DA40 G1000 GFC700 VNAV

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ZAV
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Re: DA40 G1000 GFC700 VNAV

Post by ZAV »

Lol. Just landed and messed this up after watching, thinking about it, and knowing what to do. I didn’t set the altitude lower as I hit the TOD. Know how it works. Know better. Just not an intuitive step for me.
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midlifeflyer
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Re: DA40 G1000 GFC700 VNAV

Post by midlifeflyer »

ZAV wrote: Fri Nov 20, 2020 7:31 pm Lol. Just landed and messed this up after watching, thinking about it, and knowing what to do. I didn’t set the altitude lower as I hit the TOD. Know how it works. Know better. Just not an intuitive step for me.
Tell me about it! :D Those gotchas got me too and was mentioned to me by club members a week before I started doing the video.

Suggestion. If you have a "let down" or "in range" checklist segment which you actually use in flight, add the reminder there. Or, use it al the time, even for letdown to VFR traffic pattern altitude until it becomes second nature to "set VNV = set altitude."
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Re: DA40 G1000 GFC700 VNAV

Post by dmloftus »

Great video. I've studied the function multiple times but I just think it is too much effort to set, monitor, etc as opposed to just using FLC when you need it. With the 5 minute, 1 minute VNAV requirements to TOD, it's just as easy to dial it in and hit FLC. Am I missing something? Would love to hear a compelling case for VNAV. It's great the system has the capability, I just think it is a bit cumbersome and not worth the effort.
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Re: DA40 G1000 GFC700 VNAV

Post by Boatguy »

dmloftus wrote: Sat Nov 21, 2020 4:16 pm Great video. I've studied the function multiple times but I just think it is too much effort to set, monitor, etc as opposed to just using FLC when you need it. With the 5 minute, 1 minute VNAV requirements to TOD, it's just as easy to dial it in and hit FLC. Am I missing something? Would love to hear a compelling case for VNAV. It's great the system has the capability, I just think it is a bit cumbersome and not worth the effort.
It’s simple. VNV will put you at the specified altitude and place every time. FLC will only take you to an altitude, the place where you reach that altitude is not known in advance.
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Re: DA40 G1000 GFC700 VNAV

Post by ZAV »

dmloftus wrote: Sat Nov 21, 2020 4:16 pm Great video. I've studied the function multiple times but I just think it is too much effort to set, monitor, etc as opposed to just using FLC when you need it. With the 5 minute, 1 minute VNAV requirements to TOD, it's just as easy to dial it in and hit FLC. Am I missing something? Would love to hear a compelling case for VNAV. It's great the system has the capability, I just think it is a bit cumbersome and not worth the effort.
Yes. Simply using FLC or VS mode can accomplish the same thing. I prefer FLC for climbing but like VS for descending. Probably just as easy to use those modes for simple approach procedures. Arrival procedures would seem to be easier with the VNAV I would think. I don’t have to do those with the DA40 so don’t really know.

I like to use the VNAV function when flying VFR to uncontrolled airports. I set a VNAV target 10-15 miles away and get a nice smooth descent into the airport area.
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Re: DA40 G1000 GFC700 VNAV

Post by midlifeflyer »

dmloftus wrote: Sat Nov 21, 2020 4:16 pm Great video. I've studied the function multiple times but I just think it is too much effort to set, monitor, etc as opposed to just using FLC when you need it. With the 5 minute, 1 minute VNAV requirements to TOD, it's just as easy to dial it in and hit FLC. Am I missing something? Would love to hear a compelling case for VNAV. It's great the system has the capability, I just think it is a bit cumbersome and not worth the effort.
I don't think there's a lot of effort involved and I find it fun (although I'm a bit of a geek about these things). But despite using it that way in my video, the VNAV functionality is not really designed for standard approaches. And certainly, if one has an enroute crossing restriction, easy enough to use VNAV to calculate what you need to meet it and use VS or even fly it manually. Where I think it really comes into its own is a STAR or even an approach with multiple stepdowns or crossing restrictions.
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Re: DA40 G1000 GFC700 VNAV

Post by dmloftus »

