FMS overlay approach where outbound leg is based on time
Helicopter pilot here! We in RW world are slowly moving into 21st century with fancy FMSs that can fly STARS and approches all on their own. However I think its fair to say we are still in our infancy when it comes to best practise and SOPs for using them. Therefore a question to you clever FW guys that have been doing it for years please:
NDB approach without DME which is basically a teardrop from overhead the beacon, outbound for 1min 30 secs before turning inbound. However FMS codes the end of the outbound leg as a fixed position, therefore depending on airspeed and wind, the inbound turn is started at a widely varying time after overhead. Not that it puts the aircraft outside the safe area of course, its just that the plate says "turn at 1:30 (still air)" and Mr CAA thinks we should follow the horizontal pattern on the plate, regardless of whether the outcome is safe and sensible or not.
Since as far as I can tell there is no ARINC 424 leg that terminates after a specified time, I can't help thinking that all FMSs must have the same issue and it must be one that you fixed-wing boys have had to tackle (probably many years ago). If so, please could you share the philosophy with me, and give me an idea how you check the plate against the FMS procedure when one is based on time and one on distance - and what criteria would you use to reject the FMS procedure in the database as being faulty.
Thanks in advance!