Turbulent Approach Less Flaps
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Turbulent Approach Less Flaps
Dear all,
I know that people suggest that you reduce Flaps one step when flying an approach with severe crosswind or turbulent air.
I did it my self cause I copied the procedure. Now I do question it and would like to collect different aspects and point of views and would like to understand the aerodynamic reason.
Can anybody help a little?
Thanks
Frank
I know that people suggest that you reduce Flaps one step when flying an approach with severe crosswind or turbulent air.
I did it my self cause I copied the procedure. Now I do question it and would like to collect different aspects and point of views and would like to understand the aerodynamic reason.
Can anybody help a little?
Thanks
Frank
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Turbulent Approach Less Flaps
I'd imagine the bigger surface area given by flaps means you are more susceptible to catching more of the turbulent air. I'm trying to recall something about turb. Conditions giving more rise to stalling. With the landing configuration and less flap your decreasing your chances of both of the above.
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More importantly...
Less likely to get a flap exceedance i.e. the lower flap setting usually comes with a higher limit speed i.e. gusts and large variations in IAS won't result in the flap load relief system operating or an exceedance requiring some paperwork or, worse, engineering inspection.
Was always my take on it...
Less likely to get a flap exceedance i.e. the lower flap setting usually comes with a higher limit speed i.e. gusts and large variations in IAS won't result in the flap load relief system operating or an exceedance requiring some paperwork or, worse, engineering inspection.
Was always my take on it...
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Ok, Thanks!
Some interesting points.
I see the point with the increased drag. In this case of full flaps you are more a "leaf" in the wind than with less flaps, is that what you mean?
And I see the speed limit point. But here is the next question:
Lets say you have Vref 130 Wind 30 gusting 45 (as per handbook you make additional half wind plus full gust up to a max of 20kts), meaning 130+15+15 = (130+15+the remaining 5 due to max 20) = 150kts.
Will you still add the the increment of, lets say, 8kts for lower flap selection and make it to a total of 158kts?
Best
Frank
Some interesting points.
I see the point with the increased drag. In this case of full flaps you are more a "leaf" in the wind than with less flaps, is that what you mean?
And I see the speed limit point. But here is the next question:
Lets say you have Vref 130 Wind 30 gusting 45 (as per handbook you make additional half wind plus full gust up to a max of 20kts), meaning 130+15+15 = (130+15+the remaining 5 due to max 20) = 150kts.
Will you still add the the increment of, lets say, 8kts for lower flap selection and make it to a total of 158kts?
Best
Frank
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Hi Chally604,
Not sure what the 8kts is for?
In my aircraft flap 30 limit speed is 162 knots.
At heavier, but sometimes even normal, weights our Vapp (Vref for flaps 30 plus half the stead headwind plus the full gust) will be uncomfortable close to this. In these cases we might use flaps 25 for landing as the limit speed is much higher. If we did this we'd use a Vapp of Vref for flaps 25 plus half the steady headwind component plus the gust.
Boeing say bleed of the steady headwind addition at some point before landing (i.e. between the threshold and the flare) but keep the gust addition.
Any help?
Not sure what the 8kts is for?
In my aircraft flap 30 limit speed is 162 knots.
At heavier, but sometimes even normal, weights our Vapp (Vref for flaps 30 plus half the stead headwind plus the full gust) will be uncomfortable close to this. In these cases we might use flaps 25 for landing as the limit speed is much higher. If we did this we'd use a Vapp of Vref for flaps 25 plus half the steady headwind component plus the gust.
Boeing say bleed of the steady headwind addition at some point before landing (i.e. between the threshold and the flare) but keep the gust addition.
Any help?
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Coming closer ;-)
The 8 knots are stated in the QRH as a supplement for a flap selection less than full flaps.
Actually it is 7kts for flaps 30 instead of 45 and 14kts for flaps 20 instead of 45.
This is stated in the QRH for non normal operation like single engine (F20) or stuck Flaps etc...
Now I wonder if if you would basicaly say:
Ok, Flaps 30 instead of 45 gives me an additional 7ktd as per QRH + the 20 addition due wind from the example above... Or you say:
Well I have an additional 20 anyhow and I dont care about the 7 from the QRH.
