Problem is ... one size does not fit all aeroplanes .... If one picks out half a dozen AFMs and runs the analyses for an interesting runway with several potential escape options ... consider
(a) third segment height ... 400ft to whatever the aircraft/engine combination is capable of achieving. Very useful to the ops engineer in juggling terrain problems.
(b) third segment distance. Very dependent on aircraft configuration.
(c) number of engines. WAT limit climb values differ with certification.
(d) how important is a particular aerodrome for a given operator ? If Bloggs Airlines makes the bulk of its profit from one hub, it is going to be far more interested in investing the dollars in terrain analysis for each runway at that aerodrome compared to Jones Airlines which runs through the location once or twice a week. Sometimes it just doesn't work out .. I can recall one runway for which I spent around two weeks work on terrain modelling .. eventually a ridge about 15 nm track miles on a convoluted escape path killed the one viable escape option and we ended up opting for straight ahead and living with the small ridge not all that far off the runway head ... was an interesting exercise nonetheless ...
(e) especially with twin jets having highlift devices, at WAT it is not unusual to see 40-50 nm track miles required to get the net path to 1500ft following a V1 failure.
(f) the calculation bits are the easy part .. the difficulty is getting the detailed terrain data .. and that can be a REAL pain for a difficult airport, especially when you consider that any published aeronautical data often is of very limited practical use to the escape design. Any fool with a bit of math background can set up a optimisation program to do the number crunching ... but it is all fairytale land if the terrain models are inaccurate ...
Not a simple matter to figure RTOW unless the runway is totally benign .. ie very long and the departure is over the ocean or a reasonably flat desert .....
Main thing is .. don't consider eyeballing it ... doesn't work and, as one poster suggested earlier in this thread, it just means that you have the terror of watching the hill you are going to crash into get bigger in the windscreen as opposed to not knowing what happened during the death process ...
Ops engineers are there to do the labour for you .. use them.
Last edited by john_tullamarine; 10th September 2005 at 00:48.