This question was raised as part of this discussion.
Why are accident rates higher on smaller aircraft?
It seems the safety record of military, private and small commuter planes is much less safe than that of large commercial operations and I was wondering what factors cause this?
The amount of resources that go into commercial aviation are really amazing -- the amount of time, talent, money, and effort that have gone into making the airlines the safest mode of travel known to recorded history is really extraordinary, and the results reflect that.
Design
Aircraft are expensive, but a part of that expense is the extreme care that has been taken to make them highly reliable, with redundant systems and lots of advance warning systems when something is nearing the point of failure.
Fifty years ago, aircraft were less reliable; the engineers have incorporated the lessons learned. And, considering how much money an airliner make, airlines are generally willing to pay absolutely top dollar for the very safest design possible.
Small aircraft have also benefited from this learning process, but as a matter of economics, they don't get quite as much redundancy or refinement. While 99.999% might be "good enough" for the general aviation, the airlines can afford the (high) costs of adding more 9's onto the end of that number.
Maintenance
Again, the airlines can afford a maintenance process and inspection regime that would raise the cost of flying a light aircraft significantly.
Mechanics are trained to uniform standards and work in a carefully monitored environment where parts are exactly tracked and the aircraft have an incredibly detailed history of all that's been reported and fixed over their lifespan.
Manufacturers like Boeing and Airbus can see millions of hours of data and spot trends that are developing to head off incipient problems before they become widespread. This, combined with the way that the aircraft are engineered, makes things really, really reliable.
General aviation maintenance is good -- I'm not bashing that -- but airline maintenance, especially at the major airlines, is amazing. That's not free, but the results are there.
Pilot experience and training
Light aircraft are often flown single-pilot, by a pilot who probably has under 2000 hours, and who may have flown 200 hours in the past year.
On the other hand, airline pilots are typically hired with at least 1000 to 2000 flight hours, often more, and a captain at a major airline may well have 10,000 to 20,000 hours. Added to that, the crew has probably flown between 400 to 800 hours in the last year, as well as getting multiple days of training -- both ground school and simulator -- as well as at least one if not two checkrides.
Flying is their profession, not a hobby, and they spend time continuously studying the aircraft, its systems and checklists, the environment, and the regulations. And, they're trained to work as a crew -- if one pilot is about to make a mistake, the other pilot is there to catch it and keep things on track. Not everybody flying light aircraft has these resources.
All of this is possible because, while it is all expensive, airlines can afford it.
And the records speak for themselves -- one fatality in a commercial U.S. aircraft over the last several years -- which includes many millions of flights. I don't think any other human activity -- including sleeping in your own bed at night -- can claim a similar safety record.
The relevant point isn't that light aircraft flying is "dangerous" compared to commercial aviation; it's plenty safe by normal comparisons. It's just that airline flying is so incredibly safe, any other activity will look more risky in comparison.
Another factor: commercial airliners tend to fly at high altitudes, over most bad weather and conditions of poor visibility for most of their flight time. Light planes are typically unpressurized, with a ceiling of 12,500 feet (up to 15k feet for short periods of time), which puts them in the conditions of bad weather or poor visibility, not only during takeoff and landing, but for most of their flight time.
The majority of light plane crashes are weather and visibility related... typically a VFR pilot flying into IFR conditions, becoming disoriented due to poor visibility, and crashing... such as the JFK Jr crash.
Commercial flights don't tend to have this happen, partially because the pilots are trained in IFR flying so they're less prone to spatial disorientation when they can't see the horizon, partially because they have the experience and the equipment/information to detect and avoid really bad weather, and partially because they're usually flying over most bad weather and conditions of poor visibility, not in them.
Large commercial flights, two engines, two pilots. More eyes and hands to handle loss of an engine. Very high recurrent training standards mandated.
Owner flown and other private pilot flights, it's usually attributed to lack of training. Flying into IFR weather without the rating, or practice, or equipment (think icing conditions). Or fuel exhaustion. Much less training after an initial license, or add on rating (instrument, maybe commercial, maybe other plane types. For example, mine stopped after the instrument rating, and I only flew my plane, so I just became really proficient in it).
Medium to large Business, they typically have professional pilots flying the plane. Small business might have the owner as pilot and I'd have to see stat's on their accident rate. I bet the rate is pretty low.
Then there's things like helicopter conducting sight seeing tours over the Hudson River in NYC. I think that was mechanical failure.
Military - I believe that outside of war theaters, the accidents usually occur during training, and they do a lot of it. Fly enough hours, and something is bound to break, or an unrecoverable situation occur, or just plain human error occur.
For general aviation, it's mostly the higher probability of accidents caused by bad judgement; flying VFR into IFR, running out of gas, overloaded takeoffs, incompetent handling close to the ground, etc. Whereas the airline world is highly regimented and operates on clear go-no-go criterea, with backups of backups both system wise and procedurally. When I was bush flying on floats, the dangers were mostly due to the need to make constant judgement calls on weather and loads etc. It's a world of greys, not black and white and of living by your wits. Very challenging but loads of fun.
Anyway, filter out all the GA accidents caused by incompetence and poor airmanship, and I believe you start to approach the safety of airline flying. Because if you are in a Chevy Biscayne of the sky like a Cessna 172, that is halfway well maintained, on a sunny day, full of gas, and you have some minimal level of good skills and judgment, you really really have to work at it to kill yourself.
All aircraft and pilots must meet certain standards to be deemed fit to fly. For example: all parts used in an aircraft (general, commercial, or military) must have accompanying documentation attesting to their fitness for use in an aircraft - traceability to point of manufacture, inspection, etc.. Aircraft used in commercial transport do require more frequent inspection than general aviation, but that shouldn't make general aviation less safe. Commercial pilots require more frequent medical examinations, require periodic "check rides" and generally end up more closely monitored for proficiency than private pilots. Also, commercial pilots tend to accumulate far more flying hours, so commercial pilots are usually more experienced than private pilots. That said, commercial pilots always start out as private pilots. General aviation aircraft far outnumber commercial aircraft; there are far more general aviation aircraft movements than commercial aircraft. Military aircraft have to operate in hazardous conditions - combat aircraft have to be flown to the edge of their flight envelope to gain a tactical advantage and/or escape a threat; even military transport sometimes have to be operated at their extremes to either get in and out of tight and/or unprepared places or avoid becoming a target. This sort of flying must be practiced regularly so that the pilots get it right when it matters most, so military flying is often riskier than non-military, even in peacetime.
So,
A higher incident rate among general aviation can be attributed to sheer statistics - just more of them around, and also to a lower level of pilot skill, experience, or discipline.
A higher incident rate among military aviation can be attributed to the extremes to which plane and pilot have to be pushed, and the greater likelihood that either/both will from time to time be pushed a little too far.
