St Lucia July 2022

[struth]

I hope you can swim a long way!

Its a colloquial aviation backronym... "Engines Turn Or Passengers Swim", referring to the inevitable emergency water landing of a twin engine aircraft after a double engine failure over water outside gliding range of land.

[Macca]

chance of both engines failing is so low that you'd never leave the house if that level of chance event was an issue.

According to the FAA the probability of just one (jet) engine failing is one event per 375,000 flight hours.

Someone better at maths than me can work out the chance of both going down.

[struth]

they said titanic couldn't sink too

[dave2010]

also known as Engines Turn or Passengers Swim.

See https://en.wikipedia.org/wiki/ETOPS

Did LA to Sydney years ago - 1991 I think. I can't remember all the details. Might have been a Tristar, but at least there are a few island diversions possible. On the return journey we stopped in Hawaii.

There really aren't many diversions possible on the route across to Brazil from London.

Air travel is statistically very safe - but that doesn't mean that things can't or won't go wrong. Engineering, materials and operational factors all have to be very good.

[dave2010]

chance of both engines failing is so low that you'd never leave the house if that level of chance event was an issue.

According to the FAA the probability of just one (jet) engine failing is one event per 375,000 flight hours.

Someone better at maths than me can work out the chance of both going down.

Depends if events are independent or not. If they are - just square the probabilty - but often one failure may trigger another. They may not be closely interlinked, but often there is some linkage - for example if fuel has to be moved from one side to the other - etc. I don't know how any analysis of non-independent events is done. Another linking might simply be via the environment - flying a plane on just one engine may impose a higher load on the remaining engine, thus increasing the probability that it fails. I think the ETOPS rules require some duplication of parts which might contribute to one or other engine failing - for example fuel pumps, but there's probably more to it than that.

[Roy S]

Think I’ll see if there’s a boat back

[struth]

[CageyH]

Depends if events are independent or not. If they are - just square the probabilty - but often one failure may trigger another. They may not be closely interlinked, but often there is some linkage - for example if fuel has to be moved from one side to the other - etc. I don't know how any analysis of non-independent events is done. Another linking might simply be via the environment - flying a plane on just one engine may impose a higher load on the remaining engine, thus increasing the probability that it fails. I think the ETOPS rules require some duplication of parts which might contribute to one or other engine failing - for example fuel pumps, but there's probably more to it than that.

With just one engine, you have a reduced cruise speed.
As for fuel systems, you have the normal system, the alternate system and then there is always gravity feed if the pumps fail completely.

[dave2010]

With just one engine, you have a reduced cruise speed.
As for fuel systems, you have the normal system, the alternate system and then there is always gravity feed if the pumps fail completely.

Can planes really fly with gravity feeding the fuel? I don't know - but I'd have thought that the flow rate would be too low for a jet engine.

[struth]

Can planes really fly with gravity feeding the fuel? I don't know - but I'd have thought that the flow rate would be too low for a jet engine.

yes, although there is a small gravity feed pump to help it .