Tuesday, February 05, 2008

Changing Fortunes, Changing Gears

My home airport is pretty much divided into The North Field and The South Field. During daylight hours, there are separate control towers, separate tower and ground frequencies, but one clearance delivery frequency. Jet aircraft usually depart the South Field runway while the North Field is used primarily by propeller aircraft, helicopters, and GA. In spite of this division, it is fairly common to hear an airline pilot use the North Ground frequency by mistake, as happened the other morning.
"Ground, Alaska 789, ready to push, gate 7"

"Alaska 789, contact South Ground on 121.75"

"Oh, sorry ..."

Being ready to taxi ourselves, I couldn't resist:
Good morning Oakland Ground, Cessna 12345, ready to push at the port-a-ports, VFR Lodi, request runway 33, with Lima."
The ground controller didn't miss a beat
Cessna 12345, Oakland Ground, good morning, push at your discretion, taxi runway 33, VFR at or below 2500, standby for the squawk."


For the past three weeks, the weather throughout California has been bad for flying light aircraft. For a professional flight instructor, this means an irregular working schedule and unpredictable hours. That in turn has kept me from having a regular blogging schedule, hence the delay since my last post. Lots of rain, low freezing levels, snow as low as 1500' at times. Even trying to teach on my usual days off didn't seem to work. A cold front passed, but unstable, moist air remained. I discussed the options with two different students and we agree that the end result might not be that productive, maybe even unsafe. Later the sun was shinning through broken cumulus and I wondered if I made the wrong call. A few minutes later, small hail is bouncing off my front porch and I feel better about our choice.

When an instrument approach has a Hold In Lieu Of a procedure turn (sometimes called HILO), the only way you can be assured that you have a clearance to fly the hold is to ask the controller for "Pilot Nav" or "the full approach." If you are approaching the airport such that you are flying opposite the approach course, you can let ATC vector you to the intermediate approach course (assuming there is radar coverage in your area) or you can ask for "pilot nav." Pilots often ask for the full approach to maintain instrument currency so they can put in their logbook that they flew a holding pattern.

Consider the Stockton ILS 29R.


When you load this approach in a Garmin 530 and you want the full approach, you'll need to select SC (the Locator Outer Marker) as the Initial Approach Fix (IAF). This can cause considerable confusion to the uninitiated when requesting the approach "pilot nav" because NORCAL will tell you "Proceed direct JOTLY." It's unfortunate that there are two names for what is essentially one fix, and it certainly doesn't reduce the workload in a single-pilot environment.





Take a look at the GPS flight plan. Notice that the approach is coded so that once you complete the holding pattern for course reversal, the next waypoint appears to be SIMMS which is well outside the hold boundary.



When you complete the course reversal, the leg between SIMMS and JOTLY is activated once you are established inbound. Fascinating, though I can't explain why this approach was coded this way.





Now consider the Sacramento ILS RWY 2. Like the Stockton ILS 29R, this approach has a Locator Outer Marker.



Yet when you go to load this approach, the LOM is identified as EXECC, not SA. I wish I knew why this approach is different than the Stockton ILS 29R, but I don't. The good news here is that when you ask the controller to fly this approach "pilot nav," they will tell you "proceed direct EXECC" and you'll have no trouble correlating that with the options displayed by the Garmin 530.








It seems the moral of this story for IFR pilots who fly by themselves is similar to the old Samurai adage: "Expect nothing and be prepared for anything."

6 comments:

Marcus said...

The reason that it's different is (I think) because the Garmin 530 loads the Initial Approach Fix when you selects to make a full procedure. If you take a look at the Approache plates you will see that it says "IAF" next to those fixes you mentioned!

/Marcus - Flight Instructor i Arvidsjaur, Sweden

John said...

Marcus,

Both of these approaches have the LOM listed as an initial approach fix so that doesn't really explain why Garmin lists the LOM by its two-letter identifier on the SCK ILS 29R and by its five-letter identifier on the SAC ILS 2. Unless I'm missing something ...

Ron said...

I think it activates the SIMMS-->JOTLY leg because there's nothing else to activate. If a leg is going to be used, it's gotta be that one.

John said...

Ron,

Okay, then riddle me this: Why doesn't the Sac ILS 2 list SA as an IAF (instead of EXECC) and when you're inbound in the hold, why isn't the leg COUPS->EXECC activated?

There's some sort of inconsistency in the way approaches are coded at work here, at least that's my theory. Of course it's just a theory ...

eric said...

John, what about the missed approach instructions? I know this is a somewhat backwards guess, but the IAP which lists the LOM in the Garmin as SC doesn't use it in the missed procedure.

Tony Condon said...

John-

have a few too many instrument students lately? or just gathering material for writing a Garmin users manual?