Airbuba,
I have tried to look around and find something as you had requested, but I am not sure it's a final answer to your question.
Can anyone point to a relevant document to tell which of these opinions is correct? No matter what you decide these days, it will be second guessed unless you can point to it in the book (ask me how I know
).
Have a look at this general ETOPS from CAA
CAP513, section 3.3
3.1
3.2
have the necessary information to make decisions on diversion at any point on the route.
Extended range operations are not permitted where any time limited system, that is essential for continued safe flight and landing has a minimum endurance that is less than the intended Rule Time, plus a 15 minute allowance for approach and landing at a suitable aerodrome, e.g. a cargo compartment fire suppression system.
If enhanced scheduled maintenance, replacement, and/or inspection are utilised to obtain type design approval for extended range operation, then the specified maintenance should be clearly identified in an appropriate approved maintenance manual and schedule.
Analysis of Failure Effects and Reliability1 General
The analysis and demonstration of system failure effects and reliability should be based on the maximum declared endurance of the aeroplane used in extended range operation.
Propulsion Systems
- a) An assessment of the propulsion systems reliability for particular airframe/engine combinations will be made in accordance with Appendix A.
- b) The analyses will review, in the context of extended range operations, the effects of operation with a single propulsion system, including probable damage that could result from failure of the first engine. Effects of failures, external conditions, or crew errors, that could jeopardise the operation of the remaining propulsion system under single power unit operating conditions, will be examined.
NOTE: Consideration should be given to any adverse effect of electrical failure on the aeroplane fuel supply system e.g. loss of fuel boost and transfer pumps.
Hydraulic Power and Flight Control Consideration of these systems may be combined, since many commercial aeroplanes have full hydraulically-powered controls. For aeroplanes with all primary flight controls hydraulically powered, evaluation of hydraulic system redundancy should include a determination of the ability to maintain continued safe flight and landing after the complete loss of any two hydraulic systems and either engine, unless it can be shown that such a combination of events is Extremely Improbable." unquote.
If safe flight cannot be continued safely, then a diversion is required, however, I believe safe flight can be completed as a single hydraulic failure is not an emergency or urgency.