It’s the nightmare scenario: a consumer drone flying into a jet engine. But no one has actually done the tests that could reveal what would happen and inform safety.
That’s strange, given the increasing risk of such an incident. We need to know if it could cause an aircraft engine to explode in what is known as an “uncontained failure”, with hot, fast-spinning engine parts being shed in all directions, potentially piercing wings, fuel tanks and even the cabin.
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The only airliner versus drone safety tests done in the UK so far were to assess what happens when drones strike mock cockpits. That is better than nothing, but it only gives part of the picture.
The UK Department of Transport (DoT), the and the British Airline Pilots Association, a trade union, published the results of those tests in July. The findings – summarised in a  – said three popular sizes (400 grams, 1.2 kilograms and 4 kilograms) of consumer drone can “critically damage” helicopter windshields and tail rotors, and drones of 4 kilograms and above can damage aircraft windscreens. Interestingly, though, they can’t cause serious damage if a passenger jet is travelling at its take-off and landing speed.
Those tests led to the DoT for all drone owners. But drones can easily be built beyond the sight of the law using components and software, so registration alone is unlikely to work. A similar scheme introduced in the US in 2015 has not led to a single prosecution – and near misses are still on the increase.
Experimental fudge
With “limited resources available for the study”, no actual aircraft were used in those tests. Instead, a compressed-air gun fired drones at a static piece of an aircraft’s frontal fuselage. What’s more, the gun could not take a 4-kilogram quadcopter, so the main components of one – the lithium battery, motors, camera and electronics – were fixed to a single plastic arm and fired.
That experimental fudge has upset drone enthusiasts and makers alike, who want to see all the test data. But that is unlikely to be forthcoming on what the DoT says are security grounds, presumably because it could allow an attacker to work out the precise kinetic energy needed to penetrate a passenger jet’s cockpit.
Uncontained engine failures – which can happen when birds or failed internal parts send a turbine’s fast-rotating compressors off balance, shaking the engine apart in seconds – are among the most dangerous emergencies for a passenger jet. One happened on the ground at Chicago’s O’Hare airport in 2016 and .
By conducting realistic tests, not only would we get a much better picture of all the risks drones present, we might also find out if we can minimise them through better design, or if the only real answer is the use of robust geofences – GPS-enabled no-go zones – to keep drones away from flight paths.
Realistic drone-versus-engine tests would be expensive but need to be done soon. Aviation regulators already ensure engines are as robust as possible against bird strike and sand ingestion, and drones now need to be included as well. But without proper test results, they are regulating under an extreme lack of data, one aviation lawyer told me.
Time is running out. One investigator who specialises in identifying who owns the drones found at a crime scene calls drone ingestion by an engine a “when, not if” event.
If governments are going to allow drones to ply the skies, they have to make our aviation system as safe as possible. Running tests with “limited resources” is not good enough.