But as those 7kt are related to performace and the 20 are related to weather, I guess you are better of to add both to a maximum of 27 what you do for example in this situation as well:
Singe engine - Flaps 20 - Vref plus 14.
In case you have 30 gusting 45 you would take:
Vref 130 + 15 (half steady wind) + 5 (15kts gust but as to max 20kts its only 5 knots remaining) + !!14!! (for the flaps 20 situation) =130+20+14=164
The 8 knots are stated in the QRH as a supplement for a flap selection less than full flaps.
Actually it is 7kts for flaps 30 instead of 45 and 14kts for flaps 20 instead of 45.
This is stated in the QRH for non normal operation like single engine (F20) or stuck Flaps etc...
Now I wonder if if you would basicaly say:
Ok, Flaps 30 instead of 45 gives me an additional 7ktd as per QRH + the 20 addition due wind from the example above... Or you say:
Well I have an additional 20 anyhow and I dont care about the 7 from the QRH.
But as those 7kt are related to performace and the 20 are related to weather, I guess you are better of to add both to a maximum of 27 what you do for example in this situation as well:
Singe engine - Flaps 20 - Vref plus 14.
In case you have 30 gusting 45 you would take:
Vref 130 + 15 (half steady wind) + 5 (15kts gust but as to max 20kts its only 5 knots remaining) + !!14!! (for the flaps 20 situation) =130+20+14=164
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don't change anything
sure, I heard the idea many,many years ago that you use less flaps in certain situations...
with the exception of certain engine out situations in certain planes, and flap malfunctions...
I would not change the flap setting at all. I would use the maximum flap setting authorized by the manufacturer/FAA all the time.
Why?
So, there you go...flying for years using full flaps for landing and now , for the first time in years you use less flaps...you're doing something not routine...and you are more likely to screw it up.
you are more likely to hit the nosewheel first
you might use more runway than you have available
you might be less spooled up (in a jet) and be less able to correct with power.
you will have less of a chance to see the runway off an ILS
the idea that you will have more G loading protection is sort of odd, but it is very unlikely that you will encounter turbulence that will exceed your g limits. (in 37 years of flying, I have had two turbulence events that might be called severe...never seen extreme and much of my flying has been near the highest peaks in the 48 contiguous states.
so...why not just do what you are doing all the time...certainly add the wind/gust corrections to VREF
be on your toes ( literally too)
learn how to use assymetric thrust a bit on multi's
but every landing you ever did with full flaps is that much more experience when you really need it...otherwise you might as well do partial flap landings all the time (you'll be sorry)
with the exception of certain engine out situations in certain planes, and flap malfunctions...
I would not change the flap setting at all. I would use the maximum flap setting authorized by the manufacturer/FAA all the time.
Why?
So, there you go...flying for years using full flaps for landing and now , for the first time in years you use less flaps...you're doing something not routine...and you are more likely to screw it up.
you are more likely to hit the nosewheel first
you might use more runway than you have available
you might be less spooled up (in a jet) and be less able to correct with power.
you will have less of a chance to see the runway off an ILS
the idea that you will have more G loading protection is sort of odd, but it is very unlikely that you will encounter turbulence that will exceed your g limits. (in 37 years of flying, I have had two turbulence events that might be called severe...never seen extreme and much of my flying has been near the highest peaks in the 48 contiguous states.
so...why not just do what you are doing all the time...certainly add the wind/gust corrections to VREF
be on your toes ( literally too)
learn how to use assymetric thrust a bit on multi's
but every landing you ever did with full flaps is that much more experience when you really need it...otherwise you might as well do partial flap landings all the time (you'll be sorry)
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Chally
On jets it is quite common to use less than maximum flap for landing, for a variety of reasons, not least of which is it saves (a small amount of) fuel, but also because of the risk of overstressing the flaps in gusty winds.
We always fly the appropriate Vref for the flap setting used, then add the wind additions to that. On a 737 the FMC gives a Vref for flaps 40, 30 and 15, and we use the relevant one as a baseline, with the appropriate wind increment on top.
