An observation or two ...
These are the rules, break them if you must to stay safe
(a) but just make sure you have a damned good story for the enquiry in case it turns to custard in the execution ... ie know what you are doing .. one needs to understand the why of the rules before throwing them away, regardless of the circumstances. And, yes, the (performance) rules apply while the circumstances are constrained to approximate the presumptions inherent. The further the circumstances wander, the more the Commander gets to apply his/her knowledge base and earn his/her paycheck.
(b) or, as a fine checkie once observed to me in the debrief .. "Young John, the Ops Manual has an invisible comment on the front page which says ... To be read with a modicum of commonsense "
bank angle limits to account for the degradation in a turn
Not quite right ...
(a) bank is limited to 15 degrees to put a fence around the performance loss.
(b) there is nothing to prevent a procedure specifying a lesser bank angle .. generally to accommodate a turn radius problem.
(c) the climb degradation is accounted for by routine calculations. For in service application, the AFM will specify a minimum climb gradient penalty to be applied for the particular aircraft, generally around 0.6 - 0.8 or so gradient reduction.
(d) in practice, the ops engineer addresses the penalty artificially by increasing the calculated height of down stream obstacles to provide the same result but permitting the calculation to be performed as a quasi straight ahead climb for calculation convenience.
in case of EO may no even limb at all in a turn
I have never seen a case where a competent ops engineer has not maintained the WAT limit during a turn, having applied the decrement. Not saying it doesn't happen but such would defeat the philosophy of having a WAT limit.
EO procedures clear obstacles and terrain by minimum requirements
That applies to the NFP. As the aircraft gets further away from the end of the TOD, the expected real height progressively increases above the calculated NFP
Hazelnuts, there is.
I know who HN39 is, I suspect you don't. He is quite right on this point (and an acknowledged expert in aircraft performance matters generally). I suggest that his observations and comments ought not to be disregarded lightly.
Your straight ahead path is calculated with a max 5 degree bank into the live engine
Not necessarily .. depends on the speed for the turn.
The 5 degree consideration is at, or close to, Vmc. As the margin increases, the use of a banked climb for Vmc considerations is discarded. Indeed, on some aircraft, due to systems limitations, it is impracticable to maintain a shallow bank angle and the OEI climb is done wings level.
Although some operators do impose such a requirement, it is more a stylistic encumbrance than a necessary requirement. I well recall having to do that exercise to get the tick in the box on AN F27s in a much earlier life ..
On the other hand, if systems permit and you are after the last bit of climb performance, the optimum OEI climb will be achieved somewhere around 2-3 degrees. Generally not worth the effort and we go for wings level.