Consider the NEXT failure, in a twin you are gliding, in a Quad you just may limp to somewhere. :E

Twin: Probability of second engine failure = xx * 1

Quad: Probability of second engine failure = xx * 3

:O

I don't think there's been a single case of a failure of ETOPS basic principles - i.e. a second engine failure - unless you count Air Transat Flight 236 - Wikipedia, the free encyclopedia.

Yes, and the probablility in a single is 0 - so clearly a single is infinitely safer! Lies, Damned Lies, Statistics...

(xx)quad vs (xx)twin and "the next failure"
 

This value of xx should be less when there are ETOPS ratings and procedures involved.

Either environmental or common-servicing-error reasons could also come into play to make two failures on a quad more likely than just xx-squared.

When discussing this it might be better to consider not the number of accidents due to 3/4 or 1/2 of the engines working, or 2/4-or-2/2 failing, but rather to the incidences of these failures. From that, it might be clear whether we're overdue for the first accident to occur due to engine failures taking place a long way from safety in a twin.

Very roughly, with ~1000 ETOPS flights per day, and a few reported failures per year, it seems that ~1:100,000 flights have failures, and so a double failure might only be expected every ~10,000 years. If this is valid, then the current practice should be safe enough.

Even a glider can fly :rolleyes:
It depends....
A quad on one engine will probably have problems maintaining altitude depending on weight. But it will have a better chance of getting to a suitable landing site than a twin on none.

Oh it can fly on *none* - see Gimli, and the quad-flameout in a volcalic ash cloud - but it will certainly be flying downwards. The rate-of-descent is what matters, and having one working donkey will certainly help in that regard.

Yes, a quad can fly on one, but only in a shallow glide. Can even fly on none if needs be!

https://en.wikipedia.org/wiki/British_Airways_Flight_9

Gimli was a twin, btw

Stop Press: Quad flies on one
 

http://1000aircraftphotos.com/Contri...avidJ/9578.jpg

P&W's Boeing 299Z testbed with T34 turboprop in the nose. :}

But Sir, that not a quad.

Pedant! Beancounter!

Is that the one Lord King tried to buy?

(when asked, with all the twins coming into service, why BA was still buying 4-engined aircraft, he supposedly responded with "because they don't make them with five!")

Part of the risk analysis of the 4 engine argument is a conservative assessment of the unknown. Zero risk is unattainable. On your remaining engines you still have wear out, infant mortality and random failure mode. When you mentioned lies and stratistics HDRW, I laughed when I also recall one of the models most commonly used in deciding on chances of failure of 4, 3, 2, 1 is the Monte Carlo Simulation (named after the gambling resort).

Perhaps the 'per flight' risk in the subject of this discussion was calculated as being low and that is why they decided to 'push on'. The data and engineering judgement so far (EK this incident of push on and SQ return) indicates there is not yet a consistent set of ground rules.

I'm not convinced that we need a rule, although it might quiet down the after incident challenges.

Too many what-ifs that are best handled today by pilots considering their resources both on-the-ground and in-the air.

then just to prepare for deep thinking arguments, why do we need an EROPs rule ? Has it saved anything ?

As you might suspect I see any diversion or air-turn-back as an increased risk as well as continuing.

Who can forget the A340 demonstrator at various airshows with "FOUR ENGINES FOR LONG HAUL" scrawled along the belt line in 3 metre high letters!!

That didn't last long but, then again, neither did the A340!

Not to mention a well-known UK airline that used to market the same concept:

http://www.flightglobal.com/blogs/wp...455-121296.jpg

Well until they bought their A330s. :O

losing engines....
 

Airbus 380 loses engine, goes 5000 miles.

Airbus 380 loses 2 engines, goes 10,000 miles. :8

Airbus 380 loses 3 engines, goes 15,000 miles. :8:8

Airbus 380 loses 4 engines, goes 20,000 miles. :8:8:8

;);) DoT

Simple question. Does the one engine inoperative checklist finish with the words; "land at the nearest suitable airport"?

Simple answer if you can't be bothered to read the thread George Class.


NO.....

Following it's diversion to Kuwait on the 26th Oct, the aircraft departed for it's original destination, Dubai on 28th Oct.