Duration of take off. How long generally?
Discussion
I appreciate this very much a wide ranging question, but is there an average take off time from starting off at the end of the runway to wheels lifting off the ground?
The only part of flying which makes me anxious is that period between gaining speed and then take off. It probably takes 10-15 seconds, but sometimes it feels like we've been bombing along for ages before the plane leave the ground.
It always worries me we're not getting off the ground and will all fail badly at the perimeter fence!
Taking off from Carcassonne airport yesterday on a Ryanair flight was one of those moments.
Likewise, when flying on 747's, I know the runways are longer and as such, it feels less of an issue.
This is indeed probably one of the most pointless posts ever, but thought i'd try it anyway!
The only part of flying which makes me anxious is that period between gaining speed and then take off. It probably takes 10-15 seconds, but sometimes it feels like we've been bombing along for ages before the plane leave the ground.
It always worries me we're not getting off the ground and will all fail badly at the perimeter fence!
Taking off from Carcassonne airport yesterday on a Ryanair flight was one of those moments.
Likewise, when flying on 747's, I know the runways are longer and as such, it feels less of an issue.
This is indeed probably one of the most pointless posts ever, but thought i'd try it anyway!
No need to panic- https://www.youtube.com/watch?v=lyl21SEbF_k
Worse case scenario test- fully loaded 747 (nearly 1million lb's), 100% worn out brakes, 200+mph, not allowed to use reverse thrust and stopping by brakes alone then the undercarriage has to withstand the heat for 5minutes before they are allowed to cool them, apparently no problem.
Probably best not to look at a few Russian aborted takeoffs online though...
Worse case scenario test- fully loaded 747 (nearly 1million lb's), 100% worn out brakes, 200+mph, not allowed to use reverse thrust and stopping by brakes alone then the undercarriage has to withstand the heat for 5minutes before they are allowed to cool them, apparently no problem.
Probably best not to look at a few Russian aborted takeoffs online though...
scubadude said:
No need to panic- https://www.youtube.com/watch?v=lyl21SEbF_k
Worse case scenario test- fully loaded 747 (nearly 1million lb's), 100% worn out brakes, 200+mph, not allowed to use reverse thrust and stopping by brakes alone then the undercarriage has to withstand the heat for 5minutes before they are allowed to cool them, apparently no problem.
Probably best not to look at a few Russian aborted takeoffs online though...
Jeez. Look at the rubber!Worse case scenario test- fully loaded 747 (nearly 1million lb's), 100% worn out brakes, 200+mph, not allowed to use reverse thrust and stopping by brakes alone then the undercarriage has to withstand the heat for 5minutes before they are allowed to cool them, apparently no problem.
Probably best not to look at a few Russian aborted takeoffs online though...
"Hot brakes"
Generally speaking, keeping the wheels on the floor for long enough to ensure you will meet a minimum flying speed is a good thing, rather than trying to prise the crate off the deck early!
I few out of Phoenix many years ago (back to uk, non stop, so i guess i fair old fuel load on board), in a completely full 747 (every seat full), on a 48 degC day, and it's the only time I've ever felt the onset of leading edge buffet in a commercial aircraft as the pilot lifted the main gear off after what felt like a very very long roll! The climb out was definitely very slow for the first couple of thousand feet till a bit of fuel burnt off, the gear was stowed and the altitude brought cooler air.......
I few out of Phoenix many years ago (back to uk, non stop, so i guess i fair old fuel load on board), in a completely full 747 (every seat full), on a 48 degC day, and it's the only time I've ever felt the onset of leading edge buffet in a commercial aircraft as the pilot lifted the main gear off after what felt like a very very long roll! The climb out was definitely very slow for the first couple of thousand feet till a bit of fuel burnt off, the gear was stowed and the altitude brought cooler air.......
I could be very wrong in this - and I am no authority - but my understanding is that a calculation takes place (in larger aircraft) whereby load, air density and other factors are taken into consideration and this used to calculate takeoff thrust before takeoff.
This is used to work out just how much thrust is needed to get the aircraft into the air without going full TOGA in order to reduce fuel consumption/engine wear and including local environmental factors like keeping the neighbours happy at Heathrow.
