Aviation In Canada

Wednesday, September 28, 2005

Pre-Taxi Clearances

There is a move afoot in the Moncton FIR to reintroduce "Pre-taxi clearances" at uncontrolled airports. Here is a little background.

At many towered airports, certainly the larger ones, the towers will issue "canned" clearances to IFR aircraft. They're normally based on SIDs that are published for the field, include the aircraft's flight plan route if at least the initial segments of that are acceptable (meaning don't penetrate restricted areas, have proper, valid airways/fixes within the originating FIR, and so forth), and a transponder code. The idea from the ATC side of things is to reduce coordination between the IFR unit, which is responsible for issuing IFR clearances, and the tower, who communicates with the IFR unit for said clearances and "releases" for IFR departures. Where these canned clearances aren't in effect, the tower must call the IFR ATC unit (a terminal or ACC) for each IFR clearance, and they often don't include SIDs but are the old fashioned, "full clearances" which may include things like initial headings, altitude restrictions, radial climbs and so forth.

Pilots have said they like the idea of getting pre-taxi clearances because they have the opportunity to brief the departure and if they get the same thing all the time, then there is less of an opportunity to make errors.

The idea that is being introduced is to allow FSS to issue similar canned clearances and call for a release of an IFR departure. We attempted to do this many years ago, and met only with a moderate amount of success. There are SIDs published for the target airports, but there were so many errors by flight crews in the departure instructions that it ended up being terminated and normal ops resumed. The SIDs, with the exception of Fredericton off runway 15, were all "runway heading for vectors to assigned route, maintain 5,000" were so frequently broken it was unreal. Many pilots took off and made the turn on course, and even some outright admitted they were climbing to their flight planned altitude as well. This resulted in some losses of separation as overflights and arrivals were being planned based on the SID being flown. Nobody has come up with a definite answer as to why all these SIDs were being busted, but the most prominent belief is that the mindset of the pilots being at an uncontrolled airport leads to the pilot not flying a SID. Some of them have gone so far as to say that the SID at an uncontrolled airport is confusing. Which is funny since the pilots are strong supporters of this procedure. They're saying they want the same thing everywhere they fly. So if they get a SID at Vancouver, Toronto, Halifax and so many other places, why can't they understand how to fly them at these smaller airports? We rarely ever see SIDs busted at Halifax or Moncton in our FIR, but at one point the clearances were busted upwards of 8 times a day at Saint John, Fredericton and Charlottetown.

Another aspect At uncontrolled airports, this sort of thing is a little more difficult, technically speaking. At a controlled airport, there is someone in the tower who has the authority to stop an aircraft from taxiing, entering the runway and taking off, so there is an element of control there that is needed for IFR operations. Without a tower, if a pilot believes he has a valid IFR clearance, then there is nobody who can stop him from taking off, regardless of where his traffic is.

So this will likely be implemented again in the near future. The airlines will likely fair better overall, since they have training departments to help spread the word. The individual operators are the ones who will likely have longer term difficulties with this. Here's hoping it goes well, when it goes.