Fast Jet approach "Speed at your discretion"
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Fast Jet approach "Speed at your discretion"
I'm curious about "fast" jet approaches.
Given : 20-30 nm out on a straight in approach, VMC conditions, ATC says "Cleared straight in ILS or Visual, speed your discretion".
"Average" rwy (10,000 or more / dry conditons, light winds), any other "favorable" conditions.
Assume initial speed 250 kts.
What speeds / flaps / DME etc do you fly ?
Mike
(Fast approach in a C172, 100 knots
Given : 20-30 nm out on a straight in approach, VMC conditions, ATC says "Cleared straight in ILS or Visual, speed your discretion".
"Average" rwy (10,000 or more / dry conditons, light winds), any other "favorable" conditions.
Assume initial speed 250 kts.
What speeds / flaps / DME etc do you fly ?
Mike
(Fast approach in a C172, 100 knots
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mstram,
At 20nm on the glidepath would be at 6,000ft. Therefore if you have been descended to 3,000ft you could still be at 320 kts, especially in a smaller jet (737, A320). A larger aircraft (e.g. A330) has more momentum so you need to get configured earlier. My experience with the 737 and A320 is that gear down flap 15 (737) or gear down flap 2 (A320) is a pretty effective airbrake, but not on the A330 (gear down flap 2).
At 20nm on the glidepath would be at 6,000ft. Therefore if you have been descended to 3,000ft you could still be at 320 kts, especially in a smaller jet (737, A320). A larger aircraft (e.g. A330) has more momentum so you need to get configured earlier. My experience with the 737 and A320 is that gear down flap 15 (737) or gear down flap 2 (A320) is a pretty effective airbrake, but not on the A330 (gear down flap 2).
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williamsf1
>best I have seen is 247kts @ 1.7 DME, and 8000' runway.... and normal landing roll
Was that a civilian jet .. or mi jet ?
Mike
Flap 5
>Therefore if you have been descended to 3,000ft you could still be at 320 kts
Hmm, is this something *you* have experienced ? .. Where ?
AFAIK, everywhere here in North America it's 250 kt max below 10,000.
Mike
>best I have seen is 247kts @ 1.7 DME, and 8000' runway.... and normal landing roll
Was that a civilian jet .. or mi jet ?
Mike
Flap 5
>Therefore if you have been descended to 3,000ft you could still be at 320 kts
Hmm, is this something *you* have experienced ? .. Where ?
AFAIK, everywhere here in North America it's 250 kt max below 10,000.
Mike
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In general, the landing gear should be down before intercepting the glideslope (crossing the outer marker, if in a constant descent from a long ways out), followed shortly by landing flaps. That means 170 or less at the outer marker (5-7 miles from the runway) for flaps 30 in the 744. In the 744, the longest wait is the transition from flaps 1 to flaps 5, so enough time must be given for that transition.
Without rushing things, about 10 miles before the outer marker would be the time to slow dow down and configure. Yes, it CAN be done more quickly, but the rush may induce errors.
Without rushing things, about 10 miles before the outer marker would be the time to slow dow down and configure. Yes, it CAN be done more quickly, but the rush may induce errors.
Controversial, moi?
An interesting question.
When I first converted to a jet (737-100/200) a training captain gave me a couple of helpful and slightly conservative 'gates' - 300kts. or less at 30 miles, 210kts. or less at 20 miles. They served well as 'gates'.
The standard speeds used by LHR ATC are pretty good too - 180kts. to about 10 miles, 160kts. or greater to 4 miles.
These speeds are not definitive but I have never really understood the point of flying right at the limits possible when the net gain is probably less than a minute!
Also when flying to the edge of what is possible an unexpected tailwind or a slight shortening of route by ATC can cause speed reduction to achieve a stabilised approach to be difficult if not impossible.
I have to disagree with Flaps 5 that a larger aircraft takes longer to slow. Some maybe, but the 747-400 was not noticeably more difficult than lighter Boeings apart from, as mentioned above, the longer transit time from Flaps 1 to Flaps 5.
It is far more comfortable to be slow early than sitting on the edge of your seat hoping that you can lose the speed!
When I first converted to a jet (737-100/200) a training captain gave me a couple of helpful and slightly conservative 'gates' - 300kts. or less at 30 miles, 210kts. or less at 20 miles. They served well as 'gates'.
The standard speeds used by LHR ATC are pretty good too - 180kts. to about 10 miles, 160kts. or greater to 4 miles.
These speeds are not definitive but I have never really understood the point of flying right at the limits possible when the net gain is probably less than a minute!
Also when flying to the edge of what is possible an unexpected tailwind or a slight shortening of route by ATC can cause speed reduction to achieve a stabilised approach to be difficult if not impossible.
I have to disagree with Flaps 5 that a larger aircraft takes longer to slow. Some maybe, but the 747-400 was not noticeably more difficult than lighter Boeings apart from, as mentioned above, the longer transit time from Flaps 1 to Flaps 5.
It is far more comfortable to be slow early than sitting on the edge of your seat hoping that you can lose the speed!