Thus an Airbus or Boeing pilot at Gatwick does not simply 'floor it' when not necessary - but rather applies a measured thrust to take the aircraft into the air while not stressing any part of the aircraft, or using fuel uneccesarily.
Therefore short runways will appear a little more frantic than larger ones.
Like I say - no expert - and only what I understand from Mrs Paolow's fastidious watching of 'seconds from disaster' and similar.
I'd be interested to be corrected if wrong.......
This is used to work out just how much thrust is needed to get the aircraft into the air without going full TOGA in order to reduce fuel consumption/engine wear and including local environmental factors like keeping the neighbours happy at Heathrow.
Thus an Airbus or Boeing pilot at Gatwick does not simply 'floor it' when not necessary - but rather applies a measured thrust to take the aircraft into the air while not stressing any part of the aircraft, or using fuel uneccesarily.
Therefore short runways will appear a little more frantic than larger ones.
Like I say - no expert - and only what I understand from Mrs Paolow's fastidious watching of 'seconds from disaster' and similar.
I'd be interested to be corrected if wrong.......
Concorde 
Each take off roll is different and the speeds for v1,vr, and v2 are slightly different also.
We take into account
ambient temperature, ambient pressure, wind speed and direction versus runway heading, pressure altitude, runway condition ie dry wet etc, climb gradient in 2nd and 3rd segments with regards to obstacles or noise abatement, aircraft cdl's or mel's that may effect performance and of course aircraft weight.
These will alter the length of runway required to get airborne and clear the fence height at the opposite end of the runway.
The length of time accelerating on the deck will generally be the same per aircraft weight and is achieved as stated before with the power output of the engines being limited where possible to reduce wear and fuel consumption.
I'm flying on Monday. Aircraft will be around 351 tons and it's hotting up so will be around 38 degrees C. More than likely a departure with full rated thrust and using pretty much the full runway length. Seeing those red and white lights flash by you need to trust the figures!
We take into account
ambient temperature, ambient pressure, wind speed and direction versus runway heading, pressure altitude, runway condition ie dry wet etc, climb gradient in 2nd and 3rd segments with regards to obstacles or noise abatement, aircraft cdl's or mel's that may effect performance and of course aircraft weight.
These will alter the length of runway required to get airborne and clear the fence height at the opposite end of the runway.
The length of time accelerating on the deck will generally be the same per aircraft weight and is achieved as stated before with the power output of the engines being limited where possible to reduce wear and fuel consumption.
I'm flying on Monday. Aircraft will be around 351 tons and it's hotting up so will be around 38 degrees C. More than likely a departure with full rated thrust and using pretty much the full runway length. Seeing those red and white lights flash by you need to trust the figures!
paolow said:
I could be very wrong in this - and I am no authority - but my understanding is that a calculation takes place (in larger aircraft) whereby load, air density and other factors are taken into consideration and this used to calculate takeoff thrust before takeoff.
This is used to work out just how much thrust is needed to get the aircraft into the air without going full TOGA in order to reduce fuel consumption/engine wear and including local environmental factors like keeping the neighbours happy at Heathrow.
Thus an Airbus or Boeing pilot at Gatwick does not simply 'floor it' when not necessary - but rather applies a measured thrust to take the aircraft into the air while not stressing any part of the aircraft, or using fuel uneccesarily.
Therefore short runways will appear a little more frantic than larger ones.
Like I say - no expert - and only what I understand from Mrs Paolow's fastidious watching of 'seconds from disaster' and similar.
I'd be interested to be corrected if wrong.......
Pretty much yeah, I'm no expert either just a jet jockey wannabe who hasn't even finished his PPl yet, but it's my understanding that flex takeoffs don't save fuel but infact use more. I think the name of the game for reducing fuel burn is getting to the optimum cruising altitude as quickly as possible. They do save on engine wear though. Also at some airports TOGA takeoffs are stipulated for noise abatement reasons http://www.flightglobal.com/news/articles/airbus-d...This is used to work out just how much thrust is needed to get the aircraft into the air without going full TOGA in order to reduce fuel consumption/engine wear and including local environmental factors like keeping the neighbours happy at Heathrow.
Thus an Airbus or Boeing pilot at Gatwick does not simply 'floor it' when not necessary - but rather applies a measured thrust to take the aircraft into the air while not stressing any part of the aircraft, or using fuel uneccesarily.