No idea what the Scarebus does.
On jets it is quite common to use less than maximum flap for landing, for a variety of reasons, not least of which is it saves (a small amount of) fuel, but also because of the risk of overstressing the flaps in gusty winds.
We always fly the appropriate Vref for the flap setting used, then add the wind additions to that. On a 737 the FMC gives a Vref for flaps 40, 30 and 15, and we use the relevant one as a baseline, with the appropriate wind increment on top.
No idea what the Scarebus does.
Last edited by Pub User; 28th Nov 2012 at 20:50.
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...
So, there you go...flying for years using full flaps for landing and now , for the first time in years you use less flaps...you're doing something not routine...and you are more likely to screw it up.
Not very flexible then
you are more likely to hit the nosewheel first
Why?
you might use more runway than you have available
Don't you check your landing performance?
learn how to use assymetric thrust a bit on multi's
Talk about something not routine!!
but every landing you ever did with full flaps is that much more experience when you really need it...otherwise you might as well do partial flap landings all the time (you'll be sorry)
I do, except where performance dictates otherwise
So, there you go...flying for years using full flaps for landing and now , for the first time in years you use less flaps...you're doing something not routine...and you are more likely to screw it up.
Not very flexible then
you are more likely to hit the nosewheel first
Why?
you might use more runway than you have available
Don't you check your landing performance?
learn how to use assymetric thrust a bit on multi's
Talk about something not routine!!
but every landing you ever did with full flaps is that much more experience when you really need it...otherwise you might as well do partial flap landings all the time (you'll be sorry)
I do, except where performance dictates otherwise
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I would not change the flap setting at all. I would use the maximum flap setting authorized by the manufacturer/FAA all the time.
Why?
So, there you go...flying for years using full flaps for landing and now , for the first time in years you use less flaps...you're doing something not routine...and you are more likely to screw it up.
you are more likely to hit the nosewheel first
Last edited by JammedStab; 29th Nov 2012 at 00:13.
I started using F25 instead of F30 on our B757's years ago, this is allowed in our procedures and was suggested to me one gusty night while being given a line check.
I was so impressed at how much easier it was to handle in these conditions with this reduced flap setting that I use it as a matter of course, runway length allowing.
I was so impressed at how much easier it was to handle in these conditions with this reduced flap setting that I use it as a matter of course, runway length allowing.
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Chally604,
In addition to controllability issues, by using less flap you will have a higher approach speed which will have the effect of reducing the size of the crab angle for your crosswind approach. Not usually a huge factor in planning your approach but if you're working to limits, as Tesco says, every little helps.
In addition to controllability issues, by using less flap you will have a higher approach speed which will have the effect of reducing the size of the crab angle for your crosswind approach. Not usually a huge factor in planning your approach but if you're working to limits, as Tesco says, every little helps.
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you are more likely to hit the nosewheel first
I assume you wrote this because you thought that by going faster you'd have a lower body angle. However, assuming you are flying at the correct speed for your flap setting, you will have a lower body angle with greater flap settings and I would have thought that would increase (very slightly) the chance of doinking the nosewheel first, as opposed to less flap.
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no...because as you float along, using your ''normal'' flare technique and not quite touching down,, you panic and push the plane on, but oops, you push too much and you land flat.
the FAA does require minimum flap for jets to reduce noise, but it is a legitimate landing flap setting not some reduced flap setting just out of your head.
if you have never used assymetric thrust, you don't know all the tools you have available.
it seems to me that boeing would publish different crosswind limits for different flap settings if it really made a difference...
my comment is about departing from routine...if you are in the habbit of pulling up just a bit as the ''numbers'' vanish, or the thousand foot marker vanishes beneath you, you may float.
if you are disciplined enough to just fly it on the runway with the reduced flap setting fine...but I"ll bet someone in your company will float a bit more trying for that smooth touchdown..
and of course lord spandex masher is right and I am wrong...why? because he wears spandex and we all know how irritating spandex is
the FAA does require minimum flap for jets to reduce noise, but it is a legitimate landing flap setting not some reduced flap setting just out of your head.
