JMC 250Kts Below FL100
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So many posts on the same subject and people will think that I am obsessed with flying fast at low level which isn’t so.
Vertigo I have never flown a super heavy so can’t comment on them however in my experience which includes 737 –200/300 , A320 , 757 , 767 – 200/300 up to about 180 Tonnes the technique works well. It works particularly well on the 757 as the speedbrakes are relatively good and excellent at high speed in dense air. Flanker however makes the best point, which is to try to correct the profile as early as possible and preferably before 10,000 ft. However this can often be difficult and there is much more scope after 10,000 as the FMC will be programmed to slow down thus even without speedbrakes just by maintaining your normal descent speed you can begin to recover profile. All this is of course dependant on ATC allowing a continuous descent profile. I would like to stress that we are not talking about late stages of the approach here but say between 10 and 5 thousand ft when there is little else one can do to help. In any event one must start to reduce speed by say 20 track miles or it isn’t going to happen anyway and we will need to talk nicely to ATC about some more miles!
FogMeister When you start to fly real aeroplanes in the real world and not just your computer you will see that it is not possible to ‘ always be on profile ‘.
Safe flying all!
Vertigo I have never flown a super heavy so can’t comment on them however in my experience which includes 737 –200/300 , A320 , 757 , 767 – 200/300 up to about 180 Tonnes the technique works well. It works particularly well on the 757 as the speedbrakes are relatively good and excellent at high speed in dense air. Flanker however makes the best point, which is to try to correct the profile as early as possible and preferably before 10,000 ft. However this can often be difficult and there is much more scope after 10,000 as the FMC will be programmed to slow down thus even without speedbrakes just by maintaining your normal descent speed you can begin to recover profile. All this is of course dependant on ATC allowing a continuous descent profile. I would like to stress that we are not talking about late stages of the approach here but say between 10 and 5 thousand ft when there is little else one can do to help. In any event one must start to reduce speed by say 20 track miles or it isn’t going to happen anyway and we will need to talk nicely to ATC about some more miles!
FogMeister When you start to fly real aeroplanes in the real world and not just your computer you will see that it is not possible to ‘ always be on profile ‘.
Safe flying all!
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MCRIT..
Seeing as you have decided to become personal thought i would address your comments.Yes our colleague is absoluteley right and you are an engineers nightmare, and probably to all the road users around you as well, and anybody else who happens to get into the boundary layer of your ego.
I am a subscriber to 250 <FL100 and have never once had to ask ATC for extra miles..EVER. Why for 2 reasons, firstly i plan my descents carefully, with allowances for the unexpected (as any sensible airman would), and as we all know vs go down and slowdown, if you are already slowed down then the speedbrake will then make you go down. No doubt your sterling effort to arrive that 2 min earlier, is completeley lost by downtime in maintenance because you drive the machine like a company car. But of course you wouldnt be privy to that statistic or I doubt give a toss.
Am i qualified to make these comments? well 20 years as engineer Licensed on 1-11, 727, 737, 747, 757, 767, 777, 320, DC10. A,C&E,I
Flt Eng , and now demoted to ATPL on one of the types you operate, gives me a far better all round view than you..I would love to hazard a guess at your background.
I suggest you show a little more respect for the guys who your life depends on !!!
By the way just how many G/A's have you done from screwed up approaches?
Chill and respect !
Seeing as you have decided to become personal thought i would address your comments.Yes our colleague is absoluteley right and you are an engineers nightmare, and probably to all the road users around you as well, and anybody else who happens to get into the boundary layer of your ego.
I am a subscriber to 250 <FL100 and have never once had to ask ATC for extra miles..EVER. Why for 2 reasons, firstly i plan my descents carefully, with allowances for the unexpected (as any sensible airman would), and as we all know vs go down and slowdown, if you are already slowed down then the speedbrake will then make you go down. No doubt your sterling effort to arrive that 2 min earlier, is completeley lost by downtime in maintenance because you drive the machine like a company car. But of course you wouldnt be privy to that statistic or I doubt give a toss.
Am i qualified to make these comments? well 20 years as engineer Licensed on 1-11, 727, 737, 747, 757, 767, 777, 320, DC10. A,C&E,I
Flt Eng , and now demoted to ATPL on one of the types you operate, gives me a far better all round view than you..I would love to hazard a guess at your background.
I suggest you show a little more respect for the guys who your life depends on !!!
By the way just how many G/A's have you done from screwed up approaches?
Chill and respect !
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Lowflyer,
You can not always plan your desent to the nth degree as you suggest unless you are of course always flying to airports that do not have any other traffic or other airports near them. Or are you flying around at FL190 with 25 degs of flap out and the gear down!
