New Queries with embedded answers
Question:
On departure from RWY 25L, OCEAN 2B, on initial call to departure prior to PRAWN we were given the clearance: “Climb unrestricted to 9000”.
What is the intended meaning of “unrestricted"?[
Ref is to FMC Database Coding. There are no altitude limits in the OCEAN 2B SID, other than TROUT at or above FL140.
You are correct, the OCEAN 2B SID only has TROUT FL 140 as a requirement, but FMC Database coding is the “restricted” that ATC are cancelling. For your reference, Hong Kong’s FMC coding is published in AIC03-10. I do not speak for others but the manager of HK Arrivals and Departures is presently tidying this issue up and his intention is to have all the FMC Database requirements unambiguously published on the SID charts. [As are the STAR charts which were consolidated, simplified and updated on 22 August 2013].
Along the same line…
On arrival when given an altitude crossing restriction ("cross SONNY at FL260") by a controller, then switched to a second controller and issued a lower cleared level ("descend to FL200") prior to reaching the previous fix(SONNY), is the crossing restriction cancelled, or does it still apply? The FL260 requirement still applies because it was not specifically cancelled by ATC. It would be the case where the new controller using “unrestricted” would be clearly canceling the crossing restriction("descend unrestricted to FL200"), but without the use of “unrestricted” is the crossing restriction (SONNY at FL260) still a requirement? Yes, as it is a published restriction (HK AIP ENR 1.10.5) it always applies unless specifically cancelled by ATC.
Hong Kong AIC40-12 is the reference. Part 4 dictates that the requirements at CYBER, SONNY and MAPLE always apply unless specifically cancelled by ATC. HK AIP ENR 1.10.5 notes 3, 4 & 5 is the authority.
From personal observation: ATC usually does not cancel published restrictions unless there is a pressing need and enough lead-in time for the derestriction to become effective. Aircrew often sound surprised when they query a restriction and ATC immediately replies, “Cancel the XXXXX level/speed restriction.”. When not cancelling restrictions, ATC is neither showing indifference or bloody-mindedness but, it is usually, because ATC has weighed up the workload benefit. Their reasoning is that, if there is not enough lead-in time for the derestriction to come into effect and if cancelling incurs added workload for little discernable result, then it is effectively a futile exercise. [This is why it is so important that authorities design TTRs, SIDs, STARs and IAPs that fit seamlessly. Otherwise, operational personnel (both ATC & aircrew) are constantly having to challenge each other because of the designed discontinuities or ambiguities].
Last edited by psychohk; 1st Mar 2014 at 14:35.