[SystemSafety] Boeing 787 position flaw

[Martyn Thomas]

The report says:

/[Boeing] eventually traced the root cause back to the 787’s
packet-based data transfer system, which was passing the aircraft’s
position information from the integrated surveillance system to the
ADS-B transponder, according to ICAO documents.//
//
//In rare cases, after passing a planned turn upon crossing a waypoint,
the data packets that arrived at the transponder would contain either
the aircraft’s latitude or longitude, but not both. In those cases, the
ADS-B transponder’s software would extrapolate the 787’s position based
on the previous flight track before it made a planned turn at a
waypoint. It would continue reporting the aircraft erroneously on the
incorrect track until it received a data packet containing both the
latitude and the longitude of the aircraft./

Can anyone on this list explain how this works? Presumably the Lat/Long
are provided by GPS, so why would one of them be missing in a data
packet that contains the other? And why would the transponder software
have been designed to handle such an occurrence and to extrapolate the
missing value, rather than rejecting the packet and requesting another?

Martyn



On 15/12/2015 15:54, Robert Schaefer wrote:
>
> Two ATC agencies 'blacklist' 787 over position-data flaw
> 10 DECEMBER, 2015 BY: STEPHEN TRIMBLE WASHINGTON DC
> "Most of the Boeing 787s delivered to date contain a software defect
> that, in at least five identified aircraft, have erroneously reported
> their location to controllers, prompting two air traffic management
> agencies to put the Dreamliner on a “blacklist” for certain services."
>
> https://www.flightglobal.com/news/articles/two-atc-agencies-blacklist-787-over-position-data-419916/
>
> How do you test transponders? 
> Do you fly all over the world transponding, or do you generate and
> accept test data from a stationary test site?
>
>
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> systemsafety at TechFak.Uni-Bielefeld.DE

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