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In the 737, provided you are ahead of the game with a good plan and no other restrictions you can sometimes do a thrust levers closed descent all the way from cruise. It requires 'managing' the energy of the airplane. If ATC leaves you high for a moment, get the speed back to 210 and as soon as you are cleared further down 'dive' it down by winding up the speed. If all works out well, as long as you are wel below the glide slope, you can comfortably start taking flaps 1 and reduce to 190 kts or so at around 10 miles from the threshold. As long as you are at flaps 5 and 180 by the time you intercept the glide things will work out well, unless you have a strong tail wind and a full passenger load. Gear down around 1600 RADALT or so (+/- 5 miles) and get the rest of the flaps out. Our company policy used to be stable at minimum 800 RADALT. Using 210 knots at 20 miles as a gate is too conservative and may adversely affect traffic flows and upset ATC. You just drag your feet then, waste fuel and upset the other guy on the flightdeck. A good gate to use is being 210 knots at no less than 12nm from touchdown and then further reducing it. Gear down at around 2000 AGL should work well, but take into consideration headwind/tailwind and traffic ahead of you to land or depart (use TCAS). There is nothing more satisfying then doing a thrust levers closed descent and approach with the power coming on just when you got all the flaps out, nice and stable around 1000 RADALT. Very efficient, fuel wise and time wise and comfortable for the pax.
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M.Mouse,
You can disagree but it is a fact that an A320 flaps 2 and gear down will slow down rapidly where as an A330 with flaps 2 gear down will not. That is a fact. It's down to momentum and doesn't require your agreement.
You can disagree but it is a fact that an A320 flaps 2 and gear down will slow down rapidly where as an A330 with flaps 2 gear down will not. That is a fact. It's down to momentum and doesn't require your agreement.
Much as I hate to admit it - the Yanks have got it spot on - 250 below 10000 is about right. Yes we all like flying more quickly - its an interesting challenge of judgement and can save almost two
minutes - wow. BUT don't forget that we have paying customers
behind the cockpit door who do not appreciate the trials and
tribulations of fast and rushed approaches - I've sat in the back
on enough positioning sectors to know the difference ! Apart from anything else you never know what is going to appear just
as you come out of the bottom end of that piece of fair weather
Cu - a sensible speed gives just that little extra time not to mention capacity which one day you might be grateful to have on your side.
This is not the same argument has keeping up speed at ATC request to say localiser capture or the marker in order to sequence traffic.
As the Werther's advert used to say - 'and now I'm the grandad !' .....................................
minutes - wow. BUT don't forget that we have paying customers
behind the cockpit door who do not appreciate the trials and
tribulations of fast and rushed approaches - I've sat in the back
on enough positioning sectors to know the difference ! Apart from anything else you never know what is going to appear just
as you come out of the bottom end of that piece of fair weather
Cu - a sensible speed gives just that little extra time not to mention capacity which one day you might be grateful to have on your side.
This is not the same argument has keeping up speed at ATC request to say localiser capture or the marker in order to sequence traffic.
As the Werther's advert used to say - 'and now I'm the grandad !' .....................................
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What about the time difference from 300+ kts at 20nm compared to 250 kts, or even 220 kts? I'd hazard a guess that the difference is about as long as it's taken me to type this reply!! And if the high speed approach doesn't work out, how long does a go around take?
With mandatory quick access recorders coming soon, gone are the days of the cowboys. If you want to fool around, do it on your own at your own expense, rather than with 450 pax in the back - or even 10 pax for that matter.
With mandatory quick access recorders coming soon, gone are the days of the cowboys. If you want to fool around, do it on your own at your own expense, rather than with 450 pax in the back - or even 10 pax for that matter.
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If one assumes that the requirement is to be 'stable' by 1000ft agl (ie landing flap and Vref+15 max with gear down), then with modern jet transport performance, then 210kts at 12nm on the g/s works well - call that Gate 1.
In level flight a modern jet (zero wind, anti ice off) decelerates at 1 kt per second.
So one could be at 320kts 110 seconds before 12nm finals as above, average g/spd = (320-210)/2 = 265 kts * 110 secs = 8.1 nm.
So, about 20nm to run at 320 kts level at 3800ft aal is about the max without using early gear or speedbrake.
By inference, 320 kts at 6000 ft aal is going to need remedial action!
As has been said elsewhere, it is nice to know the limits but it is preferable to land rather than go around, all for the sake of 5 seconds earlier on stand.
In level flight a modern jet (zero wind, anti ice off) decelerates at 1 kt per second.
So one could be at 320kts 110 seconds before 12nm finals as above, average g/spd = (320-210)/2 = 265 kts * 110 secs = 8.1 nm.
So, about 20nm to run at 320 kts level at 3800ft aal is about the max without using early gear or speedbrake.
By inference, 320 kts at 6000 ft aal is going to need remedial action!
As has been said elsewhere, it is nice to know the limits but it is preferable to land rather than go around, all for the sake of 5 seconds earlier on stand.
