Tuesday, March 10, 2009

Hold Everything

Piper 123, I have some good news and some bad news. Which would you like first?

We'll take the good news first.

Piper 123, when able, proceed direct Scaggs Island. The bad news is climb and maintain 6000, hold Northwest of Scaggs on the 347 radial, left turns, expect further clearance in 50 minutes.

Direct Scaggs, hold Northwest, 347 radial, left turns, 6000, further clearance in 50 minutes.

And Piper 123, I'm working with Norcal to get you in as soon as possible and I'll keep you advised.

Okay, we just need to be on the ground before midnight or the plane will be out of annual.

This exchange occurred on a night training flight a few years ago with an instrument rating candidate. We'd gone to a Sacramento area airport, he'd flown an nice ILS approach in a steady rain, executed the missed approach and then asked for our IFR clearance back to Oakland. The surface winds at Oakland had been out of the West when we departed and were not forecast to change, but change they did. Oh, and this was on a Sunday at the end of the Thanksgiving holiday and there was plenty of conflicting airliner traffic headed into Oakland and SFO.

Holding patterns themselves are not difficult to fly, but visualizing the holding pattern and determining how to enter the hold can be vexing in single pilot operations when your workload is high. Once GA pilots pass their instrument check ride, they may not be called upon to regularly demonstrate a holding pattern and it's all too easy to lose proficiency with something you don't use often. There are a bunch of details on holding procedures that often are glossed over, so I'll cover this topic in two separate posts.

A hold can specified in a Standard Instrument Departure (SID) to allow you to climb to a safe en route altitude before proceeding on course.



A hold may be specified in an Obstacle Departure Procedure (ODP) with only a textual description provided.



Standard Terminal Arrival procedures may depict holding patterns that ATC might use to facilitate the flow of traffic.



Many instrument approaches provide a holding pattern to allow you to reverse direction and get aligned with the intermediate or final approach course segment.



A hold is an idealized race track pattern anchored over a holding fix that the pilot can identify with on-board electronic navigation equipment, but the path you end up flying is usually not a perfect racetrack pattern. ATC can't really tell how accurately you're flying the hold. Center radar sweeps about every 12 seconds and a lot can happen in that time period. Approach radar sweeps more frequently, but approach controllers are too busy to spend time critiquing your holding prowess. In my experience, ATC doesn't really care how accurately you're flying a holding pattern as long as you stay at your assigned altitude in the general holding pattern area.

Holds can be over a VOR or Locator Outer Marker, they can be at the intersection of two VOR radials, or they can be on a VOR radial at a specific DME distance.





I often see pilots who try to fly the racetrack in the wrong direction, so let's be clear: Once you are established in the hold, you'll always fly the inbound course toward the holding fix. The turn to the outbound course occurs after crossing the holding fix. The outbound course is located on the holding side and is particularly important when determining the holding pattern entry because you fly to the holding fix and then turn outbound. More on that later.



The term protected side was formerly used to describe the side of the inbound course where you don't usually fly while holding, but this term was not very accurate. The protected airspace around the hold is fairly large and extends well into the non-holding side of the pattern and if you're interested in the gory details of holding pattern construction, check out Order 7130-3A. The preferred terms are now the holding side and the non-holding side. If you stray into the non-holding side you are not going to fly into a mountain or be eaten by a dragon, provided you maintain an appropriate altitude (dragons can't fly very high) and observe the maximum speed for your altitude.

The speed you fly in the hold is important because you want to stay in protected airspace. The usual holding speed limits are 200 knots below 6,000' MSL, 230 knots between 6001' and 14,000' MSL, and 265 knots at 14,000' and above. These speeds are clearly faster than the cruise speed of many light, GA aircraft, but you should still slow down to reduce your fuel consumption.

Holding patterns can be put into two broad categories; published and ad hoc. Published holds, as shown above, may be part of a SID, ODP, STAR, an instrument approach procedure, or they may even appear on an en route chart. Ad hoc holding instructions are made up by ATC on the spur of the moment and while this is rare, it's still something every instrument pilot should be prepared to handle.

Many modern GPS receivers will display hold patterns that are part of a SID, STAR, or instrument approach procedure. The GPS may even suggest the entry procedure. Autopilot-equipped aircraft with newer GPS receivers can even enter and fly the hold for you. Only one GA GPS receiver that I know of, the Garmin GNS 480, allows you to program an ad hoc hold. The bottom line is that your GPS receiver, if you have one, may or may not help you with the entry to the holding pattern. You should be prepared to figure out and fly the holding instructions that ATC throws your way using your little gray cells. More in the next post ...

4 comments:

Sarah said...

Great post. As a struggling instrument student, this was my favorite part:
ATC can't really tell how accurately you're flying the hold. ... controllers are too busy to spend time critiquing your holding prowess.

Unfortunately, I understand DEs do care. I look forward to holds Pt.2 with entry/wind correction & NDB holds "made easy". :)

John said...

Sarah,

Thanks for writing and I'm glad you liked the post. Stay tuned for part two.

Yes, instrument instructors and designated pilot examiners can be sticklers about holding procedures. One cure for that is to, if possible, perform the hold in IMC. You'd be surprised how they ease up when flying inside a cloud.

I actually enjoy flying holding patterns, as long as I don't have to do it for an hour at a time without an autopilot!

Dave Starr said...

Great story and great advice. Hmmm, would a pilot be viloated if he flew on the last day of an annual valiodity period and then ATC held jim until after midnight? LoL.

Seriously, I am not sure you know abut this accident: http://www.faa.gov/about/office_org/headquarters_offices/avs/offices/afs/afs400/afs420/acfipg/closed/media/Hist%2002-01-240.pdf

While GA pilots flying mostly in North America may never run into this exact situation, the difference in the maneuvering space between 180 knots and 230 knots is eye opening.

Who among us might not have bene tempted to consider the 180 KIAS speed imit just "administrative" and felt that it was well within the perquistes of a PIC to fly it a slightly higher speed. In this case the speed limit wasn't enforced by the rule book, it was enforced by granite.

Tangozulu said...

What a timely post! I'm learning holds right now in my IFR training. Thanks!

http://onesandzeros.tangozulu.biz/instrument-flight-rules-ifr-training/