Strong head wind on approach
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This tendency to rely on throttle to get us out of windshear difficulties intrigues me.
Would be interesting to hear how our Gliding Brothers handle windshear, to compare with how we handle glide approaches.
Is our normal rule of thumb (1.3 x Vso + half gust strength) still appropriate for our glide approaches I wonder?
sd
Would be interesting to hear how our Gliding Brothers handle windshear, to compare with how we handle glide approaches.
Is our normal rule of thumb (1.3 x Vso + half gust strength) still appropriate for our glide approaches I wonder?
sd
Why do it if it's not fun?
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S.d.
I'll wait for a glider pilot to correct me, but my understanding is that they use spoilers. Their equivalent of our adding a touch of power would be to remove a bit of spoiler.
The 1.3Vso (which is only a rule of thumb, in any case, because the POH will contain the correct figure for the aircraft) is definitely valid for a glide approach.
FFF
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I'll wait for a glider pilot to correct me, but my understanding is that they use spoilers. Their equivalent of our adding a touch of power would be to remove a bit of spoiler.
The 1.3Vso (which is only a rule of thumb, in any case, because the POH will contain the correct figure for the aircraft) is definitely valid for a glide approach.
FFF
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Sunday Driver,
Stick for airspeed, throttle for rate of decent.
If one encounters windshear on approach you'd push the stick forward to maintain airspeed which would leave you below the glideslope. You then need to add power to adjust the R.O.D - simple
I fly from a field that, in an easterly, has such strong windshear and curl over effects that I have on occasion landed on full throttle!
As for our non powered cousins - again simple.. the stick controls the airspeed and the airbrakes are, in effect the throttle - the lever even works in the same sense, I.E. forward for closed and back for fully open (the airbrakes) this really does give all the same responses as a throttle on a powered plane.
Cheers
Kingy
Stick for airspeed, throttle for rate of decent.
If one encounters windshear on approach you'd push the stick forward to maintain airspeed which would leave you below the glideslope. You then need to add power to adjust the R.O.D - simple
I fly from a field that, in an easterly, has such strong windshear and curl over effects that I have on occasion landed on full throttle!
As for our non powered cousins - again simple.. the stick controls the airspeed and the airbrakes are, in effect the throttle - the lever even works in the same sense, I.E. forward for closed and back for fully open (the airbrakes) this really does give all the same responses as a throttle on a powered plane.
Cheers
Kingy
Get someone to teach you the 'point and power' technique and you'll find that it works no matter what the headwind. Fly the corrrect POH approach speed, keep the touchdown point fixed in the windscreen, but make very frequent scans of IAS and react positively with the throttle!
The 'old' technique ('stick for speed, power for RoD') makes an approach far more difficult to refine if there is a significant change in wind gradient (not neccesarily wind shear) in the latter stages of the approach.
The 'old' technique ('stick for speed, power for RoD') makes an approach far more difficult to refine if there is a significant change in wind gradient (not neccesarily wind shear) in the latter stages of the approach.
Why do it if it's not fun?
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Well, since we're going that way..... Who cares? They both do the same thing, but in a different order!
If your speed reduces, then with "stick for airspeed" you would lower the nose to regain speed, and then have to increase power to maintain the aiming point.
With "point and power" in the same situation, you will add power to maintain airspeed, and then have to lower the nose in order to keep the aiming point in the same place.
So it makes absolutely no difference which way you do it. In fact, I can't honestly say which I use - I think I do some combination of using both the stick and the throttle together. Whether you consider this to be "stick for airspeed" and anticipating the throttle changes, or "power for airspeed" and anticipating the stick movement, is entirely up to you!
FFF
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If your speed reduces, then with "stick for airspeed" you would lower the nose to regain speed, and then have to increase power to maintain the aiming point.
With "point and power" in the same situation, you will add power to maintain airspeed, and then have to lower the nose in order to keep the aiming point in the same place.
So it makes absolutely no difference which way you do it. In fact, I can't honestly say which I use - I think I do some combination of using both the stick and the throttle together. Whether you consider this to be "stick for airspeed" and anticipating the throttle changes, or "power for airspeed" and anticipating the stick movement, is entirely up to you!
FFF
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Aim first, or Squirt first - I suspect it's related to how close you are to Vso, and whether you're on an ILS.
But I 'm still hoping for some wise words on how to arrive after the threshold when the engine stops and the wind is blowing.
