...but it is sort of rocket science, isn't it ?

[miles offtarget]

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.

[Capt Pit Bull]

Well, rocket science is easy; it is just the application of Newton's third law.

[Genghis the Engineer]

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

[lomapaseo]

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

That's what computers are for ... so the pilot can just watch

[sabenaboy]

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! :ugh:

[CI54]

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...

[Dont Hang Up]

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.

[FlightPathOBN]

Where you will make the company money is with a constrained optimized descent (http://operationsbasednavigation.com/operations-based-navigation/)

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.

[Checkboard]

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"! :rolleyes:

[Dont Hang Up]

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"! :rolleyes:




Yes I confidently predict that sometime in the future all commercial aeroplanes will have one! :8

[The SSK]

Rocket science is strictly for firework displays. Those things you fly are guided missiles.

[p7lot]

"Rocket science is strictly for firework displays. Those things you fly are guided missiles."

But guided with such style and panache....:D

[TTex600]

And to think, I always thought it was rocket surgery:)