have concerns or worries grab an instructor and bash the circuit you can't beat it for making you confident & competent. EL |
As has already said the key is airspeed. To spin you have to stall and to stall you have to have a high AoA. Just keep an eye on your airspeed, make sure its what it needs to be. Also try and avoid uses of extra rudder when near the ground. Its all common sense really.
As for what to do if you spin, well the first thing I would do is try and recover. Its the only thing you can do. Depending on height and a/c you might be lucky, you might not. Altho I don't advise testing this at low level lol. |
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The aircraft CAN NOT spin if it is flown in a balanced turn. So fly accurately - ball in the middle. If it is too slow, it could stall but if it is being flown in a co-ordinated (rudder/aileron) fashion it will not spin.
At a thousand feet, unless you were in very current practice, you'd probably buy the farm. Stik |
G_String, firstly, if you fly at the airspeeds in the pilot operating manual and fly a co-ordinated turn which is essentially keeping the ball in the middle then you won't stall.
The best bet for you is to find an instructor who is happy to take you into a full stall rather than incipient stall and to let you see how much abuse you need to give a spam can to make it stall and what warnings there are. |
The easy answer...
Look out the front window!!!
Of course staying keeping the airspeed right and keeping in balance is the key to not spinning. But that's true of any stage of flight. So what is it that makes the spin more likely to happen at this stage, apart from maybe being a little slower than during the cruise? It's pilots who are trying to look at the runway during the turn - and therefore not watching the attitude. You will not notice that your speed is wrong nor that you are out of balance if your eyes are not on the horizon! The issue is that you, naturually, want to see where you are turning towards. But in turning your head to look at the runway, you are looking away from the horizon, and therefore not aware of any changes in attitude or airspeed. The problem is worse, IMHO, in a high-wing aircraft, because the view of the runway is obscured in the turn, meaning that you probably have to shift around in your seat to see the runway - and this will naturally involve you involuntarilly moving the controls. Incidentally, I see my students loosing airspeed (in the high-wing Cessnas that I teach in) far more on the downwind-base turn than on the base-final turn. The reason, 99% of the time, is that they are trying to look at the runway to work out when to roll out of the turn. When turning final, the runway is at least ahead of you at the end of the turn, so you don't have to strain to see it. But when turning onto base in a high-wing aircraft you must have some other method of working out when to roll out of the turn. The answer? Before you roll into the turn, pick a feature just in front of the left (or right, for a right-hand circuit) wing. Then start the turn, keep looking ahead, and stop the turn when your pre-selected feature appears in the windscreen. As you roll out of the turn, you can then look at the runway and make adjustments. This will enable you to be aware of your attitude, and therefore your airspeed, right the way through the turn. To answer the second part of the question, if you ignore all the advice here and get it wrong..... I don't believe there is any way of recovering from a spin at that level in most aircraft before hitting the ground. But the training you get in spin recognition and avoidance as part of your PPL should train you to lower the nose, apply full power, level the wings and climb away well before the situation develops into a full spin. That is precisely why, for the PPL skills test, you are required to recover from this situation at the first sign of the stall, namely either the light buffet or the stall warner, whichever occurs first. FFF ------------- |
If you dont load the wing you wont stall and spin. You can bank as hard as you like providing you have a hefty decent going at the same time (and little back presure on the elevator)
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atsa2
I can pull a descending 3G turn in my beastie, mishandle the rudder and she will flick out of the turn (up) or will flick into it (down). Stik |
What you say is of course true Stik, but I think I know what atsa2ltcc is trying to say .... as I'm sure you do (are you playing Devils advocate?)
Most stall and spin accidents at this point are caused by an overshoot of the centre line. A student worried about banking too hard is more inclined to unconciously skid the aeroplane around the turn by adding more rudder. Even with a reasonable airspeed it's quite possible to cause a spin this way. Whilst a high bank angle is normally discouraged near the ground due to the increased stall speed, it's much safer than skidding, and if you have a reasonable amount of speed and don't pull too hard you will be fine. Actually, I hate the use of the term "airspeed" because it is a pretty misleading figure and so heavily influenced by other factors. AoA is much better and it's a shame that a decent AoA indicator has not been developed for light aircraft. SS |
I've said this before, try to be aware of the stick position. If you are getting towards the back stop, you are just about to stall, regardless of airspeed.