[This message has been edited by autobrakemedium (edited 01 July 2001).]
[This message has been edited by PPRuNe Towers (edited 01 July 2001).]
You can not always plan your desent to the nth degree as you suggest unless you are of course always flying to airports that do not have any other traffic or other airports near them. Or are you flying around at FL190 with 25 degs of flap out and the gear down!
[This message has been edited by autobrakemedium (edited 01 July 2001).]
[This message has been edited by PPRuNe Towers (edited 01 July 2001).]
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Much talk of "Time saving" and "Dragging it in at 250 knots".Assuming an idle descent from TOD to say 1000'agl with no speedbrake the difference between a 2 stage deceleration (ie,back to 250 at 10) and a single level deceleration at say 3000' is most certainly not several minutes as many seem to think.It is realy very marginal.You have a set amount of kinetic energy at TOD and while high speed sure does get the hieght of and increase drag you will need longer to lose the speed.
I would like to see some hard figures but "Keeping the speed up" on an idle no speedbrake approach does NOT save much time at all.
I would like to see some hard figures but "Keeping the speed up" on an idle no speedbrake approach does NOT save much time at all.
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Just a quick question, it has been mentioned on this thred about using speed to correct the profile (too high). Good idea above 10,000ft. Below 10,000ft options are suddenly running out, someone commented on using speed to correct the proflile in a low alt (below 10K) situation because if your high you have to much energy, ok so far. Now your back on profile but about 70kts too fast, havent you just changed to type of energy you have? you are still in a situation of too much energy, but now a few thousand feet lower. If you are fast what are your options? Speedbrake, more track miles to run. If you are high? flap, gear, speedbrake and more track miles to run are all options to help the situation.
Its best to be on speed and on profile, but as we all know ATC get in the way. In our company the managment have decided that it is best to be high on the profile but slow, with plenty of options at correction, than fast but at the correct alt with limited options at corrections and with the constant threat of "direct centre fix" coming over the airwaves.
What Im trying to say is if your fast, you cannot get gear and flap down, and to slow down your going to have to go high on the profile. Is it not best to do this early, say around the 10K mark, than just before you capture the glide slope?
B757, gear down, flap 30 = Six degree glide slope, this will get you out of most high on the profile situations at low altitude.
Dont mean to be patronising, sorry!!!!
[This message has been edited by Jonty (edited 02 July 2001).]
Its best to be on speed and on profile, but as we all know ATC get in the way. In our company the managment have decided that it is best to be high on the profile but slow, with plenty of options at correction, than fast but at the correct alt with limited options at corrections and with the constant threat of "direct centre fix" coming over the airwaves.
What Im trying to say is if your fast, you cannot get gear and flap down, and to slow down your going to have to go high on the profile. Is it not best to do this early, say around the 10K mark, than just before you capture the glide slope?
B757, gear down, flap 30 = Six degree glide slope, this will get you out of most high on the profile situations at low altitude.
Dont mean to be patronising, sorry!!!!
[This message has been edited by Jonty (edited 02 July 2001).]
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Jonty----
What you say makes perfectly good sense and is of course, correct.
I have found over the years that it is the junior F/O types who like the high speed at low levels. These guys are relatively new to the profession (and jets) and therefore many times have little experience at ANTICIPATING possible problems with high speed and short vectors to the FAF.
I tend to let them make these mistakes on their own rather than correcting the situation earlier.
Once bitten, twice shy seems to work well at their experience level. After many years in line training, seems the best method to me.
Others may disagree, of course.
What you say makes perfectly good sense and is of course, correct.
I have found over the years that it is the junior F/O types who like the high speed at low levels. These guys are relatively new to the profession (and jets) and therefore many times have little experience at ANTICIPATING possible problems with high speed and short vectors to the FAF.
I tend to let them make these mistakes on their own rather than correcting the situation earlier.
Once bitten, twice shy seems to work well at their experience level. After many years in line training, seems the best method to me.
Others may disagree, of course.
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Jonty, you seem to have missed the point. You say
"In our company the managment have decided that it is best to be high on the profile but slow, with plenty of options at correction, than fast but at the correct alt with limited options at corrections and with the constant threat of "direct centre fix" coming over the airwaves.
"What Im trying to say is if your fast, you cannot get gear and flap down, and to slow down your going to have to go high on the profile. Is it not best to do this early, say around the 10K mark, than just before you capture the glide slope?"
