Auto QNH correction

[Etienne]

Hi Dynon

Just a quick question:

Does the auto-correction of the QNH deactivate with an active airspeed? In other words, say you're flying an IFR approach and (as it happens in all those dark-and-stormy-night stories) your avionics breaker goes. By the time your EFIS boots up again you've descended 300'. Does the D100 try and keep the altitude it had before it died, or is it aware that it should keep the last known QNH?

Just a thought ;D
Etienne

 

[DBRV10]

The last stored QNH is "stored". Its only ever lost if you do not beack out of the menus to exit and the power is turned off.

From my observations anyway!

DB

 

[Etienne]

My experience (on the ground) is that the last altitude is remembered, and on boot, the QNH is modified to reflect that same altitude. Only if the pressure altitude of the Efis hasn't changed, then it will show the same QNH as before.

 

[dynonsupport]

David: the auto baro adjust is a recent firmware feature that allows the baro setting to be auto-adjusted between power cycles so that you don't need to adjust it very far. Because, of course, if you shut down at 300 feet MSL, you're going to be there tomorrow. But the baro has probably changed.

Etienne: The adjust is indeed inhibited when IAS>0. Though, if your EFIS reboots while you're on approach, your first step really should be to go around, if you had an EFIS problem. Then, before shooting another one, you would of course set everything up again, including checking that your baro setting is correct.

 

[dynonsupport]

Note that the baro adjust is a selectable behavior.

 

[Etienne]

Excellent!

Thanks for the reply

 

[DBRV10]

Ahhhhh thats a tricky feature!

So you say its selectable......... is it off by default or on? I will need to see this soon enough, but I refer to set it myself and never have it auto adjusting.

Cheers

DB

 

[dynonsupport]

Yes, the baro auto adjust is off by default, and can be found in SETUP > BARO > ADJUST AT BOOT: ON/OFF

 

[Ratman]

....... say you're flying an IFR approach and (as it happens in all those dark-and-stormy-night stories) your avionics breaker goes. By the time your EFIS boots up again you've descended 300'.

Etienne: ..... if your EFIS reboots while you're on approach, your first step really should be to go around, if you had an EFIS problem. Then, before shooting another one, you would of course set everything up again, including checking that your baro setting is correct.

And then, immediately after landing, call Dynon and get an internal battery so the next time your breaker trips the D100 continues to function.

 

[Etienne]

And then, immediately after landing, call Dynon and get an internal battery so the next time your breaker trips the D100 continues to function.

As with most hypothetical situations, there are many holes in the theory. The most notable being that a stuck altitude on descent is not dangerous, whereas a stuck altitude on ascent (which isn't noticed) is deadly.

I already have a backup battery, don't fly IFR, and certainly not at night. Also, if a breaker trips on finals, I would fly to the ground on backups, then figure out what had happened.

But the purpose of the story was to simply put a theoretical problem of rebooting the D100 in flight whilst changing altitudes into a real-world example.
:

Thankfully, the genii at Dynon had already thought of that scenario, and prevented the problem I imagined from happening