how does FMC update AIRAC cycle in flight in real life?

[francisleung 5]

I post the question here since a T7 flight is usually longer. What happen when we fly through the end of an AIRAC cycle? E.g. current AIRAC 1406 ends on Jun 25 at 0000Z? and at the time while in air, will the FMC auto switch to AIRAC 1407? If that is the case, the FMC would have 2 cycles in her memory right? What happen if a waypoint has changed from 1 cycle to the next? Name may change, actual location may change and sometimes deleted.

 

BTW, how is the database updated in real life? It has to be done every 2 weeks on all fleet aircrafts.

 

Francis Leung

[g_precentralis 191]

Interesting question. Usually there are 2 airacs in FMC memory, but I think you cannot (or should not) change it in flight. I believe ATC would resolve that situation together with traffic flow management, even before aircraft takes off. 

[Ralgh 43]

You land with the same cycle that you took off with. Typically the next crew to take that plane will change it to the new one.

[scandinavian13 5,192]

 

 

I post the question here since a T7 flight is usually longer. What happen when we fly through the end of an AIRAC cycle? E.g. current AIRAC 1406 ends on Jun 25 at 0000Z? and at the time while in air, will the FMC auto switch to AIRAC 1407? If that is the case, the FMC would have 2 cycles in her memory right? What happen if a waypoint has changed from 1 cycle to the next? Name may change, actual location may change and sometimes deleted.
 
BTW, how is the database updated in real life? It has to be done every 2 weeks on all fleet aircrafts.

 

When it comes to procedures, the FAA overlaps the end of a cycle (by 24 hours) with the beginning of the next, for situations like these.  That way, for the last day of the cycle, you can technically fly with either (though flying with the most current data is always advised).  With the AIRAC, operators actually receive the new one 6 days before the previous one became effective.  As an example, the current AIRAC (1406) was effective 29.May.  Operators received 1407 data 6 days prior (on the 23rd).  This allows them to tailor it and prepare it for delivery to whatever unit they happen to be using.  As such, despite the end of the cycle having a hard cutoff, the operator has plenty of time to update it prior to a flight that would span the cutoff.  As Tom mentioned, you don't change the data during the flight.

 

Updates are made via a Data Transfer Unit, and can be done at any point the aircraft flies through its maintenance station (even if it's a hub's minor maintenance facility - it's not a vastly complex process).  Different manufacturers have different procedures for updates.

 

Fun fact:

All of us actually have it really "good" when it comes to our nav data.  The NDB (nav database) on various aircraft can be pretty poor.  As an example, a major US operator has to be extremely selective with data in its 757s.  Some 757s actually only fly in certain regions because they only carry specific nav data, and even then, they only carry select procedures and airports.  Whereas we can load the whole world, and just about any procedure we want, the real units have limited space, and operators choose data appropriately.

 

 

 

I believe ATC would resolve that situation together with traffic flow management, even before aircraft takes off. 

 

ATC doesn't even play a role at all in that situation.

 

The operator is required to file a flight plan according to what it can fly.  If an aircraft doesn't have a current database, it might not be an issue if the route does not include any of the updates in the new cycle (procedures don't technically "expire" - that's how interval updates like what Jeppessen does, can work).  If ATC assigns the crew something that the FMC does not have, then they simply say "unable" and get worked in via alternate means.

 

ATC/CFMU doesn't ever enter that discussion at all.  There's no overarching authority checking and verifying every plane is on the right cycle.  It's not a field in the flight plan, and there's no visibility into that information from their side at all.  CFMU might enter the discussion if you file an unacceptable plan because you don't have the right cycle, but it's not checking the cycle directly - it's checking what's in the cycle.

 

The basic idea is "if you file it, you can fly it."  If ATC changes it to something you cannot fly, then you tell them you're unable.

[Frankophile 1]

Thanks Kyle for that very full and informative answer... and thanks also to Francis for asking the question. Don't you just love the complexity of this 'hobby' of ours.

