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IAS tolerance in controlled airspace

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IAS tolerance in controlled airspace

Old 20th Nov 2018, 13:12
  #1 (permalink)  
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IAS tolerance in controlled airspace

Hi everybody,

nowadays i fly with a lot of guys that both in US and EU are little bit sloppy in the airspeed accurancy concept.
Many times i fly with people that let the speed slightly drift up or down and they always tell me “it's ok, is -5 +10 kts”; i don't agree with this (both if you are flight a SID/STAR with “at speed.....” constraint or if you are under radar with a speed limit issued) but i don't know where i can find this in black and white.
First......am i right? Second......any suggestion to “where to find the rule”?
Thank you all for the info

pippobaudo is offline  
Old 20th Nov 2018, 14:13
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I'd suggest you look in the great big "Get a life book"

The answers to most things related to flying are in there.
Nil further is online now  
Old 20th Nov 2018, 14:18
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even ants need some lovin'
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You know what Nil further...

Strikes me your phrase 'Get a life book' applies 100%,...... to YOU.
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Old 20th Nov 2018, 14:25
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Thread Starter
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Nil further talk to us......we should feel blessed.....
pippobaudo is offline  
Old 20th Nov 2018, 14:34
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Try going +3 knots faster when given speed control by LHR tower, your company will be informed.

Airmann is offline  
Old 20th Nov 2018, 14:56
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Originally Posted by Nil further View Post
I'd suggest you look in the great big "Get a life book"

The answers to most things related to flying are in there.
Unnecessary. If a sensible reply is beneath you, why bother replying at all ???????

As others have said; try flying at +/- 10kts or +/- 20kts on approach vectoring and finals into EGLL and tell us how you get on.

Uplinker is offline  
Old 20th Nov 2018, 15:04
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In no ATC literary reference found there is a tolerance on speed. Flexibility therefore remain dubious. However, different modes in aircraft allow for more accurate speed control by the pilot, use them appropriately when speed control is requested, update the FMC in accordance with instructions.
OP's reference to speed tolerance of +10/-5 refers the values used by e.g. 737 auto throttle when to advise DRAG REQUIRED or THRUST REQUIRED, they are not the same as ATC speed tolerances, beware not to confuse these!
With Enhanced MODE S, ATC can see your actual groundspeed and IAS, so non-conformity can easily be observed and reported. If unable to comply, just advise what you can comply with. Many times ATC is more than happy to facilitate a deviation from their required if this would for instance require a landing gear to be dropped early in order to achieve their requested speed or flaps to be extended instead by crew instead of enabling them a clean configuration.

Extracts below:

CAP 493 Refers in SECTION 1: CHAPTER 13 Speed Control
1.1 Controllers may request pilots to increase/decrease speed in order to facilitate a safe and orderly flow of traffic. Speed adjustments should be limited to those necessary to establish and/or maintain a desired separation/deconfliction minima or spacing and should not be outside the speed ranges laid down in MATS Part 2. Pilots shall be advised when a speed control restriction is no longer required.
1.3 At levels at or above FL280, speed adjustments for aircraft in the cruise should be expressed in multiples of 0.01 Mach. At levels below FL280, speed adjustments should be expressed in multiples of 10 kt based on indicated airspeed (IAS).
1.5 Pilots will adhere to the speed (IAS or Mach Number) approved or assigned by ATC and will request ATC approval before making any changes thereto. Pilots of aircraft unable to maintain the approved or assigned speed (e.g. for aircraft performance reasons) will inform ATC as soon as possible. In such circumstances, controllers shall apply an alternative method to establish or maintain the desired separation/ deconfliction minima or spacing between the aircraft concerned.
2.1 For aircraft at or above FL280 that have been cleared to descend to levels below FL280, speed adjustments may be based on IAS. However, controllers should be aware that pilots might not be able to immediately change to IAS, as the timing of this change is dependent on variable aircraft system factors.
2.4 Controllers should endeavour to permit aircraft to operate in a clean configuration for as long as circumstances permit. Arriving aircraft below FL150 should not be allocated a speed of less than 210 kt (200 kt for propeller aircraft) unless within 20 track miles of the runway threshold,...
2.5 Speed control should not be applied to aircraft after passing a point 4 NM from the threshold on final approach.
4.1 Speed control phraseology is listed within CAP 413. Additional information and guidance on speed terminology, relationships, and speed control techniques, is at Appendix F.

APPENDIX F - Speed Control Guidance refers in more detail to explain what speeds are commonly used and how they relate...
Skyjob is offline  
Old 20th Nov 2018, 16:11
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Thank you very much!
pippobaudo is offline  
Old 20th Nov 2018, 17:06
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Only half a speed-brake
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The text pages for AMS used to have a state-issued table with the limits published. Nothing in there what has not been covered above.
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Old 21st Nov 2018, 16:46
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Just back from a bit of flying, good to be in the armchair again.
The answer is as always : It depends!
Into a Spanish destination , with a 3.2 degree glide and some tailwind ,I was given some flak by ATC with regards to my speed reduction some 18 miles out fully established. ( From 220 to180kts). At which I promptly replied: " Doing my best,Sir , You should join me on the jumpseat one day, You might learn something, Sir."
He responded : " Love to, Tower now, have a good day, Sir!!"
Never been to LHR, never going, but if You cant figure out your energy management after 10 minutes in the hold , ask for another 10!
Done Gatwick and they sure take no prisoners, the rest of the UK is rather flexible.
Did Orly long time ago and you for sure want to be stable on speed there as 2.5 miles is all they gave us.
Need to get that book, what was it again,,,

Cpt B
BluSdUp is offline  
Old 21st Nov 2018, 17:24
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I fly the assigned speed unless I really need to do something else. If the speed I need is more than 5kt off, I'll talk to ATC. It's rare in the US to hear ATC say they need the EXACT speed assigned.
Check Airman is offline  
Old 22nd Nov 2018, 02:22
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Surely you select the assigned speed and if the autopilot drifts a few knots fast or slow it doesn’t matter? If you can’t select the speed due to performance limitations you tell them. If you purposefully select a speed at the edge of some supposed “buffer” then you deserve to be pulled up for it.
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Old 22nd Nov 2018, 08:37
  #13 (permalink)  
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Visited NATS in Swanwick last month and they said the biggest thing they would like crews to see is accurate speed control promptly complied with when requested- it greatly helps them out. During approach into Gatwick director likes to see a decel rate of 1 knot/sec from when given 180- 160 until 4.
Lew747 is offline  
Old 22nd Nov 2018, 10:28
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Surely its a bit like asking whats the tolerance on the heading given to me by ATC... there isnt one, but your deviation may get noticed.
hoss183 is offline  

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