Composite Runway Slope
Moderator
Old Smokey,
First, my PM box was full the other day .. if you had sent anything, it would have bounced. All OK now.
Provided one stays above the polygon, there can be no situation where the profile is compromised as one can use any of the declared surfaces for the take off calculations.
The only problem is due to round off in the survey to surface calculations (inclino surveys are not common .. normally a conventional survey is used to determine obstacles) .. which are used to calculate the surfaces. However, the calculations are rounded off for publication. When the reverse calculation is done, the round off usually results in numerous intersections, although it is usually fairly obvious what the story is .. simple solution is to use the critical polygon and accept a bit of extra conservatism.
Acceleration level surface cannot be inferred from the surface data and needs other input to determine. In the case of a quick calculation and no other available data, one can only keep the acceleration segment above the polygon ... normally unduly conservative but gives the quickest calculation.
If one uses data from let down plates, be wary of
(a) trees and such like which are not normally considered.
(b) cultural obstructions such as buildings etc
(c) information panels overlying critical obstacles .. has been known to occur and is a tad awkward ...
Usually one can ferret out some commercial surveys for many places .... EOPM, published charts, whatever.
First, my PM box was full the other day .. if you had sent anything, it would have bounced. All OK now.
Provided one stays above the polygon, there can be no situation where the profile is compromised as one can use any of the declared surfaces for the take off calculations.
The only problem is due to round off in the survey to surface calculations (inclino surveys are not common .. normally a conventional survey is used to determine obstacles) .. which are used to calculate the surfaces. However, the calculations are rounded off for publication. When the reverse calculation is done, the round off usually results in numerous intersections, although it is usually fairly obvious what the story is .. simple solution is to use the critical polygon and accept a bit of extra conservatism.
Acceleration level surface cannot be inferred from the surface data and needs other input to determine. In the case of a quick calculation and no other available data, one can only keep the acceleration segment above the polygon ... normally unduly conservative but gives the quickest calculation.
If one uses data from let down plates, be wary of
(a) trees and such like which are not normally considered.
(b) cultural obstructions such as buildings etc
(c) information panels overlying critical obstacles .. has been known to occur and is a tad awkward ...
Usually one can ferret out some commercial surveys for many places .... EOPM, published charts, whatever.
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john_tullamarine,
Many many thanks. Have already used a few worms from the fresh can of worms you gave, a wee bit of optimisation for those customers desirous of using STODs as core data coming up.
Thanks for the warnings re trees, cultural obstacles etc., "my" CASA guy already thinks that the assumed trees etc. that I use are a tad conservative, but that makes him happy, and I sleep better at night too.
PM coming your way in the next few days,
Regards,
Old Smokey
Many many thanks. Have already used a few worms from the fresh can of worms you gave, a wee bit of optimisation for those customers desirous of using STODs as core data coming up.
Thanks for the warnings re trees, cultural obstacles etc., "my" CASA guy already thinks that the assumed trees etc. that I use are a tad conservative, but that makes him happy, and I sleep better at night too.
PM coming your way in the next few days,
Regards,
Old Smokey
Moderator
The AirServices procedures designer chaps can point you in useful directions for tree heights ... if you don't have specific contacts, I can pass these to you... OzExpat, likewise, would be a useful source.
