FMS gotcha

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   This weekend I experience some unexpected behaviour of my IFD540 which I am sure is by design.
I was about to depart IFR from an airport with low visibility. My filed route involved a direct to a waypoint to pick up an airway. I had programmed this route and activated the flight plan.

When I received my clearance I was given a SID. I then went into the FMS and added the departure to the departure airport.

During take-off into IMC at about 500 ft I switched on GPSS on my Aspen and pushed the HDG button of my 55x. To my surprise the aircraft turned towards the original initial waypoint and did not fly the departure as I had expected. I pressed direct to the final fix at the end of the departure which sort of fixed the situation as I couldn't work out fast enough which intermediate step in the departure to select based on where I was.

I assume what happened is that when I activated the flight plan the IFD made the segment to the original fix active. When I later added a departure sequence in between the airport and that fix (which I didn't remove) it was just skipped over by the FMS.

I wanted to alert others to this 'gotcha' to which I am sure people will respond saying is by design but that really surprised me and in less forgiving terrain could have been potentially dangerous.

Jorgen

Edited by jhbehrens - 03 Nov 2015 at 3:26pm

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jhbehrens Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 15 Dec 2012 Location: Netherlands Status: Offline Points: 122	Post Options Post Reply Quote jhbehrens Report Post Thanks(0) Quote Reply Topic: FMS gotcha Posted: 02 Nov 2015 at 5:43am
	This weekend I experience some unexpected behaviour of my IFD540 which I am sure is by design. I was about to depart IFR from an airport with low visibility. My filed route involved a direct to a waypoint to pick up an airway. I had programmed this route and activated the flight plan. When I received my clearance I was given a SID. I then went into the FMS and added the departure to the departure airport. During take-off into IMC at about 500 ft I switched on GPSS on my Aspen and pushed the HDG button of my 55x. To my surprise the aircraft turned towards the original initial waypoint and did not fly the departure as I had expected. I pressed direct to the final fix at the end of the departure which sort of fixed the situation as I couldn't work out fast enough which intermediate step in the departure to select based on where I was. I assume what happened is that when I activated the flight plan the IFD made the segment to the original fix active. When I later added a departure sequence in between the airport and that fix (which I didn't remove) it was just skipped over by the FMS. I wanted to alert others to this 'gotcha' to which I am sure people will respond saying is by design but that really surprised me and in less forgiving terrain could have been potentially dangerous. Jorgen Edited by jhbehrens - 03 Nov 2015 at 3:26pm

Gring Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 30 Dec 2011 Location: Kingston, NY Status: Offline Points: 722	Post Options Post Reply Quote Gring Report Post Thanks(0) Quote Reply Posted: 02 Nov 2015 at 6:16am
	Can you post the route and SID issued? It sounds like you already had an active waypoint when you added the SID and did not make the first waypoint in the SID the active waypoint.

AviJake Members Profile Send Private Message Find Members Posts Add to Buddy List Admin Group Joined: 26 Mar 2009 Location: Lincoln MA Status: Offline Points: 2815	Post Options Post Reply Quote AviJake Report Post Thanks(0) Quote Reply Posted: 02 Nov 2015 at 8:56pm
	Did you have an actual departure runway designated in the flight plan?
	Steve Jacobson sjacobson@avidyne.com

jhbehrens Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 15 Dec 2012 Location: Netherlands Status: Offline Points: 122	Post Options Post Reply Quote jhbehrens Report Post Thanks(0) Quote Reply Posted: 03 Nov 2015 at 3:23pm
	The filed route was EDWE DCT KUBAT N872 LILSI EHLE. I was given the EMPIT 1P departure - which implies runway 7. After I had added the EMPIT 1P departure the FMS flight plan was EDWE EMP1P EMPIT KUBAT N872 LILSI EHLE. I didn't indicate a departure runway as this departure is for a specific runway. Should I? When I clicked on the autopilot it turned to KUBAT. I just tried the above on the iPad sim and it also retained the direct to KUBAT after I added the SID. Edited by jhbehrens - 03 Nov 2015 at 4:58pm

wookie Members Profile Send Private Message Find Members Posts Add to Buddy List Groupie Joined: 18 Feb 2015 Location: Colorado Status: Offline Points: 56	Post Options Post Reply Quote wookie Report Post Thanks(0) Quote Reply Posted: 05 Nov 2015 at 3:03pm
	I would expect that you can't move into a block of waypoints without doing something specific..... for an approach it would be Activate APR or Direct to the IAF; for a departure, what? Activate Leg for the first leg? The Flight Plan should show discontinuities around the block of waypoints. BH
	BH

oskrypuch Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 09 Nov 2012 Location: CYFD Status: Offline Points: 3058	Post Options Post Reply Quote oskrypuch Report Post Thanks(0) Quote Reply Posted: 05 Nov 2015 at 6:21pm
	Actually, you can move into a logical block of waypoints, like an approach or arrival, by just selecting the waypoint (or leg) of interest.