CRM results ? 3

22.08.2007

Submission:

PANS-OPS Software and the FORTRAN implementation of the CRM both use the term "Highest" to indicate the OCH is greater than 300m, which is the upper limit of the calculation algorithm. See the current Manual on the use of the Collision Risk Model (Doc 9274-AN/904), paragraph 4.2, sub-paragraph 3: “If the user requests a minimum acceptable OCA/H but the calculated OCH would be more than 300m in Cat I and 150m in Cat II, then a report for the "Highest OCA for which risks are calculated" will be provided. In this case the minimum acceptable OCA/H cannot be calculated. What you probably have is a major obstacle higher than 300m in the final approach. The fix is to use the OAS method, which will identify the critical obstacle then increase the glide path to see if that will eliminate it. The other thing to do is to check the obstacles. I once had bad problems because I had made a mistake in the Y value of an obstacle (a Y value of 200m instead of 2000m). Note also that the description of the CRM in PANS-OPS Vol II is meagre to say the least. I hope that at the next IFPP meeting we may get an improved description that will cover the limits of the CRM including the maximum Y value considered and the way to guard against a possible second peak in risk (run the CRM a second time with a "selected OCH" above the "higher" OCH due to the first "Increased risk at higher OCH" result.

Robert Woodhouse - Procedure designer - Canada

Answer or Commentary:

(I.W.
Does any one know if the source code of the CRM program will become open source? )