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 ?

if this few extra knots enable you to use a lower flap setting (less fuel burn, less noise) for a considerable amount of time why not ask (ATC workload permitting)?

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).

Could well be the difference between being at GearDown and Flaps > 20 vs F15

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.

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.

Yes, that does seem a tad unfair, especially as the controllers can see everyone's IAS nowadays.

Having said that, the thread is about an operator who wants to slow down late rather than early.

Well, they can see what IAS you've got selected...

Actually I think the only selected (as opposed to indicated) data that is displayed to the controller is altitude.

Try this in an empty B757 with min fuel (VREF 108) - it's doable but needs planning and you need to tell the controller of the final V APP so that he can slow the following aircraft.

No, they can see what IAS you are achieving.

At 4 DME ATC can monitor not only your actual IAS but also what you have selected in your MCP speed window. Bi-annully ATC publish the statistics for who is complying and who is not. Interesting reading.

More likely answer is being Hong Kong based they are used to it. HongKong ILS 25 L/R requires 180kt from 15DME to 7 DME and then 160-150kt at 4DME.

Unless that's a relatively recent addition, I don't think you're correct. Which BDS are you getting selected speed from ?

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:

• 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

Indeed.

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.