JMC 250Kts Below FL100
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HalesandPace - Have to disagree with you there. 250 kts below 10,000' is more fuel efficient, especially if ATC bring you below your ideal profile. On the B737 if you set the cost index to zero to get the best possible range, what you get is a 250kt climb and descent. On the DC-9 we used to use a 250kt descent ALL THE WAY for fuel economy - now that really did cause an ATC log jam!
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While I'm all for maintaining high speed when offered there are times within my operations when during the shorter sectors ie 30 minutes the ladies down the back still havent finished the service and I would rather bring the speed back than hammer in to gain 2-3 minutes in the sector time !!!
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Countrybusdriver
Hear, Hear and it also gives the PA28 driver more time to see and avoid you.
I've flown (legally) in the LA basin where traffic is "integrated" and sypmpathised with the jet drivers trying to pick my Arrow out amongst the clutter, whereas a 767 does tend to get my attention pretty quickly!
Hear, Hear and it also gives the PA28 driver more time to see and avoid you.
I've flown (legally) in the LA basin where traffic is "integrated" and sypmpathised with the jet drivers trying to pick my Arrow out amongst the clutter, whereas a 767 does tend to get my attention pretty quickly!
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Higher speed descents do NOT save fuel - see Boeing general information for an explanation of this.
I am at a loss to understand how operators in the USA are any different to Europe, given the general rule of max 250 kts below 10,000 ft.
IMHO, increasing speed below 10,000 ft has little effect to regain profile if you are high. Increasing speed at "high levels" will bring you back on the profile because the TAS is higher and an increase in speed results in a lot more drag. (I seem to remember that if you want a steeper angle of descent then you need a lower Lift/Drag ratio!).
If you are below 10,000 ft or so and high on profile then, if anything, you need to start slowing up and getting some drag out!! (Flaps, Gear, Doors, Buckets - whatever you have got). Failing this then you can always enter the hold or do an orbit.
In the real world we have to strike a balance between a number of different factors, SOPs, weather, pilot experience, traffic, terrain etc. etc.
What worries me is when other pilots try to dictate how others should "fly" their aircraft. With safety in mind then the operation has to be based around the lowest common denominator - this may be "unpopular" at times but I would rather be unpopular than filing an MOR or crashing into the side of a mountain!
Finally, I seem to recall that high speed was a factor when Danair crashed at Tenerife many years ago. High speeds mean a bigger radius of turn when ATC comes up with a last minute instruction and, yes, I know they shouldn't but they do! That's what flying is all about!
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I am at a loss to understand how operators in the USA are any different to Europe, given the general rule of max 250 kts below 10,000 ft.
IMHO, increasing speed below 10,000 ft has little effect to regain profile if you are high. Increasing speed at "high levels" will bring you back on the profile because the TAS is higher and an increase in speed results in a lot more drag. (I seem to remember that if you want a steeper angle of descent then you need a lower Lift/Drag ratio!).
If you are below 10,000 ft or so and high on profile then, if anything, you need to start slowing up and getting some drag out!! (Flaps, Gear, Doors, Buckets - whatever you have got). Failing this then you can always enter the hold or do an orbit.
In the real world we have to strike a balance between a number of different factors, SOPs, weather, pilot experience, traffic, terrain etc. etc.
What worries me is when other pilots try to dictate how others should "fly" their aircraft. With safety in mind then the operation has to be based around the lowest common denominator - this may be "unpopular" at times but I would rather be unpopular than filing an MOR or crashing into the side of a mountain!
Finally, I seem to recall that high speed was a factor when Danair crashed at Tenerife many years ago. High speeds mean a bigger radius of turn when ATC comes up with a last minute instruction and, yes, I know they shouldn't but they do! That's what flying is all about!
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Hung Start. Thank you - your comments are very much appreciated and I guess I'm mainly talking about early morning and sometimes during early afternoon when it's quiet.. I gave a Speedbird a visual approach a few days ago "Wish it was like this all the time" he said. How I agree!!
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Bono Vox,
Leaving the original cruise level is not the problem.
It is when you are at FL180 flying over London (as directed by ATC) and you get given a left base for 26 at LTN.
I have never been to EGAA but I bet it is a bit different to going into London TMA airports.
LGW & LHR arn't nearly as much of a problem as you are far more "controlled".
As for the rest of your comments, well they are not very mature so I won't bother commenting!
Leaving the original cruise level is not the problem.
It is when you are at FL180 flying over London (as directed by ATC) and you get given a left base for 26 at LTN.
I have never been to EGAA but I bet it is a bit different to going into London TMA airports.
LGW & LHR arn't nearly as much of a problem as you are far more "controlled".
As for the rest of your comments, well they are not very mature so I won't bother commenting!
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Fireflybob,
You say
"IMHO, increasing speed below 10,000 ft has little effect to regain profile if you are high. Increasing speed at "high levels" will bring you back on the profile because the TAS is higher and an increase in speed results in a lot more drag. (I seem to remember that if you want a steeper angle of descent then you need a lower Lift/Drag ratio!)."
