GPS Assist At Startup

[mike_newall]

We've had 2 instances of GPS Assist on startup of the D100.

Attitude wrong, on an angle.

Left it alone for 3 minutes with everything running and then - it was back in the room, all OK.

All OK for rest of flight.

Does this sound like software or firmware - sending back is a pain until we start our US flights again in Spring.

Mike
G-IVII, UK

 

[dynonsupport]

What GPS do you have connected to your D100? You should only be able to get GPS assist if your GPS is giving us a ground speed, and some do this on the ground at times.

 

[mike_newall]

Thanks for the swift reply.

It is connected to a Garmin 430.

Are you thinking the Garmin is giving spurious information ?

If so, is there a reset/re programme etc ?

 

[dynonsupport]

The 430 will do this. When it is on the test page at boot, it lies and says it is in Kansas, going 150 knots. This will trigger our GPS assist mode. Unfortunately, it marks this data as completely valid so there is no easy way to ignore it.

Just press "ENT" on the 430 and it will go past this page and everything should be OK. Any effect on the attitude on the D100 should be momentary.

 

[Dynon]

It does sound like the GPS is providing some signifigant GPS speed, perhaps as it attains its lock. This could affect the attitude reading on the EFIS as this occurs, but after the GPS settles down this should stablize. Also, once the EFIS sees actual airspeed, airspeed itself will be used for attitude assistance. I can't answer whether there are any specific issues regarding spurious alerts by the 430 under certain circumstances or with certain versions of software. When you see this happen, have you noted what the reported ground speed is from the GPS, either on the 430 itself or on the D100's HSI page? Does it degrade to 0 over some short period of time as the lock improves?

 

[mike_newall]

Yep - 150kts on the D100 - not noticed what it says on the 430 as it is going through it's acquire phase !

And the attitude abnormality.

Perhaps we let the 430 settle down before we 'accept' it.

I will try that and report back.

Thanks for the input - most useful.

M

 

[mike_newall]

Here is another thought.

The aeroplane had stood for 3 weeks.

I wonder if the Garmin 430 backup battery is getting low ? We haven't had a low battery warning yet, but some study has shown that these last 5 - 7 years which is the age of the Garmin.

I am guessing the Garmin may then be a little lazy on startup re position.

 

[dynonsupport]

The 430 only puts out 150 knots on the test page, during boot, where it tells you to check the CDI deflections, and press ENT when all is OK. It doesn't do it whenever it has no lock. Once you press ENT all should be fine even if the 430 never gets a lock.