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vibranium-501 t1_izelvcf wrote

Reply to comment by koko-jumbo in Last Boeing 747 rolls off line after half a century of production by diacewrb

But that does mean they are reducing redundancy the same way they reduce maintenance cost.

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UncommercializedKat t1_izenlge wrote

Yes. But also less chances of failure. I think airplanes are required to be able to fly with one engine out, regardless of how many they have. Maybe some here can confirm.

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yikesbrosef t1_izensxe wrote

Yep. Google ETOPS if you’re curious what the requirements are.

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shmerham t1_izf8b2n wrote

All twin-engines need to be able to fly on a single engine regardless of ETOPS status.

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Uh-idk- t1_izghw0z wrote

all commercial flights go under the single engine rule no?

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NPCwithnopurpose t1_izfk6at wrote

From a quick google search, a 747 can’t really maintain altitude with one engine, unlike twin jets. So, 50% of engines to maintain altitude in either case, but the 747 will cost more. That said, one engine providing thrust (to exclude APUs) is better than none. Also, the loss of an engine will probably just lead to an early landing anyway. The pilot just has more options when they started with 4 engines

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anengineerandacat t1_izf54sm wrote

Higher complexity doesn't generally improve your reliability aspects though and whereas I don't know much about the 747 it's entirely possible the 4 engines aren't entirely independent.

They might share fuel-pumps per-wing, so if say something happened to fuel pump 1 out of 2 you might not have engines 1 & 2 while engines 3 & 4 are calmy doing their thing.

Less moving parts is generally always a good thing, and if it weren't a passenger aircraft potentially eliminating down to a single engine "might" be acceptable if the gliding capabilities were very good (much like some turbo-prop planes) and the risk of losing life was overall lower.

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