Stall landing/Slow landing
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A few thoughts ..
(a) final approach and approaching the flare should be conducted at a speed providing adequate margin above the stall. Generally this is accepted to be 1.3Vs in smooth conditions and a little faster if conditions are bumpy.
It is reasonable to view 1.3 as a short field factor.
Less and, generally, you are outside the certification envelope for a light aircraft. Too far less and you expose your aeroplane and occupants to an unintended stall with unpleasant and potentially expensive and/or tragic results.
If you have plenty of runway and it floats your boat nicely then, by all means, hold a low flare until the aircraft falls the last few inches to the runway. However, as a general rule, don't confuse yourself by thinking that gives you the shortest landing distance - ground roll may be short but - the overall distance will be up. Better deceleration is achieved using brakes on the ground rather than waffling through the air .. assuming that your steed has such devices.
Coming over the fence at breakneck speeds achieves little other than making for a difficult manipulative exercise and a much extended actual landing distance. The reasonable aim is to achieve/approximate the expected landing distance for the aeroplane.
Maintaining a higher speed during the circuit and initial final may provide advantages for circuit flow. However, one should consider reducing speed to something appropriate for final approach when on mid final.
(b) if you are intent on doing some arithmetic, remember to do the sums in CAS rather than IAS as the PEC back near/at stall can provide for a moderate difference between the two.
Well into the stall and all bets are off .. we all have had fun in the small single engine Cessnas stalling with the ASI indicating something approaching zero .. pretty meaningless but still fun, I guess .. however, whatever the ASI may be indicating .. it certainly doesn't mean that you are at zero speed.
If figuring for weight, run the speed sums at the square root of the weight ratio .. for a small difference a linear approximation will be fine but the error picks up as the weight difference increases.
(c) With some high wing machines one may need to be careful with flap selection in strongish crosswinds lest the fuselage airflow create problems at the tail.
(a) final approach and approaching the flare should be conducted at a speed providing adequate margin above the stall. Generally this is accepted to be 1.3Vs in smooth conditions and a little faster if conditions are bumpy.
It is reasonable to view 1.3 as a short field factor.
Less and, generally, you are outside the certification envelope for a light aircraft. Too far less and you expose your aeroplane and occupants to an unintended stall with unpleasant and potentially expensive and/or tragic results.
If you have plenty of runway and it floats your boat nicely then, by all means, hold a low flare until the aircraft falls the last few inches to the runway. However, as a general rule, don't confuse yourself by thinking that gives you the shortest landing distance - ground roll may be short but - the overall distance will be up. Better deceleration is achieved using brakes on the ground rather than waffling through the air .. assuming that your steed has such devices.
Coming over the fence at breakneck speeds achieves little other than making for a difficult manipulative exercise and a much extended actual landing distance. The reasonable aim is to achieve/approximate the expected landing distance for the aeroplane.
Maintaining a higher speed during the circuit and initial final may provide advantages for circuit flow. However, one should consider reducing speed to something appropriate for final approach when on mid final.
(b) if you are intent on doing some arithmetic, remember to do the sums in CAS rather than IAS as the PEC back near/at stall can provide for a moderate difference between the two.
Well into the stall and all bets are off .. we all have had fun in the small single engine Cessnas stalling with the ASI indicating something approaching zero .. pretty meaningless but still fun, I guess .. however, whatever the ASI may be indicating .. it certainly doesn't mean that you are at zero speed.
If figuring for weight, run the speed sums at the square root of the weight ratio .. for a small difference a linear approximation will be fine but the error picks up as the weight difference increases.
(c) With some high wing machines one may need to be careful with flap selection in strongish crosswinds lest the fuselage airflow create problems at the tail.
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Pace
Just wanted to clarify how I do my calcs in case someone misreads and runs into trouble trying it. For approach speeds that are not stated in the POH, whether in the clean or landing config I always use the 1.3 multiple but my starting number(s) for each config are taken from the bottom of the airspeed indicator green or white ranges then deducting 1MPH for each 80lbs I am under gross then apply the 1.3 to a standard and 1.25 for a short field landing.
