How can aircraft bank so steeply right after takeoff without falling?
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How can aircraft bank so steeply right after takeoff without falling?
Often right after takeoff the aircraft I am in will turn and bank 45 degrees or so (it seems to me). That reduces the vertical component of lift I guess by half since the other half of the lift is now going horizontally into the turn. But, the plane just took off and would thus not seem to have built up a lot of extra speed to be able to do this.
Obviously, it works, and I trust pilots are not cutting it too close and operate with sufficient margins. I expect that is the answer. But, it is the only aspect of flying that makes me anxious. Thank you for considering my question.
Obviously, it works, and I trust pilots are not cutting it too close and operate with sufficient margins. I expect that is the answer. But, it is the only aspect of flying that makes me anxious. Thank you for considering my question.
Dir. PPRuNe Line Service
The angle of bank in a passanger airliner will be at most 25 to 30 degrees.
The vertical component of lift is given by the formula
Lv = cos(angle of bank).
And therefore the 'G' that must be experienced for the vertical component to be equal to to 1 is 1/cos(angle of bank)
So for a 30 degree angle of bank, you'll be feeling 1.15g, which is only slightly noticable.
Science is fun!
PPD
The vertical component of lift is given by the formula
Lv = cos(angle of bank).
And therefore the 'G' that must be experienced for the vertical component to be equal to to 1 is 1/cos(angle of bank)
So for a 30 degree angle of bank, you'll be feeling 1.15g, which is only slightly noticable.
Science is fun!
PPD
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Bank angle...!
Hola Eboy -
xxx
With my airline, and most airlines, believe me, we try to operate as if we carry a bunch of eggs.
We dront try to make an omelet with our passengers...
xxx
We bank only 15º, not more than 20º when in daytime and clear.
Some departures or arrivals require us to bank 25º, sorry. Traffic separation requires it.
If it is in low clouds, we normally bank 25º (maximum 30º) as required by instrument peocedures.
If in clouds, you would not know (or feel) much difference between 15º and 25º bank.
Unless an emergency, we never would exceed 30º bank.
I am not that good at all this, so sometimes, I been to 32 or 33º... ooops!
xxx
Hey listen, I try not to spill my before landing Bloody Mary...
Makes a mess of my maps and charts...
Happy contrails
xxx
With my airline, and most airlines, believe me, we try to operate as if we carry a bunch of eggs.
We dront try to make an omelet with our passengers...
xxx
We bank only 15º, not more than 20º when in daytime and clear.
Some departures or arrivals require us to bank 25º, sorry. Traffic separation requires it.
If it is in low clouds, we normally bank 25º (maximum 30º) as required by instrument peocedures.
If in clouds, you would not know (or feel) much difference between 15º and 25º bank.
Unless an emergency, we never would exceed 30º bank.
I am not that good at all this, so sometimes, I been to 32 or 33º... ooops!
xxx
Hey listen, I try not to spill my before landing Bloody Mary...
Makes a mess of my maps and charts...
Happy contrails
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If the aircraft is flown in balance (which any professional pilot should be able to achieve, and an autopilot will also do with a high degree of success), you will not perceive the bank angle as a sideways force. So there is little direct indication of what the angle actually is.
An aircraft banked to 45 degrees and stabilised in a turn at that angle will require 40% (approx) more lift than in forward flight. For a heavy airliner (100 tons + of fuel on board just after take-off) thats a lot! If banked to 30 degrees, the increase is only about 17%. If banked to 20 degrees, the increase is about 7%. So aircraft designers tend to impose Angle of Bank limits around 20-30 degrees, so as not to have to design for regular application of extreme loads that are not really needed.
So I suspect that you may be seeing a turn of up to about 30 degrees. And if that is the extent of the bank, you can see from the figures above that not all that much extra lift is required, so the aircraft copes perfectly happily.