Energy management has to be part of an overall package within profile and sequencing management. Kinetic and potential energy can be transferred from one to the other. Flap and gear should be viewed as "irreversible" of course they are reversible, you can retract them, however try treating them as one shot operations. Should you be unlucky enough to be caught out hauling it in in high drag, the fuel penalty is significant. However should you have had the foresight and opportunity to use the speed (the drag/squared law) to reduce energy to the point wher you can haul it in clean (under the profile) the fuel penalty is much reduced. Higher speeds produce more drag and therefore disperse energy more efficiently especially at lower levels.
You may misunderstand, our company has a defined policy in writing to maintain 250 kts below 10000ft with certain noteable exceptions. None of these exceptions preclude sensibe use of the laws of aerodynamics and the characteristics of your aircraft type to integrate SAFELY into traffic patterns.
I did try hard to say nothing derogatory and something positive about 411a's comments.
[This message has been edited by beardy (edited 02 July 2001).]
"In our company the managment have decided that it is best to be high on the profile but slow, with plenty of options at correction, than fast but at the correct alt with limited options at corrections and with the constant threat of "direct centre fix" coming over the airwaves.
"What Im trying to say is if your fast, you cannot get gear and flap down, and to slow down your going to have to go high on the profile. Is it not best to do this early, say around the 10K mark, than just before you capture the glide slope?"
Energy management has to be part of an overall package within profile and sequencing management. Kinetic and potential energy can be transferred from one to the other. Flap and gear should be viewed as "irreversible" of course they are reversible, you can retract them, however try treating them as one shot operations. Should you be unlucky enough to be caught out hauling it in in high drag, the fuel penalty is significant. However should you have had the foresight and opportunity to use the speed (the drag/squared law) to reduce energy to the point wher you can haul it in clean (under the profile) the fuel penalty is much reduced. Higher speeds produce more drag and therefore disperse energy more efficiently especially at lower levels.
You may misunderstand, our company has a defined policy in writing to maintain 250 kts below 10000ft with certain noteable exceptions. None of these exceptions preclude sensibe use of the laws of aerodynamics and the characteristics of your aircraft type to integrate SAFELY into traffic patterns.
I did try hard to say nothing derogatory and something positive about 411a's comments.
[This message has been edited by beardy (edited 02 July 2001).]
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Excuse me for returning to a point that the subscribers of high speed gave up on a while ago.
Peoples arguments that 250 below FL100 doesn´t take much longer than 300, hang their hats on a 30-35 mile straight in. I agree, in that case the savings are negligable. But I do an awful lot of approaches where we have to be at FL 100 with more than 60 trackmiles. Sometimes much more! So I haven´t quite given up on the good sense in keeping speed high if allowed.
People are talking rushed approaches and being high, with unnecessary go arounds to follow. Sure, don´t get pulled into something that you´re not comfortable with. But I´m talking well planned and excecuted highspeed approaches. They can give our pax and my conx times, just those extra few minutes that they need. Sometimes it doesn´t matter, sometimes it helps a lot. And with our company 1000-1100 flights a day, a few minutes here and there, CAN count.
Peoples arguments that 250 below FL100 doesn´t take much longer than 300, hang their hats on a 30-35 mile straight in. I agree, in that case the savings are negligable. But I do an awful lot of approaches where we have to be at FL 100 with more than 60 trackmiles. Sometimes much more! So I haven´t quite given up on the good sense in keeping speed high if allowed.
People are talking rushed approaches and being high, with unnecessary go arounds to follow. Sure, don´t get pulled into something that you´re not comfortable with. But I´m talking well planned and excecuted highspeed approaches. They can give our pax and my conx times, just those extra few minutes that they need. Sometimes it doesn´t matter, sometimes it helps a lot. And with our company 1000-1100 flights a day, a few minutes here and there, CAN count.
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2 aircraft arrive at a holding fix at about the same time. At FL60 was an ATP (215kt flat out). JMC 757, 1000 feet above and just ahead of said ATP. By asking for 280kt for 2 minutes, in an area where wide heading splits would have been difficult, JMC pulled far enough ahead of the ATP to allow a descent through its level, then reduced speed in a normal manner and completed a thoroughly unrushed and safe approach. Otherwise it would have been into the hold for JMC or 210kt or slower and a wider circuit to follow the ATP.
There is nothing wrong with a bit of extra speed if it is used wisely and for the good of all airspace users.
Thanks for the information in this thread.
(typos)
[This message has been edited by cossack (edited 03 July 2001).]
There is nothing wrong with a bit of extra speed if it is used wisely and for the good of all airspace users.
Thanks for the information in this thread.
(typos)
[This message has been edited by cossack (edited 03 July 2001).]
