ATPL · Extra · Operational Procedures Atpl Ground Training… lesson — Page 130, Lesson 205

I want to walk you through the next part of the transatlantic crossing planning — the allocation of flight levels within the MNPSA, and then how domestic and random routes fit into the picture. Let’s start with the allocation of flight levels. The Track Message, or TM, for a given route specifies which flight levels are available. In theory, all the RVSM flight levels — that’s Reduced Vertical Separation Minimum, so flight levels 290 through 410 inclusive — should be available for allocation. But in practice, that’s not always the case. For the more popular routes, more flight levels are usually available than for the less popular ones. Generally speaking, flight levels 290 and 300 are too low for normal traffic, and flight levels 400 and 410 are just a touch too high for efficient operation. There’s also an important operational objective here: freeing up RVSM flight levels for non-OTS traffic. That means traffic that is not using the Organised Track Structure. This is in keeping with the goal of making as much airspace available for non-NAT Track traffic as possible, and it also offers flexibility for random routes — routes that are not part of the published OTS. Let me give you a concrete example from the excerpt. For the westbound OTS track labelled A, the allocation of flight levels was as follows: EAST LVLS NIL; WEST LVLS 310 320 330 340 350 360 390. So eastbound levels were nil — none allocated — and westbound levels were 310, 320, 330, 340, 350, 360, and 390. The inclusion of EAST LVLS NIL implies that for the period of the OTS, all traffic going in the opposite direction along this route would be random route traffic. In fact, it is unlikely that contra-direction traffic — traffic going the opposite way — would be accepted into the OTS now because of RVSM. Before the introduction of RVSM, at least one level was always reserved for contra-direction traffic. That’s no longer the case. Now let’s move to domestic routes. The Track Message also includes details of specific routing from domestic airspace to the entry point for the route, and also from the exit point back into domestic airspace. This allows domestic airspace managers to ‘flow manage’ transatlantic traffic into the domestic airways or high-level route system within the receiving Flight Information Region, or FIR. For route A, the TM included: EUR RTS WEST NIL; NAR N464B N466B N468B N472B N474B. That means there are no specified European routes to the start point — EUR RTS WEST NIL — and from CIMAT, the North American routings, abbreviated NAR, are N464B, N466B, N468B, N472B, and N474B. Finally, let’s talk about random routes. The use of the OTS is not mandatory. Operators may plan to use any other route, and such routes are called random routes. Examples of a random route could be: the reciprocal of an OTS track — that is, flying the same line but in the opposite direction; a track that follows part of an OTS track; a route that crosses 30 degrees west outside of the relevant OTS; a track that is completely outside of the OTS; or a track that crosses one or more OTS tracks. In any event, operators are required to consider the implications of planning such routes, and the Oceanic Area Control Centres, or OACCs, will apply whatever restrictions are necessary to random routes in order to protect the OTS traffic. The use of the unrestricted flight levels — those not included in the Track Message for each route — would be appropriate for random routes. If an operator wishes to plan a route that uses part of the OTS, then the outside routes — meaning the most northerly or most southerly — should be planned to be used for the part of the OTS to be flown.