I have dim gliding memories, where you turn base with plenty of height, poke the nose down to achieve some stupendous airspeed (60k in a T29 seems to stick in my mind) thus ensuring adequate airspeed for an arrival after the threshold, at which point excess airspeed and height are sliced off with the spoilers. (Maybe modern gliders are different?)
The guidelines one receives for engine-out arrivals seem a bit vague in comparison - normal approach speeds, point at 1/3 the way along the runway / field. Not a lot about allowing for windshear.
Any thoughts?
sd
But I 'm still hoping for some wise words on how to arrive after the threshold when the engine stops and the wind is blowing.
I have dim gliding memories, where you turn base with plenty of height, poke the nose down to achieve some stupendous airspeed (60k in a T29 seems to stick in my mind) thus ensuring adequate airspeed for an arrival after the threshold, at which point excess airspeed and height are sliced off with the spoilers. (Maybe modern gliders are different?)
The guidelines one receives for engine-out arrivals seem a bit vague in comparison - normal approach speeds, point at 1/3 the way along the runway / field. Not a lot about allowing for windshear.
Any thoughts?
sd
Why do it if it's not fun?
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S.d.
For a forced landing from any kind of altitude, you aim 1/3 of the way into the field, as you say. If you encounter a bit of windshear, this gives you 1/3 of the field to play with. Only when you are certain of making the field do you add flaps, one stage at a time, which gradually moves your aiming point to the start of field. If there was anything near the field which would suggest the presence of windshear (trees on short final, for example) , I would leave the flaps as late as possible, and leave the aiming point a fair way into the field.... but to tell the truth, you really shouldn't be looking at a field with trees on short final as a forced landing site unless you're very short of options.
When you're in the circuit, it's a little bit harder. All the way around the circuit until shortly before turning final, you should (in the ideal world) be able to make the field - from late downwind onwards this will involve turning directly towards the numbers. In the real world, certainly in the UK, noise abatement often means this isn't possible, in which case you should be looking for potential forced landing fields just as you would during the cruise.
But once you're approaching or on final, if you have any power, it's a different matter. How to handle it would, I guess depend on the field. A couple of the runways at my home airfield have houses on short final - in these cases, I will always land a considerable way onto the runway, so there is no danger of landing on the houses if the worst happens. This, of course, is a situation where the runway is long enough to do this safely. If the runway isn't long enough, then you don't have so many options, and planning for a glide approach is probably the best thing you can do. I would be very cautious about using a short field with obstacles before the start of the runway, though.
However, realisistically I doubt that this issue arises very often. Engine failures are going to happen when the engine is under stress. Flying down final with the engine at 1500rpm is certainly not going to stress it too much. I would guess (does anyone have any figures to confirm or deny this?) that engine failure on take-off is actually a problem which warrants far more attention, since the engine is going to be highly stressed, and also not as warm as if it had been running at cruise power for some time.
FFF
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For a forced landing from any kind of altitude, you aim 1/3 of the way into the field, as you say. If you encounter a bit of windshear, this gives you 1/3 of the field to play with. Only when you are certain of making the field do you add flaps, one stage at a time, which gradually moves your aiming point to the start of field. If there was anything near the field which would suggest the presence of windshear (trees on short final, for example) , I would leave the flaps as late as possible, and leave the aiming point a fair way into the field.... but to tell the truth, you really shouldn't be looking at a field with trees on short final as a forced landing site unless you're very short of options.
When you're in the circuit, it's a little bit harder. All the way around the circuit until shortly before turning final, you should (in the ideal world) be able to make the field - from late downwind onwards this will involve turning directly towards the numbers. In the real world, certainly in the UK, noise abatement often means this isn't possible, in which case you should be looking for potential forced landing fields just as you would during the cruise.
But once you're approaching or on final, if you have any power, it's a different matter. How to handle it would, I guess depend on the field. A couple of the runways at my home airfield have houses on short final - in these cases, I will always land a considerable way onto the runway, so there is no danger of landing on the houses if the worst happens. This, of course, is a situation where the runway is long enough to do this safely. If the runway isn't long enough, then you don't have so many options, and planning for a glide approach is probably the best thing you can do. I would be very cautious about using a short field with obstacles before the start of the runway, though.