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I do not have my PPL so ignore me if this makes no sense! - I am trying to finish and get the first milestone!
When I did my Flying Scholarship, I was always taught once you have commited to the "death turn" never increase the bank angle. If you are going to over shoot the runway hold the turn a little longer to turn you back on an intercept heading and re-establish the centreline. If not or you have doubt - Go Around. It was always said to me that you are going to probably be losing airspeed in the turn, and although you'll be fine at a normal bank angle if you increase it you could increase the stall speed above your current speed. so it's best to keep the stall speed where it is, and if you get buffet reduce the bank angle - and Go Around! It is a while ago I did this so memories are old... but that's what I remember. |
stiknruda..
Read my full post! "With little elevator back pressure". I would be impressed if you could do a 3g decending turn without elevator pressure! |
... and so another well-intended thread spirals into a high-G manoeuvre :D
I think you've had the answer G_STRING, packaged in several ways. Watch the bank angle and the airspeed and all will be well. Don't forget that a higher airspeed is required to avoid a stall when the bank-angle is increased. That is what catches lots of people out. Talk of Angle-of-Attack and loading the wings is much more "right-on Piloty" and in keeping with "grass roots flying", but not very helpful to a low-hours pilot IMHO. 2D |
I am slightly concerned that the suggestions for an hour or two of dual with an instructor could be misinterpreted as being sufficient to eliminate the prospect of a classic spin-during-turn-to-final accident.
The fact is that many properly trained, high-time, experienced pilots have been killed in this sort of accident; it is something that we all have to be constantly aware of. You can be the best pilot in the world, but if you are momentarily distracted by something, or fatigued at the end of a long flight, a low-level spin can still bite you. One of the best discussions of this topic is Leighton Collins' artilce "The Dangers of the Air", which is found near the end of Langewische's classic Stick and Rudder. AoA is much better and it's a shame that a decent AoA indicator has not been developed for light aircraft |
I am slightly concerned that the suggestions for an hour or two of dual with an instructor could be misinterpreted as being sufficient to eliminate the prospect of a classic spin-during-turn-to-final accident. FFF --------------- |
Well yes, I suppose so; although come to that, reading about the problem in a book or magazine article would be an even cheaper method of understanding.
I am in no way against dual instruction, which is usually the most effective way to sharpen up one's flying. My point is simply that even a great instructor can only provide limited protection against this potential accident ... constant wariness is really the only reliable safeguard. |
Atsa/ss
contrary to how you read my post, I wasn't disagreeing with Atsa - what I was trying to reinforce was that turns need to be co-ordinated. It was because of the relatively low experience level that some on this forum have that I keep banging on about coordination. It doesn't matter how fast you are going, if you pull to wings critical (AoA) and then apply too much rudder or too little rudder you will flick/snap and that could just be your entry into your first and last fully developed spin. Alternatively, if you are going too slowly, the same scenario reoccurs - but only if you mishandle the rudder. MLS12 - many aircraft have a perfectly good AoA indicator - it is called the stick! The aeroplane will stall with the stick in same position across the range of airspeed! What I mean, before I get shot down, is that in my aeroplane, with the power at idle and the aircraft decellerating through 60mph with the stick coming back to hold the nose up, the stall break will come at the same stick position as it will if I am accelerating through 120mph, with full power on and pull the stick back. So once your muscle memory maps arm position to stall - you have your very own built in AoA indicator. Stik |
An hour or two with an instructor who doesn't have a lot of stall/spin/aerobatic time is unlikely to help much.