Think about TAS/EAS and limiting mach numbers. At higher levels EAS/mach is definitely limiting. Think of it all as number of molecules of air passing over your surfaces per unit time. Higher speeds at lower levels increases drag significantly more than at higher levels. Otherwise we would all cruise round at high speed/low level to save fuel (since ,in the cruise, thrust only has to overcome drag). Now there's an idea
You say
"IMHO, increasing speed below 10,000 ft has little effect to regain profile if you are high. Increasing speed at "high levels" will bring you back on the profile because the TAS is higher and an increase in speed results in a lot more drag. (I seem to remember that if you want a steeper angle of descent then you need a lower Lift/Drag ratio!)."
Think about TAS/EAS and limiting mach numbers. At higher levels EAS/mach is definitely limiting. Think of it all as number of molecules of air passing over your surfaces per unit time. Higher speeds at lower levels increases drag significantly more than at higher levels. Otherwise we would all cruise round at high speed/low level to save fuel (since ,in the cruise, thrust only has to overcome drag). Now there's an idea
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Beardy, thanks for your contribution!
I would admit that I am not 100% sure about the theory but I do know that angle of descent depends on the lift/drag ratio!
Perhaps some aerodynamics boffin out there could let us know!
I will go away and think about it but it probably depends on the exact numbers!
Essentially my point is that there is not much point getting back on the profile by increasing speed at the lower levels if you are going real fast at the bottom because you may then end up with an unstabilised approach which defeats the whole object of the exercise.
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I would admit that I am not 100% sure about the theory but I do know that angle of descent depends on the lift/drag ratio!
Perhaps some aerodynamics boffin out there could let us know!
I will go away and think about it but it probably depends on the exact numbers!
Essentially my point is that there is not much point getting back on the profile by increasing speed at the lower levels if you are going real fast at the bottom because you may then end up with an unstabilised approach which defeats the whole object of the exercise.
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Beardy you beat me to it! Your responce to Fireflybob is correct, form drag is in relation to speed and high speed at low level has much more effect than at altitude due to relative air density. With regard to the policy that some have of trying to slow down early when above the profile in order to get the gear/flaps out to help recover the plot this technique simply does not work best. It might make you feel better to have low speed but in terms of losing energy from the system the most efficient method is to maintain high speed with full speedbrake and go down first ( high speed, full speedbrake, dense air = lots of drag ) then slow down second. Have a think also about the go-around situation. If you really are too hot and high and have to give it away, which would you rather, a go-around from low airspeed with high rate of descent or one from level flight with high speed. Answers on a post card! As a further thought on this, using the low speed technique how do you know if you are going to be stabilised in time by 500’ AAL? Its very difficult. However using the high speed method its simple. You descend through the profile ( below the glide ) level off with idle power and let the speed decay if you intercept the profile again before the speed is back you need to make another plan!
To sum this all up imposing a rigid ‘250 below 10’ SOP does not make things easier for the pilot. Quite the reverse it removes a useful tool which can help us efficiently manage our descent profile. It is like banning the use of speedbrake to make our lives more difficult. Thus the argument re. training/low experience does not hold up. Indeed most JMC Trainers wish to see a change to this SOP. For those who quote the USA at us, those who have operated large aircraft both there and in Europe will know that ATC environment is very different with fare less segregation of fast/slow traffic in the US hence a blanket ban on high speed makes more sence.
To sum this all up imposing a rigid ‘250 below 10’ SOP does not make things easier for the pilot. Quite the reverse it removes a useful tool which can help us efficiently manage our descent profile. It is like banning the use of speedbrake to make our lives more difficult. Thus the argument re. training/low experience does not hold up. Indeed most JMC Trainers wish to see a change to this SOP. For those who quote the USA at us, those who have operated large aircraft both there and in Europe will know that ATC environment is very different with fare less segregation of fast/slow traffic in the US hence a blanket ban on high speed makes more sence.
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There is, as they say, more than one way of "skinning a cat".
I am not advocating that one should never exceed 250 kts below 10,000 ft. There are occasions when this is quite appropriate.
Remember that angle of descent depends on the lift/drag ratio (and not just the drag). If you increase speed then lift AND drag will increase - what happens to the lift/drag ratio is somewhat debatable although, I agree, application of speedbrake will change this.
Perhaps we have drifted a little off the topic of this thread but nevertheless it's an interesting discussion.
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I am not advocating that one should never exceed 250 kts below 10,000 ft. There are occasions when this is quite appropriate.
Remember that angle of descent depends on the lift/drag ratio (and not just the drag). If you increase speed then lift AND drag will increase - what happens to the lift/drag ratio is somewhat debatable although, I agree, application of speedbrake will change this.
Perhaps we have drifted a little off the topic of this thread but nevertheless it's an interesting discussion.
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mcrit
I don't like keeping the speed on <10 if high,though I guess it depends how high.You have to slow down sometime and I think 10K is a reasonable place to do so.If you have to go-around at high speed and clean you really have misjudged it!
You have lots more options at slower speed and I think its easier to judge if you're already configured.Also fast you'll be catching the guy ahead at 100+ kts which will impress the controllers.
Slowing up calms it all down and I think that helps the situation.I've seen a high speed approach turn to ratpoo because of a small problem which I don't think would have had the same effect if we had been slower.
