Gary, modern ejection seats have attitude sensing
systems and you can eject inverted. The seats are
rocket powered and fly the seat around to go up.
The Yak 38 had an automatic seat probaly without
attitude sensing. See here: https://en.wikipedia.org/wiki/Yakovlev_Yak-38
Mike
At 12:51 PM 8/18/2016, you wrote:
Reminds me of the automatic override emergency
seat ejection system, that was in use (for a
very short time), many years ago. Apparently the
system was not set up to deal with inverted
flight - ouch! Gary -----Original Message-----
From: Aus-soaring
[mailto:[email protected]]
On Behalf Of Simon Hackett Sent: Thursday, 18
August 2016 12:17 PM To: Discussion of issues
relating to Soaring in Australia. Subject: Re:
[Aus-soaring] [gfaforum] Airpath compass > If
the GPS system goes down, getting lost is the
least of your problems. I can think of only two
scenarios - hostile action (probably nuclear
war) or a Carrington event. In any case over
the next few years we will be talking around 100
GNSS satellites from several independent
systems. GPS/Glonass receivers are commonly
available and GPS/Glonass/Galileo/Beidou/QZSS
are increasingly available. > One of those rare
times that I pipe up on something here these
days. Hereâs evidence of such a double failure
in recent times, due to neither of your
scenarios, in a real aircraft with a lot of
internal redundancy:
http://www.bushflyingdiaries.com/2013/10/double-gps-system-failure.html
And I have another GPS failure mode to relate.
It amounts to âhuman error in running the GPS
network, triggering a software driven example of
poor choice in system specification' For a week
or two, a year or two back (Iâd have to dig up
the dates) the entire fleet of Pilatus PC-12âs
in Australia had non-functional GPS systems, due
to what turned out to be a stuffup in the
configuration of a satellite on the northern
edge of the Australian region, that started
presenting invalid SBAS data that the PC12
Honeywell GPS systems decided was an attempt to
subvert the GPS system. In response, in
accordance with the (then) software specs (i.e.
not a bug, but an intentional feature), the GPS
systems on board shut down on the basis of not
being able to trust the data being received. It
arguably should have just shut down SBAS
reception and reported that and kept right on
going otherwise - but thatâs not how the
system designers had specified the outcome in
the presence of bad SBAS data. It took Honeywell
about a week to identify the cause and come up
with the (obvious) workaround - disable SBAS at
each aircraft start (its on by default) - until
the Satellite itself got fixed (and it did then
get fixed). In that week or so in the middle,
the entire Australian fleet of PC-12NGâs
(including mine) had no onboard GPS that worked.
Amusingly, the less sophisticated GPS in my iPad
kept running with AvPlan just fine (redundancy,
redundancy, redundancy) The washup here is that
another scenario exists in addition to hostile
action or a Carrington Event - human error in
the operation of the GPS system itself, combined
with GPS receivers that are too smart for their
own good (arguably also human error - in terms
of specification of how theyâre to work in the
presence of doubtful input data). The root cause
here appears to have been a botched
configuration change on a *production* satellite
somewhere in the vicinity of the equator. Simon
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