STIK, Quite unusual for most aircraft not to spin one way or the other without dancing on the rudders. If you've time to dance on the rudder you've got time to release the back pressure on the stick which is the actual cause of the circumstances you find yourself in. I believe the key for the final turn is bank angle. Way back when I started gliding I had it knocked into me 'well banked final turn', 'MINIMUM 30 degrees'. This came back to me during commercial training, all turns in the circuit EXACTLY 30 degrees. So what is the point? Well, in a glider there is a lot of wingspan which, if you try to cheat, helping get the last bit of turn with a touch of rudder or just fly inaccurately, creates a considerable difference in airspeed over the respective surfaces. If you're already to slow this may be the final nail in your coffin. If you fly too slowly through a steeper turn you get a high rate of descent and the nose drops but all you have to do is level the wings and you're flying again. One way you die, the other you live. In the commercial training the point was to improve your judgement so that you only made the exact required turn instead of 45 at 30 degrees, 30 at 20 and the final part of the turn at 5 or 10 degrees. My gliding and training remain fresh in my mind; when I do a visual approach, coming in on base or from 45 degree base, I still wait until what I reckon to be the right moment to make the 30 degree banked turn instead of waffling onto the final course. |
Way back when I started gliding I had it knocked into me 'well banked final turn', 'MINIMUM 30 degrees'. |
Of course the simple answer was given very early on. Watch attitude, moniter airspeed, stay co-ordinated and all will be well. There ends the thread!
But no! ... the great thing about these forums is the further debate, and the lessons you can learn from them. It's all very well to then pipe up, complain and say that we're all just going to confuse the poor student, but what does that achieve? We could start a new thread, but then the momentum is lost. Nope, I like the way these things blossom. Hopefully even a student pilot will soon get the basic answer to his/her question, but will often learn more by lstening to the debate of those with more experience. I'm not sure if this Talk of Angle-of-Attack and loading the wings is much more "right-on Piloty" and in keeping with "grass roots flying", but not very helpful to a low-hours pilot IMHO. Bank angle does increase stall speed, higher G does increase stall speed ... but niether cause spins in any greater way than any other stall. If co-ordinated a quick nudge forward will (usually) get the wing biting again. Some aeroplane flik ... but usually there has to be some rudder influence to cause this. The above may sound Gung Ho .. but that is not the intention. I simply believe .... no, I KNOW, that a skidding turn onto finals is far far more likely to result in a spin than a well banked co-ordinated turn. Obviously it's far better to judge it all correctly to make sure you roll out nicely on the centre line from a gentle well judged turn, or go around if the picture looks wrong. But in the real world we tend to try and correct our mistakes even if it's not always the wisest thing to do. But if you are to try and correct an over cooked final turn ... use a well banked turn ... not an over ruddered one :uhoh: ! SS |
When scratching for lift in very tight turns and nibbling the stall buffet, you do learn a lot about the effect of bank and g on stalling. gliders are much more benign than most light aircraft a skidding turn onto finals is far far more likely to result in a spin than a well banked co-ordinated turn. |
Turning downwind to base I take off power while banking to 45 degrees and pull back on the stick to bleed off airspeed to 1.3 - 1.4 VS while staying level.
Then add flap once below the speed to put them out -- newer pilots may want to be wings level before adding to the workload. Trim on base once flaps down if not before. Turning base to final -- 45 degrees is good. If you're undershooting the turn you can take off some bank, but lets not be adding bank past 45. Turning final, you do not want to be bleeding off airspeed as there's not much to give away; so, it's a descending turn with much less back pressure than turning base. 45 degrees gets the turn done efficiently and gives any X-wind towards the runway less time to blow you past final -- a wider downwind may help in these conditions -- no point making it harder for yourself when it's like that. Shallow turns lead to the temptation to help it around with rudder and get yourself in a spin. |
>What is the best way to ensure that you DON'T inadvertently spin the aircraft on turn from base to finals?
Practice simulated base-final turns at altitude until you learn the feel and what the attitude of the plane looks like at various bank angles / speeds etc. Go with an instructor at first if you're unsure. Flying by "numbers" is all well and good, but you should be able to fly *without* the aid of the AS indicator (VFR of course), just by using the attitude and feel of the plane. What plane do you fly? Some, like a 172 are very reluctant, almost impossible to spin, even when you *want* them to :) Mike |
Join long final................
:p |
'right-on piloty' and 'grass roots'
As well it might be but for good reason. Low houred PPL's are quite capable of understanding the issue here and the importance of angle of attack must be continously emphasized! Such as when increasing the angle of bank also lower the nose. Staring only at the ASI is not the answer to preventing a stall.
