LHR 160 till 4dme
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Joined: Jul 2018
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From: hong Kong
LHR 160 till 4dme
Followed a B77W belonging to a Hong Kong based airline into LHR yesterday onto 27R. In the LAM hold they were asking for 165 till 5dme then 160 at 4 from the controller. This was approved. By chance, I met the crew signing in at the hotel and politely asked "why" the non-standard requests ? "Fuel saving and noise abatement tactics was the reply".
Anybody else do this ?
Anybody else do this ?
Joined: Jan 2006
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From: US
They're either at F20 or greater than F20. Maintaining 165 kts instead of 160 kts won't change the required flap setting.
The difference in fuel burn between 165 kts vs 160 kts is minimal, especially when it's for maybe 500-1000' (2-3 nm).
The difference in fuel burn between 165 kts vs 160 kts is minimal, especially when it's for maybe 500-1000' (2-3 nm).
Joined: Mar 2002
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From: UK
165 vs 160 could mean the difference between needing to lower the gear or not.
e.g. at 235T, Vref = 145. You can maintain 165 kts with F15 (Vref+20), however to decelerate further you would have to select G/D F20 and then a further stage to F25/F30 which would allow you to reduce to 160 kts. If this was required at some distance before your stabilisation point then this would be undesirable, hence the request to maintain 165 kts.
If they were lighter, e.g. at 220T landing weight, Vref = 140 and they would have been able to maintain 160 with F15.
e.g. at 235T, Vref = 145. You can maintain 165 kts with F15 (Vref+20), however to decelerate further you would have to select G/D F20 and then a further stage to F25/F30 which would allow you to reduce to 160 kts. If this was required at some distance before your stabilisation point then this would be undesirable, hence the request to maintain 165 kts.
If they were lighter, e.g. at 220T landing weight, Vref = 140 and they would have been able to maintain 160 with F15.
Joined: Jul 2006
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From: London
Generally it are the Euro Wings crews who don't maintain their assigned speed and slow down way early without telling ATC. Have done a few go-arounds being the aircraft behind them. It's a pity LHR controllers don't send the offending aircraft around but the unlucky ones behind it.
Joined: Mar 2006
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From: USA
165 vs 160 could mean the difference between needing to lower the gear or not.
e.g. at 235T, Vref = 145. You can maintain 165 kts with F15 (Vref+20), however to decelerate further you would have to select G/D F20 and then a further stage to F25/F30 which would allow you to reduce to 160 kts. If this was required at some distance before your stabilisation point then this would be undesirable, hence the request to maintain 165 kts.
If they were lighter, e.g. at 220T landing weight, Vref = 140 and they would have been able to maintain 160 with F15.
e.g. at 235T, Vref = 145. You can maintain 165 kts with F15 (Vref+20), however to decelerate further you would have to select G/D F20 and then a further stage to F25/F30 which would allow you to reduce to 160 kts. If this was required at some distance before your stabilisation point then this would be undesirable, hence the request to maintain 165 kts.
If they were lighter, e.g. at 220T landing weight, Vref = 140 and they would have been able to maintain 160 with F15.
Joined: Jan 2008
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From: Reading, UK
Generally it are the Euro Wings crews who don't maintain their assigned speed and slow down way early without telling ATC. Have done a few go-arounds being the aircraft behind them. It's a pity LHR controllers don't send the offending aircraft around but the unlucky ones behind it.
Having said that, the thread is about an operator who wants to slow down late rather than early.
Joined: Mar 2002
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From: UK
Nothing prevents you selecting it and no you don’t, but F20 has the same manoeuvring speed as F15 (i.e. Vref+20). To slow further (to 160 as in the example I gave previously) you need F25/F30 which would sound the gear warning if selected before the gear is down.
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From: USA
Got it. thanks
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From: Reading, UK
Joined: Jan 2000
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From: FL410
Many aircraft have a similar issue regarding speed control, like the 737NG, depending on weight you can maintain 160kts or a little higher may be required. As all operators are environmentalists and noise pollution specialists (citizens under flightpath) would prefer us pilots to fly with gear up until 4/5nm, then a slightly higher speed is better than the alternative option.
In regards transponder and ADS-B:
In regards transponder and ADS-B:
- ELS (Elementary or Basic Surveillance Functionality):
- Aircraft identity unique
- Altitude reporting in 25ft increments
- Transponder capability report
- Flight status (air/ground)
- SI code
- EHS (Enhanced Surveillance)
- FMS Selected Altitude
- Turn Information: Roll Angle, True Track Angle, Track Angle Rate
- Ground Speed
- Magnetic Heading
- Achieved Indicated Air Speed (IAS)/Mach (not selected/commanded)
- Barometric Climb Rate
- TCAS RA Information
Joined: Jan 2008
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From: Reading, UK
You also get Baro Pressure Setting, as part of the Selected Vertical Intention (BDS 4,0) message and TAS, as part of the Track and Turn (BDS 5,0) message.
But none of the standard EHS messages contain Selected Speed, hence my doubt re the previous poster's assertion that ATC can see that.