Yup, that is indeed the basic general rule you have quoted, but also read:

 

http://www.alantyson.../aics/4Y138.PDF

 

Where you will notice that the 250 knot speed limit is dependant largely on the need to see and avoid, i.e. in large part pertaining to VFR flight safety, and therefore also pertaining to flights not directly under ATC control for the purpose of either speeds, headings, altitudes or collision avoidance. Thus in certain sections of controlled airspace, and when under ATC control or for other reasons specified in that NATS circular, the 250 knot limit can indeed be overruled.

 

For an obvious example, the BAC Concorde would have not been able to even take off if that rule did not have exceptions which could be granted, and as we know, the Concorde certainly did take off. but even with less speedy jet airliners, they all pretty much climb more effectively at over 250 knots, which is another reason why the rule can also often get waived.

 

Al

 

Are you saying that your ATC over there gives out a general 'no speed restriction' release without reference to any particular fix? Because the only time I've ever been cleared in a general way to go faster than 250 below 10,000 in the USA was during the high speed departure trials in Houston a decade ago. When ATC tells me "no speed restriction at TXMEX" it only pertains to the published crossing speed at an intersection on a SID or STAR. It doesn't mean I can break any other speed limit. For example, if a STAR had a speed restriction of 280 at a certain fix at 12,000', the no speed restriction only means that I can go fater than 250 at that fix. It still doesn't mean I can go above Mach 1. Or if there was a published speed restriction of 210 at a fix at 8,000', the 'no speed restriction at WAKEM' only means that I can cross it at up to 250. It doesn't release me to cross it at 300 knots at 8,000'.

 

Now, it I was flying a 747 at a weight whose minimum clean speed was 260, then I can go at 260 even if I was below 10,000' and ATC understands this and this is pretty normal and happens all the time. But to release planes to go faster than 250 below 10,000 for no reason is just not done in the USA. And it is not how the 'no speed restriction' phrase is used here.

Nah, all I was saying was that ATC can tell you 'no speed restriction', and that the 250 knots rule has exceptions. It does generally mean stuff such as 'you can go faster than the 185 knots indicated on the chart for the approach you are flying' when you here it on an approach frequency, but I was also pointing out that ATC can also allow an aircraft to blow past the 250 knot limit on a climb, and do indeed do that sometimes.

 

I hardly think that anyone is likely to interpret it as: 'Goose, it's time to buzz the tower at 500 knots' when they are on a descent to an approach or something. Although again there are exceptions, so on occasion that too can happen, since everyone has of course seen plenty or warplanes at airshows doing 400-500 knots at low level, and I have in fact been passed by RAF aircraft doing pretty near those kind of high speeds at low level on occasion when they were practicing combat flying.

 

Al

Are you saying that your ATC over there gives out a general 'no speed restriction' release without reference to any particular fix?

 

The answer is in the UK is yes.

 

The Detling/Dover SID I gave as an example is flown in Class A airspace to which the general rule 250kts/10000ft doesn't apply. However that rule is applied by a note on the SID. If ATC choooses it can simply say "No speed restrictions" without any reference to a fix,

The answer is in the UK is yes.

 

The Detling/Dover SID I gave as an example is flown in Class A airspace to which the general rule 250kts/10000ft doesn't apply. However that rule is applied by a note on the SID. If ATC choooses it can simply say "No speed restrictions" without any reference to a fix,

 

Ok. We had something similar in the US many years ago. They did it with the Houston Class B airspace, where on departure, they would say 'no speed restriction' and we could climb out at over 250. But that was ended after a few months and they have not done anything like that since anywhere else here. Problems they encountered were people hitting birds at speeds at which the planes were not designed to hit birds at, and people climbing out too shallow due to the high speeds and punching out into the undersides of the Class B airspace.

With regard to the OP, another thing to watch out for of course, is that some aeroplanes with retractable landing lights would have their hinge mechanism damaged at 250 knots, and it is quite common to have landing lights on below 10,000.

 

Al

Problems they encountered were people hitting birds at speeds at which the planes were not designed to hit birds at, and people climbing out too shallow due to the high speeds and punching out into the undersides of the Class B airspace.

 

If ATC removes ATC speed restrictions that doesn't absolve pilots from their responsibilties to fly at safe speeds and to stay within their assigned airspace. Pilots can stilll continue to fly at 250 kts - they are not obliged to fly any faster.