Therefore short runways will appear a little more frantic than larger ones.
Like I say - no expert - and only what I understand from Mrs Paolow's fastidious watching of 'seconds from disaster' and similar.
I'd be interested to be corrected if wrong.......
No help to the OP, but it reminded me a lot of years ago, we were taking off from Newcastle airport, nose of the aircraft came up then nothing, nose of the aircraft came back down and the noise from the engines increased, me starting to think WTF, then the aircraft took off normally, when at cruising height the pilot came over the intercom and explained that the aircraft was heavier than he had calculated and needed extra speed to take off, I looked at my wife and said it was her fault, no not that she was over weight but at that time my son was a very fussy eater and one of the few things he would eat were tinned steam puddings,so our luggage had them packed in ever space, not sure if my memory is correct but I think the luggage allowance 30 or so years ago wasn't as small as it is now.
Some really informative replies here, thanks folks.
I think I'm right in thinking that if things are not going to plan by a certain time, the plane can still be brought to a safe stop so long as the wheels are still on the ground then......
Thus, my fear of running out of runway is not one to be awfully concerned about as the decision to abort will be taken prior to the wheels leaving the black stuff.
However, once off the ground, if there is an issue, even at 5 feet, the outcome could be much different.....
I think I'm right in thinking that if things are not going to plan by a certain time, the plane can still be brought to a safe stop so long as the wheels are still on the ground then......
Thus, my fear of running out of runway is not one to be awfully concerned about as the decision to abort will be taken prior to the wheels leaving the black stuff.
However, once off the ground, if there is an issue, even at 5 feet, the outcome could be much different.....
MattS3 said:
Some really informative replies here, thanks folks.
I think I'm right in thinking that if things are not going to plan by a certain time, the plane can still be brought to a safe stop so long as the wheels are still on the ground then......
Thus, my fear of running out of runway is not one to be awfully concerned about as the decision to abort will be taken prior to the wheels leaving the black stuff.
However, once off the ground, if there is an issue, even at 5 feet, the outcome could be much different.....
Only just getting the rear wheels off the ground. Loss of one engine...not sure if you lose all thrust right away from a bird strike. Still it takes off and go's around for a nice safe landing.I think I'm right in thinking that if things are not going to plan by a certain time, the plane can still be brought to a safe stop so long as the wheels are still on the ground then......
Thus, my fear of running out of runway is not one to be awfully concerned about as the decision to abort will be taken prior to the wheels leaving the black stuff.
However, once off the ground, if there is an issue, even at 5 feet, the outcome could be much different.....
https://www.youtube.com/watch?v=9KhZwsYtNDE
Munter said:
Only just getting the rear wheels off the ground. Loss of one engine...not sure if you lose all thrust right away from a bird strike. Still it takes off and go's around for a nice safe landing.
https://www.youtube.com/watch?v=9KhZwsYtNDE
Always re-assuring to see just how calmly these situations are handled (as to be expected with the level of training), but still incredibly re-assuring.https://www.youtube.com/watch?v=9KhZwsYtNDE
The answer is, it varies because there are a number of considerations to take into account, including a/c performance and Field length factors.
For an a/c operating to the ‘Scheduled Performance A’ regulations (which cover just about every airliner) a number of criteria have to be met such that following the failure of the most critical engine at any stage in flight, the a/c can continue to its destination, make an approach, overshoot, divert to the nominated alternate airfield, make an approach, overshoot, make a second approach and land.
With regards to the take-off there are primarily 3 criteria that have to be met:
Firstly, in the event of an engine failure before the stop/go decision speed the a/c must be able to stop safely. This decision speed is termed V1 and depends upon a number of factors including the a/c weight, the ASDA (Accelerate-Stop Distance Available), the runway condition (ie whether it is wet/contaminated), and the runway gradient. However, stopping at V1 requires an average pilot to be able to stay within 15ft of the runway centreline with maximum braking, reverse thrust (if available), speed brakes (if applicable) and maximum rudder deflection.
Since there is the requirement to stay within 15ft of the centreline (and not go spearing off into the bondu) V1 is limited by Vmcg1 (Minimum Control Speed on the Ground 1 engine inoperative). If you think about it, V1 must be above Vmcg1. Since Vmcg1 is a control speed it is affected by the air density, so Pressure Altitude and Air Temperature must be taken into account.
