Originally Posted by
Spotted Reptile
If you lose one engine, the chances of losing the other are a lot higher in this scenario, and then it's the desert and bye bye.
Are they? Do you have a statistical source for this? The central assumption behind ETOPS is that cruise engine failures are
independent of one another with one engine operating at Max Continuous Thrust for the maximum ETOPS time limit.
If there is a
dependant relationship between the two engines (common fuel source or an engine failure damages another engine) then this assumption is no longer valid, and getting on the ground ASAP is a must. A blade failure at cruise altitude is likely to be a random event
within the ETOPS time limit (ie the second engine suffering a random failure with say a 180 minute ETOPS segment is vanishingly small).
Even if there is a identical common point of failure of engine maintenance for both engines, the chances of the both failures occurring within the one flight is statistically incredibly small. In other words, the engineering is designed to get you home from the the worst case scenario. Sure, it would feel very very uncomfortable, but it will work.
We accept this engineering rational every time we go flying in a twin. Here is a primer from EASA on the IFSD rates and engineering assumptions:
Extended Range Operation with Two-Engine Aeroplanes ETOPS Certification and Operation. Have a look at section 3: RISK MANAGEMENT AND RISK MODEL (page 35), see Figure 1 and look at the IFSD rates per 1000 flight hours, and how they derive Figure 2 and the IFSD rate as ETOPS segments goes out towards 10 hours (0.010 failures per 1000 flight hours). If the second engine still works after the first blows up, it will keep working until you land.
Recent incidents that shows that dual engine failures were
dependant:
US Airways Flight 1549,
QF32 and
Air Transat 236. In all cases, there was a dependant relationship between the failures (external, birds for Sully, engine disintegration causing a second engine problem for QF32 and the Air Transat crew mishandling a fuel leak causing a common point of failure for the Azores Glider)
Having said all that, in this scenario I would be proceeding to the nearest runway that I believed was safe given my knowledge of the local environment. For me, YPLM is OK, for another pilot who is less familiar with the area that may be YPPH.
This short video shows where a random independent process becomes dependent one. The final simulation appears to defy logic and reason and does not produce the expected normal distribution.