[SystemSafety] GPS jamming

Dewi Daniels dewi.daniels at software-safety.com
Fri Jul 12 14:16:02 CEST 2019


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.


Dewi Daniels | Director | Software Safety Limited

Telephone +44 7968 837742 | Email d <ddaniels at verocel.com>
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,
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On Fri, 12 Jul 2019 at 12:32, Peter Bernard Ladkin <ladkin at causalis.com>

> 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
> 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).
> Prof. Peter Bernard Ladkin, Bielefeld, Germany
> MoreInCommon
> Je suis Charlie
> Tel+msg +49 (0)521 880 7319  www.rvs-bi.de
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