St Lucia July 2022

[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.

[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.

[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 .

[walpurgis]

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.

Jets may look normal, but everything is actually built upside down to avert this exact problem .

[Roy S]

787-8 - G-TU1B ('Alfie') did it in 7:29 !

That’s me in the red t shirt

[dave2010]

Jets may look normal, but everything is actually built upside down to avert this exact problem .

Surely, Sir, you are joking? Aren't you?

Longest flight I can remember was Shanghai to LHR, though Bangkok to LHR and LHR to Beijing are also long. I actually can't remember if we did LA to Sydney without a stop - which is certainly possible nowadays. LHR to SF or LHR to LA can take varying times - even if done in one shot. Depending on the wind they may take 10 hours, but if the jet stream isn't helping then 12 hours might be needed. I thought LHR to Delhi was less time - but it's not a lot shorter. London to Havana is also quite a long flight.