G'day,
First some legal requirements.
1. In order for you to fly an instrument approach legally, it must be verified and published by the state. Therefore the approach must be validated and published by Airservices Australia as part of DAP. This is why RAAF approaches are unable to be flown by civillians, as the RAAF approaches are not published by the state (AsA)
2. If it is an approach that is not to be made available to the public (ie RNP or privately funded) it still has to be published, but useable info is removed from the plate. Thes approaches are normally the plates that have "For CASA Approved Operators Only"
The above therefore means that theoretically, provided you know the design rules, anybody can design an approach. It must then be handed over to AsA for validation and flight checking, then it will be published and made available to Jeppesen/Garmin for coding etc. Of course AsA and possibly Jepp will charge for this. And they can also refuse to do it.
There used to be a mob in Melbourne (Harts?) with a design certificate and if I recall correctly their going rate for an approach was about 15-25k depending on complexity.
As for accurate survey, the THLD coords and elevs do need to be known. But as far as the coords drifiting over time, this is incorrect. Unless they issue an amendment to the WGS84 datum, which they haven't done since 1984 then the coords don't change. What does change is the magnetic bearing of the inbound tracks, this is why there is a legal requirement to have approaches revalidated every 12 months.
Other things to consider is how to keep track of new obstacles? Who is going to pay for the revalidation every 12 months? Who is going to pay to have amendments published (AsA and Jepp) Who is your approach going to be available to? Do you need approval from the CASA for the approach? Do you need approval from local council?
Thats just off the top of my head. Its been a few years since I was active in the design area, and I am sure there are other things to consider. In short you can make a request to AsA. If they deem it suitable they will probably help you out. If you do it yourself, it can cost alot of money.
BIG QUESTION: Do you really need one??
Cheers
Alpha
