GTN750 weird suspend during departure procedure

[DesertNomad]

When flying the FMG8 at KRNO off of 16R, the GNT750 goes into a suspend mode at 4815' (400 AGL). Why?

There is nothing on the departure procedure plate about this. The turn is not until 3 miles south at RITJU and there is a mountain just to the left immediately after takeoff.

 

[chartbundle]

It should be suspending until you hit 400, not at 400. Departure procedures don't start until 400' AGL(unless stated otherwise). I can't convince the altitudes in the trainer to work right so I'm not sure if it's doing the right thing or not.

 

[DesertNomad]

That could be it. During the takeoff roll, I am not watching the 750. I guess there is no way for it to know I am at 400'. For this particular one, is there any reason not to unsuspend it when I take the runway? It just seems like a hassle to have to manually do something at a rather busy time.

 

[chartbundle]

That could be it. During the takeoff roll, I am not watching the 750. I guess there is no way for it to know I am at 400'. For this particular one, is there any reason not to unsuspend it when I take the runway? It just seems like a hassle to have to manually do something at a rather busy time.

Why wouldn't it know you're at 400? It's a GPS designed to get you to nearly the same performance level as an ILS on an approach so surely it can figure out 400 AGL. So, the question is, did it not unsuspend on its own once you passed 400 AGL?

Of course, now that I found some documentation apparently that's not good enough so yes you have to unsuspend on your own. http://static.garmin.com/pumac/190-02052-00_1.pdf

For this departure unsuspending it early wouldn't be an issue, as you still have to head to the first fix before any turns. For departures with an immediate turn it wouldn't go so well.

 

[DesertNomad]

It certainly does not unsuspend on its own. I fly this departure every time I leave Reno (my home base). I guess it could know 400' but it is not in any kind of LPV mode on departure. I am just surprised at this behavior vs the 530 I pulled out.

I guess the 400' is assumed since the departure plate makes no mention of it (and if you are still not to 400' at RITJU, you've got much bigger problems).

 

[luvflyin]

Why wouldn't it know you're at 400? It's a GPS designed to get you to nearly the same performance level as an ILS on an approach so surely it can figure out 400 AGL. So, the question is, did it not unsuspend on its own once you passed 400 AGL?

Of course, now that I found some documentation apparently that's not good enough so yes you have to unsuspend on your own. http://static.garmin.com/pumac/190-02052-00_1.pdf

For this departure unsuspending it early wouldn't be an issue, as you still have to head to the first fix before any turns. For departures with an immediate turn it wouldn't go so well.

Ah ha. Now I know why SUSP kept coming back on when I had cleared it on a GNS simulator doing a Missed Approach. Good find

 

[aterpster]

When flying the FMG8 at KRNO off of 16R, the GNT750 goes into a suspend mode at 4815' (400 AGL). Why?

There is nothing on the departure procedure plate about this. The turn is not until 3 miles south at RITJU and there is a mountain just to the left immediately after takeoff.

The turn is 3miles south of the LOC DME, not 3 miles south of RITJU. It also requires a climb gradient of 740' /nm to 8,000. Perhaps the GTN750 went into SUS because you weren't achieving the altitude? The older avionics aren't that smart.

 

[aterpster]

I ran it in the G-1000 trainer with an anemic climb rate. It did not go into suspend. It turned at RITJU.

 

[SbestCFII]

The units never unsuspend on their own. You have to manually unsuspend once you are started a charted action that is not part of the procedure in the unit database. For example, when you reach the missed approach point (MAP), you will generally start a climb. At the MAP, the "SUSP" notification on the GPS will annunciate. That's your cue to start the climb and once you bebin that task, you manually unsuspend the unit and it will begin the next leg that will lead you to the missed approach holding fix. A departure wouldn't be much different. For a departure procedure, you generally have a little manual mental flying to do, such as "when departing Rwy 20, turn left heading 150" The plan is suspended, waiting for you to manually "unsuspend" once you have cllimbed out and on heading 150, for the GPS to guide you for the rest of the procedure. I think the guidance from Garmin is pretty concise.

 

[aterpster]

The units never unsuspend on their own. You have to manually unsuspend once you are started a charted action that is not part of the procedure in the unit database. For example, when you reach the missed approach point (MAP), you will generally start a climb. At the MAP, the "SUSP" notification on the GPS will annunciate. That's your cue to start the climb and once you bebin that task, you manually unsuspend the unit and it will begin the next leg that will lead you to the missed approach holding fix. A departure wouldn't be much different. For a departure procedure, you generally have a little manual mental flying to do, such as "when departing Rwy 20, turn left heading 150" The plan is suspended, waiting for you to manually "unsuspend" once you have cllimbed out and on heading 150, for the GPS to guide you for the rest of the procedure. I think the guidance from Garmin is pretty concise.

Can you provide an example of a departure procedure where a Garmin unit will go into suspend?

 

[SbestCFII]

Can you provide an example of a departure procedure where a Garmin unit will go into suspend?

Hugo 3 out of JQF. You depart 02 or 20 and climb to the specified heading 016 for RWY 2 and "left turn to" 150 departing RWY 20, the GNS is showing SUSP. The procedure has you climb and stays in suspend until you activate the depature with the correct transition, but ATC will often clear you direct to XXX, in which case you press FLP, scroll to the direct-to waypoint, hit direct to and enter and you're on your way.

 

[aterpster]

Hugo 3 out of JQF. You depart 02 or 20 and climb to the specified heading 016 for RWY 2 and "left turn to" 150 departing RWY 20, the GNS is showing SUSP. The procedure has you climb and stays in suspend until you activate the depature with the correct transition, but ATC will often clear you direct to XXX, in which case you press FLP, scroll to the direct-to waypoint, hit direct to and enter and you're on your way.

I can't find that departure at JQF. It should say "MANSEQ" in that case, such as the TORO 7 at KMRY. The OP was about the MUSTANG 8 at KRNO, which doesn't have a heading.

 

[Martin Green]

The GTN would have gone into SUSP mode the moment that the pilot entered the FMG8 DEP procedure into the unit before takeoff.

Garmin Publication 190-02052-00 (December 2015) states:

"Reasons the navigator may suspend and require manual leg sequencing include:
...
Anytime the navigator requires pilot action in order to determine when to begin the next navigation leg:
...
Legs that end at a specific altitude, if the navigator does not have a baro-corrected altitude input (for example, "Climb to 2500, then...")...

The first leg of the FMG8 departure procedure requires a climb on the IRNO ILS back course to a specific altitude of 4815' BEFORE turning on course to FMG. It is up to the pilot to tell the GTN when that altitude is reached by tapping UNSUSP whereupon the GTN will begin to sequence to the next waypoint, FMG.

 

[DesertNomad]

It is odd that the FMG8 plate makes no mention of 4815'.

 

[Martin Green]

It is odd that the FMG8 plate makes no mention of 4815'.

The 4815’ comes from the fact that departure procedures normally start at 400’ above the airport elevation. KRNO airport elevation is 4415’ so that’s where the 4815’ comes from.

 

[aterpster]

It is odd that the FMG8 plate makes no mention of 4815'.

It's not an RNAV procedure. It's a LOC BC procedure and the turn is at RIJTU or the IRNO 3.0 DME with a minimum climb gradient of 740' per NM to 8,000 or 525' per n.m with wx of at least 600 and 1 1/4.