Another factor limiting V1 will be the braking performance of the a/c. V1 can not be greater than Vmbe (Maximum Brake Energy speed) since, obviously, we don’t want our wheels bursting into flames after a rejected take-off.
Secondly, in the event of an engine failure above V1 (stop/go decision speed) the a/c must be able to get airborne safely within the TORA (Take-Off Run Available). The consideration here is the speed at which the a/c gets airborne, Vr. In fact Vr is the speed at which the a/c is rotated into the take-off attitude and will depend upon the weight of the a/c.
However another factor comes into play here, that of being able to control the a/c. The book states that there must be sufficient control available to keep the a/c straight using up to 150lbs of rudder force and up to 5 degrees of bank away from the dead engine. The player here is Vmca1 (Minimum Control Speed Airborne 1 engine inoperative). Again, if you think about it,Vr must be greater than Vmca1; in fact Vr>1.05 Vmca1. Since Vmca1 depends upon air density, Pressure Altitude and Air Temperature must be taken into account.
Thirdly, following rotation the a/c must be able to get airborne safely. For older types the rules are that the a/c must be able to reach a Screen Height of 35ft by the end of the TODA (Take-Off Distance Available) at a speed of V2. For newer types the Screen Height is 50ft.
V2 is defined as: ‘The speed at which a sufficient margin of control exists for the average pilot whilst maintaining the optimum climb gradient for obstacle clearance following failure of the most critical engine’.
If you think about it, V2 must be greater than Vmca1 otherwise you would lose control; additionally it must be greater than Vs (Stall Speed) or you’d fall out of the sky. Thus V2>1.1 Vmca1, V2>1.2 Vs
For an a/c operating to the ‘Scheduled Performance A’ regulations (which cover just about every airliner) a number of criteria have to be met such that following the failure of the most critical engine at any stage in flight, the a/c can continue to its destination, make an approach, overshoot, divert to the nominated alternate airfield, make an approach, overshoot, make a second approach and land.
With regards to the take-off there are primarily 3 criteria that have to be met:
Firstly, in the event of an engine failure before the stop/go decision speed the a/c must be able to stop safely. This decision speed is termed V1 and depends upon a number of factors including the a/c weight, the ASDA (Accelerate-Stop Distance Available), the runway condition (ie whether it is wet/contaminated), and the runway gradient. However, stopping at V1 requires an average pilot to be able to stay within 15ft of the runway centreline with maximum braking, reverse thrust (if available), speed brakes (if applicable) and maximum rudder deflection.
Since there is the requirement to stay within 15ft of the centreline (and not go spearing off into the bondu) V1 is limited by Vmcg1 (Minimum Control Speed on the Ground 1 engine inoperative). If you think about it, V1 must be above Vmcg1. Since Vmcg1 is a control speed it is affected by the air density, so Pressure Altitude and Air Temperature must be taken into account.
Another factor limiting V1 will be the braking performance of the a/c. V1 can not be greater than Vmbe (Maximum Brake Energy speed) since, obviously, we don’t want our wheels bursting into flames after a rejected take-off.
Secondly, in the event of an engine failure above V1 (stop/go decision speed) the a/c must be able to get airborne safely within the TORA (Take-Off Run Available). The consideration here is the speed at which the a/c gets airborne, Vr. In fact Vr is the speed at which the a/c is rotated into the take-off attitude and will depend upon the weight of the a/c.
However another factor comes into play here, that of being able to control the a/c. The book states that there must be sufficient control available to keep the a/c straight using up to 150lbs of rudder force and up to 5 degrees of bank away from the dead engine. The player here is Vmca1 (Minimum Control Speed Airborne 1 engine inoperative). Again, if you think about it,Vr must be greater than Vmca1; in fact Vr>1.05 Vmca1. Since Vmca1 depends upon air density, Pressure Altitude and Air Temperature must be taken into account.
Thirdly, following rotation the a/c must be able to get airborne safely. For older types the rules are that the a/c must be able to reach a Screen Height of 35ft by the end of the TODA (Take-Off Distance Available) at a speed of V2. For newer types the Screen Height is 50ft.
V2 is defined as: ‘The speed at which a sufficient margin of control exists for the average pilot whilst maintaining the optimum climb gradient for obstacle clearance following failure of the most critical engine’.
