RFJ,
somewhat dismayed to read your dismissive response
My response certainly was not intended to be dismissive and, should folk have read such into it, my correction to them and apologies to your good self.
Rather, two main points were pertinent -
(a) certification (and, it follows, "safety" .. however that may be defined) is probabilistic rather than absolute. With the exception of limited circumstances (and even then only somewhat generic) there are no guarantees with aircraft (or machines and life in general - other than death and taxes, I guess) ... only probabilities .. it is the responsibility of crews to do their level best to stack the dice to an appropriate level of risk for each operation - not always nil risk, not even always minimum risk .. but always an appropriate level of risk .. which involves technical and operational knowledge, experience, skill, etc., etc. The level of risk appropriate for one operation may well not be appropriate on another etc.
While I acknowledge the usefulness of SOP, a rigid and blind adherence to procedure or an irrationally misplaced belief in cant has the potential for disaster. A very wise greybeard checkie once observed to me (as a young chap on my first jet during a line check) .. "lad", said he, "lad, the Ops Manual lacks one phrase on page one .. and that is 'to be read with a modicum of commonsense' ".
(b) given that you are styled as a consultant, I hoped (and still do) to generate a useful (and objective) debate on these matters for the educational benefit of the new chums amongst our ranks .. such debates are just about always useful and a major thrust of Tech Log policy.
as a moderator you have a resposibility to your pilot readers to have a better grasp of the subject matter.
I take a slightly contrary view regarding responsibility.
Moderators, in my view, are here to
(a) maintain the basics of site and forum order without imposing idiosyncratic views of the world on discussions
(b) stimulate discussion on occasion
Site policy is for moderators not to stray outside their fields of competence if entering discussion. We all have other usernames to cover those discussions where our competence is no more than routine.
So far as my grasp on the present subject matter is concerned, I have a passing knowledge of things relating to piloting (but, certainly, not to the extent as many others here who are far more experienced) and, more particularly, engineering/maintenance activities .. possibly, on occasion and in respect to the latter, even enough for gov'mint work.
If you stop before V1 you WILL stay within the ASDA. Why are you introducing a doubt in a pilots mind ?
I suggest that the statement would be more reliable if one observed something along the lines of "providing that real world conditions, aircraft capabilities, and crew performance together reasonably replicate certification postulates, then there is a high probability that the operation will match expectations inferred in the certification process and data".
Clearly, history has many examples of a singular lack of success in many areas, including ASDA exceedances. Pilots should always have doubts (perhaps "cautious concern" might be a better term ?) in their minds .. (that's why the Commander gets paid the big bucks) .. so that they plan and act cautiously with appropriate and due consideration of and to all those matters which conspire to subvert the intent of the certification process in the real world.
He/she who blindly believes that the process and rules will look after everything .. is either an incredibly optimistic individual or an accident waiting for the "right" set of circumstances to eventuate. The task for the skilled aviator is to subvert Lady Luck's best endeavours to bring him/her unstuck .. one recalls the old lemma .. "the superior aviator .. uses his(her) superior judgement ... to avoid the need for the display of his(her) superior skills".
Stopway and clearway are totally different surfaces - one refers to ASDA the other TODA - see CAP 168.
Indeed. My concern with your earlier statement related to the apparent inference that stopways might routinely include frangible obstructions .. the stopway can support the weight of the aircraft it may contain frangible obstacles which could cause minor damage to the underside of the aircraft.
Specific standards detail will vary slightly with jurisdiction. You have cited CAP168 .. that document, while permitting a restricted stopway use of frangible obstructions in very limited circumstances restricts maximum height to a value which doesn't sit all that well with your more general statement. Hence my observation that the statement may have been more appropriate to clearway design standards.
However, I'm not an airports engineering expert by any means .. I'll leave the expert comments to our good colleague OverRun should he choose to play in this thread.
The reference to the take off climb surface.......... sorry, but run out of patience.
Might I invite you to cite an authoritative source which supports your contention that ... this also applies to the Take off climb surface, still 35 feet clear of the limiting obstace if necessary out to 15 km .. in which case, I shall both enhance my existing knowledge base and apologise most obsequiously.
The net surface may involve such a clearance from the bumpy bits but the real world obstacle to aircraft clearance (which will approximate something between net and gross but probably reasonably close to gross) .. will be greater and, indeed, increase with distance from the runway. I read into your comment that you intended the latter meaning ? If the former, then I recant.
have faith in the certification rules - they do work.
I've done sufficient test and performance scheduling work ... far too many associated sums .. and been frightened witless by aeroplanes far too many times .. to have the same level of faith as you obviously do.
I prefer to see certification as my starting point ... and a starting point which defines the routine limit of prudence.
The very fact that the certification rulebook is an ever evolving animal suggests that one should have a degree of circumspect regard for such things.
Let the detailed discussions continue ... as for me .. so far I prefer Denti's more pragmatic views on life, death and the universe ...