We were recently scolded by an Air Traffic Controller for not adhering to a routing clearance. We were told to proceed direct to waypoint HAZEL then on course. The direct course to HAZEL and the outbound course from HAZEL to our next point differed by 160 degrees. Our Gulfstream's Honeywell Flight Management System and autopilot applied turn anticipation in order to roll out on the course outbound from HAZEL. While halfway through the turn, the controller asked us where we were going. We replied we're turning to proceed on course. The controller said we were supposed to fly direct to HAZEL and that we never got closer than 8 miles to HAZEL. While we disagree with their estimate of how far away from HAZEL we actually were (the other pilot and I saw it as 6 miles), the question remains what is the acceptable limits of turn anticipation and are we in danger of being violated for following the guidance of our navigation system that was properly programmed and, as best we could tell, operating correctly?
Acceptable Turn Anticipation Limits
- Thread starter Pacman45
- Start date
Fearless Tower
Touchdown! Greaser!
Can ATC even do that? Give you a direct to that requires a 160 degree turn to the next point? Sounds kind of ridiculous. I thought there were limits on stuff like that.
RussR
En-Route
There is a HAZEL fix in England. If that's the one the OP is talking about (and flying a Gulfstream, it may be), be aware that UK air traffic rules may be different than U.S. rules.
mscard88
Touchdown! Greaser!
Never had a problem with that using FMS, ATC expects it, or should. Maybe you had an inexperienced controller but they still should know and expect it. If it were a trainee in position their monitor should have corrected it. Common sense tells you if you're at cruise airpseed you won't be able to make an abrupt turn.
luvflyin
Touchdown! Greaser!
The 'then on course' makes it sound like this might have been part of a Departure. Was it? Where was it? Was it a 'published departure procedure,' or did they just say "direct HAZEL then on course?"
So HAZEL is a waypoint in the London Terminal Area (UK). We were stable at 250 KIAS, but there was a 40 knot wind in our face which would have the effect of pushing us away from HAZEL as we began our 160 degree turn. I think the flight management system uses groundspeed though to compute its turn anticipation. The routing was to accommodate our departure from Farnborough over to Northolt on the other side of London (across Heathrow's airspace). They wanted to make sure we were level at 4,000 feet before turning northeast, which we were.
Was this part of a procedure? Was it published as a flyover waypoint? It appears the (UK) CAA does use a lot of flyover waypoints in their procedures.
We were not given a departure procedure to fly. There is a departure procedure that depicts HAZEL, but it is not a Fly Over waypoint on that procedure. We were simply given departure instructions: "Fly runway heading to 1200', then turn left heading 220 degrees and climb to 3,000." After leveling at 3,000' they gave us the direct HAZEL on course clearance and climb to 4,000.' I'm hoping a more savvy supervisor might have pointed out to our controller that we were executing the instructions correctly in conformance with performance based navigation (PBN) protocols (turn anticipation).