The aircraft cannot be spinning when no Yaw is present therefore as some have already stated FLY in BALANCE, ball in the middle! |
As I suspect you know, my comments were not aimed at the advice "fly with the ball in the middle". I was questioning the value of going down the route of wing loading and similar...
2D |
Gulp.
1/(cos45) = 1.41
So, umm, if you fly base at 1.3Vs and then turn finals at 45 AoB... You're cutting it a bit fine - flaps down or not. |
a skidding turn onto finals is far far more likely to result in a spin than a well banked co-ordinated turn. Of course no-one should argue that a properly balanced turn is the safest. |
Miserlou wrote:
STIK, Quite unusual for most aircraft not to spin one way or the other without dancing on the rudders. If you've time to dance on the rudder you've got time to release the back pressure on the stick which is the actual cause of the circumstances you find yourself in. Whilst I don't for one second disagree with you, I refer you to my earlier and often reiterated comment; if the aeroplane is flown in a balanced turn it will not spin! I spin my aeroplane virtually every week, errect multiple rotations, errect accelerated, errect flattened, errect flattened with power, inverted, inverted flattened. Some crazy rides! Whilst I think that it is an unnecessary burden to stipulate that the PPL fraternity must have spin training, I do believe that it is of serious value. Several hundred hours ago, I thought I could fly - until I went flying with a chap who made the aeroplane dance and cavort through the sky, we went up and down, round and around and although the aeroplane stall speed was placarded at 63mph, the needle was often sub 40 and yet the aerolane was flying happily. When we landed I asked a few pertinent questions and then reality dawned - I had a few hundred hours on singles and twins but I couldn't actually fly. All I could do was operate the airframe to a prescribed set of numbers and "drive" it from A to B. I've spent the last ten years trying to "learn how to fly". Any info I post on here is just me trying to help others understand the fundamentals. Stik |
I know exactly where you're coming from. I learned to fly gliders first until I could get a power licence so I could fly aeros. Twas before gliders became properly aerobatic.
The problem is that if one is, how should one put it, negligent enough to let the speed fall to such an extent that a stall is iminent, how can one be expected to keep the ball in the middle? Typically, while holding the aircraft in a full stall, one or the other wing wil drop and be caught on the rudder; one cannot consider this as a stable flight condition. Also, if you are using the standard Pitts approach technique, I'd like to ask how this is relevant. You may make a perfectly balanced final turn, but then push in the crossed controls to keep the runway in sight. Of course it's the stick position that's going to kill you. Brendan showed me some flat turns a few years ago. Picture this. Halfway down the downwind and he simulates an engine failure. Rolls into a steep dive towards the runway, becoming level and parallel to the runway at about 5-10 feet. Then bootful one way, bootful t'other way and flare onto the runway. No messy (and dangerous) low level turns (as long as you've got the speed). Another lesson learnt! |
Long before getting to the base to final turn, make sure the trim is set to the right setting so that the elevator is at neutral load before going in to the turns. Is it flying hands off downwind? If it is, OK, if not, sort it. If the trim is wrong, then that's one more thing that can cause problems, as the loading can end up feeling all wrong. If it's right, then if you let go as such, it's going to come back to something close to where it should be, which may be the difference between comfort and strife.
don't mess with flaps in the turn, get them sorted out wings level, and trim again. That way, you've reduced your work load. Flying close to the ground is inherently more dangerous than flying at comfortable heights, so the concentration levels have to be higher. If you've passengers on board, shortly before entering the circiuit, politely suggest something like "it's about to get busy now, please don't talk to me unless I say something to you, I need to make sure I don't miss anything from ATC. Thanks." You might need to vary that a little if everyone is on headsets, but I'm sure you get the picture. Then, don't talk to the passengers unless it's something to do with their safety or similar, and concentrate on making sure that it all happens the way it's supposed to. |
I may have got this wrong, but I thought there was more risk from over-ruddering (slipping) then using aileron (cross controlling) as a (flawed)method in correcting the initial error. A skidding turn in comparatively safer. Co-ordinated turn: good. Excess top rudder (slip): OK if you are doing it (side slip) intentionally to lose height, and watching airspeed and attitude. Excess bottom rudder (skid): bad. |
Dusty_B, Yes the load factor can go up to 1.41 which raises the stall speed approx. 19%.