If you think about it, V2 must be greater than Vmca1 otherwise you would lose control; additionally it must be greater than Vs (Stall Speed) or you’d fall out of the sky. Thus V2>1.1 Vmca1, V2>1.2 Vs
Edited by Ginetta G15 Girl on Thursday 17th April 14:50
Ginetta G15 Girl said:
The answer is, it varies because there are a number of considerations to take into account, including a/c performance and Field length factors.
For an a/c operating to the ‘Scheduled Performance A’ regulations (which cover just about every airliner) a number of criteria have to be met such that following the failure of the most critical engine at any stage in flight, the a/c can continue to its destination, make an approach, overshoot, divert to the nominated alternate airfield, make an approach, overshoot, make a second approach and land.
With regards to the take-off there are primarily 3 criteria that have to be met:
Firstly, in the event of an engine failure before the stop/go decision speed the a/c must be able to stop safely. This decision speed is termed V1 and depends upon a number of factors including the a/c weight, the ASDA (Accelerate-Stop Distance Available), the runway condition (ie whether it is wet/contaminated), and the runway gradient. However, stopping at V1 requires an average pilot to be able to stay within 15ft of the runway centreline with maximum braking, reverse thrust (if available), speed brakes (if applicable) and maximum rudder deflection.
Since there is the requirement to stay within 15ft of the centreline (and not go spearing off into the bondu) V1 is limited by Vmcg1 (Minimum Control Speed on the Ground 1 engine inoperative). If you think about it, V1 must be above Vmcg1. Since Vmcg1 is a control speed it is affected by the air density, so Pressure Altitude and Air Temperature must be taken into account.
Another factor limiting V1 will be the braking performance of the a/c. V1 can not be greater than Vmbe (Maximum Brake Energy speed) since, obviously, we don’t want our wheels bursting into flames after a rejected take-off.
Secondly, in the event of an engine failure above V1 (stop/go decision speed) the a/c must be able to get airborne safely within the TORA (Take-Off Run Available). The consideration here is the speed at which the a/c gets airborne, Vr. In fact Vr is the speed at which the a/c is rotated into the take-off attitude and will depend upon the weight of the a/c.
However another factor comes into play here, that of being able to control the a/c. The book states that there must be sufficient control available to keep the a/c straight using up to 150lbs of rudder force and up to 5 degrees of bank away from the dead engine. The player here is Vmca1 (Minimum Control Speed Airborne 1 engine inoperative). Again, if you think about it,Vr must be greater than Vmca1; in fact Vr>1.05 Vmca1. Since Vmca1 depends upon air density, Pressure Altitude and Air Temperature must be taken into account.
Thirdly, following rotation the a/c must be able to get airborne safely. For older types the rules are that the a/c must be able to reach a Screen Height of 35ft by the end of the TODA (Take-Off Distance Available) at a speed of V2. For newer types the Screen Height is 50ft.
V2 is defined as: ‘The speed at which a sufficient margin of control exists for the average pilot whilst maintaining the optimum climb gradient for obstacle clearance following failure of the most critical engine’.
If you think about it, V2 must be greater than Vmca1 otherwise you would lose control; additionally it must be greater than Vs (Stall Speed) or you’d fall out of the sky. Thus V2>1.1 Vmca1, V2>1.2 Vs
There is not a chance I could be bothered to type that out for a random person on an Internet forum.For an a/c operating to the ‘Scheduled Performance A’ regulations (which cover just about every airliner) a number of criteria have to be met such that following the failure of the most critical engine at any stage in flight, the a/c can continue to its destination, make an approach, overshoot, divert to the nominated alternate airfield, make an approach, overshoot, make a second approach and land.
With regards to the take-off there are primarily 3 criteria that have to be met:
Firstly, in the event of an engine failure before the stop/go decision speed the a/c must be able to stop safely. This decision speed is termed V1 and depends upon a number of factors including the a/c weight, the ASDA (Accelerate-Stop Distance Available), the runway condition (ie whether it is wet/contaminated), and the runway gradient. However, stopping at V1 requires an average pilot to be able to stay within 15ft of the runway centreline with maximum braking, reverse thrust (if available), speed brakes (if applicable) and maximum rudder deflection.
