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Mrmartinnico
21st May 2021, 16:17
Can anyone help me out here?
I have been wondering about this "Runway update" callout. There's tons of videos of cockpit-recorded takeoffs (From Aer Lingus specifically), where they apply takeoff power, read the corresponding FMA Lines, and then say "runway update".
According to current FCOM revisions, this is not a standardized procedure callout, (may be an airline operation manual one though). So this led me to dig into some manuals a bit more.
Further reading into the FMGS Systems, I soon realized the FM Position Update on takeoff (which is a thing) is inhibited during GPS Primary operations, or as we all know, basically during every normal modern Airbus aircraft operation. So, even if the crew was operating under NON GPS Primary conditions, such as Radio positioning update of the FMS, there is not indication on any display units AT ALL of this Update! As far as I'm concerned, the FMS updates its position automatically upon application of TO power, but no pilot indications are given. Does anyone know what they're looking when they say it?
Furthermore, does anyone really know why they say it at all?
Thanks in advance!

FlightDetent
21st May 2021, 17:19
Speculation: Before GPS POS, possibly on a different type or even manufacturer, TOGA selections re-sets the FMS position to runway threshold coordinates.

That's what the T. O. Shift is there for on the mainstay A320 PERF TKOF page. Even today.

This position update could be essential for achieving long-range navigation accuracy outside radio coverage, going trans-Atlantic for instance.

Perhaps carried over from legacy operations / procedure commonality purposes?

It could well be a requirement for NAT and guess they do some MFF.

Mrmartinnico
21st May 2021, 17:27
Absolutely agree with you, the importance of the TO SHIFT is precisely described in the same chapter of the FCOM.
I don't think it's related to NAT, as I've seen it on flights to other European countries.
Nevertheless, as I stated before, TO Update is inhibited when GPS Primary is active, and even if it wasn't, what do you think the crew could be looking at when they call out the "runway update"? There's no indications to the pilot of this self-updating process of the FMS.

"‐ At takeoff, when the FM position is updated to the runway threshold position as stored in the database, possibly corrected by the takeoff shift entered on PERF TO page. ‐ In flight, the FM position approaches the radio position or the GPS position at a rate depending upon the aircraft altitude. Note: The FM position update at takeoff is inhibited when GPS PRIMARY is active."

FlightDetent
22nd May 2021, 01:50
You missed my point, 4th sentence is the suggested answer to your dilemma. Sorry for not being clearer.

MCDU2
17th Jun 2021, 20:34
To the OP.......There are few if any airlines in the world that are 100% compliant with a manufacturers SOPs. Many (perhaps most) will say they comply fully but when you deep dive you soon find that there are numerous reasons why an airline could differ in their application or interpretation of standard calls or SOPs. Sometimes its even required by a regulator.

As an aside you are probably watching some old video clips. The PF will only call the FMA in our latest standard calls SOPs. A silent check/scan of the FMS aircraft position on the ND is made but no verbal call. We follow our Ops Manuals Part A and B for standard callouts and operational aspects of how to fly the aeroplane in accordance with company policy. We would rarely have a need to go into the FCOMs for a reference to an SOP but I am aware that there are some airlines who have effectively copied and pasted the FCOMs into their Ops manuals.