if you have never used assymetric thrust, you don't know all the tools you have available.
it seems to me that boeing would publish different crosswind limits for different flap settings if it really made a difference...
my comment is about departing from routine...if you are in the habbit of pulling up just a bit as the ''numbers'' vanish, or the thousand foot marker vanishes beneath you, you may float.
if you are disciplined enough to just fly it on the runway with the reduced flap setting fine...but I"ll bet someone in your company will float a bit more trying for that smooth touchdown..
and of course lord spandex masher is right and I am wrong...why? because he wears spandex and we all know how irritating spandex is
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Easy question 
It's even easier to answer when you try to fly airplane. I fly gliders myself though I have CPL but no job...
When you fly in turbulent air you want bigger wing loading, smaller coefficient of lift and better controllability.
Flaps will increase coefficient of lift and wing area so it's opposite what you want. So the airplane will feel any gust and will be even more difficult to control. So that's why in gliders we land with landing flaps in normal days and +2 in windy days. Also at the beginning of the tow we use -1(yes gliders have negative flaps) so you don't hit ground with wing tip which is a foot from the ground and wingspan is almost like on 737...
Also on turbulent days I prefer to fly with water ballast so I don't get sea-sick. Water ballast increase wing loading so glider is not going up and down in the smallest updrafts.
I hope my answer explains the question
It's even easier to answer when you try to fly airplane. I fly gliders myself though I have CPL but no job... When you fly in turbulent air you want bigger wing loading, smaller coefficient of lift and better controllability.
Flaps will increase coefficient of lift and wing area so it's opposite what you want. So the airplane will feel any gust and will be even more difficult to control. So that's why in gliders we land with landing flaps in normal days and +2 in windy days. Also at the beginning of the tow we use -1(yes gliders have negative flaps) so you don't hit ground with wing tip which is a foot from the ground and wingspan is almost like on 737...
Also on turbulent days I prefer to fly with water ballast so I don't get sea-sick. Water ballast increase wing loading so glider is not going up and down in the smallest updrafts.
I hope my answer explains the question
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Woooww...
Are we all all in the same industry?
As I posted this, I was guessing I will get two answers:
1) Idiot why dont you know?
2) Do it this way and go back to the books...
But this turned out not to be THAT easy.
Interesting. I can follow most inputs logically but I get the feeling it is more personal attitude than airmen ship or procedure.
I guess I might continue using less flaps as I had 40 gusting almost 60 in a quiet small plane a few days ago. I used on flap setting less and I was surprised how easy to flare and to land the plane was.
the last 3 ft over the runway turn out to be quiet calm anyhow.
Was one of my best landings
Best
Frank
Are we all all in the same industry?
As I posted this, I was guessing I will get two answers:
1) Idiot why dont you know?
2) Do it this way and go back to the books...
But this turned out not to be THAT easy.
Interesting. I can follow most inputs logically but I get the feeling it is more personal attitude than airmen ship or procedure.
I guess I might continue using less flaps as I had 40 gusting almost 60 in a quiet small plane a few days ago. I used on flap setting less and I was surprised how easy to flare and to land the plane was.
the last 3 ft over the runway turn out to be quiet calm anyhow.
Was one of my best landings
Best
Frank
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no...because as you float along, using your ''normal'' flare technique and not quite touching down,, you panic and push the plane on, but oops, you push too much and you land flat.
An alternative to your suggestion, that most of us mere mortals might carry out, would be to hold the attitude and allow the aircraft to settle. If it's going to land long then we go around. No need for theatrics and certainly no need for pushing forward, which we've been taught not to do from day 1 (despite some recent events in NRT 
)
the FAA does require minimum flap for jets to reduce noise, but it is a legitimate landing flap setting not some reduced flap setting just out of your head.
Since you're so concerned that we're doing non-standard things and this is going to end in tears, please point me to the Boeing Training Manual where it discusses using asymmetric thrust in any part of operation, bar trying to stop on slippery runways. I'm willing to do so with reduced flap settings.