How to know what to insert in the TO SHIFT in airbus MCDU?

Question

I understand that TO SHIFT is used when departing from an intersection to update the position of the aircraft in the lack of gnss. But how do I know what to put in the TO SHIFT? Is it availabe in the ADC?

Thanks in advance!!

Answer 1

The TO SHIFT is entered either in meters or feet depending on your operators selection of units ([M] or [FT] will displayed next to the field). This image from the FCOM shows an example with 900 m takeoff shift:

^{(Airbus A320 FCOM - Auto Flight - Flight Management - Takeoff Update)}

To figure out the takeoff shift for a given intersection, look at the Takeoff Run Available section on the ground chart. Here is an example for London Stansted (EGSS):

If you want to takeoff from runway 04 at intersection K1 you calculate the difference from rwy head:

$$ \text{TO SHIFT} = 3049 \, \text{m} - 2823 \, \text{m} = 226 \, \text{m} $$

Answer 2

Takeoff shift is the Take off Run Available (TORA) minus take off distance available from the intersection.

For example, if a runway has a TORA of 3400 meters and your intersection take off distance is 2600 meters, takeoff shift will be 800 meters.