[SystemSafety] Boeing 787 position flaw

[paul_e.bennett at topmail.co.uk]

On 15/12/2015 at 11:51 PM, "Bernd Sieker" <sieker at causalis.com> wrote:
>
>On 15.12.2015 18:08, Martyn Thomas wrote:
>
>> 
>> 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?
>
>My understanding is that the transponder does reject the malformed
>packet and goes into dead-reckoning mode, extrapolating the course
>from previously received well-formed packets. So it does not use 
>the
>single lat or long value from the malformed packets.
>
>This behaviour seems reasonable to deal with an occasional single
>packet garbled in transmission.
>
>In effect, the airplane would send position reports as if it were
>continuing straight on instead of making the planned turn at the 
>waypoint.
>
>
>> 
>> Martyn

In which case there should be a limit to the number of estimated 
positions it made. Even including a marker that states the position 
is estimated would be a help.

Regards

Paul E. Bennett IEng MIET
Systems Engineer

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