However, realisistically I doubt that this issue arises very often. Engine failures are going to happen when the engine is under stress. Flying down final with the engine at 1500rpm is certainly not going to stress it too much. I would guess (does anyone have any figures to confirm or deny this?) that engine failure on take-off is actually a problem which warrants far more attention, since the engine is going to be highly stressed, and also not as warm as if it had been running at cruise power for some time.
FFF
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Beagle,
Nah mate, that doesn't work for me - I fly taildraggers into often extremely short strips, I'm right on the back of the drag curve anyway and lowering the nose is quicker..!
I may dump some slip instead of increasing power though, but that decision would be involuntary on the day - you just tend to do things without thinking..
Kingy (call me a traditionalist)
Nah mate, that doesn't work for me - I fly taildraggers into often extremely short strips, I'm right on the back of the drag curve anyway and lowering the nose is quicker..!
I may dump some slip instead of increasing power though, but that decision would be involuntary on the day - you just tend to do things without thinking..
Kingy (call me a traditionalist)
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Approach/Landing speed for 172SP...
Dude -
According to the POH for the 172SP (model year 2003) the normal landing speed is "60 -70 kts with flaps down" (obviously this decays in the flare), I elected to use the upper end of the range plus an extra 5 knots given the high winds.
I had covered 410nms that day, it had been almost constant mountain wave after mountain wave and moderate turbulence (a staggering 171kt GS at one point though
). It has been my experience that when the winds are as strong as they were that day, it's a good idea to come in 5 - 10kts faster as the aircraft is a good deal more responsive close to the ground. When the gusts start buffeting the plane around just prior to touch down you have a lot more room to manoeuvre.
Perhaps someone with more experience would do it differently but have always found my landings turn out just fine this way. The following day after this journey I had to accept 21kts at 90 degrees to the runway at another airport. It was the last day of my holiday and the best landing I had done the whole trip - I put it down to using 75 (After I was on the ground however, it was certainly entertaining trying to negotiate 5 taxiways and 3 holding points in a 21kt wind 
!
Haul.
According to the POH for the 172SP (model year 2003) the normal landing speed is "60 -70 kts with flaps down" (obviously this decays in the flare), I elected to use the upper end of the range plus an extra 5 knots given the high winds.
I had covered 410nms that day, it had been almost constant mountain wave after mountain wave and moderate turbulence (a staggering 171kt GS at one point though
). It has been my experience that when the winds are as strong as they were that day, it's a good idea to come in 5 - 10kts faster as the aircraft is a good deal more responsive close to the ground. When the gusts start buffeting the plane around just prior to touch down you have a lot more room to manoeuvre.Perhaps someone with more experience would do it differently but have always found my landings turn out just fine this way. The following day after this journey I had to accept 21kts at 90 degrees to the runway at another airport. It was the last day of my holiday and the best landing I had done the whole trip - I put it down to using 75
(After I was on the ground however, it was certainly entertaining trying to negotiate 5 taxiways and 3 holding points in a 21kt wind !Haul.
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Engine failures are going to happen when the engine is under stress. Flying down final with the engine at 1500rpm is certainly not going to stress it too much
Do a Hover - it avoids G
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Health Warning
If there are any low hour pilots reading some of the dogmatic assertions that have popped up in this thread please use your head before doing as they suggest.
Ask yourself what will happen if you are close enough to the ground to be really concerned about hitting it (less than 100 ft say) and feel the urge to get speed back by lowering the nose.
Having a never ending argument about what to do on an approach at a safe height is one thing. Doing what some assert is the ‘right’ thing in the wrong place will kill you.
If there are any low hour pilots reading some of the dogmatic assertions that have popped up in this thread please use your head before doing as they suggest.
Ask yourself what will happen if you are close enough to the ground to be really concerned about hitting it (less than 100 ft say) and feel the urge to get speed back by lowering the nose.
Having a never ending argument about what to do on an approach at a safe height is one thing. Doing what some assert is the ‘right’ thing in the wrong place will kill you.
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Sorry Haul, I stand corrected!
It just sounded a little fast for an old C172.
Actually, it wouldn't matter so much if you touched down with a high IAS in a stong headwind because the stress on the aircraft would be less than a full stall landing on a calm day!
Adding 5 kts sounds very sensible for a 40 kt wind, I probably wouldn't have even taken off!
It just sounded a little fast for an old C172.
Actually, it wouldn't matter so much if you touched down with a high IAS in a stong headwind because the stress on the aircraft would be less than a full stall landing on a calm day!
