fdr,
Good post ... but, may I offer a few comments ? .... (and, as the hyperlink to airliners.com is to the homepage ... could you edit your post to give the full URL so that we can find the pix which you would have us see, please ? .. thanks in anticipation ...)
(a) you seem to presume that the takeoff is
ALWAYS AEO TOD limited ie there will be a 15 percent pad. This usually will be the case for low weight, low altitude, low OAT, takeoffs ie where the OEI performance is comparatively good and the AEO factor results in the AEO case being the more limiting for the AFM schedules. More generally, though, in real world commercial operations, the OEI case will be the more limiting and the 15 percent pad associated with the AEO case becomes irrelevant. More importantly, the heavyweight takeoff aircraft on a limiting runway is going to be
VERY close to the end of the TORA (runway) when it finally drags itself into the sky ..... seeing you mentioned Professor Emery's website ... do have a look at the
picture of CX taking off halfway down the page .....
Then again,
(i) sometimes you might be WAT or ASDR-limited and the porridge pot becomes a little stickier if a pilot is of a mind to do some sums ...
(ii) often an aircraft will have a nasty little first segment due to the time it takes for the wheels to tuck themselves away .. with little or next to no climb at all in the OEI case ..... and this might extend to a comparatively significant distance past the end of the runway .... the ops engineers take it into account but, often, pilots don't give it a second thought ...
(b) contributors may not realise that Professor Emery's hyperlink (as listed in the previous post) was back to a PPRuNe thread ? Emery is a regular visitor to PPRuNe and greatly do we value his occasional contributions in the discipline of airport engineering. The educational value of PPRuNe to industry participants is one of the benefits of this site which Danny et al continue to pursue ... to the benefit of all who play here in the sandpit.
(c) the regulatory standards built into the AFM should be viewed as reference data in that, if the takeoff is conducted in conditions and using techniques equivalent to the certification procedures used during the aircraft's development, then the distances achieved will be fairly close to the AFM data. Unfortunately we work in the
REAL world which often is considerably at variance with the idealised certification world .. so, on occasion, the prudent operator/crew puts a few extra cushions on the seat for comfort.
That application of the Standards do, on the very great majority of occasions, result in aircraft achieving flight ... suggests that ICAO and the various State implementations of ICAO requirements have got it reasonably right ....
Most people would be aware that, as the technological capabilities improve, the Standards are revised to take advantage of such capabilities by mandating their direct or indirect incorporation in aircraft design and manufacture.
However, woe betide the operator or pilot who routinely ignores the differences between the certification and real worlds of operation ..... Generally, the pilot is not equipped with the tools to apply commercially acceptable margins for real world variance from the certification assumptions .. but the responsible operator, through the use of in-house or subcontracted operations engineers, does the work and presents the results for the use of crews and dispatch personnel.
(d) the TORR limitation (clearway restriction) is occasionally, but not always, relevant to the particular takeoff. Boeing's suggestion for one Type (and I guess that the other Boeing and Airbus Types are similar) is that, by the time you are within 2000ft of the runway head in adverse conditions such as windshear ... then it is time to rotate, regardless of other considerations, if you are to have a reasonable chance of getting airborne before the end of the runway ...
(e) so far as V1 is concerned ... the waters are easily muddied in the real world case as the certification conditions are not always easily replicated ... In the case of an ASD-limited takeoff with a failure very close to V1 and a subsequent rejection ... ? .. rather you than me ...
(f) I trust that your level of cynicism is not quite so high as your post suggests ? .. but, then again, perhaps the smiley at the bottom indicates that you are, like most of us, a pragmatist ...
