SCalc is a tool that provides information to assist ATC in performing tactical delays.
| The output of this tool should only be an additional source of information, it should not be relied upon as 100% accurate, and is not a substitute for situational awareness. |
Overview
There are three different ways of specifying a delay;
- You know the time delay that must be applied in minutes by a certain fix
- You know a target time at which the aircraft should reach a fix
- You know how many track miles you want to open up
- A required speed to meet a restriction
- Vectoring alternatives to acheive a restriction
Inclusions:
The calculator takes into account the change in Mach with altitude
Omissions:
The calculator does not (yet) take into account any descent or climb
Using the Tool
Button Bar
Use the button bar to select input type you are using;
| HELP | Display this information |
| DELAY | You have a target 'Delay', e.g. 2 minutes |
| DIST | You have target Distance for separation |
| TIME | You have a target 'Time' e.g. 1302 |
| RESET | Clears the calculator |
Enter Data
 |
GS | Groundspeed e.g. 490 | FL | Flight level e.g. 330 |
DTR | Distance to run to point at which separation required e.g. 500 |
either |
dT | delta Time - the Delay in mins e.g. 2 |
t | Target Time in hhmm e.g. 1320 |
dnm | delta nautical miles - separation required in nm e.g. 10 |
Once this is done, the page will calculate. Changing any of the values will result in the page immediately recalcuating.
The last box, MIAS is for the current indicated Mach as reported by the aircraft. Entering the current MIAS will allow the calculator to adjust the target Mach to take into account any winds aloft.
Reading the Outputs - Speed
 |
M |
The target 'along track' mach to meet the requirement. |
| GS | groundspeed to reach the requirement. | |
| dT | extra minutes delay before reaching fix. | |
| or | ||
| dnm | separation distance gained. |
Additionally, you may see the word 'HOLD' appear under the speed - this is just an indication that you may want to consider holding instead of speed reduction.
Reading the Outputs - Vectors
Vectoring off track slightly provides an alternative to speed control. The tables in the calculator assume the aircraft is maintaining it's current speed and being vectored off track.
Two tables are presented providing two vectoring alternatives. Each contains the same two columns:
| Turn | The angle to turned off track |
| Time | The time to fly that new heading |
 | Direct The first table, 'Direct', calculates for turning off track, then turning direct to the fix. |
 | Return The second table, 'Return' calculates for turning off track, then turning back to rejoin track. In this instance, the aircraft must turn back to intercept the track at the same angle it left; to do this turn in the opposite direction by twice the original angle. e.g. Turn left 30 degrees for 5 minutes. To rejoin track after 5 minutes, turn right 60 degrees and intercept. |