[SystemSafety] GPS jamming

Peter Bishop pgb at adelard.com
Sat Jul 13 12:18:19 CEST 2019

I am not an expert, but I understand EGNOS works out corrections to
standard GPS signals
based on a limited number of ground stations (who obviously know where
they are).

If spoofing is in a localised area, the ground stations (located
elsewhere) would not see the spoof (just the regular satellite signals),
so the resultant broadcast Egnos correction data would just make a small
correction to the spoofed GPS signal.

Or have I got this completely wrong?

Peter Bishop

On 12/07/2019 13:16, Dewi Daniels wrote:
> Peter,
> That is indeed very chilling. It seems that we have an aircraft
> operating with certified kit that ended up 12nm off course in
> mountainous terrain. Either the certified equipment on board the
> aircraft did not work as intended, or even more chilling, there is a
> fundamental problem with WAAS. I hope it's not the latter. The WAAS
> technical specification promises that "WAAS provides the additional
> accuracy, availability, continuity and integrity necessary to enable
> users to rely on GPS for all phases of flight, from en route through
> approaches with vertical guidance, at all qualified airports within
> the WAAS LPV coverage area". This does not appear to have been the
> case in this instance.
> Yours,
> Dewi Daniels | Director | Software Safety Limited
> Telephone +44 7968 837742 | Email d
> <mailto:ddaniels at verocel.com>ewi.daniels at software-safety.com
> <mailto:ewi.daniels at software-safety.com>
> Software Safety Limited is a company registered in England and Wales.
> Company number: 9390590. Registered office: Fairfield, 30F Bratton
> Road, West Ashton, Trowbridge, United Kingdom BA14 6AZ
> On Fri, 12 Jul 2019 at 12:32, Peter Bernard Ladkin
> <ladkin at causalis.com <mailto:ladkin at causalis.com>> wrote:
>     On 2019-07-12 12:21 , Mike Rothon wrote:
>     > The incident report is available on the NASA ASRS database at
>     > https://asrs.arc.nasa.gov/search/database.html. Search by Report
>     Number (ACN) for 1565516.
>     >
>     > It was a Cessna Citation 560XL, a mid-size business jet. These
>     are reasonably well equipped, usually
>     > a single or dual Honeywell Primus 1000 package (when built).
>     >
>     > I thought this system was capable of DME/DME as well, but I have
>     no idea how the solution would be
>     > compared or prioritised against a solid WAAS signal.
>     There is a presentation about the airport (KSUN, Hailey-Friedman
>     Memorial Airport at Sun Valley,
>     Idaho, from 2012 at
>     http://iflysun.com/wp-content/uploads/2016/12/FMAA-Power-Point-Presentation-010312.pdf
>     Horizon Air
>     seems to fly in there, with Q400 aircraft and a custom RNP (one
>     slide says they don't use the "Y"
>     procedure). There are two poor-resolution approach plates, RNP-W
>     and RNP-Y, both for RWY 31.
>     There are better-resolution plates available on the WWW, for example:
>     RNAV Y RWY 31
>     https://resources.globalair.com/dtpp/globalair_06239RY31.PDF
>     RNAV X RWY 31
>     https://resources.globalair.com/dtpp/globalair_06239rx31.pdf
>     RNAV W RWY 31
>     https://www.platinumairways.org/files/DOTW_Charts/KSUNcharts.pdf
>     There is part of the sectional at
>     https://skyvector.com/?ll=43.503780556,-114.295558333&chart=301&zoom=1
>     There is a fairly wide E-W
>     plain south of the airport, at elevations 4800'-6000' it seems,
>     and the mountains start about where
>     the airport is, with peaks at over 10,000' N, E and W.
>     Besides the RNAV, there is an NDB/DME approach also, coming off an
>     NDB and DME which is about 10nm
>     away from the airport. Decision point (visual contact) is about
>     5nm away from the runway, and 5nm
>     beyond the NDB/DME installation. There is no kit at the airport
>     itself.
>     Fix PRESN is named in the report. PRESN is an IAF for all these
>     approaches. Note the controller says
>     tower says AC just reported PRESN, and ARTCC radar was showing him
>     12nm NW of that.
>     The plates give the WAAS data, so KSUN is served by WAAS. Hard to
>     say how well, though.
>     The MSA is 13,000, and they were performing an approach to an
>     airport at 5320' (note two of the
>     above plates have this, and one has 5318'), so they will be
>     spending a lot of time on that approach
>     below the tops of the terrain, which in the vicinity of the
>     airport go up to almost 9000'. To be
>     12nm off track in that situation is exceptionally dangerous. To
>     see on the plate where the AC was
>     when he thought he had just passed PRESN, note that JUNOL to CAKIR
>     (the go-around point on the RNAV
>     approach) is about 10nm.
>     I agree with Mike's assessment that the incident is "chilling".
>     In comment on Dewi's and John's speculation that he might have
>     been operating with non-certified
>     kit, given it was a Citation I doubt it. In response to Dewi's
>     query if it is legal to fly IFR with
>     non-installed kit, the answer is no. The aircraft can only use
>     installed and regularly calibrated
>     kit and it is in the maintenance logbook what that is (with the
>     certificates if it is installed
>     post-delivery).
>     That doesn't stop the cowboys, though. But they tend to stop
>     themselves, in Darwinian fashion -
>     every US flight school has its story about the pilot who used to
>     go file IFR here and there without
>     an IFR rating - and how long he lasted (it is invariably a male,
>     and invariably a couple of years at
>     most).
>     PBL
>     Prof. Peter Bernard Ladkin, Bielefeld, Germany
>     MoreInCommon
>     Je suis Charlie
>     Tel+msg +49 (0)521 880 7319  www.rvs-bi.de <http://www.rvs-bi.de>
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Peter Bishop
Chief Scientist
Adelard LLP
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