[cannonplug 126]

When I fixed planes back in the 90s, the data came on 3.5" floppies. Any idea what they're using these days? CD/DVD? Flash drives?

[scandinavian13 5,192]

 

 

Any idea what they're using these days? CD/DVD? Flash drives?

 

All of the above - depends on the manufacturer of the box.  Delivery to the client also depends on the subscription.  LIDO, Jepp, FAA, and so on, have different methods of delivery.  From the client to the box may also be different.

 

Some providers provide data tailoring, so they might actually just deliver the information on the appropriate medium for your aircraft.  Others (like the FAA) don't, so you have to tailor it in-house, and then put it on the required medium (floppy, USB, etc) for whatever the DTU requires.

 

One of the manuals for one of the boxes I was looking at earlier actually mentioned accepting Zip Disks...haha...can I get that on a 5.25" too???

[g_precentralis 191]

 

I guess I've chosen a wrong word. When I said "together" I didn't mean they sit down together and discuss the problem, nor I said they will check your cycle.

 

ATC does play a role in that way, if there is for example a new airway is introduced instead of old one, they have to manage traffic mess because there will be aircraft with old and new cycle FPs both approved for flight. In European skies, where they change airways every minute or so (exaggerated), it can become quite "messy" and enough to kick you (visitor) out from control room.

 

But, my point was that's not a pilot problem at all. As you said "if you file it, you can fly it"

[cannonplug 126]

Thanks, Kyle. I figured some of the old methods would still be in use. . . .

 

 

can I get that on a 5.25" too???

 

 

Funny, my wife and I were just the other day talking about how fascinated we were with 5.25" floppies saying: "Wow, they can fit that much information on that little thing?" Today, kids marvel at those floppies as well, but for an entirely different reason.  :(

[Airjep 1]

Hi Francis

 

New database always comes in 2 versions old and new. Normally they are updated a week before they expire and you can change between new and old anytime. Changing to early will also give you an warning on most FMC's today.

 

Regarding the amount of data is of course as mentioned depending on how much you can store in the system, but in the end also depending of how much you want to pay each month. Less data equals cheaper and so on B)

 

Where I work we update with 3.5 disks either from a loader or the aircraft have a disk drive installed where you can install disk and select what you want to upload.

We also have a small kind of laptop where all our software is installed and with that it is possible to load also the database and all kind of other software for computers.

Like the FADEC computer on a CFM engine you can upload the hole software from this unit and after approx.. 25 min. You have a new software installed on the engine ^_^

This is how much we are depending on computers today LOL.

 

Jesper

[jonesrob 97]

In the 80's we had the data on tape cassettes; the guys from the nav office would travel around UK to catch the fleet as they came in on the last rotation, and do the update.

 

Rob.

[scandinavian13 5,192]

 

 

ATC does play a role in that way, if there is for example a new airway is introduced instead of old one, they have to manage traffic mess because there will be aircraft with old and new cycle FPs both approved for flight. In European skies, where they change airways every minute or so (exaggerated), it can become quite "messy" and enough to kick you (visitor) out from control room.

 

haha - absolutely right.  I see what you mean now.

(And I'm with you on the airways over there - it's crazy!)

[aceridgey 330]

Our 737s  and 757s (Including 737 NG) update the nav cycle with a guy coming round with a floppy disk.

 

 

Fun fact.

 

When our 757's do the North American Charters, the 757 memory for nav data is not sufficient enough to have both Europe and the US airports. We're talking about computers around 25-30 years old here. A gigabyte of data was difficult to come by without building a pc the size of a house

 

Alex

[Goof 38]

 

(And I'm with you on the airways over there - it's crazy!)

oh yes.. Never try to file a valid flightplan between two regional airports in Germany.. CFMU and airway structure can be cruel :lol: and if you have one.. it isn´t valid the next day as everything has changed

 

god i love directs :wub:

[pcubine 143]

 

 

Some 757s actually only fly in certain regions because they only carry specific nav data, and even then, they only carry select procedures and airports.

Kyle

 

Off-Topic  I don't believe this is modeled in the CS 757. HaHa! What do think?