Here’s an interesting graph that compares Class A mishap rates for USN manned aviation (pretty much from float plane to Super-Hornet) against the USAF’s drone programs. Interesting that both programs steadily track down decade by decade, even in the absence of formal system safety programs for most of the time (1).
The USAF drone program start out with around the 60 mishaps per 100,000 flight hour rate (equivalent to the USN transitioning to fast jets at the close of the 1940s) and maintains a steeper decrease rate that the USN aviation program. As a result while the USAF drones program is tail chasing the USN it still looks like it’ll hit parity with the USN sometime in the 2040s.
So why is the USAF drone program doing better in pulling down the accident rate, even when they don’t have a formal MIL-STD-882 safety program?
Well for one a higher degree of automation does have comparitive advantages. Although the USN’s carrier aircraft can do auto-land, they generally choose not to, as pilot’s need to keep their professional skills up, and human error during landing/takeoff inevitably drives the mishap rate up. Therefore a simple thing like implementing an auto-land function for drones (landing a drone is as it turns out not easy) has a comparatively greater bang for your safety buck. There’s also inherently higher risks of loss of control and mid air collision when air combat manoeuvring, or running into things when flying helicopters at low level which are operational hazards that drones generally don’t have to worry about.
For another, the development cycle for drones tends to be quicker than manned aviation, and drones have a ‘some what’ looser certification regime, so improvements from the next generation of drone design tend to roll into an expanding operational fleet more quickly. Having a higher cycle rate also helps retain and sustain the corporate memory of the design teams.
Finally there’s the lessons learned effect. With drones the hazards usually don’t need to be identified and then characterised. In contrast with the early days of jet age naval aviation the hazards drone face are usually well understood with well understood solutions, and whether these are addressed effectively has more to do with programmatic cost concerns than a lack of understanding. Conversely when it actually comes time to do something like put de-icing onto a drone, there’s a whole lot of experience that can be brought to bear with a very good chance of first time success.
A final question. Looking at the above do we think that the application of rigorous ‘FAA like’ processes or standards like ARP 4761, ARP 4754 and DO-178 would really improve matters?
Hmmm… maybe not a lot.
1. As a historical note while the F-14 program had the first USN aircraft system safety program (it was a small scale contractor in house effort) it was actually the F/A-18 which had the first customer mandated and funded system safety program per MIL-STD-882. USAF drone programs have not had formal system safety programs, as far as I’m aware.