I respect
@lisadoc's expertise. As one with degrees in engineering and physics, and a 30 year career applying that knowlege, I'm more than highly sceptical that the above scenario would result in little or no damage. I would expect the turbine to be pretty much destroyed.
To be clear, I didn't say that. Taking a Mavic, or a Phantom, or even a baseball, down the core would potentially cause significant damage to a modern jet engine. Taking a Mavic outside the core could potentially cause significant damage to fan blades, or only minor damage - it just depends. Either way, with most modern commercial aircraft, that damage would not likely be catastrophic (irrespective of the phase of flight), as it would/should be contained to that engine and most aircraft can fly/takeoff/land with only one engine available. Since drones don't tend to fly in large flocks, incidents like the "Miracle on the Hudson" are also not likely, since impacting multiple engines with a drone is virtually impossible.
However, the assumption that a strike involving a drone would necessarily involve an engine is misplaced. Let's take as our basis, the one other flying object impacting aircraft that we do have data for - birds. With all bird strikes, only 13% involve a strike with an engine. That leaves 87% impacting another component of the aircraft. Beyond that, some type of damage (minor or major) results only 30% of the time a strike occurs in an engine. This would assuredly be much higher for a drone in the engine. However, for the remainder of the components, damage occurs only approximately 8% of the time. And these figures (the percentages with damage) are likely significantly inflated, due to the fact that most strikes without damage go unreported. The FAA estimates that only 20% of all strikes are reported, meaning 80% of the strikes that occur never make the database. For other parts of the aircraft, this means that damage probably occurs in only roughly 1-2% of the strikes.
Even if you double or triple these figures(or heck, even multiple them by 100) for drones, the result means that an incident with a drone will likely not be significantly damaging. Coupled with the astonishing low rate of drone strikes per flight hour (of the drones, not the aircraft: see above), the overall
risk of a drone striking a commercial airliner is exceedingly low.
Risk, as I noted previously, is probability times severity. Even if you assume an elevated severity measure for a drone strike (not one that I would make but for the sake of other's arguments, I will assume this), the other factor - probability - is vanishingly small. There are other risks that would also result in quite severe consequences (e.g. someone with a Stinger missile sitting just outside an airfield) with a much greater certainty and to a much higher severity degree, but we don't irrationally chase every potential risk out there.
I'm not suggesting that drone operators be allowed to do whatever they want, whenever they want. I think that most potential significant instances involving drones would be with "bad actors", who, despite regulation or law would not be stopped if they had ill intentions to act negatively to impact aviation. The question is, are we going to treat the voluntary guidelines currently in place that guide the remainder of the UAS community as sufficient or do we feel the need to impose significant restrictions on recreational (or even commercial) drone operators? It's a legitimate question worthy of debate, but it is also critical to not fall victim to the emotional or ill-informed arguments that are often proffered in this field, especially as it pertains to risk.
