(CNN) Ukraine’s Zelensky fires Air Force chief, days after fatal F-16 crash; Patriot Likely Cause

(CNN) Ukraine’s Zelensky fires Air Force chief, days after fatal F-16 crash.

The most likely cause is not a hardware failure, but an administrative  failure of the IFF Mark XII (identification friend or foe) protocol, resulting in a Patriot friendly fire incident.  Mark XII is 20  years old. Absent recent upgrades, the system is not as foolproof as current technology  permits.

An IFF transponder, as carried by an F-16, is an  automatic combination of a receiver and transmitter. When it receives an query from a friendly force, the transponder:

  • Validates the request as originating from a friendly force. This is the result of a successful cryptographic operation, which requires that the aircraft IFF  computer, and ground computers, are programmed with an identical code  that changes frequently.
  • If the aircraft  IFF computer validates the request, it responds with the current altitude. Upon receipt by ground receivers, the aircraft is marked as friendly. Absent recent military upgrades, this response does not provide the location, which must be separately determined from the ground.
  • If the IFF request is not validated, there is no response; the aircraft status defaults to foe, allowing anti-aircraft systems to engage.

Mark XIIA Identification Friend or Foe (IFF) Mode 5 began U.S. deployment around 2013. It provides ground air defense with exact location of the friendly aircraft. Prior systems do not. The web suggests that few foreign customers have this upgrade. See Korea – F-16 Identification Friend or Foe (IFF) & Link 16 Upgrades.

In the absence of Mode  5, location must be determined by a separate system, radio direction finding (RDF). Contrary to the impression given by old war movies, it has, since 1926, been an instantaneous procedure.  Nevertheless,  it is a separate system from a Patriot battery target radar, with the difficulties of system multiplicity.

So these things must be reliable, synchronous parts of the kill-chain:

  • The aircraft IFF and the ground query system codes must be up-to-date.
  • The RDF system must provide accurate information.
  • That information must be communicated to all Patriot batteries.
  • The Patriot battery must integrate this information.
  • The Patriot battery targeting function must be blocked.
  • Besides administration, all the  hardware has to work.

Any failure in the chain potentiates  a friendly fire incident.

Since the IFF Mark XII protocol was adopted 20 years ago, GPS has made precise location awareness almost trivial. Mark XIIA Mode 5 can respond to query with position, in a secure manner, by use of encryption. In future developments, the query function could be integrated into the radar itself, using code division multiplexing (CDM), reducing the administrative burden of separate systems. See (IEEE) MIMO radar: Time division multiplexing vs. code division multiplexing. This is an expensive move, but likely in view of the heightened awareness  required with swarm drones.

Was Zelensky justified in firing Mykola Oleshchuk? Perhaps it was triggered by Oleshchuk’s attack on a member of parliament. Quoting (Al Jazeera) Zelenskyy fires Ukraine’s air force commander after deadly F-16 crash:

The dismissal came on the same day that Oleshchuk directed scathing criticism at a lawmaker who is deputy head of the Ukrainian parliament’s defence committee for her claims that the F-16 was downed by a Patriot air-defense system. Ukraine has received an unspecified number of the US-made systems.

Their nerves are frayed. In Japan, they say, “Fix the problem, not the blame.”