Adding 5 kts sounds very sensible for a 40 kt wind, I probably wouldn't have even taken off!
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John Farley,
I have a vast amount of respect for you Sir and being a humble PPL I'm hardly qualified to argue but;
Would you not agree that as PIC your primary function is to remain in control of the aircraft at all times. Therefore, if the ASI dropped off the clock even below 100ft, the safest and quickest way to get flying again is to reduce the angle of attack of the wing as a stalled aircraft is not in control....
May I also say that wind gradient/shear is unusual in that it robs potential energy from the aircraft, and the only way to get back that 'lost' energy would be to add power or make the aircraft more efficient so the reduced energy would do. (I'm thinking glider airbrakes, reducing side slip etc.)
I accept that this is a hugely complex area with many factors that none of us have touched on yet and with over 900 hits this thread will have been read by some very inexperienced people. I would hate to think someone that hurt themselves following my advice so don't listen to me.
The message is clear however - wind shear will rob energy from you, so you have to deal with it one way or another, and yes that can be by doing nothing if you have excess airspeed 'in the bank' that you are happy to throw away. It's really about understanding the forces involved and using skill and judgment to fly the aircraft - come to think of it, that sums up the whole art of flying...
Cordially
Paul King
I have a vast amount of respect for you Sir and being a humble PPL I'm hardly qualified to argue but;
Would you not agree that as PIC your primary function is to remain in control of the aircraft at all times. Therefore, if the ASI dropped off the clock even below 100ft, the safest and quickest way to get flying again is to reduce the angle of attack of the wing as a stalled aircraft is not in control....
May I also say that wind gradient/shear is unusual in that it robs potential energy from the aircraft, and the only way to get back that 'lost' energy would be to add power or make the aircraft more efficient so the reduced energy would do. (I'm thinking glider airbrakes, reducing side slip etc.)
I accept that this is a hugely complex area with many factors that none of us have touched on yet and with over 900 hits this thread will have been read by some very inexperienced people. I would hate to think someone that hurt themselves following my advice so don't listen to me.
The message is clear however - wind shear will rob energy from you, so you have to deal with it one way or another, and yes that can be by doing nothing if you have excess airspeed 'in the bank' that you are happy to throw away. It's really about understanding the forces involved and using skill and judgment to fly the aircraft - come to think of it, that sums up the whole art of flying...
Cordially
Paul King
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Hmmn, 'Principles Of Flight' was never my strong point, but where has all the talk of stalling on approach come from?
I am asking this genuinely.
Whenever I am required to make an aircraft stall I always end up having to really work hard at it. This makes me think that when coming in on an approach - unless you make a concerted effort to climb without adding any power - what is going to induce a stall?
If windshear is encountered - flying from a strong head wind down into a strong tailwind for example - at worst, will the aircraft not pitch down (rather than stall) and start to descend rapidly (worst case)?
If I was fairly low at this point my clenching butt muscles would tend to dissuade me from pitching down but I would likely put full power in and try and hold a level attitude briefly until there was sufficient airspeed and oompf to get a climb going (not much above stall) or to maintain a ROD - whatever is required.
Now, I may just have proved how little I do know, but I'm keen for someone in the know to clear it up. I had always thought that you just do what works at the time rather than having a set role for 'stick' and 'power'
Haul.
I am asking this genuinely.
Whenever I am required to make an aircraft stall I always end up having to really work hard at it. This makes me think that when coming in on an approach - unless you make a concerted effort to climb without adding any power - what is going to induce a stall?
If windshear is encountered - flying from a strong head wind down into a strong tailwind for example - at worst, will the aircraft not pitch down (rather than stall) and start to descend rapidly (worst case)?
If I was fairly low at this point my clenching butt muscles would tend to dissuade me from pitching down but I would likely put full power in and try and hold a level attitude briefly until there was sufficient airspeed and oompf to get a climb going (not much above stall) or to maintain a ROD - whatever is required.
Now, I may just have proved how little I do know, but I'm keen for someone in the know to clear it up. I had always thought that you just do what works at the time rather than having a set role for 'stick' and 'power'
Haul.
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Haul,
Right, this positively my last post on this thread...
Think about it - the wing only 'knows' about the airflow over it at any one time:
let's say the aircraft approaches at 60k, stalls at 40k and is flying into a 30k headwind. Ground speed would be 30k - OK?
