Comment by mrpippy

15 days ago

I don't think there are diversion points, you either keep going to destination or turn around. The A380 is rated for ETOPS-330, that's 5hr30min from a diversion airport.

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mrpippy

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bangaladore  15 days ago

Incase anyone is wondering about ETOPS-N

For example, if an aircraft is rated for ETOPS-180, it means that it is able to fly with full load and just one engine for three hours. [1]

Obviously in this case it 5hours 30 minutes on one engine at full load.

-- Slight edit: Unclear if with a 4 engine its rated with 2 functional or still 1 functional engine.

[1] https://en.wikipedia.org/wiki/ETOPS#Usage

  • chippiewill  15 days ago

    I believe it's not just that it is able to fly with 1 engine. It's that the probability of a secondary engine failure in that time is below a certain threshold. Most twin engine planes can fly perfectly fine for basically any distance with an engine out, ETOPs provides confidence that the other one won't fail too.

  • nickff  15 days ago

    It is my understanding from a (no-longer-available) MIT OCW aircraft systems design video that these requirements are based on one engine failure on the aircraft, regardless of the number of engines on the aircraft.

  • jccooper  15 days ago

    ETOPS per se makes no sense for a 4 engine aircraft (the T in the acronym is "twin-engine".) Three- or four-engine aircraft have equivalent engine-out long-range operations ratings, though.

    • thombat  15 days ago

      Apparently the acronym can now be read as the blander "ExTended OPerationS", or according to the ICAO all such flights can be referred to as EDTO (Extended Diversion Time Operations", which is less fun to say out loud and loses the joke definition "Engines Turn Or People Swim")

  • NikkiA  11 days ago

    There is a runway (YWKS) on antarctica 'moderately' close to the point where the midpoint of the great circle for that flight is, I'm willing to bet it's used as a diversion point for ETOPS purposes for those flights. It couldn't handle airliners daily, but in an emergency (in summer at least) I bet it could be mobilized just fine.

    edit: allegedly YWKS does have a regular A319 service from Australia.

  • DoesntMatter22  11 days ago

    In practice do they normally fly that far between possible landing spots? My understanding is that they try to normally stay within 2 hours of a possible landing spot

  • tonyhart7  15 days ago

    does aircraft only operate engine as minimal as possible to save fuel or they burn more if they use fewer engine to having engine work extra because of its weight ?

    • sitharus  15 days ago

      Yes they’ll use more fuel than running on all engines. They always load the extra fuel that would be required for the maximum flight time with an engine out.

      The extra fuel burn is due to the drag from pushing a non-working engine through the air, and from the rudder deflection to counteract the unequal thrust. It’s less of an issue on a four engine aircraft with a single engine out as they can increase thrust on the remaining engine on the side with the engine out.

      Extra fuel burn is also required because a twin engine aircraft with an engine out can’t maintain the normal cruising altitude, and the higher you are the more efficient the engines are.

      Thrust can’t be reduced much to save fuel because the speed margins at altitude are quite narrow - if they reduce thrust and therefore airspeed they’ll descend.

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coin  14 days ago

> The A380 is rated for ETOPS-330

I thought ETOPS is for 2 engine aircraft. Are there minimum diversionary requirements for 4 engine aircraft?