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Top of Descent alert

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dfw11411 View Drop Down

Joined: 22 Oct 2019
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    Posted: 04 May 2022 at 1:36pm
Just upgraded from Garmin 430s to IFD 440s. Still learning but I'm very pleased. Ecstatic, actually.

On my 430s I was able to set a default descent VSI (-500 fpm) and a target AGL (2,000 AGL) for destinations. Flying an activated flight plan would have the 430 alert me to the automatically calculated TOD. I set this up just once and never had to bother with it again. It worked every time for all destinations.

From what I've read (and I'm still reading!) There isn't a function like this on the IFD? I can set the default descent VSI in settings (its defaulted to -500 fpm) but I have to add a target altitude for each destination in every flight plan? Am I missing something?

I should mention that I don't understand what Transition Altitude and Transition Level are. I cannot find an explanation. Thanks for any help provided.
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oskrypuch View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote oskrypuch Quote  Post ReplyReply Direct Link To This Post Posted: 04 May 2022 at 1:55pm
There most certainly is a TOD indication, and even a tone, and I love it!

All it needs is ONE vertical constraint. I always put in the destination airport +1000ft, over the destination airport, when I enter a flight plan so I always have something. You don't want to be caught with too much energy. That is typically supplanted while enroute by ATC instruction and/or an approach.

In North America the transition level is FL180+ everywhere, and not a consideration unless you regularly fly in Class A airspace.

* Orest

Edited by oskrypuch - 04 May 2022 at 1:58pm
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AviSteve View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote AviSteve Quote  Post ReplyReply Direct Link To This Post Posted: 04 May 2022 at 2:02pm
On the IFD, the altitude constraints for each leg come from the database.  You can override them by hand if you want.  If a leg doesn't have an associated constraint, then you can enter one by hand.  Sounds like that's the case you're wanting.  But yes, you need to enter the target altitude.  When you start the entry on a destination airport, though, it will default to 1000 AGL five miles before the airport.

Transition altitude is the altitude at which you should set the altimeter to 29.92 in order to start flying with reference to flight levels.  In the US, 18000 feet.  Once you're in the flight levels, the transition level is the flight level at which you set the altimeter back to local pressure and start flying with reference to MSL altitudes.
Steve Lindsley
Avidyne Engineering
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