Updating AIRAC navdata in the heavies
 

I was just wondering, how is the NAVDATA updated in the FMC's of large aircraft such as 76/74/73's etc.

Also, what if during a night flight, the AIRAC was due to change over night, and you flew into the new AIRAC data period, with the old AIRAC...what happens then?

Nav Data is loaded using a portable data loader (PDL) or an airborne data loader (ADL) from one or more standard (but differently formatted) 1.44 floppies.

The PDL is a portable unit which is plugged into the a/c system and the data transfered.

The ADL is a floppy drive directly wired into the a/c which does the same job as the PDL.

Each database is valid for 28 days and a new database is loaded into the FMC several days before the current one is due to expire. So the database should always be valid. However in the event that the data base can not be loaded or is lost in the post :D
then there is provision in the MEL to operate with an expired database. The crew will cross check waypoints and other data with their 'Jepps' charts to ensure currency.

Hope this helps,

Cheers.

Thanks for clearing things up, just something I had always wondered :>

As stated the Airac cycle is every 28 days. Every country promulgates and publishes any changes due to take effect within their airspace 28 days in advance. On the "Update" date, all relevant changes from every state's AIP are incorporated into a major database. A certain major UK airline runs two flight planning/navdata computers in tandem. One is live, and the other is a working copy.

All updated changes to standard routes as a result of the Airac cycle are loaded into the "dummy" system and checked for integrity. This can take an entire night shift for two nav data specialists, who will run each route on the dummy system to ensure that there are no route discontinuities. Once validated, the dummy system is copied over onto the live system, and engineering then updates each aircraft's FMS database in the manner descibed in the previous post.

Hope that helps.


Blue skies.