...but it is sort of rocket science, isn't it ?
Thread Starter
Join Date: Mar 2003
Location: Seat 1A or 1B
Posts: 112
Likes: 0
Received 0 Likes
on
0 Posts
...but it is sort of rocket science, isn't it ?
Hello all.
I may be opening a can of worms here, but hope you can help.
I recently attended a lecture given by a director of ground ops, (former tug and tow-bar driver), in which he explained that he would view it as a simple and wonderful thing if in future the pilots would put their newspapers down, pay some attention, and fly the company aircraft more efficiently.
He had recently conducted a 'survey', and concluded that we could achieve constant descent approaches (and so use less fuel), if we just put our minds to it.
After all, he told us time after time after time, ' it's not rocket science !'.
Those sort of management cliches normally induce me to immediately look out of the nearest window and muse over what the score might be in the Test match, or whether Australia might have picked Mike Hussey over Michael Clarke to replace Ricky Ponting during the last Ashes, but this time it did get me thinking.
... but it is sort of rocket science isn't it ?
I know there is residual thrust and all that, but I mean closing the thrust levers at FL360 and doing that energy compensation thing all the way to touchdown, (which is of course what we try to do already, despite transiting the London TMA four times a day) must be sort of parabolic or hyperbolic or something ?
Anyway, as a simple B737 skipper that's where my schooling runs out, but I'm sure there are people here who might be able to help with some theory.
Thanks in advance,
Miles Off-Target.
I may be opening a can of worms here, but hope you can help.
I recently attended a lecture given by a director of ground ops, (former tug and tow-bar driver), in which he explained that he would view it as a simple and wonderful thing if in future the pilots would put their newspapers down, pay some attention, and fly the company aircraft more efficiently.
He had recently conducted a 'survey', and concluded that we could achieve constant descent approaches (and so use less fuel), if we just put our minds to it.
After all, he told us time after time after time, ' it's not rocket science !'.
Those sort of management cliches normally induce me to immediately look out of the nearest window and muse over what the score might be in the Test match, or whether Australia might have picked Mike Hussey over Michael Clarke to replace Ricky Ponting during the last Ashes, but this time it did get me thinking.
... but it is sort of rocket science isn't it ?
I know there is residual thrust and all that, but I mean closing the thrust levers at FL360 and doing that energy compensation thing all the way to touchdown, (which is of course what we try to do already, despite transiting the London TMA four times a day) must be sort of parabolic or hyperbolic or something ?
Anyway, as a simple B737 skipper that's where my schooling runs out, but I'm sure there are people here who might be able to help with some theory.
Thanks in advance,
Miles Off-Target.
Last edited by miles offtarget; 1st Jun 2011 at 07:00.
I reckon that rocket science involves the Tsiolkovsky equations - which are reasonably straightforward.
Range and endurance is the Brequet equations, not even from the same continent!
But the maths are pretty similar, and built upon Newtons laws and fairly straightforward calculus on path of a body with changing mass.
G
Range and endurance is the Brequet equations, not even from the same continent!
But the maths are pretty similar, and built upon Newtons laws and fairly straightforward calculus on path of a body with changing mass.
G
reckon that rocket science involves the Tsiolkovsky equations - which are reasonably straightforward.
Range and endurance is the Brequet equations, not even from the same continent!
But the maths are pretty similar, and built upon Newtons laws and fairly straightforward calculus on path of a body with changing mass.
G
Range and endurance is the Brequet equations, not even from the same continent!
But the maths are pretty similar, and built upon Newtons laws and fairly straightforward calculus on path of a body with changing mass.
G
Join Date: Sep 2001
Location: Third planet from the sun
Posts: 383
Likes: 0
Received 0 Likes
on
0 Posts
It's not difficult when...
Aah, the day the enroute ATCO tells me at FL360: "ABC123, when ready, start descent, free speed, direct routing approved, you're number 1 and cleared to land on RWY XX" then it will not be rocket science. I don't even need a fancy computer telling me what to do!
All the other days it will be very difficult as you hardly ever know exactly what to expect!