The only time I stray north from those numbers is when there is a xwind pushing up against my personal limits (which are under the POH published demonstrated number) and decide that instead of a no flaps clean approach I will go to a negative 7 degrees flap setting which is unique to my aircraft (a taildragger) and recommended by the manufacturer in xwinds, however I do not know what the exact stall is in that config as its not in the POH or AI markings so I stay a bit faster than what the clean stall calc would be which I think is good practice in the xwind anyway.
[SIZE="3"]Disclosure: the writer as stated before is a rank amateur and none of the above should be paid heed to and taken as gospel and is purely for conversational purposes only, the above practice is my personal methods based on trying different things with the plane and always remember opinions are like assholes, everybody has one. Bottom line, listen only to your instructor [/SIZE]
Taking clean speeds they could be fixed at 1.3 times the stall speed in clean configuration but you could make that 1.5 times the stall speed or more!
The only time I stray north from those numbers is when there is a xwind pushing up against my personal limits (which are under the POH published demonstrated number) and decide that instead of a no flaps clean approach I will go to a negative 7 degrees flap setting which is unique to my aircraft (a taildragger) and recommended by the manufacturer in xwinds, however I do not know what the exact stall is in that config as its not in the POH or AI markings so I stay a bit faster than what the clean stall calc would be which I think is good practice in the xwind anyway.
[SIZE="3"]Disclosure: the writer as stated before is a rank amateur and none of the above should be paid heed to and taken as gospel and is purely for conversational purposes only, the above practice is my personal methods based on trying different things with the plane and always remember opinions are like assholes, everybody has one. Bottom line, listen only to your instructor [/SIZE]
Last edited by piperboy84; 16th Apr 2013 at 11:59.
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Piper don't do it by airspeed.
Fill you aircraft up to the MLW.
Put a bit of string on the airframe/window.
Then go up to 1000 feet and desend in landing config at the POH speed.
Take note of angle of said bit of string.
This is then you angle of approach. Then go to your min weight you can manage again at the same alt. Then configure and pitch to the same angle. See what the speed is. The POH is the max speed and the last one is the min speed. Then make up a table for the weights between the two.
The stall is the critical angle of attack. The approach is something which is an angle of attack less than this by a safe margin. The speed is just the thing we can see in the cockpit all you are doing by changing the speed with weight is getting the angle off attack correct
Fill you aircraft up to the MLW.
Put a bit of string on the airframe/window.
Then go up to 1000 feet and desend in landing config at the POH speed.
Take note of angle of said bit of string.
This is then you angle of approach. Then go to your min weight you can manage again at the same alt. Then configure and pitch to the same angle. See what the speed is. The POH is the max speed and the last one is the min speed. Then make up a table for the weights between the two.
The stall is the critical angle of attack. The approach is something which is an angle of attack less than this by a safe margin. The speed is just the thing we can see in the cockpit all you are doing by changing the speed with weight is getting the angle off attack correct
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For decades the Americans flew the space shuttle with zero landing incidents or accidents, the space shuttle had a high wing loading and a high rate of descent on approach and the landings were hand flown with no incidents.
Chuck, I imagine that you were trying to contradict my post so why would you refer to an example that validates it?
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bb74 the bit of your post that is simply wrong was the reference to high wing loading aircraft dropping like a stone when power is removed - it just ain't so.
What I believe to be the case is that if you're flying at a speed where there is a lot of induced drag and you close the throttles, especially when the propellers are of the constant-speed variety, then you're going to go down quickly.
Just wanted to clarify how I do my calcs in case someone misreads and runs into trouble trying it. For approach speeds that are not stated in the POH, whether in the clean or landing config I always use the 1.3 multiple but my starting number(s) for each config are taken from the bottom of the airspeed indicator green or white ranges then deducting 1MPH for each 80lbs I am under gross then apply the 1.3 to a standard and 1.25 for a short field landing.
Last edited by Piper.Classique; 16th Apr 2013 at 20:36.
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In my experience of Cessna 152 and 172 the POH is correct. My instructor told me never to land with a stall, and have never done so.
