Important point in the last three posts .. missing the hard bits depends on planning and executing the departure in 3D .. ie vertical (climb gradient and speed control) and laterally (straight tracking and turn radius which is critically dependent on speed control).
whether to make a level acceleration or not where a relatively close-in obstacle is concerned
Company SOP or special procedure for the runway must specify what the ops engineers expect the pilot to do .. if they don't then you need to go thump the ops engineer's or chief pilot's table ... hard and loud.
Making a level acceleration ... versus maintaining configuration and V2 - V2+10 ... and then making the turn at 15º of bank is not such a good idea
The two cases will give wildly different splays .. if you pick the wrong option that might not be a successful life strategy. While either case can be calculated, the preferred option (if there are real obstacles) is to keep the initial climb speed .. reason ... it all gets too variable in the real world considering the actual gradient profile and speed history to the turning point. Hence, with the acceleration option, the ops engineer should be factoring a lot more fudge and padding to allow for variation from the plan .. end result is usually going to be less payload than the simpler maintain initial climb speed plan. (Caveat .. the early acceleration may be the better plan if the turn is to avoid a simple obstacle and the main limiting critical obstacle(s) is(are) a long way down track. However, the better procedural option most of the time is the low speed case)
I am told that the performance engineers have to make such an assumption when preparing RTOWs for runways with close-in obstacles
As ops engineers (performance engineers .. whatever tag you prefer) we make lots of assumptions .. but an assumption is useless if the guy implementing the story (the pilot) is kept in the dark as to the assumptions .. bit like pin the tail on the donkey.
Wouldn't it be nice if the theoriticians were to tell those of us who might have to put their wonderful ideas worked out in a nice warm office into practice on a dark and stormy night?
Yes, indeed ... not only nice but essential if you want to have a reasonable chance of making pensionable age ... and one of the reasons why the ops engineer who flies (or keeps a close liaison with the flying folk) has a generally better output than the backroom guy who tries to do it in isolation ...
Last edited by john_tullamarine; 23rd February 2006 at 23:02.