The loss of an Azerbaijan Airlines aircraft during a routine flight from Baku to Grozny on 25th December raises some troubling questions about Russian air defence command and control.
Azerbaijan Airlines flight 8243 from Baku to Grozny in southwest Russia never reached its destination. Instead, the Embraer E190AR airliner crashed at 10.28 Azerbaijan (AZT) time on 25th December, hitting the ground three kilometres/km (1.9 miles) from Aktau International Airport on Kazakhstan’s Caspian Sea coast. The aircraft had left Baku at 07.55AZT, according to reports, bound for Grozny International Airport in southwest Russia. At around 08.20AZT the aircraft entered Russian airspace and soon after the crew reported the loss of Global Positioning System (GPS) PNT (Position, Navigation and Timing) signal reception. GPS, like most Global Navigation Satellite Systems (GNSSs), transmits PNT signals on frequencies of between 1.1 gigahertz/GHz and 1.6GHz.
Theirs not to make reply
The loss of the GPS signal had a knock-on effect on the aircraft’s Automatic Dependent Surveillance-Broadcast (ADS-B) transmissions. ADS-B responds to interrogation challenges from Air Traffic Control (ATC) Secondary Surveillance Radars (SSRs). When challenged the aircraft’s SSR transponder will squark on frequencies of between 978 megahertz/MHz and 1.090GHz. ADS-B information conveys several details about the flight including the aircraft’s identity, route and position. The latter factor is derived from the aircraft’s GNSS PNT receiver. With this information unavailable, it appears the aircraft was unable to share information on its location. The loss of the GPS signal was reported by the crew to air traffic controllers. According to flightradar24, the aircraft stopped sending GPS data between 08.25AZT and 08.37AZT. From 08.37AZT until 08.40AZT flight 8243 was transmitting incorrect position information. GPS transmissions stopped once more between 08.40AZT and 09.03AZT. They briefly reactivated between 09.03AZT and 09.04AZT before another gap in transmissions which lasted until 10.07AZT. From 10.07AZT until the crash at 10.28AZT the aircraft was transmitting correct GNSS information. Reports on 26th December by the Associated Press alleged that GPS jamming may have been a contributing factor for the crash.
Analysis performed by the gpsjam.org website reveals that Grozny, and its surrounding area, was subjected to high levels of GNSS interference on 25th December 2024. Grozny International Airport is to the north of the city and would have been subjected to that interference. The interference has been blamed on Russian GNSS jamming above the city and its environs. Russian authorities acknowledged that GNSS jamming was being performed at the time to protect the city against Ukrainian kamikaze Uninhabited Aerial Vehicle (UAV) attack. Jamming and spoofing the incoming GNSS PNT signals UAVs may rely on to navigate to their targets is a standard counter-UAV tactic. This may explain why flight 8243 lost the GNSS signal, possibly because of jamming, and then transmitted incorrect GNSS information, possibly because of Russian GNSS spoofing.
Theirs not to reason why
GPS jamming may not have been the only contributing factor. Pictures of the aircraft’s wreckage show the fuselage pockmarked with holes consistent with shrapnel. Fragmentation warheads employing shrapnel are commonly used in Surface-to-Air Missiles (SAMs). Euronews reported on 24th January that the aircraft was downed by a 96K6 Pantsir-S1 (North Atlantic Treaty Organisation reporting name SA-22 Greyhound) series short-range air defence system. Open sources state that the Pantsir-S1 employs 57E6 radio frequency/optically guided SAMs equipped with high-explosive fragmentation warheads.
The Pantsir-S1 is equipped with two radars; one of which is used for target acquisition and the other for fire control. Target detection is provided by the system’s 2RL80 S-band (2.3GHz to 2.5GHz/2.7GHz to 3.7GHz) radar which has a range of circa 27 nautical miles/nm (50km). Once a target is detected, engagement is managed using the system’s 1RS2-1 X-band (8.5GHz to 10.68GHz) and Ku-band (13.4GHz to 14GHz/15.7GHz to 17.7GHz) radar. The 1RS2-1 has a 15nm (28km) range. Sources suggest that the Pantsir-S1 is fitted with an integral Identification Friend or Foe (IFF) interrogator embedded within the 2RL80 radar. The interrogator operates in the Ultra High Frequency (UHF: 300MHz to three gigahertz) waveband. This should mean that the 2RL80, and hence the Pantsir-S1, easily receives ADS-B transmissions. However, if these ADS-B transmissions are being disrupted through jamming, can they still be received by the IFF?
Was there a man dismayed?
If the track on the radar screen of a Pantsir-S1 air defender is showing no ADS-B information, or that information is shown as incorrect, is that air defender going to presume the track is hostile? Armada has performed analysis of Russia IFF systems in the past and noted some of their shortcomings. For example, Russia’s Parol IFF system was said to be unable to receive civilian SSR squarks. Friendly military aircraft will have their Parol IFF transponders activated and will be responding positively to friendly interrogations. Hence, all aircraft not responding to the Parol interrogations are assumed as hostile, even if they cannot answer a challenge.
If GNSS jamming did prevent the Pantsir-S1 crew receiving ADS-B squarks, there are other ways that an aircraft’s identity can be verified. Simply having a laptop with a feed from a site such as flightradar24 could be helpful. Matching radar track data of the local area with the website feed may have informed the Pantsir-S1 crew that the aircraft was friendly. However, if the airliner’s transponder was unable to relay correct ADS-B information, this could have affected the quality of track data the website was showing. When playing back the flight on flightradar24, there is a gap between 08.07AZT and 10.07AZT. During this time no information regarding the flight appears to be available. Does this mean that the aircraft simply looked like an unidentified track to Russian air defenders and hence a potential target?
Even if this had been the case, why was someone in the local Russian air defence command and control structure responsible for protecting Grozny and its locale not monitoring ATC chatter? A simple air-band radio, with a suitably sited antenna, would have picked up radio traffic between the aircraft and air traffic controllers in range. Flight 8243’s crew warned that they had lost GPS navigation after entering Russian airspace. Surely this should have prompted an immediate ‘weapons tight’ order to Russian air defenders given that either incorrect ADS-B information was being shared, or that this information was unavailable for a particular flight? Were local air defenders warned that GNSS jamming was taking place and that this may affect civilian ADS-B transmissions? The loss of flight 8243, and 38 of its souls, has prompted many questions, whether Russian authorities provide answers remains to be seen.
by Dr. Thomas Withington
