CoP movement near the stall as slats deploy
Thread Starter
Join Date: Jun 2022
Location: Seattle
Posts: 103
Likes: 0
Received 0 Likes
on
0 Posts
CoP movement near the stall as slats deploy
Hi all,
Imagine a scenario when you are approaching the stall in clean configuration at 10,000ft (any swept wing airliner type). At the first sign of stall - stall warning, stick shaker, rumbling etc you pitch forward firmly to reduce AoA and on some types you select the first stage of flap. Usually this mean the slats deploy. What does the centre of pressure do in this case? You haven’t stalled and you’ve reduced AoA so by now it should be moving aft.
Thoughts?
BD
Imagine a scenario when you are approaching the stall in clean configuration at 10,000ft (any swept wing airliner type). At the first sign of stall - stall warning, stick shaker, rumbling etc you pitch forward firmly to reduce AoA and on some types you select the first stage of flap. Usually this mean the slats deploy. What does the centre of pressure do in this case? You haven’t stalled and you’ve reduced AoA so by now it should be moving aft.
Thoughts?
BD
Join Date: Oct 2019
Location: north of Harlow and south of Cambridge
Posts: 109
Likes: 0
Received 3 Likes
on
3 Posts
It appears...
You answered the question yourself.
Perhaps depends upon the rate of rotation of the wing around the lateral axis, the resultant change of relative wind vs the rate of respective flap and slat extensions and resultant change of effective camber of wing/flap/slat combined profile.
Perhaps depends upon the rate of rotation of the wing around the lateral axis, the resultant change of relative wind vs the rate of respective flap and slat extensions and resultant change of effective camber of wing/flap/slat combined profile.
Join Date: Jun 2007
Location: Wanderlust
Posts: 3,410
Likes: 0
Received 0 Likes
on
0 Posts
Hi all,
Imagine a scenario when you are approaching the stall in clean configuration at 10,000ft (any swept wing airliner type). At the first sign of stall - stall warning, stick shaker, rumbling etc you pitch forward firmly to reduce AoA and on some types you select the first stage of flap. Usually this mean the slats deploy. What does the centre of pressure do in this case? You haven’t stalled and you’ve reduced AoA so by now it should be moving aft.
Thoughts?
BD
Imagine a scenario when you are approaching the stall in clean configuration at 10,000ft (any swept wing airliner type). At the first sign of stall - stall warning, stick shaker, rumbling etc you pitch forward firmly to reduce AoA and on some types you select the first stage of flap. Usually this mean the slats deploy. What does the centre of pressure do in this case? You haven’t stalled and you’ve reduced AoA so by now it should be moving aft.
Thoughts?
BD
Never seen this before, in all jet transports I’ve flown stall recovery was accomplished with no configuration change, that included the after recovery phase
Join Date: Oct 2019
Location: north of Harlow and south of Cambridge
Posts: 109
Likes: 0
Received 3 Likes
on
3 Posts
he asked the question…
I simply replied to the question.
which was not “what is the correct stall recovery procedure.”
it would also depend upon the situation.
If memory serves, there was a sentence allowing the addition of Flaps 1 in the stall or windshear section in the 737 QRH or FCTM if close to terrain and the flaps were up. Not able to find it immediately, but will continue looking. Perhaps it has been removed.
if I owned my own 737 or 320, I would take it up and play with it to see why the “no configuration change” was so important and see what would happen.
like I said, he asked the question which included a configuration change.
which was not “what is the correct stall recovery procedure.”
it would also depend upon the situation.
If memory serves, there was a sentence allowing the addition of Flaps 1 in the stall or windshear section in the 737 QRH or FCTM if close to terrain and the flaps were up. Not able to find it immediately, but will continue looking. Perhaps it has been removed.
if I owned my own 737 or 320, I would take it up and play with it to see why the “no configuration change” was so important and see what would happen.
like I said, he asked the question which included a configuration change.
Last edited by 70 Mustang; 19th Jun 2023 at 08:43.
A320 memory actions contain the words “if clean and below 20k ft, flap 1 select”. As mentioned above, it comes after “flight path, recover smoothly” so is not there to unstall the wing, but to aid manoeuvring after the wing is unstalled.
Thread Starter
Join Date: Jun 2022
Location: Seattle
Posts: 103
Likes: 0
Received 0 Likes
on
0 Posts
Thank you Mustang for reading the question 
During stall training we recover from the stall and then select flaps 1 which gives us the slats. My question is not about that.
My question is what happens to the center of pressure when you select flaps 1/slats out? Not stalled, nose down, wings level, airspeed increasing. Assume pitch is constant to the wing is not rotating around it’s lateral axis.
During stall training we recover from the stall and then select flaps 1 which gives us the slats. My question is not about that.
My question is what happens to the center of pressure when you select flaps 1/slats out? Not stalled, nose down, wings level, airspeed increasing. Assume pitch is constant to the wing is not rotating around it’s lateral axis.
