Question about ToT

[FrostLaufeyson]

I would like to ask if all of you here have used the ToT function.
I participated in a mission a few days ago and needed to rush to waypoint 3 at a certain time. The line connecting waypoint 3 to waypoint 4 is our attack route, so the time requirement is relatively strict.
Our waypoints are all stored in SEQ1, we all use Zulu time, choose waypoint 3, and set ToT.
But there are some problems in the task execution, because we are not very clear about the calculation logic of ToT. I had no problems flying, but none of my wingmen understood the logic behind this feature, such as how it calculates the time if I fly away from the waypoint. All I know is that it has something to do with the waypoints selected in the flight plan, and I see different airspeeds required when switching to different waypoints.
The manual also only explains the operation of this function.

[AstonMartinDBS]

Maybe this short tutorial helps:

 

[AstonMartinDBS]

12 hours ago, FrostLaufeyson said:

[...] how it calculates the time if I fly away from the waypoint. All I know is that it has something to do with the waypoints selected in the flight plan, and I see different airspeeds required when switching to different waypoints.

After proper setup ToT via the HSI format page you have to observe the carrot in the HUD and/or the (current/required) ground speed shown in the HSI, to reach the target waypoint exactly at the desired time.

Optionally you can define a desired (ground) speed at which you wanna approach the target. In that case the entered speed is considered for calculating the required speed from the penultimate to the last waypoint.

[FrostLaufeyson]

8小时前，AstonMartinDBS说：

After proper setup ToT via the HSI format page you have to observe the carrot in the HUD and/or the (current/required) ground speed shown in the HSI, to reach the target waypoint exactly at the desired time.

Optionally you can define a desired (ground) speed at which you wanna approach the target. In that case the entered speed is considered for calculating the required speed from the penultimate to the last waypoint.

From what I learned now, is this right?

However, I am still not quite sure how the GSPD is calculated after setting it up.

[Harker]

The GSPD entry refers to the last leg of the Sequence, e.g. if WP5 is the TGT, the GSPD entry refers to the ground speed you wish to fly between WP4 and WP5.

If you have SEQ boxed, it should adjust the desired speed between the previous WPs in the sequence, so you can arrive at WP4 and then fly at the set GSPD, to arrive at TGT, at the desired TOT.

[AstonMartinDBS]

18 hours ago, FrostLaufeyson said:

However, I am still not quite sure how the GSPD is calculated after setting it up.

I don't know the exact formula, but the required ground speed (REQD GSPD) will be continuously re-calculated - so it varies, depending on the deviation of your current GSPD to the REQD GSPD and the distance to the Target-WP (where you set your ToT). The more and longer your GSPD is below the REQD GSPD and the closer you are to the Target-WP, the faster the REQD GSPD will increase and vice versa. And if you strictly meet the REQD GSPD over the whole distance to the Target-WP, the REQD GSPD will never change (theoretically).

Hope that helps.

Edited July 18, 2023 by AstonMartinDBS