250 kts/FL100 - Help!
Guy’s,
Was hoping that someone might be able to put me out of my misery with respect to the FL100, 250kts speed limit issue. I personally think the issue is universally misunderstood by many flight crew, the confusion amplified by modern FMS systems which introduce an arbitrary 250kt speed limits into the a/c guidance @ FL100/10000’
I’ll limit my discussion to the UK to keep things simple. The ANO roughly states the following:
The 250kts speed limit does not apply to:
Flights in Class A and B airspace
IFR flights in Class C airspace (currently no class C in UK)
IFR flights in Class D airspace when authorised by an ATC unit
Test flights in accordance with specified conditions
Aircraft taking part in flying displays when authorised by the CAA
Aircraft subject to written permission granted by the CAA
Aircraft not subject to the ANO
It is quite interesting (or perhaps not!) that the ANO is quite specific with regards to class D airspace, in that it infers that ATC have the authority to set the law, as it were, with respect to speed limits. Elsewhere, except for the above cases, we have to assume that the standard 250kts limit stands below FL100.
This has resulted in, in my opinion, some ambiguous situations developing. To set a brief scene, my home airfield lies under the Daventry CTA (class A, base level 45) and below this, the aerodrome CTR begins (Class D). Commonly, on arrival under radar vectors, approaching FL100, crews will query “any speed control” to which ATC will usually respond “no ATC speed”. This has lead to me wonder on many occasions – is the controller advising that there will be no speed limit on entering the class D zone, or does (s)he mean that no specific speed is required to enable him/her to expeditiously/safely control the traffic flow (as there in no legal speed limit at FL100 on this routing)
Further to this, is my understanding correct in that a controller has no authority to authorise speed above the limit should he vector us through, say, class E airspace or outside of controlled airspace.
Finally, the grey area of departures. Most published departure plates have a speed limit stated of “250kts or less below FL100”. Is it to be assumed that this is an automatically issues ATC speed limit, as the class of airspace the departure utilises may not warrant such a speed limit. Is there any difference if you are placed under radar vector as opposed to continuing with the published departure?
I genuinely believe many of these issues are not understood fully amongst the flight deck fraternity! For those of you who (like myself) don’t have anything better do on Good Friday, it might provoke some discussion
Regards,
Cuban_8.