This article will not address the legal aspect nor the international law implications of one nation blocking GNSS reception over the territory of another sovereign nation. This is above my pay grade. Let me just say that the issue is under discussion at all levels starting from the UN to ICAO to NATO and the US military. But there is a long way between international discussion “Pacta Sunt Servanda” and the real world. Just look at the Ukraine.

Inertial system use dead reckoning DR for navigation. If you know your starting point and have good enough accelerometers you can calculate with great precision your current present position. How ever INS and RLGs will accumulate an error over time. This error will be regarding Location PP, heading of the platform and to a certain extant the speed. These errors can and are corrected by updating the present position using a different source. Normally this sensor is GPS (or another GNSS).

The backup for GNSS as an update source for airplane position is using ground based DME transmitters.

Israel’s airspace and for that matter the entire world’s airspace is relying increasingly on satellite-based navigation. – PBN (Performance Based Navigation) an airline/airplane/crew can fly with different approval levels based on qualifications all the way from takeoff to 200 feet on approach based on PBN.

In Israel you almost never get Radar-Vectored for final approach.

The layout of DME beacons near TLV airport, is not optimal due to the shape of the country which is long and narrow – this presents a geometric challenge as some angular difference is required for the position calculation. This layout and geometry do not allow for DME based position update for all approaches to runways 30 21 26 during what can be referred to as base leg.

Worldwide there is a trend of decommissioning VORs and DME beacons. GNSS is becoming the only source for updating PP.

I am not familiar with current technology that allows ATC personnel, specifically Approach and tower controllers to know what is going on at the airport surrounding. Not in terms of distance nor altitude.

However, there is one piace of technology which is relevant – commercial airplanes that are flying at these places. We onboard have everything needed to know what’s going on. A jetliner is a giant GPS receiver with a computer that analyses how good or bad the reception is.

This information must be relayed in real time to ATC they do not have access to this information. Pilots do. We must relay every anomaly observed as soon as we can.

So other than navigation accuracy what else is influenced? Well, quite a lot of systems use GPS data. These include EGPWS Ground proximity warning system, false alarms, navigation and heading accuracy, ADS-B in and out. AFS-B out will be switched off automatically by the airplanes computers thus degrading ATC abilities and pilots Situational Awareness. When you do not see any airplane over Israel – this is not a FR24 bug. It is because there is a GPS blockage and all the airplanes stop transmitting on ADS-B.

Spoofing is something that as far as I know happens only over the Black Sea while President Putin is on vacation, And the Russians spoof the naval vessels to believe they are at an airport. This is done to prevent drones from taking of as they are prevented by Geo-fencing from doing so.

Boeing airplanes seem to be prone to have degraded capabilities in a less-than-100%-of-sensors-fully-functioning environment, compared to Airbus airplanes. Like, the 737 Max with an AOA malfunction and the 777 Radio altimeter to 5G interference. Some Boeing models are using raw data GPS present position unfiltered and not “Best available” present position. This results in EGPWS false alarms low altitude EICAS alerts regarding ADS-B and heading issues on HUD.

The issue of Airplane systems performance in a GPS blocked environment is not regulated under CFR 14 FAR part 25.

How dangerous is the situation?

Well as a stand-alone issue it is not that threatening as of now.

However, aviation safety is based on layers of risk mitigation. Swiss cheese. The person who is blocking GPS over Israel Lebanon Cyprus and Turkey just removed a layer.

We must adjust.

We should not get used to the No-GPS-No-Problem state of mind.

The space shuttle “Challenger’s” cash is attributed to Normalization of deviation.

Authorities should not wait for the problem to go away.

Redesigning an airplane’s Avionics system takes decades and will most likely not happen without legal requirements and enforcement.

But ATC should practice more Radar Vectors.

And mostly the DME should not only not be decommissioned, but more beacons should be added.

We must adjust

We must not sit and wait for this to go away.

We must not get used to sub-standard environment, we have to treat it as a threat to safety.

Stay safe.

ICAO on GNSS jamming.

IATA paper





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