Boatguy wrote: Sat Nov 21, 2020 5:20 pm
dmloftus wrote: Sat Nov 21, 2020 4:16 pm Great video. I've studied the function multiple times but I just think it is too much effort to set, monitor, etc as opposed to just using FLC when you need it. With the 5 minute, 1 minute VNAV requirements to TOD, it's just as easy to dial it in and hit FLC. Am I missing something? Would love to hear a compelling case for VNAV. It's great the system has the capability, I just think it is a bit cumbersome and not worth the effort.
It’s simple. VNV will put you at the specified altitude and place every time. FLC will only take you to an altitude, the place where you reach that altitude is not known in advance.
So I've been playing with VNAV since reading this string and I find it very useful to ensure I don't bust altitude coming into Bravo controlled airspace. I'm constantly crossing ATL when I fly back to LZU from Florida. I simply pick a waypoint just outside the Bravo shelf and set the VNAV altitude. Before I always had to make sure my FLC path would suffice. Learn something new everyday!
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Re: DA40 G1000 GFC700 VNAV

Post by midlifeflyer »

dmloftus wrote: Tue Jan 26, 2021 10:32 pm So I've been playing with VNAV since reading this string and I find it very useful to ensure I don't bust altitude coming into Bravo controlled airspace. I'm constantly crossing ATL when I fly back to LZU from Florida. I simply pick a waypoint just outside the Bravo shelf and set the VNAV altitude. Before I always had to make sure my FLC path would suffice. Learn something new everyday!
The best thank you I can ever get!
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Re: DA40 G1000 GFC700 VNAV

Post by dmloftus »

midlifeflyer wrote: Wed Jan 27, 2021 10:24 am The best thank you I can ever get!
Yes, thanks again for your video, very helpful. I'm curious about the choice in your video to set your target altitude at 2300 feet as you initially engage VNAV when you have interim steps to 3200 and then a step to 3000 in the vertical profile. I have tried a few multi-step downs and I chose to set the target altitudes for each of the steps. In your example, I would set the target altitude for 3200 feet before the first step down, once I reached 3200 I would dial in 3000 on the second. Then I would arm the approach mode once on the final inbound to enable glide path. If you're flying this in Kansas, it probably doesn't matter. But having flown a lot in mountainous areas in NorCal, I would just be nervous setting a target altitude that low that far ahead. If you accidentally hit FLC or somehow the system had a glitch, I would not want the target altitude set much below my immediate next waypoint, lest I have a CFIT episode ;-)

The other important reminder I'd mention when descending on VNAV is Mixture. The first few times I played with VNAV, I was so engrossed in what the G1000 was doing that I almost forgot to enrich the Mixture! As I was approaching my 4000' Bravo shelf, I looked down and my EGT's had climbed several hundred degrees from my leaned cruise settings. Luckily power was only about 16" for the descent so the CHT's stayed reasonable. And fortunately I was by myself so I had no passengers in range of my long string of expletives. But it shows how automation (especially when learning new features) can take you out of your rhythm. Had I blindly pushed the power back to 24" at BOD I might have been in trouble.
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Re: DA40 G1000 GFC700 VNAV

Post by midlifeflyer »

dmloftus wrote: Wed Jan 27, 2021 5:28 pm I'm curious about the choice in your video to set your target altitude at 2300 feet as you initially engage VNAV when you have interim steps to 3200 and then a step to 3000 in the vertical profile.
In this case it was to demonstrate that you can do that. Set it and forget it. (Not really - you always have to monitor automation.) The only requirement for VNV to work is that the target altitude is at or below the VNV target. I could have set it for the airport elevation on the ground and it would have worked the same. OTOH, as you suggest, I can set it step by step.

Understanding what the system allows is one thing. Technique in using it is a different issue and can be situation-dependent. I can see your concern in mountainous terrain, but once cleared for an approach or a "descend via" a STAR, why not? Let's take an example in your neck of the woods - the OAK RNAV Y 28R.
210127 Temp.jpg
You are approaching from the northeast at 5,000' when you get your clearance. "Proceed direct NAGVY. Cross NAGVY at 4,200, Cleared for the Oakland RNAV 29R Approach." There are a number of techniques for flying this approach, including not using VNV at all. But in terms of using coupled VNV, it seems to me you have two choices.
  1. Set 4200 as target altitude. Engage VNV. After crossing NAGVY, set 3400 as target altitude. Engage VNV. After crossing GROVE, set 2700 as target altitude. Engage VNV. After crossing URZAF, set 2100 as target altitude. Engage VNV.
  2. Set 1500 as target altitude. Engage VNV
You indicate you would be concerned with accidentally hitting VS or FLC and blowing through your altitude. Personally, I'd be more concerned about forgetting a step down and messing up the profile.
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