[SystemSafety] GPS jamming

Peter Bernard Ladkin ladkin at causalis.com
Fri Jul 12 13:32:11 CEST 2019

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

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


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

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