Since there is the requirement to stay within 15ft of the centreline (and not go spearing off into the bondu) V1 is limited by Vmcg1 (Minimum Control Speed on the Ground 1 engine inoperative). If you think about it, V1 must be above Vmcg1. Since Vmcg1 is a control speed it is affected by the air density, so Pressure Altitude and Air Temperature must be taken into account.
Another factor limiting V1 will be the braking performance of the a/c. V1 can not be greater than Vmbe (Maximum Brake Energy speed) since, obviously, we don’t want our wheels bursting into flames after a rejected take-off.
Secondly, in the event of an engine failure above V1 (stop/go decision speed) the a/c must be able to get airborne safely within the TORA (Take-Off Run Available). The consideration here is the speed at which the a/c gets airborne, Vr. In fact Vr is the speed at which the a/c is rotated into the take-off attitude and will depend upon the weight of the a/c.
However another factor comes into play here, that of being able to control the a/c. The book states that there must be sufficient control available to keep the a/c straight using up to 150lbs of rudder force and up to 5 degrees of bank away from the dead engine. The player here is Vmca1 (Minimum Control Speed Airborne 1 engine inoperative). Again, if you think about it,Vr must be greater than Vmca1; in fact Vr>1.05 Vmca1. Since Vmca1 depends upon air density, Pressure Altitude and Air Temperature must be taken into account.
Thirdly, following rotation the a/c must be able to get airborne safely. For older types the rules are that the a/c must be able to reach a Screen Height of 35ft by the end of the TODA (Take-Off Distance Available) at a speed of V2. For newer types the Screen Height is 50ft.
V2 is defined as: ‘The speed at which a sufficient margin of control exists for the average pilot whilst maintaining the optimum climb gradient for obstacle clearance following failure of the most critical engine’.
If you think about it, V2 must be greater than Vmca1 otherwise you would lose control; additionally it must be greater than Vs (Stall Speed) or you’d fall out of the sky. Thus V2>1.1 Vmca1, V2>1.2 Vs
Edited by Ginetta G15 Girl on Thursday 17th April 14:50
Well done.
Topbox said:
Ginetta G15 Girl said:
The answer is, it varies because there are a number of considerations to take into account, including a/c performance and Field length factors.
For an a/c operating to the ‘Scheduled Performance A’ regulations (which cover just about every airliner) a number of criteria have to be met such that following the failure of the most critical engine at any stage in flight, the a/c can continue to its destination, make an approach, overshoot, divert to the nominated alternate airfield, make an approach, overshoot, make a second approach and land.
With regards to the take-off there are primarily 3 criteria that have to be met:
Firstly, in the event of an engine failure before the stop/go decision speed the a/c must be able to stop safely. This decision speed is termed V1 and depends upon a number of factors including the a/c weight, the ASDA (Accelerate-Stop Distance Available), the runway condition (ie whether it is wet/contaminated), and the runway gradient. However, stopping at V1 requires an average pilot to be able to stay within 15ft of the runway centreline with maximum braking, reverse thrust (if available), speed brakes (if applicable) and maximum rudder deflection.
Since there is the requirement to stay within 15ft of the centreline (and not go spearing off into the bondu) V1 is limited by Vmcg1 (Minimum Control Speed on the Ground 1 engine inoperative). If you think about it, V1 must be above Vmcg1. Since Vmcg1 is a control speed it is affected by the air density, so Pressure Altitude and Air Temperature must be taken into account.
Another factor limiting V1 will be the braking performance of the a/c. V1 can not be greater than Vmbe (Maximum Brake Energy speed) since, obviously, we don’t want our wheels bursting into flames after a rejected take-off.
Secondly, in the event of an engine failure above V1 (stop/go decision speed) the a/c must be able to get airborne safely within the TORA (Take-Off Run Available). The consideration here is the speed at which the a/c gets airborne, Vr. In fact Vr is the speed at which the a/c is rotated into the take-off attitude and will depend upon the weight of the a/c.
However another factor comes into play here, that of being able to control the a/c. The book states that there must be sufficient control available to keep the a/c straight using up to 150lbs of rudder force and up to 5 degrees of bank away from the dead engine. The player here is Vmca1 (Minimum Control Speed Airborne 1 engine inoperative). Again, if you think about it,Vr must be greater than Vmca1; in fact Vr>1.05 Vmca1. Since Vmca1 depends upon air density, Pressure Altitude and Air Temperature must be taken into account.
