747 Takeoff speeds
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747 Takeoff speeds
As long as the runway could give adequate V1 how would you 747 pilots feel about an increase in Vr by 10 kts, thus an increase in V2 by 10 kts? I understand that V2 must be accomplished such that if the critical engine fails you must be able to make obstacle clearance.
If operational procedures were to change such that a "variable" Vr was used to enhance climb how would you pilots feel? In this I mean: Leave V1 the same as you have it today. Your initial Vr would still be the same as today. But if nothing has gone wrong(ie. engine failure) you stay on the runway till you reach your optimal Vr. If something does happen you can climb at any point between the two Vr points. Lets call them Vr "initial" and Vr "optimal". All of the safety margins are still the same. If an engine fails between Vr initial and Vr optimal the plane's increased velocity will only help engine out climb and remember you can rotate anytime between the two Vr points in case of an emergency. Vr optimal would have to be such that if critical engine fails at Vr the plane can still make obstacle clearance.
This second scenario will give you more altitude at cutback due to increased climb rate. Some of you already initiate cutback below 1000'. This will put you above 1000' ft at most airports that can handle a 747.
If operational procedures were to change such that a "variable" Vr was used to enhance climb how would you pilots feel? In this I mean: Leave V1 the same as you have it today. Your initial Vr would still be the same as today. But if nothing has gone wrong(ie. engine failure) you stay on the runway till you reach your optimal Vr. If something does happen you can climb at any point between the two Vr points. Lets call them Vr "initial" and Vr "optimal". All of the safety margins are still the same. If an engine fails between Vr initial and Vr optimal the plane's increased velocity will only help engine out climb and remember you can rotate anytime between the two Vr points in case of an emergency. Vr optimal would have to be such that if critical engine fails at Vr the plane can still make obstacle clearance.
This second scenario will give you more altitude at cutback due to increased climb rate. Some of you already initiate cutback below 1000'. This will put you above 1000' ft at most airports that can handle a 747.
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It seems you've thought about this a lot, but what would be the point of extending the time spent on the take-off run to get the extra 10kts? In order to gain the 10kts extra that you've suggested you'd swallow up loads of extra tarmac. If you'd taken off at the original Vr speed you'd soon reach the Vr+10 speed. (More drag force on an aircraft with it's wheels on the ground then when it is climbing out.)
If you did an experiment where the Vr+10 take-off was compared to a standard Vr take-off you'd find that the standard aircraft would be higher and faster at a given distance than the Vr+10 aircraft. All due to an aircraft being a more efficient machine in the air than on the ground.
Hippo.
If you did an experiment where the Vr+10 take-off was compared to a standard Vr take-off you'd find that the standard aircraft would be higher and faster at a given distance than the Vr+10 aircraft. All due to an aircraft being a more efficient machine in the air than on the ground.
Hippo.
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747FOCAL-
As 411A has said, many carriers employ the option of the "overspeed" t/o. Many more have the option (in case of a microburst/windshear threat) of delaying the rotation for as much as 20 kts if the runway will allow it.
HIPPO-
I think you'll find the opposite to be true. Delaying your rotation will put you faster and higher, not the other way around. V2 is well below your best angle of climb and best rate of climb.
As 411A has said, many carriers employ the option of the "overspeed" t/o. Many more have the option (in case of a microburst/windshear threat) of delaying the rotation for as much as 20 kts if the runway will allow it.
HIPPO-
I think you'll find the opposite to be true. Delaying your rotation will put you faster and higher, not the other way around. V2 is well below your best angle of climb and best rate of climb.
Guest
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Thanks gentlemen for your input.
Those who answered higher altitude are correct in what I am trying to do. Those of you that currently fly the flaps 20 takeoffs certainly know why.
I am going to the sim.
None of you answered about your feelings on how it might make you feel as a pilot. I am very interested in that.
You gents get allot of time to think about flying. I think a great contest would be for a pilot to define the best flight configuration and parameters at MTOW for 747-400 to put it at the highest altitude possible at cutback.
Is that workable?
Could be cool??
Those who answered higher altitude are correct in what I am trying to do. Those of you that currently fly the flaps 20 takeoffs certainly know why.
I am going to the sim.
None of you answered about your feelings on how it might make you feel as a pilot. I am very interested in that.
You gents get allot of time to think about flying. I think a great contest would be for a pilot to define the best flight configuration and parameters at MTOW for 747-400 to put it at the highest altitude possible at cutback.
Is that workable?
Could be cool??
Guest
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747FOCAL,
What you are trying to do is already available as a B747 procedure, its called improved climb.
Basically its a case or trading excess field length for speed, but all 3 speeds are increased and not just the V2.
BTW, why dont you just use Flaps 10 rather than 20?
Mutt
[This message has been edited by mutt (edited 15 February 2001).]
What you are trying to do is already available as a B747 procedure, its called improved climb.
Basically its a case or trading excess field length for speed, but all 3 speeds are increased and not just the V2.
BTW, why dont you just use Flaps 10 rather than 20?
Mutt
[This message has been edited by mutt (edited 15 February 2001).]
Guest
Posts: n/a
747focal,
as mutt said, this procedure is called Improved Climb or Increased V Speeds ie. converting excess runway into speed to improve 2nd segment climb performance. this procedure is not limited to any aircraft type but applicable to all perf A aircraft. all CAA licence holder will remember this during their Performance A exam.
many considerations have been taken into account before one can undertake such procedures eg. runway limit, climb limit, obstacle limit, brake energy limit, etc. if i recall correctly, there also a V1/Vr ratio to consider.
it brings to mind an IP in our company who teaches such procedures on a field length limited runway !!
HS
Edited for typos
[This message has been edited by HighSpeed (edited 15 February 2001).]
as mutt said, this procedure is called Improved Climb or Increased V Speeds ie. converting excess runway into speed to improve 2nd segment climb performance. this procedure is not limited to any aircraft type but applicable to all perf A aircraft. all CAA licence holder will remember this during their Performance A exam.
many considerations have been taken into account before one can undertake such procedures eg. runway limit, climb limit, obstacle limit, brake energy limit, etc. if i recall correctly, there also a V1/Vr ratio to consider.
it brings to mind an IP in our company who teaches such procedures on a field length limited runway !!
HS
Edited for typos
[This message has been edited by HighSpeed (edited 15 February 2001).]
