More about the last scenario

[James Carlson]

I've read through the Pilot Workshop discussion about this scenario and 
about the issues behind it, and I figured it required an update.

One issue to consider is that until you're established on a published 
segment, you can't descend from the altitude they give you.  So, if you 
do go for the VTF line given by the Garmin unit, you'll need to pay 
close attention to crossing HAREK.  (Granted, with the position of the 
aircraft and the vector given, that should be a fraction of a second in 
this particular case, but there could be a different scenario when it's 
not.)

Another is that they can't vector you directly to the FAF on a GPS 
approach unless you're doing a procedure turn or HILPT.  There are other 
places they can't vector you towards, notably any fix that either 
starts, ends, or is inside a RF (curved) segment (7110.65Z 4-8-1(i)(3)). 
  You can fly RF segments as long as your installation allows it (many 
now do), but must start the approach elsewhere.

Based on that restriction, an interpretation of that "intercept the 
final approach course" instruction where you turn towards the airport on 
the extended runway centerline via the FAF seems suspicious to me, 
because you wouldn't actually be established on the approach until the 
FAF, and that means this extended centerline sounds very much like a 
vector ... and a vector that's not allowed for this kind of approach.

This leaves either intercepting the course given by Garmin (and, unknown 
to our scenario pilot, the one also expected by ATC), or intercepting 
whatever segment is ahead on our assigned vector, or asking for 
clarification and/or a direct-to fix on the approach.  There are a lot 
of cases where just doing what the box says is not the best idea, but in 
this case I think it's a good option.  Particularly so given that in 
order to vector an aircraft to a final approach course, ATC must have 
that course depicted on their scope, and that happens to match what 
Garmin shows.

I suspect this is a scenario where there's no perfectly satisfying 
answer -- especially given the lack of other references for this 
particular and unusual case -- but it does raise some issues worth 
considering.

-- 
James Carlson         42.703N 71.076W         <carlsonj at workingcode.com>