Why is a procedure turn required if you are more or less on the final approach course?

Question

From this question. I am not instrument rated. The answers to the question explain, from the point of view of the plate instructions, if a PT is required or not. The OP was failed for not performing a hold.

However, I can't see why a turn or hold is required at all. If you are approaching within say 30 degrees, why would you not simply turn onto the final approach course and fly the approach (assuming that you are cleared of course)?

If you were simply cleared direct to BEJCY and cleared for the approach, then your instructor is correct and you should have completed the procedure turn as charted.

The OP was approaching from SSW from AUGIE so continuing to BEJCY puts him 21 degrees to the South. Why not just turn right onto 007?

I am assuming no ATC instructions to do anything other than the published approach.

Answer 1

Read that other question again. He was approaching from the SSW and made an assumption based on the approach segment from AUGIE. He wasn't actually on the AUGIE-BEJCY leg as it would be impossible to be there if he were approaching from the SSW.

His clearance was "Direct BEJCY cleared for the GPS 01 approach". That clearance, in lieu of any specific instructions about the procedure turn, requires that the procedure turn be flown. He assumed that because he was roughly on the extended centerline of the runway SSW of the airport that he was exempt. However, there is no charted course there labelled "NoPT", so his assumption was incorrect.

Back to your question of why someone flying from that location would have to fly the PT, and the answer generally boils down to "TERPS". The leg from AUGIE can be flown at 3000 ft while the area minimum safe altitude is 3100 ft. It is very likely the minimum enroute altitude over that area is higher than 3100 feet. This means a pilot that is using BEJCY as the IAF may be considerably higher altitude than 3000 ft. On this approach you ideally want to be at 2500 ft by the FAF at CUCTO. If you are approaching BEJCY from any direction other than AUGIE this means you cannot start your descent from whatever altitude you are at down to 2500' until passing BEJCY. The procedure turn is not only for course alignment but also to descend to the procedure altitude from the enroute environment.