Takeoff shift A320
Thread Starter
Joined: Dec 2008
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From: Birmingham
Takeoff shift A320
Hi folks,
Nearly all of our A320 have gps and are well equipped. The fctm says that the aircrafts with fms2 inhibit the takeoff shift when they have gps primary. So why do we enter the shift? I don't see any reason for that. Gps failure is pretty unlikely and the time window is very small between line and takeoff power.
Any thoughts?
Nearly all of our A320 have gps and are well equipped. The fctm says that the aircrafts with fms2 inhibit the takeoff shift when they have gps primary. So why do we enter the shift? I don't see any reason for that. Gps failure is pretty unlikely and the time window is very small between line and takeoff power.
Any thoughts?
Joined: Jan 2000
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From: Asia
With non GPS aircraft, if the shift is not entered it updates the position to the numbers when take off is commenced therefore there will be an error if T/O starts somewhere else. This error is applied as a bias to each waypoint afterwards.
I heard that if a shift is not entered on GPS equipped aircraft, constraints may not be met on the SID as the aircraft has less distance than it thinks to reach a required altitude.
I heard that if a shift is not entered on GPS equipped aircraft, constraints may not be met on the SID as the aircraft has less distance than it thinks to reach a required altitude.
Thread Starter
Joined: Dec 2008
Posts: 181
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From: Birmingham
Oh ok never heard about that. So the shift you are entering is important for the climb calculations and restrictions? Is that Right? I was thinking that the shift is only important for the position update at the runway in case you don't have gps. So any mechanics here who can confirm that?
Joined: Sep 2010
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From: U.S.A
"So why do we enter the shift?"
Probably because
"Nearly all of our A320 have gps and are well equipped."
Which means not all have GPS. The procedure is probably in place so that you do the same thing across the fleet and therefore don't forget to do it when flying a non gps machine.
Probably because
"Nearly all of our A320 have gps and are well equipped."
Which means not all have GPS. The procedure is probably in place so that you do the same thing across the fleet and therefore don't forget to do it when flying a non gps machine.
Joined: Apr 2004
Posts: 509
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From: United States of Europe
with "GPS Primary"once Take-Off Thrust is Applied, the FMS automatically updates its position.
With GPS Primary there is no requirement to enter the TO SHIFT. However do take into account that if you should encounter a loss of GPS Primary before applying take-off thrust, that you will have an instant map shift. DME/DME updating will take place once airborne, but probably not in time to prevent a late first turn. So no harm in inserting the TO SHIFT anyway.
As mentioned: TO SHIFT does affect the FPLN predictions (i.e. later lift-off), so constraints could be missed as a consequence. Having said that: FMGS predictions are not to be used in the planning stage as primary means of ensuring SID gradient compliance.
Joined: Oct 2015
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From: 43N
OPEN DES is correct - Thales New FM Pilots Guide Release 1A
"Position update
NO GPS [A/C CONF]
Aircraft with no GPS: An automatic position update at runway threshold is performed when the thrust levers are set in the take-off position. If a take-off shift is entered in the PERF TAKE-OFF page, the FMGC position is updated to the coordinates of the take-off shift.
GPSOPT [A/C CONF]
Aircraft with GPS: No position update occurs when the thrust levers are set to the FLEX or TOGA detent."
"Position update
NO GPS [A/C CONF]
Aircraft with no GPS: An automatic position update at runway threshold is performed when the thrust levers are set in the take-off position. If a take-off shift is entered in the PERF TAKE-OFF page, the FMGC position is updated to the coordinates of the take-off shift.
GPSOPT [A/C CONF]
Aircraft with GPS: No position update occurs when the thrust levers are set to the FLEX or TOGA detent."
Joined: Apr 1999
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From: UK
Best response I've had on this subject is that it's useful for crew SA when dealing with multiple possible intersections for departure. As far as the aircraft is concerned it's pointless, but it's a good reminder that if your shift doesn't tie up with your intersection then maybe you've got the numbers wrong.
Joined: Apr 2004
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From: UK
Best response I've had on this subject is that it's useful for crew SA when dealing with multiple possible intersections for departure. As far as the aircraft is concerned it's pointless, but it's a good reminder that if your shift doesn't tie up with your intersection then maybe you've got the numbers wrong.
Joined: Apr 2013
Posts: 999
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From: Earth
My view on it:
Its an ops procedure if both gps are inop / GPS primary not active, to have a nav accuracy as high as possible.
At takeoff the FM position is updated to the runway threshold position as stored in the database.
A takeoff update requires that the takeoff runway is part of the flight plan. This provides the most accurate position update.
If the takeoff run starts at an intersection, with gps primary not active, enter a takeoff shift on the PERF TO page to refine the takeoff update.
An accurate takeoff update ensures a more precise aircraft position during departure.
Its an ops procedure if both gps are inop / GPS primary not active, to have a nav accuracy as high as possible.
At takeoff the FM position is updated to the runway threshold position as stored in the database.
A takeoff update requires that the takeoff runway is part of the flight plan. This provides the most accurate position update.
If the takeoff run starts at an intersection, with gps primary not active, enter a takeoff shift on the PERF TO page to refine the takeoff update.
An accurate takeoff update ensures a more precise aircraft position during departure.
Joined: Nov 2006
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From: Tropics
Seems like Airbus has just updated the entire FCOM suite. Anyone received it from their company yet?
Apparently now we are to insert TO SHIFT regardless GPS primary or not. FCOM Normal procedures now state so, and under the system description the "IF GPS NOT PRIMARY" note has also been taken away for the TO SHIFT update section.
This is just one of the many changes Airbus introduced in this update
Apparently now we are to insert TO SHIFT regardless GPS primary or not. FCOM Normal procedures now state so, and under the system description the "IF GPS NOT PRIMARY" note has also been taken away for the TO SHIFT update section.
This is just one of the many changes Airbus introduced in this update
Only half a speed-brake
Joined: Apr 2003
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From: Commuting not home
FCOM/PRO/NOR/SOP/06/D/TAKEOFF DATA INSERTION (PERF TAKEOFF PAGE)
"TO SHIFT................................................AS RQRD
Enter the takeoff SHIFT distance, if takeoff is to be from an intersection.
This is essential for position updating at takeoff and, consequently, for navigation accuracy."
My oldest FCOM is 2008, with quite few editions between that one and the latest, the sentence is perfectly unchanged, applicable for all A/C in fleet.
Question: Where from did we learn not to enter TO SHIFT w/GPS? It was a long time ago, still I seem to remember that as a change, "from today onwards we will not enter ...."
"TO SHIFT................................................AS RQRD
Enter the takeoff SHIFT distance, if takeoff is to be from an intersection.
This is essential for position updating at takeoff and, consequently, for navigation accuracy."
My oldest FCOM is 2008, with quite few editions between that one and the latest, the sentence is perfectly unchanged, applicable for all A/C in fleet.
Question: Where from did we learn not to enter TO SHIFT w/GPS? It was a long time ago, still I seem to remember that as a change, "from today onwards we will not enter ...."