Throw in birds/light ac/GPWS/low experience levels/manoeuvrability etc and my minds made up. 230kts/Gear + Speedbrake works 'till the controller decides to vector you for 20 more miles just in case.
Fireflybob
250 kts we're on about- not km/hr.hehe!
I don't like keeping the speed on <10 if high,though I guess it depends how high.You have to slow down sometime and I think 10K is a reasonable place to do so.If you have to go-around at high speed and clean you really have misjudged it!
You have lots more options at slower speed and I think its easier to judge if you're already configured.Also fast you'll be catching the guy ahead at 100+ kts which will impress the controllers.
Slowing up calms it all down and I think that helps the situation.I've seen a high speed approach turn to ratpoo because of a small problem which I don't think would have had the same effect if we had been slower.
Throw in birds/light ac/GPWS/low experience levels/manoeuvrability etc and my minds made up. 230kts/Gear + Speedbrake works 'till the controller decides to vector you for 20 more miles just in case.
Fireflybob
250 kts we're on about- not km/hr.hehe!
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Flanker
I think that you may be missing the point a tad. I'm not talking about high speed for the hell of it rather as a way to correct a profile with too much energy in it. If your app. was 'ratpoo' with high speed and speedbrake then it would have been even worse at low speed. That is FACT, its phisics.
I think that you may be missing the point a tad. I'm not talking about high speed for the hell of it rather as a way to correct a profile with too much energy in it. If your app. was 'ratpoo' with high speed and speedbrake then it would have been even worse at low speed. That is FACT, its phisics.
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mcrit
Bit patronising there I thought.If you read the first line of my post it says if high which I think means too much energy.
The approach was already ratpoo but a minor problem made it worse.
I got an A in physics but don't have a clue what you mean!
Bit patronising there I thought.If you read the first line of my post it says if high which I think means too much energy.
The approach was already ratpoo but a minor problem made it worse.
I got an A in physics but don't have a clue what you mean!
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Well Flanker I apologise I did not intend to be patronising.
My point is this: If you are passing say 12,000 ft and are for example 4000 ft above profile the best chance you have of a normal, on speed, on G/S approach ( ie unhurried and safe ) is to maintain high speed say 300 Kts with speedbrake until you are BELOW profile and level and then slow down still with the speedbrake ( which of course becomes less and less effective as you slow down ). I would not advocate high speed on the glide or even planing to maintain high speed during the app. But I will say again it is a useful tool when required. And leads to a far more ‘normal’ approach in the end. When training new FO’s its those who end up with a very high rate of descent at a late stage of the approach who get into the most difficulties. Often as a result of getting high on the profile then slowing to 250 below 10 then slowing further to try and get all the flap out then with idle power, full flap, 4 whites and full fly down with no real idea of weather or not they are going to intersept the G/S before 500’ ( latest ). My aim in this is not to be a ‘Cowboy’ but rather to give the best chance of a stable and safe approach.
My point is this: If you are passing say 12,000 ft and are for example 4000 ft above profile the best chance you have of a normal, on speed, on G/S approach ( ie unhurried and safe ) is to maintain high speed say 300 Kts with speedbrake until you are BELOW profile and level and then slow down still with the speedbrake ( which of course becomes less and less effective as you slow down ). I would not advocate high speed on the glide or even planing to maintain high speed during the app. But I will say again it is a useful tool when required. And leads to a far more ‘normal’ approach in the end. When training new FO’s its those who end up with a very high rate of descent at a late stage of the approach who get into the most difficulties. Often as a result of getting high on the profile then slowing to 250 below 10 then slowing further to try and get all the flap out then with idle power, full flap, 4 whites and full fly down with no real idea of weather or not they are going to intersept the G/S before 500’ ( latest ). My aim in this is not to be a ‘Cowboy’ but rather to give the best chance of a stable and safe approach.
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No problem.
I think that technique works if you're a bit high, but I would slow down if very high.I think aggressively getting on profile by 10000ft is the answer if possible.In the example you gave thats quite a lot to get off,are you 757 or 320? Headwind only IMHO.
Anyway I normally prefer slowing down,certainly by 20 track miles.We have the same rule, I remember it being a bit unpopular at FLC,at least initially.
I think that technique works if you're a bit high, but I would slow down if very high.I think aggressively getting on profile by 10000ft is the answer if possible.In the example you gave thats quite a lot to get off,are you 757 or 320? Headwind only IMHO.
Anyway I normally prefer slowing down,certainly by 20 track miles.We have the same rule, I remember it being a bit unpopular at FLC,at least initially.
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MCRIT, valuable information for us ATCOs.
I see you are a 757 pilot, would the 'high speed with speedbrake' approach be as benificial on other types or is it more appropriate for 'slippy' A/C like the 757 ?
In my experience most of the big heavies (747,MD11,A340) prefer to slow down first.
I see you are a 757 pilot, would the 'high speed with speedbrake' approach be as benificial on other types or is it more appropriate for 'slippy' A/C like the 757 ?
In my experience most of the big heavies (747,MD11,A340) prefer to slow down first.