Say you're cruising at FL240 at a IAS of 290-310 kts. If you're asked by ATC to reduce to 250kts (hypothetically
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If aircraft have to reduce their speed below a speed that is 'normal' for descent it would indeed be better to let them descend a bit earlier so that they are below the altitude profile and then they can reduce the speed and is the less steeper descent more manageable. Of course the most efficient (excluding operational or time costs, but fuel wise) is to reduce the speed already just prior descent and have a continious descend to avoid a level segment at lower altitude. But of course in busy airspace or airports this is most of the time not feasible I assume
Yes indeed, top of descent is in most cases much earlier than Brussels Acc. It will require very performant, interconnected ATC systems to do a pre-sequencing using speed control starting at cruise level. Something to aim forOf course the most efficient (excluding operational or time costs, but fuel wise) is to reduce the speed already just prior descent and have a continious descend to avoid a level segment at lower altitude. But of course in busy airspace or airports this is most of the time not feasible I assume![]()
If you encounter such a situation, you can be sure that the controller has screwed him/herselfThe most difficult is when they keep you high during vectoring, and then ask you to reduce to 210-220kts and descend at the same time. This is very difficult to manage as the speed brakes have very few effect with such a low speed. In that case you have to give priority to speed or to altitude.
No idea who you're talking aboutThat's until cost index n°6 airline arrives in the way with their 245kts as from ToD though...
Most airlines (unless the pilots are paid by the hour) use a descent speed of about 280kts.
Unless you're in the Gimli glider, that isHmmm... always dreamed to do that on short final too... but nope, not allowedjan_olieslagers wrote: ↑Yesterday, 17:53
:If I wish to descend rapidly - which is standard practice under certain conditions - a sideslip is the standard answer. Which will indeed increase drag dramatically, while at the same time reducing wing efficiency, thus reducing lift. And I absolutely love side-slipping! But I can imagine it is one of those things one doesn't do to the unsuspecting innocent passengers of an airliner...
Funny thing is, I recently had a talk with a colleague from approach who had a plane (E190 iirc) at FL80 15nm final. I was surprised to hear that in order to catch the glide they ask to reduce instead of increase. That's not a thing that would happen in an ACC environmentHowever, if you're still too high and/or too fast close to the airport, increasing speed doesn't make sense anymore (of course). It's time to slow down and increase drag with the landing gear & flaps
Probably for the same reason, sequencing arrivals is on of the most difficult things to learn for trainee controllers. You really need to grow experience on what speeds and levels are 'right' and what is too fast/slow, too high/low...Descent planning (or energy management) is one of the most difficult thing to learn for ab-initio F/O's. It can be tricky as a descent is never the same twice; it depends on traffic, wind, speed, distance to be flown etc... On top of that, it also needs to be performed in an efficient way; that's where you can save fuel.
Very interesting read guys, let's continue this way.737MAX wrote: ↑19 Oct 2019, 09:23Hmmm... always dreamed to do that on short final too... but nope, not allowedjan_olieslagers wrote: ↑18 Oct 2019, 17:53thank you!
If I wish to descend rapidly - which is standard practice under certain conditions - a sideslip is the standard answer. Which will indeed increase drag dramatically, while at the same time reducing wing efficiency, thus reducing lift. And I absolutely love side-slipping! But I can imagine it is one of those things one doesn't do to the unsuspecting innocent passengers of an airliner...
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However, if you're still too high and/or too fast close to the airport, increasing speed doesn't make sense anymore (of course). It's time to slow down and increase drag with the landing gear & flaps.
To give an idea; the rate of descent at minimum clean speed (approx 210kts on a 737NG) is around 1000ft; increasing to easily 3000ft+/min with 300kts.
Descent planning (or energy management) is one of the most difficult thing to learn for ab-initio F/O's. It can be tricky as a descent is never the same twice; it depends on traffic, wind, speed, distance to be flown etc... On top of that, it also needs to be performed in an efficient way; that's where you can save fuel.
It's strange that you say FL240 at the boundary is too low. Whenever possible, I use 'when ready descent...' and almost never I see an aircraft leveling of at FL240 to start the descent later. Coming from KOK yes, then quite often descent starts 10 nm or more past KOK...Arriving via ARVOL 25L in Brussels means FL240 at the boundary (which is too low) and you will have to maintain FL80 until you are abeam with RWY25R north of Brussels as departing traffic is cleared to FL60/FL70 below you. You become then too high if you are all by yourself, and possibly too low if ATC requires extra miles due to traffic. When possible for ATC, you'll be given the track miles they expect you to fly so you can adapt accordingly (ironically, that is usually not given when there is too much traffic and that's when you would need it the most...).
The trick is not to allow pilots to choose their speedI can imagine! Add to that annoying pilots who want to fly different speeds all the time -)Probably for the same reason, sequencing arrivals is on of the most difficult things to learn for trainee controllers. You really need to grow experience on what speeds and levels are 'right' and what is too fast/slow, too high/low...
I have to say that in Belgium, ATCO's are quite well trained for efficient vectoring.
The trick is not to allow pilots to choose their speed
I cannot speak about modern planes, but from a programmer's point of view it would be a lot easier. I have over and again insisted that, in the 21st century, magnetic information should be used only in extreme cases - after all, who uses a compass, today? Using only "true" headings would, for one example, get us rid of the changing of runway ID's every so many years. And true headings are not that difficult to calculate with trigoniometric difference calculations between (gps-derived) coordinates. Adjusting for magvar* adds a lot of complexity, since magvar changes both with location and with time. There are solutions to that, but the problem shouldn't exist.Could a modern aircraft fly a track, just as easily?
I'd say 60 nm if you get the ARVOL-BUN shortcut and can intercept at 10nm. Probably around 80 to 90 nm if you have to follow the STAR and intercept at around 20 nm.How many track miles from the boundary to the ILS25L for a usual approach into BRU?
I guess you're talking about the 737NG? Surprised to hear that an autopilot track selection does not exist on that plane, it's not as if the design predates GPS... I suppose the MAX - if we see it in the air again - has the feature as well? Any idea about other types?On the 737 you can only select a heading on the autopilot, you would need to adapt the heading by yourself to continue on the requested track. But for modern planes () like the 787, you can switch that autopilot mode between heading and track easily.
Well, if you have spend tremendous time and effort in repainting runways, and updating AIPs and FMS's, just because magvar changed by 1 degree and the magnetic runway direction is now 014 iso 015, then I think you have a very valid point! Magnetic is a relict, everything true please!Here in Western Europe, magvar is negligible, making the point rather moot