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Ukraine International Flight PS 752: A Shakespearean Tragedy?

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The past couple of weeks have played out like some macabre adaption of the Bard’s greatest works. The opening scene was the attack on the US Embassy in Baghdad by Iranian backed militias recruited, trained and directed by Major General Qasem Soleimani of the Islamic Revolutionary Guard Corps (IRGC).  

The attack on the Embassy was in response to the seemingly never-ending cycle of violence in the Middle East. The militias had attacked Kirkuk airbase and killed an American contractor and the US responded by launching airstrikes on militia facilities in both Iraq and Syria, killing some 25 militia personnel. The Embassy attack came directly after a funeral for those killed in the airstrikes and it is still uncertain if the assault was pre-planned or simply a violent extension of the mourning.

The IRGC, however, must have calculated that the US has something of a trigger-point when it comes to Embassy attacks: the bombing of the Beirut Embassy in 1983 and the hostage taking in Iran in 1979 still linger long in the corporate memory. The latter, although not resulting in US casualties, was seen as a key factor in President Carter’s election loss in 1980 and 2020 is, after all, an election year. The parallels are important to consider.


In response, the main act of the Tragedy was the precision strike by a UAV on General Soleimani’s convoy near Baghdad airport. Exactly as per the script, the General was killed along with many in his security detail and little/no collateral damage inflicted. Revenge was inflicted by the forces of ‘good’ and the ‘villains’ retreated to lick their wounds and consider their next step. 

The third act, and one that many observers fervently hoped was also the denouement, was the retaliatory missile strike on US bases in Iraq. The IRGC carefully calibrated this attack; a significant number of ballistic missiles were fired to look good on the domestic newsreels but launched at a time when most personnel would be in bed and not vulnerable in the open. Furthermore, the use of ballistic missiles rather than militia-fired rockets is in itself telling: the rocket plumes and trajectories of ballistic weapons are eminently observable by satellites fitted with specialist sensors that detect the rocket motor and by ground/ship based Anti-Ballistic Missile (ABM) radars. These systems enabled sufficient warning to be provided for personnel to get into cover. 

There is also the rumour that the IRGC tipped off elements of the Iraqi forces, who, in turn either deliberately or via behavioural change, would have cued the US forces that something was afoot. If the militias had used closer range systems, such as 122mm rockets, then warning time is significantly reduced. 

I’ve had the ‘pleasure’ of being on the receiving end of both ballistic missile and short-range rocket attack; with the former, the warning was sufficient to seek hardened protection and wait. With the latter, there is barely time to roll out of bed and pull the ‘Kevlar duvet’ over oneself before the explosions start. Therefore, the use of ballistic missiles was, in my opinion, a very carefully judged attempt at de-escalation by the IRGC and elements of the Iranian regime. Enough to assuage hurt pride and the embarrassment of so easily losing a senior commander, but not violent enough to invite further US retaliation. 

Like so many Tragedies, both Shakespearean and more modern, the tale then features a dramatic twist. When I first heard reports of a Ukrainian International Airlines aircraft, Flight PS752, crashing near Tehran, I, like many of my defense and aviation colleagues, instinctively thought it was an accident with a bizarre timing coincidence. The initial photographs of the wreckage appeared to confirm the hypothesis that it was an uncontained engine failure, leading to catastrophic break-up of the engine on the wing.

When a turbofan engine disintegrates, the turbine blades can break up and create a cloud of high energy, high temperature fragments. These fragments can puncture the fuselage, leaving shrapnel-like damage, and cut control systems as well as hydraulic and fuel lines. 

Such an uncontained failure was the primary cause behind the Sioux City DC-10 crash in 1989, and, more recently, to a Southwest Airlines 737-700, Flight 1380, in April 2018. This latter incident was my unconscious confirmation bias for Flight PS752, which was a similar 737-800 series aircraft. In the Southwest incident, the engine exploded causing fragment damage to the fuselage, an explosive decompression in the cabin and resulted in the partial extraction through a broken window of a passenger who, sadly, later died from her injuries. 

My imagined sequence, therefore, for Flight PS752 was a catastrophic engine failure, loss of cabin pressure, possible loss of flight controls and a crew struggling desperately to save a wounded aircraft and, ultimately, failing.

Why did I not assume it was a Surface to Air Missile attack? I just couldn’t see how an Air Defence battery could mistake an airliner departing a major international airport on an established Standard Instrument Departure (SID) and ‘squawking’ an allocated IFF (Identification Friend or Foe) transponder code for a threat. 

The ‘squawk’ is important. All aircraft operating in Controlled Airspace are allocated a discrete transponder code to aid Air Traffic Controllers to identify, track, deconflict and control aircraft. As the radar beam passes over the aircraft, the transponder is triggered to respond with both the 4-digit code, and also, if Mode ‘Charlie’ is selected, a read-back of the aircraft’s current altitude above mean sea level. Military SAM radars also have an IFF Interrogator which can distinguish civil ‘squawks’ and, using appropriate cryptographical codes, determine which military aircraft are friendly and which are potential threats. 

Therefore, if fitted with such a simple method of determining ‘friend’ from ‘foe’ why did the SAM battery open fire? At the top level, it’s either a deliberate act or a tragic mistake.