All the other days it will be very difficult as you hardly ever know exactly what to expect!
Join Date: Feb 2003
Location: Kuala Lumpur
Posts: 49
Likes: 0
Received 0 Likes
on
0 Posts
If it's not "rocket science", everybody would be doing it right now, right?
Problem is, there is theory, which is what we learn in the classroom, and actual real world situation.
He should stick doing what he does best, and reserve this kind of smart aleck statements while having his drink with his drinking friends, instead of trying to show how smart he is in front of people who have been doing this thing for years upon years...
Problem is, there is theory, which is what we learn in the classroom, and actual real world situation.
He should stick doing what he does best, and reserve this kind of smart aleck statements while having his drink with his drinking friends, instead of trying to show how smart he is in front of people who have been doing this thing for years upon years...
As someone in the business of Air Traffic Management research for over 20 years, I have to say that the constant descent, engine idle approach is very much an ATC system issue rather than a piloting issue. It is in fact the 'holy grail' of ATM research.
The flight crew could probably get it spot-on most times - maybe every time with the help of a computer to accurately nail the TOD.
The secret is to only let one aeroplane into the sky at a time. More than that and they have a nasty habit of interacting in a 'safe separation' kind of way. When there are hundreds of aircraft up there the interactions become chaotically complex - not in the sense of being dangerous, but in the sense of defying any truly analytical solution to gaining the maximum efficiency for each and every flight.
Many attempts have been made. Much faith was put on 4D trajectories through the 90s. However any speed adjustments made more than an hour out have a habit of being rendered pointless by some unforseen interaction in the last 20 minutes.
So far, the only really succesful solutions for well spaced arrivals tend to be based on path extension (and even here the computer assistance tools may provide only a marginal improvement on old fashioned ATCo skill). And this is of course totally contrary to the aspiration of constant / idle descent.
The flight crew could probably get it spot-on most times - maybe every time with the help of a computer to accurately nail the TOD.
The secret is to only let one aeroplane into the sky at a time. More than that and they have a nasty habit of interacting in a 'safe separation' kind of way. When there are hundreds of aircraft up there the interactions become chaotically complex - not in the sense of being dangerous, but in the sense of defying any truly analytical solution to gaining the maximum efficiency for each and every flight.
Many attempts have been made. Much faith was put on 4D trajectories through the 90s. However any speed adjustments made more than an hour out have a habit of being rendered pointless by some unforseen interaction in the last 20 minutes.
So far, the only really succesful solutions for well spaced arrivals tend to be based on path extension (and even here the computer assistance tools may provide only a marginal improvement on old fashioned ATCo skill). And this is of course totally contrary to the aspiration of constant / idle descent.
Join Date: Mar 2011
Location: engineer at large
Posts: 1,409
Likes: 0
Received 0 Likes
on
0 Posts
Where you will make the company money is with a constrained optimized descent
This involves using idle descent from FL400/350 down to FL50, and driving the ac through the approach. This allows ATC to manage the mult-variant que, provide separation, and timing, WITH current ATC tools.
The pilot can calc TOD knowing current weight and MET, and the variable TOD can be managed as the FL50 point is set with speed, as an example of 210.
This way, all of the ac in the que have the same basis point for ATC to manage, and the beauty of a constrained optimized descent.
The fuel savings are much more than idle descent final approach.
This involves using idle descent from FL400/350 down to FL50, and driving the ac through the approach. This allows ATC to manage the mult-variant que, provide separation, and timing, WITH current ATC tools.
The pilot can calc TOD knowing current weight and MET, and the variable TOD can be managed as the FL50 point is set with speed, as an example of 210.
This way, all of the ac in the que have the same basis point for ATC to manage, and the beauty of a constrained optimized descent.
The fuel savings are much more than idle descent final approach.
The flight crew could probably get it spot-on most times - maybe every time with the help of a computer to accurately nail the TOD.
The flight crew could probably get it spot-on most times - maybe every time with the help of a computer to accurately nail the TOD.
"the help of a computer"!
