250kts below 10000ft. Kias or Groundspeed ?

[-sam-]

Hi there,

Is this speed limit measured in Kias or Ground Speed ?

Thank You

[XP1900]

kias

[Brett_Henderson]

It's KIAS..

When planes capable of going faster than 250kias are below 10,000msl ;

[-sam-]

Thank for the answers !!
I

[Nexus]

In real life, the ATC gets aircraft data that is directly derived from the airliners transponders.
Important here is that the transponder is mode- S.
This is a very advanced device which enables airliners to be "Enhanced Surveillance " (EHS) compliants.

With EHS, ATC can see vertical speed, IAS/mach speed, mag heading etc of the target aircraft.

[RitterKreuz]

Real ATC radar indicates ground speed... they frequently ask;

"Delta 123 heavy say airspeed."

if the pilot replies that he is indicating 250 but the controller sees a ground speed on his scope of say 340 he knows something is amiss.

they usually ask your speed when they are going to assign you a speed restriction for example: "Delta 123 cross FORUM intersection at 210 knots or slower." you might cross it indicating 210 even though his scope says 230 or 190 etc. Controllers usually factor this in with their speed assignments and assessments.

generally when you pass 10,000 feet its normal to set the pointer right on 250 knots. if you bump over it by 10 knots who cares - just power back a hair or so.