I’m hesitant to put down a few words on drones after the London Gatwick event. It may not be a time to be best received but at least the event is fresh in people’s minds. December’s unfortunate events at Gatwick struck me as being a poor example of risk management. Accepted that the outcome was a safe one.
Is it right to be risk averse? This is not a simple question given that “risk” runs a huge spectrum. Slicing it into two, we have the product of the likelihood of an event and the severity of the same event. To simplify let’s just talk about the worst-case severity and that’s generally a catastrophe.
In flying terms that’s the loss of an aircraft and all on-board. In aviation there are emergency procedures, built-in redundancy and a whole host of safety measures to reduce, mitigate or eliminate risk. Yes, it’s not practically possible to eliminate risk in all events.
Put a drone and an aircraft in the sky together and there’s a risk of collision. Sharing airspace means managing risk. There’s no zero-risk solution except to stop the operation of either the drone or the aircraft. If not zero risk, then what risk is acceptable?
There’s a classical probability term known as “extremely improbable”. It’s often expressed as a probability of catastrophe per flight hour of aircraft operation. Much of the design of a large civil aircraft is built on this simple idea.
In the case of a drone suspected of being a hazard to aviation its not so easy to do a safety assessment on the fly. Normally, a great deal of factual evidence is complied and reviewed as part of any assessment. There’s a sprinkling of professional judgement that comes into play too.
This is where the precautionary principle[1] can be useful. If as in the Gatwick case, little is known about the offending drone then its better to assume the upper limit of what it could be. The problem with being precautionary is that the approach has the tendency to escalate. Examples of that are emergency calls to the local police about red lights in the sky around Redhill. The lights turned out to be attached to tall construction cranes.
There then needs to be a counterbalance to this escalation and I’d call that; comparative risk. Since the dawn of aviation there have been other hazards in the air. These are birds. Some are small and flock together[2] and others are large[3]. This risk is managed but it still produces a good number of incidents and accidents.
The drone collision risk can be managed. What we saw at Gatwick was a poor example of risk management. Some drone sightings may have been police surveillance drones.
Ideally, since all airports have the same risk to address, there would be a set of common procedures that would be deployed in the event of drone encounters. The drone risk cannot be eliminated. So, a common approach to risk reduction and mitigation measures needs to be in place. I suggest that needs to be done in Europe and done quickly.
[1] http://ec.europa.eu/environment/integration/research/newsalert/pdf/precautionary_principle_decision_making_under_uncertainty_FB18_en.pdf
[2] https://en.m.wikipedia.org/wiki/Ryanair_Flight_4102
[3] https://en.m.wikipedia.org/wiki/US_Airways_Flight_1549
John Vincent 