TOT guidance with GSPD inserted gives wrong required ground Speed

[Fresh]

Hi,

I've experienced a couple of occasions where the required ground speed puts me at TOT over the waypoint before my target, i.e. at my IP. I have not been able to find what causes this. I created a mission to test this. It has 6 waypoints, each 6nm apart from each other (total 36nm). If you delete waypoint 3 the total distance is then exactly 30 nm. Flying at 360 knots GS means it takes either 6 minutes or 5 minutes (depending if you delete waypoint 3 or not). If I delete waypoint 5 the total distance and time is the same, since it is a straight line between waypoint 4 and 6.

In the replay you can see the HSI wants me to come to a standstill at waypoint 4. Something is breaking the calculation. I have SEQ1 boxed, AUTO is boxed and the next waypoint ahead is selected.

This sometimes works and sometimes it doesn't. Deleting a waypoint in the sequence (before entering any TOT data) might be one of the causes, I can't show it conclusively.

Fresh

TOT with GSPD bug.trk TOT Test Caucasus.miz

Edited May 17 by Fresh

[JJK]

The waypoint you select in the HSI is the WP from which the calculation will begin. 

If you select WP 1, you must start from WP 1; if you select WP 3, you must fly directly to WP 3 and then fly to all subsequent wp`s

so that you reach the entered GSPD from the second-to-last to the last WP. 

It also works without GSPD, just with TOT. You can also fly directly to the TOT WP by setting the TOT WP in the HSI. 

Don't forget Auto and Zulu Time.
 

--

Edited May 18 by JJK

[Phantom711]

@JJK

Yes, we (fresh and me) are aware of all that. 
And yet in an MP mission the required GS indication made us arrive over the IP(!) at the TOT we had entered.

I was able to reproduce the problem on that particular mission with the SEQ we had set.

Now due to a mix of preset waypoints and some custom waypoints our SEQ is not the usual 1-2-3-4-5-6 but 50-13-51-52-12, where 12 was the TGT.

If we don‘t select a GS for the last leg, the system works as advertised.

Also if I try it in a more „clinical“ environment with a 1-2-3-4-5-6 SEQ, it works correctly with a set GS for the last leg.

I will create a track tomorrow maybe.

Edited May 18 by Phantom711