minimumunstick:
I understand your example, but it does not necessarily have to be vectoring. Just to give you an example let's say you are on an airway somewhere or whatever (doesn't really matter) and ATC says "descend to X feet (altitude for final approach segment) proceed direct to X (name of IAF), cleared X approach" and as a complete coincidence when you turn direct you see you are established on the exact inbound course. You maintain this inbound course as you navigate towards the IAF which also is the start of a course reversal procedure to establish you on the course you are already on.
Assuming these conditions, would you complete a lap in the racetrack or not?
Again, I can only speak for FAA-dom. Here is what I believe is an example that is on point. The graphic below shows both the VOR or GPS-A IAP for KEMT (east of LAX), and the associated airway structure, which is in very busy airspace. Often, a peashooter arrives from the east on V-264.
Case A: The aircraft is assigned the MEA (6,000) and simply cleared for the shown IAP. Can the pilot go straight-in or does he have to do the course reversal holding pattern (called HILPT in FAAese)? 6,000 is not compatible with the procedure so the pilot is obligated to do the HILPT. But, he had better well advise approach control of his intentions, otherwise the pilot and the controller won't be on the same page. They should be, but FAA ATC, especially in busy radar terminal airspace, tend to invent their own "rules."
Case B: 15 miles east of POM on V264 ATC clears the pilot to descend to and maintain 4,000. This is "legal" because the minimum vectoring altitude along the airway in this area is 4,000. (Of course, this invokes the fine point: can the pilot fly the airway below its MEA or does he have to be provided a direct-to-POM clearance? Not resolved for many years). In any case, at 4,000 everything is set up for a straight-in approach from POM. But, is it legal since it is not a "vector to final?" No, it isn't. It will be one of these days for ground-based IAPs (it is now for RNAV IAPs) but only if the clearance is to a charted intermediate fix (IF). There isn't any charted IF on this IAP. There should be, it is POM. But, this IAP is so old that that it was last issued before the FAA was charting IFs.
Would I go straight-in in Case B? Yes, it would be "counter-productive" not to, even though technically not "legal." But, what if I were receiving a check ride from a disgruntled FAA inspector? Well, in that case I would query ATC, "Am I cleared for a straight-in IAP from over POM?" If the controller's response was ambiguous I would then advise him that I have to do a circuit in the HILPT. He would probably go a bit nuts at that point. But, he also may then resolve the issue by saying, "maintain present heading for vectors to the final approach course."
I know for a fact these ambiguities go on all the time with this particular IAP. Some controllers (but not all by any means) vector the aircraft slightly south of POM, descend them to 3,000 and then point them at the segment between POM and FLYIN, which is clearly a vector to the final approach course. (although it should be at 3,700, not 3,000, but that is another issue for another day.)
