GPS Sequencing

What an IFR navigator does with your flight plan, and why — read live off real coded procedures. Ground-school for the box; the thumbs go on the trainer app.

Loading puts the approach at the end of the plan and changes nothing about where you are going. The destination airport is still ahead of you, so the box flies there first and then back out to the transition. Activating makes the transition the active leg, direct from present position. The plan looks identical either way — only the magenta leg differs.

Most fixes are fly-by: the turn starts early, so the aircraft rolls out on the next leg without overshooting. The amber ring on the map is where that turn begins — it moves with groundspeed and with how sharp the turn is. A flyover fix gets no anticipation at all; the leg stays active until the aircraft is past the fix. Missed approach points are flyover.

Automatic sequencing stops at the missed approach point, in a hold, and on a leg that ends at an altitude rather than a fix. SUSP means the box is waiting for you: the active waypoint stays put no matter how far past it you fly. A hold coded in lieu of a procedure turn is the exception — one circuit, then it continues inbound by itself.

OBS freezes the active waypoint and hands you the course. Sequencing stops until you turn it off — which is what you want to hold a course to or from a fix, and is a trap left on by accident. On legs that cannot take a manual course the same key reads SUSP instead, and unsuspends.

On an ILS, localizer, LDA or SDF the navigator hands the needle to the VLOC receiver by itself — but only with the approach activated, the right frequency active rather than sitting in standby, the aircraft within 1.2 nm of the final approach course, and between 2.0 and 15.0 nm from the FAF. Join inside 2 nm and it will not switch at all. There is no automatic switching on a VOR or a backcourse.

The navigator prints a facility name under the frequency from its own database and your GPS position. It does that whether or not anything is being received — including for a frequency sitting in standby. Identifying is the Morse the receiver decodes off the active frequency, with the ident audio up. Watch the Nav receiver panel through all three.