Some points:
On any checkout flight every instructor will tell you something different and that what any other instructor told you is likely to kill you. This is not true - every instructor is qualified to instruct, they just have different opinions, that's all. There's more than one way to fly a Cessna, despite what you read in PPRune
Do what your instructor says but read the POH cover to cover. Most instructors don't get you to do that.
It's not necessary to suddenly kill the power when you round out. Doing it gradually leads to a better landing IMO and is kinder on the engine. Leaving a bit of power on when landing and taking the power off completely after touchdown also works nicely.
Some points:
On any checkout flight every instructor will tell you something different and that what any other instructor told you is likely to kill you. This is not true - every instructor is qualified to instruct, they just have different opinions, that's all. There's more than one way to fly a Cessna, despite what you read in PPRune
Do what your instructor says but read the POH cover to cover. Most instructors don't get you to do that.
It's not necessary to suddenly kill the power when you round out. Doing it gradually leads to a better landing IMO and is kinder on the engine. Leaving a bit of power on when landing and taking the power off completely after touchdown also works nicely.
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Flying Beyond the Stall
Hi, there is a PPL training exercise (10A Slow Flight), where your instructor may require you to 'Fly Beyond The Stall' using high power and a very high nose attitude.
This is flight beyond the peak of the Coefficient of Lift curve, on the negative portion of the curve. Where if you pull back on the column, the plane stalls further and descends, and if you push forward you get more lift and the plane climbs.
I think that any landing in this configuration would result in a tail strike, as the pitch attitude is over 20 degrees.
This is flight beyond the peak of the Coefficient of Lift curve, on the negative portion of the curve. Where if you pull back on the column, the plane stalls further and descends, and if you push forward you get more lift and the plane climbs.
I think that any landing in this configuration would result in a tail strike, as the pitch attitude is over 20 degrees.
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we sure talk different...ever hear of flying behind the power curve?
I know in the USA we have to teach many types of landing...including short field, short field over an obstacle, soft field and combinations of each. full stall landings are taught too and ''normal'' landings.
landing ''with power on past touchdown'' can be useful if you are landing on a soft field (grass, mud etc)...but please think like a carpenter with different grades of sand paper.
each landing (each grade of sandpaper) has its place and it takes an artist to know which one to use.
I know in the USA we have to teach many types of landing...including short field, short field over an obstacle, soft field and combinations of each. full stall landings are taught too and ''normal'' landings.
landing ''with power on past touchdown'' can be useful if you are landing on a soft field (grass, mud etc)...but please think like a carpenter with different grades of sand paper.
each landing (each grade of sandpaper) has its place and it takes an artist to know which one to use.
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in some trainers it is quite easy, with engine off, near the tie down spot, to have the student sit in the plane and the instructor push down (at the right spot) to push the tail down and the nose up to allow the student to ''see'' the landing attitude without the noise or time criticality.
Thank you for a couple of useful additions to the discussion, Sevenstrokeroll.
I would also point out that in a tailwheel aircraft the landng attitude is easy to see on the ground. Just put it back down like that.........
Another thing. If the aircraft is properly trimmed, by which I mean no load required to hold the attitude required (Did I need to say that? Sadly, yes)
You can feel the lift decreasing in the hold-off, the aircraft wanting to sink to the ground.
Here in France we teach different sorts of landing, too. Soft field comes naturally in the winter, as our 800 metre long 90 metre wide grass gets soggy. We have to use our imagination for the obstacle clearance but the ditch and road at the end is provided by the council. We go elsewhere for tarmac, runways of normal proportions, and slopes.
We have runway lights, no centreline lighting, no papis. If anyone would like to experience landing in a black hole they are welcome to visit.
I would also point out that in a tailwheel aircraft the landng attitude is easy to see on the ground. Just put it back down like that.........
Another thing. If the aircraft is properly trimmed, by which I mean no load required to hold the attitude required (Did I need to say that? Sadly, yes)
You can feel the lift decreasing in the hold-off, the aircraft wanting to sink to the ground.
