The probability of being in a fatal airline accident is ridiculously small, so small in fact that if you make it to the airport, the odds are well in your favour you’ll get to your destination airport (The chances you won’t are around 0.5 x 10^-6)*.
Airliners have lots and lots (and lots!) of redundancy in their systems and propulsion though, so you’d expect that even if they suffer a single failure, they could ride it out and land safely somewhere……..General Aviation aircraft, particularly your typical Cessna style Single Engine Piston powered machine, have somewhat less layers of redundancy (the lack of a second engine being the obvious one!).
Next to pilot error, engine failure is going to be the most likely cause of an emergency / accident. It’s about 0.00315789% probable of occurring* (2006-2007 it happened just 24 times for 760,000 hours flown by GA aircraft, 4 of which were on the ground).
As a result, the rules for how low you can fly come from Rule 5 of the ‘Rules of the Air’, it’s goal is to ensure pilots are flying high enough at all times such that should they suffer an engine failure, the pilot has enough altitude to make an emergency landing without endangering those on the ground.
It defines three key provisions:
- 500ft : An aircraft must not fly closer than 500ft to any person, vessel, vehicle or structure.
- 1000ft: When flying over the congested area of any city, town or settlement, an aircraft must fly high enough to land clear of the area without damage to people and property on the surface should an engine fail. OR fly not less than 1000ft above the highest fixed object within 600m of the aircraft – whichever is higher.
- 1000 People: When flying over an organised open air assembly of more than 1000 people, the aircraft must fly high enough to land clear of the assembly without danger to people and property on the surface should the engine fail. OR fly not less than 1000ft above the assembly – whichever is higher
So how safe is it to fly in a single engine piston class general aviation aircraft? EASA (European Aviation Safety Agency), have done some risk assessment work.
They found that the fatal accident rate in a single engine general aviation aircraft caused by engine failure, was 0.66 x 10^-6 per flight hour (0.00000066). So statistically, you’d have to fly a little over 1.5 million hours before the accident would occur……I’m willing to bet most non-instructor GA pilots in the UK don’t clock more than 100 hours per year, so statistically it’s still an unbelievably safe way to travel.
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