I don’t buy into the deliberate act hypothesis. What would be the regime’s motive for committing such a heinous crime? If we assume that the ballistic missile strike was calibrated to draw a line under recent events, then there would be little to gain politically by shooting down an airliner and inflaming tension yet again. Furthermore, if the regime wanted to send a message to the US and its allies, why select an airliner from a non-aligned country, full of 3rd party nationals and your own? The world is very sensitive when it comes to attacking airliners; they are patently non-combatants and much of the world’s trade depends upon them receiving safe passage, free from interference. 

Any sympathy that Iran may have accrued as a result of onerous US sanctions and the assassination of a top military officer will inevitably diminish or evaporate as a result of this act. The evident dislocation that the regime suffered trying to respond to the incident is also telling — there appeared to be significant confusion over what had happened. They genuinely did seem to be ignorant of the role of the IRGC in the incident in the immediate aftermath. One can only imagine the horror at discovering their culpability. 

There does remain a lingering possibility that someone at a senior level in the IRGC felt that Soleimani’s death had not been adequately avenged by the missile strikes. Ordering the shootdown of a foreign airliner seems an odd way of expressing such bloodlust given that the IRGC employ proxy militias all over the region and have extensive low-tech threats that can challenge and attack shipping in the North Arabian Gulf. Regimes such as Iran also tend to deal harshly with commanders who go ‘off message’ – it would take someone very senior to calculate they could make such a move and survive the consequences.

Therefore, in my opinion, the principle of Hanlon’s razor applies here. It was not a calculated, malicious act, but a tragic mistake, effected at the lowest unit level. But why?

To understand ‘how’ if not ‘why’ it’s important to put oneself in the position of the SAM Battery crew. The current ‘official’ position from the IRGC is that the airliner was approaching a ‘sensitive site’. This statement is informative. The IRGC would have been informed, at a senior level, of the missile strikes. Doubtless, as any sensible military organisation would do, they would have likely, tacitly, informed their missile crews that the possibility of a US strike would be higher than normal that night – therefore, there is the distinct possibility that the SAM Battery was on an enhanced state of alertness.

Anyone that has studied the ‘Western Art of War’ will understand that the Suppression or Destruction of Enemy Air Defenses (S/DEAD) is a key battlespace shaping activity to permit NATO aircraft to operate at greater freedom. Therefore, sitting in a SAM Battery radar or command and control vehicle has the effect of placing a target on one’s forehead. The shootdown of an RAF Tornado GR1 by a US Patriot missile system during Operation Iraqi Freedom in 2003 was caused by the failure of the Tornado’s military Mode 4 IFF and the flight profile as it recovered to Ali Air Salem airbase closely approximating that of an Anti-Radiation Missile (ARM). The Patriot crew, understandably nervous they were being targeted, acted under self defense. 

There is a credible theory that the Iranian SAM battery, tasked with protecting a sensitive IRGC site, as well as guarding Tehran itself, and already on a heightened state of alert, suddenly detected a target on their screens as it climbed into the radar horizon. Doubtless, IRGC SAM batteries are briefed to expect ‘pop up’ attacks deep in their own airspace from B2 Spirit stealth bombers. What we don’t know is the Command and Control chain influence upon permission to fire, nor the extant rules of engagement.

Most Middle Eastern countries, due to their largely conscripted armies and fears over reliability, have highly centralised command structures, requiring a high-level commander to approve weapon release. Indeed, this very convoluted firing chain has been successfully exploited by Allied and Israeli air forces over recent campaigns. The IRGC are, presumably, considered more reliable and politically pure. Learning from the experience of other Middle Eastern countries, they may well have granted a higher level of autonomy to individual battery commanders, especially in a potential ‘use it or lose it’ situation against a radar picture that is within the parameters of an expected ARM attack delivered by a Low Observable platform. 

In such circumstances, only a few seconds are available for appreciation, decision and action. It is analogous to a cop shooting a suspect dead thinking he’s reaching for a weapon, only to find they were trying to get their phone out of their pocket. Pressure, fear and expectation are all powerful drivers.

The remaining mystery is the IFF. Most SAM systems have IFF interlocks of some sort on the firing system – helping to prevent ‘blue on blue’ engagements. The ATC radar trace, if released, will show if PS752’s transponder was working correctly. There remains a possibility that the crew were changing squawks as part of the SID prior to handover to another ATC agency, or, in doing so, had inadvertently left the transponder in ‘Standby’ mode rather than reselecting it ‘On’ (it is common practice in aviation to select the transponder to Standby whilst changing squawks to avoid inadvertently cycling through an emergency squawk code and causing ATC to react). However, the most obvious point of technical failure in the SAM unit is the IFF interrogator.

Sadly, the most obvious point of ultimate failure remains the SAM crew. Despite increasing automation, over 80% of all air accidents are still caused by Human Error. We are imperfect machines. Perhaps the crew were tired, on edge and startled by the sudden appearance of a target seemingly matching an expected threat system. Perhaps they were scared. Perhaps they were still angry at the loss of a senior commander. Perhaps the IFF interrogator was defective - perhaps they never even checked it. For whatever reason, ultimately, they took the shot.

They will now have to live with the consequences of that fatal decision. Like all flawed heroes and tragic villains in Shakespeare’s work they will suffer the fate that’s due – and one that will inevitably be unforgiving in order to provide the necessary closure to all of the injured parties.