bookworm wrote:
With a GNS 430, if I approach from the NW with DCT OGALO, it would probably warn me of a steep turn at OGALO.
I do not think the navigator should do that by issuing arbitrary turns which are not designed into the approach. You may end up outside the protected area of the approach. The approach is designed to confine you to an area where terrain clearance is assured provided you follow the altitude restrictions. The little sectors associated with each IAF tell you from what approach sector you should use them and the MSA in that sector.
So if you are approaching from the NW you should use CR202 or CR204, and fly 5 NM to OGALO. At 120 KTS that is 2,5 minutes. If you went direct to OGALO (on a heading of 129° for example) you would need to perform a teardrop which implies flying outbound for at least one minute, then do a 240° turn (80 s) and fly back to OGALO (another minute) so you would end up with 3:20 instead of 2:30.
You will also note that the approach is designed in such way that it keeps you at 5 NM from the extended runway centerline until you are on the approach end of the runway so that you will not fly above another aircraft on final or performing a go-around.
Apart from the CAA guide that I posted earlier, there is a very complete guide to RNAV on the PPL/IR site – available as PDF.
With modern navigators, is the T really necessary?
With a GNS 430, if I approach from the NW with DCT OGALO, it would probably warn me of a steep turn at OGALO.
With the GTN 650, I imagine it would draw a nice arc on the screen to turn me a few miles before OGALO and establish me on the OGALO to CR208 leg as I roll out. Why would I go to CR202 or CR204?
Were you being serious?
The T really really isn’t much more than that; i.e. a way to elegantly reverse course for those coming from the “wrong” side…
bookworm wrote:
Why would I go to CR202 or CR204?
Because the procedure is designed to be flown that way!
In the US. this type of approach is likely to have a HILPT at OGALO so that one option is to do a hold for the course reversal to join the intermediate approach course. The whole point of the T design is to eliminate the PT. The approach is also designed to allow aircraft with a variety of performance capabilities to fly the procedure with or without radar being necessary. The T is easy to fly, just select the most appropriate IAF to begin the procedure. You fly a downwind, base, and final. What could be easier?
Niner_Mike wrote:
So I learned that ATC are NOT considering an ILS approach to be similar to an LPV approach.
An ILS procedure is a precision approach. If one is cleared for an ILS approach, the GS intercept altitude is built into the instructions for vectors to final. An RNAV approach may or may not have vertical guidance, and the aircraft may or may not be equipped to fly one with vertical guidance. In the US we are not cleared for an LPV, but for an RNAV approach. It is up to the pilot and their equipment if they chose to fly the LPV or LNAV/VNAV or LNAV procedure. The controller really doesn’t know or care what are capabilities are or how we intend to fly the procedure. RNAV approaches are designed from the beginning to use RNAV form of navigation to join and fly the procedure, so vectors are not usually needed. It is much easier for a controller to simply clear the aircraft to a fix to join the approach.
NCYankee wrote:
HILPT
A what?
Google knows everything 
HILPT = " Holding pattern in lieu of procedure turn "
Once I have learned all these abbreviations I will be too old to fly …
Flyer59 wrote:
Once I have learned all these abbreviations I will be too old to fly …
I think that’s a very US-centric abbreviation.
NCYankee wrote:
In the US. this type of approach is likely to have a HILPT at OGALO so that one option is to do a hold for the course reversal to join the intermediate approach course. The whole point of the T design is to eliminate the PT. The approach is also designed to allow aircraft with a variety of performance capabilities to fly the procedure with or without radar being necessary. The T is easy to fly, just select the most appropriate IAF to begin the procedure. You fly a downwind, base, and final. What could be easier?
What could be easier? A single omnidirectional IAF with no PT. At the moment, we’re limited by PANS OPS to 110 degree turns at the IAF, above which a PT is required. So the T or Y is provided to avoid the need for a PT, but the cost is extra track length.
Why not allow turns of 150 or 170 degrees at the IAF? A turn through a greater angle requires a longer stabilisation distance between the IAF/IF and the FAF, but for the most part the distances are built-in, particularly at the lower speed categories. Flying a T is generally less hassle than a PT, but it’s still typically 3 miles more than necessary to achieve the objective of stabilising the aircraft on the final approach track before the FAF.
OK, you probably couldn’t make it truly omnidirectional because an aircraft that, on the way to the IAF/IF, passes the FAF at less than its turn diameter cannot make the turn. But you could catch a lot more than a 180 degree arc in the “straight-in” sector using a combined iAF/IF.
