Mine won’t do that, but will make the turn very close to the WP. If you’re at the right altitude you should be stablized at the FAF. But of course BITLI and then ADURI is better :-)
I think he is suggesting making it a fly-over as part of an approach. Naturally a GPS unit could achieve this but I doubt regulators would accept the lack of certainty around the path and the risk of a high speed meaning the aircraft couldn’t make the radius required.
Peter wrote:
I am probably missing the point too, but my understanding of bookworm’s post is that he was suggesting saving time / track miles.
Yes, thank you for the diagram. That’s exactly what I’m suggesting. You describe is as “slightly horrible” but I don’t see why.
Well, to be perfectly clear, I’m not suggesting doing that, I’m asking why approaches cannot be designed to permit that. The answer is in the stabilisation distances required before the FAF.
But could we not create a table of max turn angle at the IAF/IF (which is currently 110 degrees) as a function of speed and length of the intermediate segment?
A couple of points. All the waypoints are fly-by waypoints except the MAP waypoint. There is only 3.5 NM between BITLI and ADURI, which is such a short distance, this approach would need to be limited to Category A and B aircraft. Standard rate turn is 3 degrees per second and rate based autopilots such as the Stec autopilots will only command a turn of 90% of that rate. So, in a 180 degree turn, you will have used up close to 80 seconds including the roll in and roll out. At 120 kts, the 3.5 NM leg is only 105 seconds long if flown as a straight leg. I am sorry, but I just don’t see any advantage to saving 25 seconds, even if you have to pee real bad.
In the US, controllers may only clear an aircraft direct to the intermediate fix if the angle does not exceed 90 degrees and a step down fix between the intermediate fix and FAF by 30 degrees. This is independent of whether an autopilot is used or not.
Finally, the suggestion to use parallel track won’t work because parallel track is disabled on an approach.
Thanks NCY!
I guess via BITLI is the best way!
The DFC90 would fly this intercept nicely though
NCYankee wrote:
In the US, controllers may only clear an aircraft direct to the intermediate fix if the angle does not exceed 90 degrees and a step down fix between the intermediate fix and FAF by 30 degrees.
What if the IF is also an IAF as here?
bookworm wrote:
What if the IF is also an IAF as here?
It is pretty standard that the center T fix is both an IF and an IAF. When both, there is a hold depicted at the IAF/IF as a HILPT (Hold In Lieu of a Procedure Turn), so if you are coming from the airport side to the fix, the hold is mandatory. When coming from the side away from the runway, the 90 degree rule still applies and if direct to the IAF(IF) one can be cleared straight in, meaning the hold is not permitted.
In general, if a PT or HILPT is charted, it must be flown unless one of the following 4 conditions is met:
1) Aircraft is being vectored to final (direct to the fix is not a vector)
2) Aircraft is cleared straight-In (Bonanza 345, cleared direct CONEL, cleared straight in RNAV RWY 2 approach Rock Hill, Maintain 3000 until established)
3) The route is not along a feeder or within a feeder segment that is charted as NoPt, (No Procedure Turn) meaning the Hold is not allowed along this route.
4) Timed holds are being conducted and the aircraft is already in holding.