Here in France we teach different sorts of landing, too. Soft field comes naturally in the winter, as our 800 metre long 90 metre wide grass gets soggy. We have to use our imagination for the obstacle clearance but the ditch and road at the end is provided by the council. We go elsewhere for tarmac, runways of normal proportions, and slopes.
We have runway lights, no centreline lighting, no papis. If anyone would like to experience landing in a black hole they are welcome to visit.
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piper...isn't it funny about trim? once you master trim, the flying is so much easier.
I would also say to take a brick or two and place it under the nose wheel to show the landing attitude.
just like food has become so refined as to be less nutritious, flying has become so automated as to be less organic
I would also say to take a brick or two and place it under the nose wheel to show the landing attitude.
just like food has become so refined as to be less nutritious, flying has become so automated as to be less organic
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Hi 7/R, I think the two terms are different...
Flying on the back-side of the power curve occurs below Max L/D speed (below Vy.) Whereas Beyond the Stall is at Vs or less.
This chap is most likely just beyond Vs , by using power, to 'prop-hang' the last few yards onto the grass. (and it looks as if his tail-wheel will land first.)
Flying on the back-side of the power curve occurs below Max L/D speed (below Vy.) Whereas Beyond the Stall is at Vs or less.
This chap is most likely just beyond Vs , by using power, to 'prop-hang' the last few yards onto the grass. (and it looks as if his tail-wheel will land first.)
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I am going to add a couple of points for thought? Firstly why do you want to judge a 10 foot point for the flare?
Could that be 20 feet? 10 feet ? 5 feet ? or even 2 feet ?
Landing at just above the stall has little to do with landing an aircraft other than meeting the published stopping distance as I have stated before it is quite possible to land an aircraft which stalls at 60 kts at 120kts if you have the skills.
At 1.3 times the stall gives you a buffer to change AOA and hence loose speed without stalling before contacting the runway but it is a misunderstanding to connect these speeds with actually landing which could be at any speed.
I had a friend who had a control problem in a Citation who landed at Edinburgh at 200 kts when his VREF should have been 105 kts !!!
Way above even the tyre limits but he stopped safely.
Pace
Could that be 20 feet? 10 feet ? 5 feet ? or even 2 feet ?
Landing at just above the stall has little to do with landing an aircraft other than meeting the published stopping distance as I have stated before it is quite possible to land an aircraft which stalls at 60 kts at 120kts if you have the skills.
At 1.3 times the stall gives you a buffer to change AOA and hence loose speed without stalling before contacting the runway but it is a misunderstanding to connect these speeds with actually landing which could be at any speed.
I had a friend who had a control problem in a Citation who landed at Edinburgh at 200 kts when his VREF should have been 105 kts !!!
Way above even the tyre limits but he stopped safely.
Pace
Last edited by Pace; 18th Apr 2013 at 12:11.
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Captain flew for 24/7 next to me at Kudos at Southend ; )
Not surprised they were as white as sheets as the radar traces showed their landing speeds at 200 kts ( yikes)
Yes around 5 years ago
But just used it as an example to remove a misconception regarding stall and landing an aircraft
Or for that matter a flair point
Pace
Not surprised they were as white as sheets as the radar traces showed their landing speeds at 200 kts ( yikes)
Yes around 5 years ago
But just used it as an example to remove a misconception regarding stall and landing an aircraft
Or for that matter a flair point
Pace
Last edited by Pace; 18th Apr 2013 at 12:51.
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And to confirm the "fly by the book" and the "every aircraft is different" comments:
The SA Bulldog's short field landing technique involves keeping the power on all the way to touch down, on the back side of the drag curve. 55kn is my memory. You need the power to maintain that speed, and have enough energy to flare, although despite getting into the landing attitude with power still on, flare will be minimal. Power comes off and flaps come up as soon as you touch the ground...
The technique requires practice and it isn't the normal landing pattern...
The SA Bulldog's short field landing technique involves keeping the power on all the way to touch down, on the back side of the drag curve. 55kn is my memory. You need the power to maintain that speed, and have enough energy to flare, although despite getting into the landing attitude with power still on, flare will be minimal. Power comes off and flaps come up as soon as you touch the ground...
The technique requires practice and it isn't the normal landing pattern...