Why the 250kt speed limit below 10,000ft?

Yes, got it for safety reasons (eg turbulence, performance). Not relevant anymore for me in the „light twin“ I fly.

JasonC wrote:

Strictly not possible in USA as controllers can’t authorise a breach of the FARs

It is (or was) possible in the USA: in the Houston class B, an experimental “no speed limit” departure was put into place (it was NOTAMed for years, and what you’d hear from ATC would be “Airliner 1234 [clearance] no speed limit”, and from then on the aircraft could exceed 250kts. It was only on departure, and I believe the practise has now been ended so the 250kt limit is back.

The speed limit is always indicated, so it can be all over. Head/tailwind is the same for everybody in the same sector, so ATC can manage it.
When the traffic is light, we often hear “free speed” on the radio for flights approaching EKCH. The correct read-back includes “thank you” generally.

Snoopy wrote:

Often had clean speed of 280. No problem, even in usa. Only ones not so happy were germans because of class E shared with some vfr traffic. I think TMZ/RMZ post SERA took care of that.

In classes D, E, F and G the 250 kt speed limit for IFR below FL100 is mandated by SERA and can’t be lifted by ATC. TMZ/RMZ doesn’t matter. A competent authority can lift the speed limit for specific aircraft types if it is necessary for technical or safety reasons.

In classes A, B and C, there is no speed limit for IFR in SERA, but there are frequently airspace speed limits and these can be lifted by ATC.

(The same goes for VFR, except that the 250 kt “unliftable” SERA speed limit also applies in class C.)

Thanks

alioth wrote:

It is (or was) possible in the USA: in the Houston class B, an experimental “no speed limit” departure was put into place (it was NOTAMed for years, and what you’d hear from ATC would be “Airliner 1234 [clearance] no speed limit”, and from then on the aircraft could exceed 250kts. It was only on departure, and I believe the practise has now been ended so the 250kt limit is back.

It was never legal but was done a lot. The rule was clarified and ATC told to stop doing it.

Peter wrote:

What would be the explanation for my post above which is UK airspace?

Class A. No speed limit.

Peter wrote:

The 250kt speed limit below 10000ft does not apply in Class A?

No. VFR it applies in C-G, IFR D-G.