French ATC question
I was rather hoping that there may be an ATCO (preferably who works the Brest UIR's) lurking in these hallowed halls to answer a question.
Yesterday I was returning from the Canaries to the UK in a B767 at FL380, approx. 25nm behind another UK airlines' B757 at FL360 on the same routing. Winds and temperatures in the upper levels were pretty consistent, so TAS and ground speed were in the same ball park, as were Mach numbers for both types.
On first contact with Brest I heard the B757 being cleared (without asking) direct to BARLU from PATEL. "Nice one" I thought, because this typically saves 4 or 5 minutes by elimating a substantial dog leg provided by the standard routing.
We made our introductory call and were cleared PATEL POMTA BARLU (essentially the standard "dog leg" routing). Having heard the B757’s advantageous clearance we naturally asked if the same was available, only to be told that this was not possible.
[thinks] "Hmmm, very strange." So we said that changing FL's was not a problem (up or down) if it would facilitate direct BARLU. The reply was a most insistent not possible. We were having a nice day so I sure as hell wasn't going to spoil it by pressing the point and continued on the Canine route.
On examination of the Jeppesen airways charts it was evident that the direct track from just north of PATEL to BARLU passes through one Danger Area and very close (if not JUST) through another. The first has an upper limit of FL275 and the other by NOTAM, to which I could find no reference of activation. So that didn’t provide an obvious answer.
Close scrutiny of TCAS appeared to show arbitrary routings inasmuch that some aircraft (in both directions at various levels) were enjoying direct routings whilst others were not. Lateral spacing did not appear be the causal factor.
Sorry if this is a bit verbose, but I’ve tried to provide as much info. as possible to paint a picture from the pilots’ point of view.
So – why the direct routings vs. stick to the Airway in this case? Thanks for any light that can be shed on this (quite) common brain teaser.