Sende in the Dronnes


On March 4th 2014 Janes Defence reports that the UK government has Released To Service (RTS) the new UK-built Watchkeeper Unmanned Aircraft System (UAS). The Watchkeeper was intended for service in Afghanistan as early as 2007 however the RTS process has brought on extensive delays – brought on in no small part because of concerns over civilian safety.

The RTS greenlighting of the Watchkeeper means that it is now considered safe enough to be used over civilian populations in the UK.

“These delays largely result from the Watchkeeper being the first UAS to go through the RTS process, which follows the MoD’s rigorous safety and airworthiness reviews to ensure the system can be safely operated over the UK and beyond, with certification to the same safety standard as manned aircraft.” 

The Watchkeeper is a UK-built drone derived from the Israeli-made Elbit System Hermes 450 which the UK has used in deployment in Afghanistan since 2007. The Hermes and the Watchkeeper share some components including the air-frame, two sensor mounts and two mounts for fuel tanks under the wings.

The two sensor arrays on the Watchkeeper are a synthetic aperture radar/ground-moving target indicator (SAR/GMTI) radar and a rear-mounted electro-optical/infrared (EO/IR) turret. SAR/GMTI is an active radar system (meaning it transmits radio waves and reads the reflection) that can be used to find and identify stationary and moving targets. This is a pic of what things on the ground might look like to a Watchkeeper operator via that radar:


The turret is a passive system that uses infrared heat signatures to differentiate between objects and is particularly optimized for finding warm things like people. This is what things look like through a similar FLIR system:


As currently specified the Watchkeeper can track targets for continued surveillance and can also “paint” them with a laser designator for targeting by weapons launched from somewhere else. The Israelis are rumored to have outfitted the Hermes 450 with Hellfire missiles (one slung under each wing from the fuel-tank mounts) although they have never publicly admitted to this configuration. Presumably the Watchkeeper could be configured the same way however there’s no indication that the UK plans to do this.

The British Army has logged over 86,000 flight hours with the Hermes 450 and has confirmed that they have crashed 8, which is likely one of the reasons that the UK decided to build their own derivation. Two documented Hermes 450 crashes in Afghanistan – one at the Bastion air base and one near Sangin (crash-landing in a mine-field no less) and another crash in Israel were all due to engine failure. The Watchkeeper has a new fuel-injected rotax engine built in France which should make it more reliable, especially at higher altitudes.

One crash per 10K hours of flight time is abysmally bad. While the British public doesn’t seem to mind terribly about surveillance in the UK nor about drone strikes elsewhere, they would likely be more upset if drones were raining out of the sky at a rate of 1 per 10K hours of flight time.


The extensive analysis of the crash at Bastion also finds a number of supporting problem areas involving training and logistics and notes that “most of the identified factors were driven by the fact that the H450 aviation system was an Urgent Operational Requirement (UOR)”. When the Hermes 450 was initially chosen the UK felt that they desperately needed a sustained-duration surveillance drone in Afghanistan so they deployed the 450 under a UOR. This means the minimum amount of testing needed for the military to feel confident that it the equipment will work (at least as well as the Israelis no doubt promised it would) but not any more, and a lack of experience in the army (as opposed to the RAF) with UORs for aircraft is noted in the report as an issue.

Another interesting observation from the MAA report is that the operators issued a command to the 450 so that it would go into a specific mode and got an unexpected (to them) response, causing the the UAS to perform a “non authorized manoeuvre at low altitude”. This meant that when the engine finally died of overheating the 450 went into a fail-safe circular glide pattern roughly where the failure happened. It didn’t try to land (which likely would have been possible) it just glided into the tarmac.

Its unclear if the UK government plans to use the Watchkeeper domestically for surveillance or if they will be flown over the UK for training only. It is clear that they felt that they needed to spend over half a decade testing and tweaking the design so that it would be suitably safe for sustained flight over the territorial UK. This could simply be a responsible government doing the necessaries to ensure that a critical piece of war materiel is safe to operate incidentally over civilians. That’s obviously true. It could additionally presage future Watchkeepers – possibly even a future armed variant – patrolling domestic UK skies but only time will tell on that account.


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