Important to all Procedure designers - 3

28.10.2004

Submission:

First, let us be clear which product we are discussing. There are two - the PANS-OPS OAS CD, and the PANS_OPS Software.


PANS-OPS OAS CD

This PANS-OPS OAS CD replaces the current OAS tables. The program screen layout is similar to the present tables, with the addition of a top section in which to enter LLZ-THR distance, GP angle, AC geometry, RDH and Sector width, and a lower section with an X, Y, OAS height calculator. Note that the link between aircraft category and aircraft dimensions introduced at OCP/13 means that the constants and template coordinates will have to be adjusted for aircraft dimensions - this makes it even more important to automate the calculations.


PANS-OPS Software

This is a new ICAO product which contains:

a new implementation of the CRM,
a global navaid/aerodrome/obstacle database
the OAS tables and OAS height calculator linked to specific aerodromes contained in the global database.
An Analyse program linked to specific aerodromes in the database which first eliminates obstacles below the Basic ILS Surfaces, assesses the remainder against the OAS and against the CRM.
A set of simple tools (conversions, turn parameters, minimum distance between waypoints etc.)

I believe that Mr. Whitworth's comments relate to the first, the PANS-OPS OAS CD, and my responses are as follows.

It is my understanding that the PANS-OPS OAS CD will be provided as an integral part of the next update of PANS-OPS Vol II, and will completely replace the previous tables. For those who may want the tables, they will be available on the same CD in a pdf file. As far as I know there is no extra charge for the CD.

Because all the relevant calculations are still included in PANS-OPS, the program results can always be verified manually. Checks have already been done to verify the effects of all the variables and such checks may be easily replicated by users. I think that ICAO should be contacted about their policy regarding upgrades.

Regarding checking of the software, I think this is for ICAO to clarify. However, regarding software, I do have a very good example which I think answers your question - in the early 1980s, I was dealing with exemptions from the UK ANO, and an airline asked whether they could use a computer program to calculate Concord weight and balance, instead of carrying a performance engineer on every flight (the calculations were very complex).The official answer from the legal eagles was to the effect that 'we do not mind if you use an abacus, as long as you get the sums right'.

Further, as you all will know, insurance is nearly impossible, and most freelance designers have to insist on protection from the contracting agency. On a lighter note, remember that it is not easy to sue a UN Agency, and one in Quebec would be under the Quebec Civil Code, not US law.

Software vendors should be aware that ICAO does not 'endorse' third party products. Note also that the PANS-OPS OAS CD is being provided by ICAO to address an identified safety issue. ICAO found that many agencies had failed to make adjustments required in PANS-OPS. Presumably, in many cases, this was due to lengthy and error prone manual calculations involved. While the more complex and versatile commercial packages could provide the same solution, these are beyond the finances of many design organisations.

The comment regarding software documentation covers two areas:

1) The "Document CD-101" is the PANS-OPS Software CD itself (described earlier) and has full user documentation. It is a new implementation of the source code of the original CRM

2) The PANS-OPS OAS program is based on the algorithms and code contained in NLR Memorandum IN-81-007 U "Description of Program Booklet for the calculation of ICAO OAS data", dated 12/02/81, which should be available from that agency. The calculation of the OAS height is relatively simple. The heights of all the surfaces are calculated from the (adjusted) constants, and the highest is the OCH at that location. Note that the PANS-OPS OAS CD does not calculate the OCH. This calculator is not rocket science. It just saves a lot of work.

As to the name "PANS-OPS OAS CD-ROM" - it is indeed a CD-ROM and it contains the PANS-OPS OAS data; hence the name.

Now concerning the "PANS-OPS Software" manual, PANS-OPS Software is a new ICAO product. It contains a new implementation of the FORTRAN CRM. It uses the same algorithms described in the CRM Software Manual (Doc 9387), although certain programming anomalies have been rectified. These anomalies affected program functioning, not the risk calculations. See the description of the software in the initial paragraphs of this comment.

The PANS-OPS Software already contains a Basic ILS Surface calculator, similar to the OAS calculator.

I do not agree that litigation, liability and commercial interests were not issues when the CRM was first developed. I was there, and I assure you they have always been present.

On a final note I think software will be an effective solution to many procedure design tasks, and more importantly, reduce the number of errors and anomalies that I have seen in published procedures.


Robert Woodhouse

Procedure designer, ICAO OCP member (retired), Software technical adviser.