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Comment by sitharus | Hacker News Reader

At at guess, because the maximum landing weight of a A330 is 187,000 kg but the maximum takeoff weight is 242,000 kg. They'd have to burn off fuel before landing or risk crushing the landing gear.

The A330 doesn't have fuel dumping nozzles as standard equipment so that may not have been an option.

Edit:

From a slightly dodgy source http://www.pprune.org/tech-log/117765-a330-fuel-consumption.... they'd burn 6 tonnes on takeoff and another ~7 in the 1.5 hours before the engine failed, and approx another 7 before landing but I don't know what the consumption would be like for a single engine return.

That gives 20 tonnes total fuel burn. At those figures the 5:40 flight would take 41.5 tonnes of fuel, plus a bit extra.

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You are almost certainly correct. Getting rid of fuel to get down to max landing weight is a concern any time there's a problem this early in a long flight.

And needing to sometimes fly a bit before you can land safely is, well, the whole idea behind ETOPS. For those unfamiliar with the acronym (officially: "ExTended OPerationS", sarcastically: "Engines Turn Or Passengers Swim"), it refers to a certification process for twin-engine aircraft, to demonstrate that they can safely operate far from any airport, since their engine reliability is sufficient to allow extended periods of single-engine flight if and when necessary.

An ETOPS rating is given in minutes. For example, ETOPS-60 would mean the plane is approved to fly routes that might require up to 60 minutes of single-engine flying in order to reach a landing site after one engine fails. The Airbus A330 is approved (depending on the exact variant and configuration the airline buys) for either ETOPS-180 or ETOPS-240.

ETOPS is covered in this easy-to-digest video by Wendover Productions: https://www.youtube.com/watch?v=HSxSgbNQi-g

I haven't watched that one, but the ones I have watched have been... a bit spotty/incomplete about aviation stuff.

You can land safely above maximum landing weight, although it might cause damage to the tires or in extreme cases to the landing gears. Overweight landings are performed frequently[1] in emergencies, especially when an emergency occurs on or right after take-off.

There may still have been other overriding reasons not to land at the closest airfield in this case. We just don't know enough yet.

[1] http://avherald.com/h?search_term=overweight+landing&opt=0&d...

ETOPS originally meant "Extended-range Twin-engine Operational Performance Standards". Just a way to get approval to fly planes with only two engines over large bodies of water, with rules specifying how far they can be from the nearest airport where they could land in case of an emergency.

The odd issue is why the vibration continue after he shut down the engine?

Was it an avionics issue instead? Two previous issues[1] have occurred in the same airspace (near Learmonth) with similar Airbus aircraft from Qantas.

"The incident again fueled media speculation regarding the significance of the Harold E. Holt facility, with the Australian and International Pilots Association calling for commercial aircraft to be barred from the area as a precaution until the events are better understood, while the manager of the facility has claimed that it is "highly, highly unlikely" that any interference has been caused."

[1] https://en.wikipedia.org/wiki/Qantas_Flight_72#Subsequent_Qa...

The vibration continued because the shut off turbine was windmilling, AFAICS. Nothing you can do. Except reducing airspeed to zero AKA landing the bird.

Windmilling with an ingested turbine blade :(

One would think that fuel dumping nozzles should be required equipment.

My other thought as to why they went back is that they could get the aircraft repaired more easily there.

Anyways, glad it turned out alright!

It depends on the aircraft. The FAA requires (and therefore every airline that wants to fly to the US has) fuel dumping if the aircraft cannot perform a go-around (aborted landing) after an engine failure. A modern twin-engine aircraft can do this so they omit the complexity and weight of the fuel dumping system.

If the worst happens an overweight landing is an option, it's just not desirable. The landing gear should be able to handle it without collapsing but may take significant damage.

So why not circle above the airport it's already near, instead of heading off for another one and just hoping it makes it?

If the other engine goes, odds are they're not going to make any airport, even the nearby one, even if they're circling it. If Perth has better facilities for handling the problem, and it's "we'll make it there or we won't make it anywhere", might as well go back to Perth.

That I can't say. Perhaps Perth was a much better equipped airfield. If you're going to hang around in the air for two hours you may as well get somewhere better able to handle your emergency. The chances of a dual engine failure on an ETOPS-240 (240 minutes single engine operation) certified plane are very small.

Perth isn't an airfield, it'a a major city :) For comparison, Learmonth/Exmouth has a population of ~2000 people, Perth has a population of 2 million.

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