View Full Version : Speeds (IAS) on Descent

13th Nov 2003, 14:07

Looking for a source document/feedback on the following:

Aircraft is tracking via a STAR. The STAR has a speed restriction of NA250IAS below A100.

ATC instruct pilot to descend at 280KTS.

Q1. Does this mean that a/c will descend at 280 until approaching A100 then reduce to 250/A100 or remain at 280KTS below A100?

Q2. If instructed to descend at 230KT could the pilot increase to NA 250KT once below A100?

Overall - How do you interpret the speed assignment vs. airspace/procedure requirements for your operations??

Just interested.


13th Nov 2003, 15:49
When in doubt just ask ATC....


Night Watch
13th Nov 2003, 16:00
The speed restriction on the STAR remains until ATC cancels it. If they want you to maintain 280kts on decent they would say "Descend not above 280kts, cancel speed restriction on the STAR"

If not cleared via a STAR ATC will say "cancel speed restrictions above and below 10000' "

If given a speed restriction of 230kts, it then become limiting. Therefore you can't increase to 250kts.

hope that answers your Question.

16th Nov 2003, 17:55
AIP ENR 12.3.6 and 12.3.7 (http://www.airservicesaustralia.com/pilotcentre/aip/aip/enr/153948.pdf) is your answer.


"ABC, cleared JENNA 3 arrival (http://www.airservicesaustralia.com/pilotcentre/aip/dap/PPHSR01-094.PDF) , ASPIC transition, Runway 21, instrument procedure, descend F210..." and

(a) nothing else!

(b) "not above 270 knots"

(c) "not above 230 knots"

(d) "best speed, cancel STAR speed restrictions above and below A100"

You then:

(a) descend at your SOP speed, reducing to 250KIAS by A100

(b) fly no faster than 270 knots above A100, reducing to 250 knots by A100

(c) descend at 230 knots, above and below A100. Don't increase speed -- you have been issued a speed limit! (just like Night Watch said).

(d) fly as fast as you like above and below A100 (within aircraft limitations:ok:

How do you interpret the speed assignment vs. airspace/procedure requirements for your operations??

First -- ATC don't go issuing speed restrictions for no reason (exception: Darwin ATC :hmm: ). You are being sequenced for the runway.

So if a speed restriction is issued, although it is possible to be slower, best to stick to the speed you were given (reducing to 250 as applicable).

If you are number 3 in a sequence of 5, you are not being very helpful if you were asked to fly the STAR at 240kts and you reduce to 220 kts fifty miles out. The poor controller will see lovely separation between you and the fellow in front of you, but will be tearing his hair out trying to further slow down/add track miles for the two behind you.

Likewise, its not all that smart to maintain 300kts to the field if it busts airframe limitations, bounces the pax around like flies in a bottle, or has you configuring late, fast and high and going around.

ATC speed instructions are subordinate to flight manual limitations/pax comfort/weather considerations/pilot judgment. Just remember to let them know if you can't give them what they ask for.:)

17th Nov 2003, 04:37
The answer to Q1 may depend on the country in which you are flying. In the US, ATC cannot clear or require a pilot to go >250 KIAS below 10,000' MSL (FAR 91.117.a). ATC is not "the Administrator" in this context -- such waivers must be by formal Letter of Agreement or Waiver, such as those that apply to published Military Training Routes.

This contrasts with FAR 91.117.b, where "ATC" may authorize a speed above 200 KIAS within Class C or D airspace.

17th Nov 2003, 07:49
In the UK all STAR and SID charts in relation to speed restrictions state "unless otherwise advised by ATC". If you have been given speed 280kts then you have been otherwise advised, most ATCO's where I work always say "speed ***kts until advised".

Agree with FlyinWithoutWings though, IF IN DOUBT ASK ATC as often the safety (ie separation) is going to be compromised if you do not fully comply, which only leads to more nasty forms through the postal system.