I trust that SNS3Guppy and his/her 747 spend most of their time during their initial climb in IFR within CAS? Am I wrong?
lucaberta, Yes, but my concern was this quote:
As a function of our IFR clearance, and our operations specifications issued to us by the government agency that oversees our operation...which includes operation in uncontrolled airspace. We don't ask what type of airspace we're in during a flight under IFR. We don't particularly care if it's class A, B, C, D, E, G, etc.
If you're asking about the permission for making a high speed climb, the requirement for 250 knots below 10,000, where applicable, applies only if the minimum safe speed of the aircraft is below 250 knots. We don't need permission. We "ask" as a courtesy, for a high speed climb, but also often simply inform ATC about our climb speed. ATC expects it. The one exception will be times when a departure procedure may require a slower speed and a configuration change may be delayed because until those requirements are met, the SID or DP establishes the speed. At that point, our primary concern is meeting climb gradients and crossing restrictions.
An IFR clearance should normally keep an aircraft inside CAS. If a pilot is unable to comply with the clearance or SID for any reason, ATC would need to be informed.
My concern is that from what was written earlier, in some cases this apparently may not happen due to the lack of performance of a heavily laden aircraft. Pilots were warned that aircraft flying in Class G, and not in contact with the same ATC unit should be aware that they may suddenly be confronted with a "heavy" leaving CAS at 300kts below 10,000ft. The UK ANO specifically forbids this. SNS3Guppy seemed to be unaware of this UK rule. If he doesn't operate in UK (but I think he possibly does, after all the thread was opened by a UK poster) then I don't give two hoots.