Flying over the ocean on two engines: how ETOPS works

In this article · 5 sections

The worry, and the rule behind it
First: the airplane can fly on one engine
What ETOPS adds
What it means for you
Keep reading

The worry, and the rule behind it

"What if one engine stops halfway across the Atlantic?" is one of the most common long-haul fears. Regulators thought about exactly that question, and wrote a whole set of rules around it. They're called ETOPS (Extended Operations).

Under US rules, a two-engine airliner may not be flown on a route that takes it more than 60 minutes from an adequate airport, at one-engine-inoperative cruise speed, unless the airline is approved for ETOPS.^{1, 2} Approval is given for a specific diversion time, such as 120 or 180 minutes, and comes with extra requirements.^{2, 5}

First: the airplane can fly on one engine

Twin-engine airliners are certified to keep climbing with one engine inoperative, at set minimum climb gradients.⁶ Our engine-failure explainer covers this in more detail.

ETOPS is about making sure that, if it ever happens far from land, everything needed for a calm diversion is already in place.

What ETOPS adds

1. Planned airports along the way. The flight is planned with ETOPS alternate airports within the approved diversion time, and their weather is checked as part of dispatch.⁵

2. Extra fuel for the worst moment. The airplane must carry enough fuel to reach an ETOPS alternate from the most critical point of the route, assuming an engine failure, a loss of cabin pressure, or both. That calculation must also allow for stronger-than-forecast headwinds, possible icing, and 15 minutes of holding before an approach and landing.³

3. Special maintenance. Before every ETOPS flight, a qualified technician must complete and sign off a pre-departure service check, including the engines' oil levels and consumption.⁴ Airlines also must not do the same maintenance task on both engines (or other paired critical systems) in one visit unless a different technician does each one, or a second qualified person supervises, with verification afterwards.⁴ The idea is that one mistake can't affect both engines.

4. Watching engine reliability. Airlines must track the rate at which engines are shut down in flight across their ETOPS fleet, report every in-flight shutdown and diversion to the FAA within 96 hours, and run a full review if the rate goes above set limits.⁴ They also monitor engine health and oil use on every ETOPS departure.⁴

What it means for you

If you're on a twin-engine jet over an ocean, your flight was planned with diversion airports, fuel for the worst-case point, and an airplane that was checked specifically for this kind of flight. A diversion would be inconvenient. It's exactly what the system is designed to handle.

Keep reading

Quick answers

Can a two-engine plane fly over the ocean?

Yes, under FAA ETOPS rules. A twin may not fly more than 60 minutes from an adequate airport on one engine unless the airline holds ETOPS approval, which adds requirements for planning, fuel, maintenance and engine reliability.

What happens if an engine fails over the ocean?

The crew diverts to a planned ETOPS alternate airport. ETOPS flights must carry fuel to reach one, calculated for an engine failure at the most critical point, and airliners are certified to keep climbing on one engine.

What does ETOPS 180 mean?

It means the flight may be planned up to 180 minutes from a suitable airport, measured at one-engine-inoperative cruise speed.

Are ETOPS planes maintained differently?

Yes. Before each ETOPS flight a qualified technician must complete a pre-departure service check, and the same person generally may not work on both engines in one maintenance visit.

Sources

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