Join Date: Jun 2007
Location: Wanderlust
Posts: 3,410
Likes: 0
Received 0 Likes
on
0 Posts
"When stall indications have stopped, and when the aircraft has recovered sufficient energy, the flight crew can smoothly recover the initial flight path. If in clean configuration and below FL 200, during flight path recovery, the flight crew must select FLAPS 1 in order to increase the margin to AOAstall."
The word used for selection of flap1 is "must".
Join Date: Jun 2007
Location: Wanderlust
Posts: 3,410
Likes: 0
Received 0 Likes
on
0 Posts
Thank you Mustang for reading the question
During stall training we recover from the stall and then select flaps 1 which gives us the slats. My question is not about that.
My question is what happens to the center of pressure when you select flaps 1/slats out? Not stalled, nose down, wings level, airspeed increasing. Assume pitch is constant to the wing is not rotating around it’s lateral axis.
During stall training we recover from the stall and then select flaps 1 which gives us the slats. My question is not about that.
My question is what happens to the center of pressure when you select flaps 1/slats out? Not stalled, nose down, wings level, airspeed increasing. Assume pitch is constant to the wing is not rotating around it’s lateral axis.
At the first sign of stall - stall warning, stick shaker, rumbling etc you pitch forward firmly to reduce AoA and on some types you select the first stage of flap.
Even though flaps up takeoff is indeed very remote, myself I have missed the flaps 1 slot completely during acceleration (sim session) and went flaps up from 5. And I have seen one of my FO's do the same thing. As the aircraft is accelerating not that much of a deal you could say. During initial training long time ago I was warned for big brain farts with stories where stressed people apparently overloaded so much they went flaps up when requested gear up as well.
Thread Starter
Join Date: Jun 2022
Location: Seattle
Posts: 103
Likes: 0
Received 0 Likes
on
0 Posts
I’m not being specific to type vilas. You are being specific to the A320. I said “any swept wing airliner type”.
Anyway this is pedantic because I’m not asking anything about the stall or it’s recovery. I’m asking about the movement of center of pressure. I don’t know how I can make this any clearer?
Anyway this is pedantic because I’m not asking anything about the stall or it’s recovery. I’m asking about the movement of center of pressure. I don’t know how I can make this any clearer?
It's a Boeing phrase used for many types and the FCTM always refers to "inadvertent up selection for takeoff".
Even though flaps up takeoff is indeed very remote, myself I have missed the flaps 1 slot completely during acceleration (sim session) and went flaps up from 5. And I have seen one of my FO's do the same thing. As the aircraft is accelerating not that much of a deal you could say. During initial training long time ago I was warned for big brain farts with stories where stressed people apparently overloaded so much they went flaps up when requested gear up as well.
Even though flaps up takeoff is indeed very remote, myself I have missed the flaps 1 slot completely during acceleration (sim session) and went flaps up from 5. And I have seen one of my FO's do the same thing. As the aircraft is accelerating not that much of a deal you could say. During initial training long time ago I was warned for big brain farts with stories where stressed people apparently overloaded so much they went flaps up when requested gear up as well.
Join Date: Mar 2009
Location: USA
Posts: 9
Likes: 0
Received 0 Likes
on
0 Posts
DC 10 slats would deploy automatically if the stick shaker was activated. This might occur on a heavy weight T/O with turbulence. Additionally, one could expect the moniker, “Slats”, for the rest of the trip.
Re the A320, at my airline, clean stall is trained
1. lower the nose(reduce AOA), wings level, as you call for flaps 1, then check speed brake retracted.
Slats lowers stall speed by approximately 15 kts.
Re the A320, at my airline, clean stall is trained
1. lower the nose(reduce AOA), wings level, as you call for flaps 1, then check speed brake retracted.
Slats lowers stall speed by approximately 15 kts.
Join Date: Oct 2019
Location: north of Harlow and south of Cambridge
Posts: 109
Likes: 0
Received 3 Likes
on
3 Posts
I'll bring the big guns in!
Do a Google search:
Aerodynamics for Naval Aviators pdf
It will take you to the FAA website and a pdf document you can download.
If after reading it carefully, you cannot find the answer to your question in that book,
You don't need to know it! 😀
Aerodynamics for Naval Aviators pdf
It will take you to the FAA website and a pdf document you can download.
If after reading it carefully, you cannot find the answer to your question in that book,
You don't need to know it! 😀
Join Date: Jun 2007
Location: Wanderlust
Posts: 3,410
Likes: 0
Received 0 Likes
on
0 Posts
DC 10 slats would deploy automatically if the stick shaker was activated. This might occur on a heavy weight T/O with turbulence. Additionally, one could expect the moniker, “Slats”, for the rest of the trip.
Re the A320, at my airline, clean stall is trained
1. lower the nose(reduce AOA), wings level, as you call for flaps 1, then check speed brake retracted.
Slats lowers stall speed by approximately 15 kts.
Re the A320, at my airline, clean stall is trained
1. lower the nose(reduce AOA), wings level, as you call for flaps 1, then check speed brake retracted.
Slats lowers stall speed by approximately 15 kts.