And GA typically flys the approach around 85% of gross which lowers the stall speed 8% yielding a 9% increase in typical GA SE a/c. stall speed varies with: root(LF) x root(weight/gross) You can load up the back seats with fellow pilots and go up to 5000 AGL and see just how much biceps is required to stall out of a coordinated descending turn to final. Yes, it is much easier to stall out at rearward CGs, but will still take considerable muscle in your average standard airworthiness certified spamcan and is much harder with just one or two up front. |
I may have got this wrong, but I thought there was more risk from over-ruddering (slipping) then using aileron (cross controlling) as a (flawed)method in correcting the initial error. A skidding turn in comparatively safer. SS Edited in later ... FREDAcheck Sorry, I see you pretty well answered my point to Justinmg in your following post. I really must read subsequent posts before jumping in both feet first :\\ SS |
After reading the 'instructors who refuse to spin' thread on the instructors forums: What is the best way to ensure that you DON'T inadvertently spin the aircraft on turn from base to finals? Also, should you be unfortunate enough to spin at this point, is there ANYTHING at all you can do, being so close to the ground? 2. a. Fly at correct airspeed, the point Stik makes about the stick position is very true; where I come from the stall is called the 'over-pull' 2.b. Coordinated turns. Forget about top/bottom rudder; skidding slipping just keep that ball in the middle 3. Find yourself a good instructor that can show you the edge of the envelope. a. Those that have hang-ups about stall/spins are unlikely to be able to give you the appropriate experience. b. If you have never spun you may not appreciate the potential hazards of them at low altitudes. Have fun. |
Thanks for all the replies -- brilliant. Didn't think there would be so many. Have read them all with interest, and hopefully have taken all comments on board.
Whilst on the subject of slipping turns: I fly a cessna 172, and if high on finals for any reason, often use crossed controls to lose excess height. (Please note that I don't do this in the turn onto finals, but when the wings are level). I find this effective, but again, is there any danger of spinning? Also, some say you shouldn't slip a cessna -- others say you shouldn't slip a cessna with any degree of flap on, (which is what I've always been led to believe). Sorry to sort of hijack my own thread, but do all you guys/girls of much more experience than myself out there have any input on this as well? Thanks for a very interesting thread so far G_STRING |
It's always interesting reading these discussions and getting various views. I think a lot of the information given to students is based around the most appropriate way of learning, without overloading them.
Its all very well reading of detailed AoA and banking figures when you have hundreds of hours experience, but when learning, something fairly simple is, in my opinion, easier to take in. When I was learning, the main things I was told at the beginning were: 1) Put flaps down when level - this makes it easier to judge any pitch changes, and if you do have a problem with them going down asynchronously it's easier to recognise and sort out. 2) Watch your airspeed and attitude. 3) Bank at 20-25 degrees, maximum of 30 when turning onto base and final. 4) Keep balanced. 5) If you go through the centreline, keep going and turn back - don't overbank - if it's looking too bad go-around. If you keep the airspeed at the right amount, and don't bank more than a certain amount while properly balanced, then you won't have a problem with stalling. Once you're lucky enough to have lots of experience then you can start to push the envelope a bit more. Although I've read many things about the fact that the stalling airspeed changes in various conditions, and I understand what that's about, knowing that for 30 degrees of bank an airspeed of X will keep you away from the stall is useful when setting out. As an aside, is there a condition of flight that will allow the plane to stall without the stall warner going off? For example, a skidding turn so that the airflow over the stall warner is disrupted? |
As an aside, is there a condition of flight that will allow the plane to stall without the stall warner going off? For example, a skidding turn so that the airflow over the stall warner is disrupted? I would hazard a guess and say that in a skidding turn where the stall warner equipped wing (there's usually only one) is on the outside of the turn, it would be quite possible that the inside wing could stall before the warner (on the outside wing) reaches it's trigger AoA. Whilst on the subject of slipping turns: I fly a cessna 172, and if high on finals for any reason, often use crossed controls to lose excess height. (Please note that I don't do this in the turn onto finals, but when the wings are level). I find this effective, but again, is there any danger of spinning? SS |
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