What if the headwind suddenly reduces to 5k - the airspeed would be 30+5=35k i.e. 5k below the stall speed.
What actually happens this is usually accompanied by an increase in ROD which will reduce G so the wing does not actually stall for a moment (indeed if the pilot did nothing the aircraft would recover all by itself, all be it with a substantial loss of height). The trouble is an un-weary pilot could easily be fooled into thinking an involuntary pitch down had occurred increasing the ROD - this could make him pull just when he should push leaving him deeply stalled a few moments later when the forces begin to balance themselves out again. Add a bit of yaw into the pot and it's a classic stall/spin scenerio...
OK, this is an extreme example but I'm trying to prove a point here..
Kingy
Right, this positively my last post on this thread...
Think about it - the wing only 'knows' about the airflow over it at any one time:
let's say the aircraft approaches at 60k, stalls at 40k and is flying into a 30k headwind. Ground speed would be 30k - OK?
What if the headwind suddenly reduces to 5k - the airspeed would be 30+5=35k i.e. 5k below the stall speed.
What actually happens this is usually accompanied by an increase in ROD which will reduce G so the wing does not actually stall for a moment (indeed if the pilot did nothing the aircraft would recover all by itself, all be it with a substantial loss of height). The trouble is an un-weary pilot could easily be fooled into thinking an involuntary pitch down had occurred increasing the ROD - this could make him pull just when he should push leaving him deeply stalled a few moments later when the forces begin to balance themselves out again. Add a bit of yaw into the pot and it's a classic stall/spin scenerio...
OK, this is an extreme example but I'm trying to prove a point here..
Kingy
Last edited by Kingy; 22nd Jan 2004 at 04:06.
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Kingy,
The scenario you describe I understand.
What I was (perhaps unsuccessfully) trying to say is that I find it hard to believe that any windshear would be so violent and complete in it's change of velocity that the aircraft would not have time to pitch down with the loss of momentum, and thus preclude a stall.
Which I think we agree on...
But I'm not sure that the following action...
... would be the natural response from an average pilot I would have thought that not 'pulling' without some thrust to go with it, and at least having a glance at the ASI, would be a pretty ingrained motor skill for a pilot?
It's been a long day, maybe I'm missing the point
Cheers,
Haul.
editted for dodgy speeling
The scenario you describe I understand.
What I was (perhaps unsuccessfully) trying to say is that I find it hard to believe that any windshear would be so violent and complete in it's change of velocity that the aircraft would not have time to pitch down with the loss of momentum, and thus preclude a stall.
Which I think we agree on...
... What actually happens this is usually accompanied by an increase in ROD which will reduce G so the wing does not actually stall for a moment.
... un weary pilot could easily be fooled into thinking an involuntary pitch down had occurred increasing the ROD - this could make him pull just when he should push leaving him deeply stalled a few moments later...
I would have thought that not 'pulling' without some thrust to go with it, and at least having a glance at the ASI, would be a pretty ingrained motor skill for a pilot?It's been a long day, maybe I'm missing the point
Cheers,
Haul.
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OK THIS is my last post..!
Quickly I'd like to say:
1. The slower the airspeed of the aircraft the more it affected by relatively minor wind gradients. E.G. I have an aircraft that approaches at 50-55 and stalls at 40MPH - a common 10kt shear is a large percentage of that speed. So yes, a situation like this is not too uncommon.
2. Think about how much emphasis is placed during training on avoiding 'coffin corner' during the turn from base to final - doesn't that show that when the picture looks wrong a pilot is liable make basic, gross mistakes that seem inconceivable from the comfort of our armchairs - my argument is, when faced with a sudden pitch down/increase in ROD near the ground, a basic instinct would be to pull.. (yes, I've done it)
Kingy
Quickly I'd like to say:
1. The slower the airspeed of the aircraft the more it affected by relatively minor wind gradients. E.G. I have an aircraft that approaches at 50-55 and stalls at 40MPH - a common 10kt shear is a large percentage of that speed. So yes, a situation like this is not too uncommon.
2. Think about how much emphasis is placed during training on avoiding 'coffin corner' during the turn from base to final - doesn't that show that when the picture looks wrong a pilot is liable make basic, gross mistakes that seem inconceivable from the comfort of our armchairs - my argument is, when faced with a sudden pitch down/increase in ROD near the ground, a basic instinct would be to pull.. (yes, I've done it)
Kingy