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GRT Autopilot fly a pre-programmed vertical non-approach descent?

walkman

Well Known Member
Lets say I'm cruising along at 11,500 and want to be at 3,000 a couple of hundred miles down the road, and I want to descend at a set pre-determined airspeed or vertical speed, can I do it?

I can set up the descent on the 430w, but it just tells me when to start the descent what altitude to be at during the descent. It doesn't send that info to the a/p.......or can it?

I can set up an altitude and rate in the a/p and do it NOW, but is it possible to set it up to have it happen when I get to the descent point?
 
To the best of my knowledge, no. With some work you could program in the calculated descent point as a waypoint in your gps flight plan, just as a reminder of when to initiate the descent.

You know about the green arc on the map, using it to adjust the descent rate?
 
Sure, altitude preselect works well!

Lets say I'm cruising along at 11,500 and want to be at 3,000 a couple of hundred miles down the road, and I want to descend at a set pre-determined airspeed or vertical speed, can I do it?

Yes, with at least a GRT H1 and assuming a TruTrak AP like the DII VSVG altitude preselect works well. Assuming the AP is engaged and you are cruising at 11,500, you go to the PFD, select 3,000 with the right knob. It should prompt you to select either a vertical descent rate (-XXX per minute) or airspeed. I have mine set to prompt for vertical descent rate. It will push over and descend at -XXX feet per minute and then level at 3,000. Picking your descent rate sets the distance covered while descending. Works the same in climb.

Hope that helps.
 
Bill, you misunderstood the question. He wants to program the autopilot now, to begin a descent at some fix 100 miles away. Basically, he'd like to have a vertical flight plan, just like the usual horizontal one. I do not know how to do that.
 
I know about the green banana. I'd sort of like to do a "fly to the green banana" if that makes any sense.

Say I need to be under a class b shelf, or crossing a fix at a certain altitude, and I want to descend at a given speed or rate, have the a/p trigger its descent when it calculates its time.

sounds like its not doable.
 
You're correct. You can't preprogram it to do this. Like stated above, you could make a vnav waypoint to alert you of the need to descend, but the a/p won't fly the vertical feature without input from you.

I use the green arc to double check my mental calculations when I set in the preselected altitude.

We'd need an FMS with VNAV functions to do what you're asking.

I just calculate the time/distance required to be at a certain place/altitude and set the Rate of Descent and then when the green arc stabilizes I fine tune it. works like a champ.
 
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I know about the green banana. I'd sort of like to do a "fly to the green banana" if that makes any sense.

Say I need to be under a class b shelf, or crossing a fix at a certain altitude, and I want to descend at a given speed or rate, have the a/p trigger its descent when it calculates its time.

sounds like its not doable.

Just because no one does it doesn't mean it isn't doable - I have been asking for the same thing from numerous manufacturers for a long time - maybe someday we'll get it. Would really be handy !
 
Just because no one does it doesn't mean it isn't doable - I have been asking for the same thing from numerous manufacturers for a long time - maybe someday we'll get it. Would really be handy !

I agree. I'd really like to pre program my flights to miss certain airspace floors. I was shocked when I started flying the -8 with all the "magic" on board that this isn't an option. Does not seem like it would be that hard.
 
Just because no one does it doesn't mean it isn't doable - I have been asking for the same thing from numerous manufacturers for a long time - maybe someday we'll get it. Would really be handy !

The Trutrak Sorcerer has a built in VNAV function that allows you to program a descend-to altitude over a certain distance. It will automatically adjust the descent rate with changing speed to maintain the profile and arrive at the target altitude by the specified distance. It isn't automatically tied to a waypoint or fix, but it does give you a way to descend under an airspace shelf simply by your distance from the edge of it. Just thought I'd put that out there. :)
 
Garmin G3X does this. VNAV.

Are you sure? We're not talking about 'VNAV', but 'programable VNAV'.
Can you pre-program the G3X to do this: climb to 3000; on reaching fix ABC climb to 5000; on reaching fix DEF descend to 2000?

Or, in the ideal world: begin a descent at 500 ft per minute at a point to be determined by the electronics so as to arrive at ABC at 3000'.

But really guys, these autopilots are so capable, manually figuring and initiating these things is good, just to keep the pilot in the loop.

Keeps you awake. Otherwise, you'll need a sleep apnea test -:)
 
The honest truth is that it is most certainly doable, but not quite as simple as one might think. As my trusty friend Lucas said, the sorcerer does VNAV today...now it's not preprogrammable, but it's there. To make it preprogrammable and easy from an AP point of view would require a waypoint where you want to start and then the AP could descend to an altitude by the next waypoint.

The biggest problem is that it's more difficult to program it all into the GPS / EFIS than simply using the reminder that many of these systems have already built in, and then just telling the AP to go to the desired altitude in the desired distance.

All of that being said...I do believe that you can preprogram the AFS 5000 series with things like this and the trusty remote controlled AP will follow what is programmed.

Clear as mud? Good.

Lucas is going to yell at me for posting, again! :)
 
Vnav

The G3X in fact does pre programmed VNAV very well. I use it all the time.
I fly regularly between CLT and CVG, both class B 's. I always have a need to descend below the outer rings and set up the VNAV as soon as I reach cruising alt. so I won't forget and have to scramble. For instance, flying direct to KHAO from CLT I will put my cursor on the course line where it intersects the first outer ring, I then hit direct. I am now going direct to a new waypoint called (MAP) on my original course. I then select my flight plan and ADD KHAO back onto the end. I then go to the VNAV page and select MAP as the VNAV waypoint. I have the option to cross that waypoint at an MSL altitude or a target altitude (X) amount above that waypoint and/ or at an offset distance from that waypoint. I also select the target rate of descent I want.
In the above case I need to cross the ring at below 5000 ft MSL. I set the VNAV to cross 1 mile south of the ring at 4800 MSL. Then I punch the VNAV button on the G3X or GMC 305 which arms the autopilot to begin the descent at the appropriate time. Works like a champ!
 
Bob,
Yes I am sure. Jon has found a good use for this but there is a simpler way for most and it fits your original question. However I do not believe it will do a climb, only a decent.
Here is the VNAV set-up from the G3X.
15qdsus.jpg
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As you can see, it will do a decent FPM, Final altitude and distance from or to a waypoint.
It is designed to do this for a future waypoint in a flight plan. Unlike Jon who sets this point as direct-to. It gives a screen message, VSI and GP indicators and will drive the A/P for this profile.
 
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I really like my new GRT Hxr, but I miss this function from my old Cheltons. It's a shame that Chelton decided to get out of the EAB market. The Chelton Sport was way ahead of almost everybody else in functionality.
 
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