Thirdly, following rotation the a/c must be able to get airborne safely. For older types the rules are that the a/c must be able to reach a Screen Height of 35ft by the end of the TODA (Take-Off Distance Available) at a speed of V2. For newer types the Screen Height is 50ft.
V2 is defined as: ‘The speed at which a sufficient margin of control exists for the average pilot whilst maintaining the optimum climb gradient for obstacle clearance following failure of the most critical engine’.
If you think about it, V2 must be greater than Vmca1 otherwise you would lose control; additionally it must be greater than Vs (Stall Speed) or you’d fall out of the sky. Thus V2>1.1 Vmca1, V2>1.2 Vs
There is not a chance I could be bothered to type that out for a random person on an Internet forum.For an a/c operating to the ‘Scheduled Performance A’ regulations (which cover just about every airliner) a number of criteria have to be met such that following the failure of the most critical engine at any stage in flight, the a/c can continue to its destination, make an approach, overshoot, divert to the nominated alternate airfield, make an approach, overshoot, make a second approach and land.
With regards to the take-off there are primarily 3 criteria that have to be met:
Firstly, in the event of an engine failure before the stop/go decision speed the a/c must be able to stop safely. This decision speed is termed V1 and depends upon a number of factors including the a/c weight, the ASDA (Accelerate-Stop Distance Available), the runway condition (ie whether it is wet/contaminated), and the runway gradient. However, stopping at V1 requires an average pilot to be able to stay within 15ft of the runway centreline with maximum braking, reverse thrust (if available), speed brakes (if applicable) and maximum rudder deflection.
Since there is the requirement to stay within 15ft of the centreline (and not go spearing off into the bondu) V1 is limited by Vmcg1 (Minimum Control Speed on the Ground 1 engine inoperative). If you think about it, V1 must be above Vmcg1. Since Vmcg1 is a control speed it is affected by the air density, so Pressure Altitude and Air Temperature must be taken into account.
Another factor limiting V1 will be the braking performance of the a/c. V1 can not be greater than Vmbe (Maximum Brake Energy speed) since, obviously, we don’t want our wheels bursting into flames after a rejected take-off.
Secondly, in the event of an engine failure above V1 (stop/go decision speed) the a/c must be able to get airborne safely within the TORA (Take-Off Run Available). The consideration here is the speed at which the a/c gets airborne, Vr. In fact Vr is the speed at which the a/c is rotated into the take-off attitude and will depend upon the weight of the a/c.
However another factor comes into play here, that of being able to control the a/c. The book states that there must be sufficient control available to keep the a/c straight using up to 150lbs of rudder force and up to 5 degrees of bank away from the dead engine. The player here is Vmca1 (Minimum Control Speed Airborne 1 engine inoperative). Again, if you think about it,Vr must be greater than Vmca1; in fact Vr>1.05 Vmca1. Since Vmca1 depends upon air density, Pressure Altitude and Air Temperature must be taken into account.
Thirdly, following rotation the a/c must be able to get airborne safely. For older types the rules are that the a/c must be able to reach a Screen Height of 35ft by the end of the TODA (Take-Off Distance Available) at a speed of V2. For newer types the Screen Height is 50ft.
V2 is defined as: ‘The speed at which a sufficient margin of control exists for the average pilot whilst maintaining the optimum climb gradient for obstacle clearance following failure of the most critical engine’.
If you think about it, V2 must be greater than Vmca1 otherwise you would lose control; additionally it must be greater than Vs (Stall Speed) or you’d fall out of the sky. Thus V2>1.1 Vmca1, V2>1.2 Vs
Edited by Ginetta G15 Girl on Thursday 17th April 14:50
Well done.
And way to technical for people who have little aviation technical background/knowledge.
Just to correct 1 point she makes....
V1 is not a decision speed,.......
For all intents & purpose, if you reach V1 there is no decision to be made you only have 1 option & to me, that's NOT a Decision
Just to correct 1 point she makes....
V1 is not a decision speed,.......
For all intents & purpose, if you reach V1 there is no decision to be made you only have 1 option & to me, that's NOT a Decision
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