Origin of the 250 knots below 10,000 ft rule
The 250 knot max speed below 10,000 ft has been around for a long time. From where did this rule originate? And what started it?
Is it because of collision risk (birds or other aircraft) minimisation? Or is it to standardise speeds below 10,000 ft purely for ATC purposes.
In Australian airspace, it is common practice for pilots of jets to request "high speed " climb below 10,000 ft - meaning they are happy to ignore the 250 knot tradition. It is just as common for ATC to request inbound aircraft to "cancel restriction" below 10,000 ft in order to facilitate flow control, and usually crews are happy to oblige.
While ATC might find it aids their task by encouraging high speed below 10,000 ft, it begs the question that if ICAO specified 250 knots below 10,000 ft for safety reasons, then why should this rule be broken so frequently in Australia by mutual agreement between pilots and ATC? Complacency on the part of both parties, perhaps?