Hope thats not too circular an explanation (they limit to 30 degrees to avoid big loads, so that's probably what you're seeing, so that's OK because they limit to that to avoid big loads, so ...)
Sven
An aircraft banked to 45 degrees and stabilised in a turn at that angle will require 40% (approx) more lift than in forward flight. For a heavy airliner (100 tons + of fuel on board just after take-off) thats a lot! If banked to 30 degrees, the increase is only about 17%. If banked to 20 degrees, the increase is about 7%. So aircraft designers tend to impose Angle of Bank limits around 20-30 degrees, so as not to have to design for regular application of extreme loads that are not really needed.
So I suspect that you may be seeing a turn of up to about 30 degrees. And if that is the extent of the bank, you can see from the figures above that not all that much extra lift is required, so the aircraft copes perfectly happily.
Hope thats not too circular an explanation (they limit to 30 degrees to avoid big loads, so that's probably what you're seeing, so that's OK because they limit to that to avoid big loads, so ...)
Sven
Everything is under control.
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Yes, I see the aircraft is not so banking as much as I perceive, and thus the loss of lift is not that great. Thank you for your informative responses.
Eboy
Yes, "tilting"/banking the aircraft could cause a reduction in the upwards component of lift if nothing was done to compensate. However what usually happens is that the total lift produced by the wing is increased by increasing the wing's angle of attack - simply put the pilot will pull back ever so slightly on the controls ( you may perceive this in the cabin as a slight increase in "g"..end result of all this is the upwards component of lift - the component opposing gravity - remains the same and the aircraft doesn't fall to Earth. As an extreme example you can fly a 60 degree banked turn and not "fall" as long as the total lift is increased to double the value needed for straight flight = you would be pulling 2g..well above anything you would expect to experience in an airliner
.
As others have said airlines have strict rules on bank angles ( typically no more than 25 -30 degrees) and don't allow turns on take off until well above the ground ( again typically 400 feet or more). Most airlines monitor compliance with these rules and a whole host of others through the Flight Data Recorders - see Mike Jenvey's comment.
.As others have said airlines have strict rules on bank angles ( typically no more than 25 -30 degrees) and don't allow turns on take off until well above the ground ( again typically 400 feet or more). Most airlines monitor compliance with these rules and a whole host of others through the Flight Data Recorders - see Mike Jenvey's comment.
A very good question Eboy, and one I always wonder myself! I sit there thinking why doesn't the pilot wait till we are going a bit faster before making a 90deg bank(!)
Some good answers too, helps us understand why we don't fall out of the sky above the runway!! My physics A level was a very long time ago...
Some good answers too, helps us understand why we don't fall out of the sky above the runway!! My physics A level was a very long time ago...
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Take yourself gliding and you can learn all about angles of bank, G, angles of attack, stalling & spinning and so on for relatively little money, compared to any kind of power flying.
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eBoy
I am a frequent passenger and I have also a few hundred hours piloting light aircraft.
I won't add to the excellent responses you have already received, other than to say that bank angle often seems to me to be far steeper than it is, when viewed through a small window.
When you feel it is 45 degrees, its probably 20 or 25 and if you were in an aircraft that did a 45 degree bank, you would likely be convinced that it had stood on its wingtip
I am a frequent passenger and I have also a few hundred hours piloting light aircraft.
I won't add to the excellent responses you have already received, other than to say that bank angle often seems to me to be far steeper than it is, when viewed through a small window.
When you feel it is 45 degrees, its probably 20 or 25 and if you were in an aircraft that did a 45 degree bank, you would likely be convinced that it had stood on its wingtip
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Eboy:
If you'd really like to understand how all this works the best way is to go to the local flying/gliding club and take a few lessons. You don't need to complete a course (hard work) but just trying a few turns for yourself will totally change the way you feel about flying.
You could also ask an instructor to show you a steep turn, but don't try it yourself!
You could also ask an instructor to show you a steep turn, but don't try it yourself!
