When you can’t land – Teardrop, Direct or Parallel
Air Force instrument training was old-school: manual systems, old avionics and an all-in-one HSI/RMI. The entry position at my airline was as a Flight Engineer on the B-727. In those days, new-hire hazing – I mean, training–was administered by old-school flight engineers in an aircraft with exclusively antique systems and avionics. While the teaching etiquette of the MD-80 instructors was more politically correct, the focus remained on antique avionics. The need for an understanding, or at least an appreciation, of those antique navigational instruments is now fading away, but it’s not gone yet. We were recently given an old-school clearance from ATC and some of that old-school knowledge proved useful.
Snow plowing, extreme weather and incidents such as a blown tire or a VIP event are the most common reasons for a short-notice airport closure. But, I’ve also encountered unusual reasons like earthquakes, forest fires and social unrest. Closures due to extreme weather are not only common, but happen every day. ATC knows that we don’t like to hold (and we’re sometimes not very good at it) and it’s more work for them to construct multiple patterns, so they normally issue speed assignments and radar vectors to avoid holding. But, inevitably, a few aircraft will need to hold for a closure. During our arrival into RDU, a T-storm overhead closed the field. The rain shower and resultant low visibility were not necessarily a show stopper, but the announcement of microbursts was. We have corporate guidance relative to windshear and microbursts at my carrier. At the captain’s discretion, windshear is a “proceed with caution” event, if the report is not referenced to the landing runway. A microburst alert at any location on the field requires an immediate go-around, hold or a diversion to an alternate.
Straight out of a simulator exercise
The holding clearance we received was old-school: Hold east, on the RDU 095 degree radial, 35 mile fix, left turns, ten mile legs, EFC 2140. The approach controller had used his picture of the weather and our location to build a pattern outside of the rain showers – he was doing us a favor and he got it right. But, the clearance to make this happen was straight out of a simulator exercise. Nowadays, holding is almost exclusively issued at a published fix that has a published holding pattern. “Cleared direct to OCRAP, hold as published, EFC 2140.” If not to a fix with a published pattern, then to a published fix with a follow-on description of the desired pattern at the fix. Very seldom is the pattern defined using an antique and inaccurate reference such as a VOR, NDB, marker beacon or Grandma Mollie’s clothes-line pole.
Sorry, but you have to memorize four components to get the holding problem right: speed, direction of turns in the hold, entry procedures, and timing (or leg lengths). In the U.S., the maximum speeds (you can hold slower if you want) are: 200 kts below 6k, 230 kts 6,001 to 14,000 and 265 kts from 14,001 and up. Timing is one minute inbound below 14k, and 1-1/2 minutes above 14k. If not issued a holding leg length they expect you to use time. I will always ask for a distance instead of a time because it’s easier. And because holding isn’t confusing enough already, ICAO (Mexico uses ICAO), Canada, and military holding speeds are different from each other and the U.S. So, look them up before you leave the country and put a sticky note on your forehead. The big thing that will help with holding is to remember there is a “protected” side which is on the holding side of the radial, and an unprotected side. If you fumble around on the protected side it’s mostly okay. Fumbling around on the unprotected side is bad. Holding speeds, direction of turns, timing or distance and entry techniques are all designed to keep you in the chunk of airspace that is protected on the holding side.
Figuring out how to enter a holding pattern was my nemesis for years. There are many manuals, study guides and instructor techniques that explain how to enter a holding pattern. I’ve heard most of them and tried to find one that I could remember … and failed miserably. With hopeful optimism and humility I offer the one that finally made sense and stuck with me: T-D-P. Teardrop-Direct-Parallel. I bought an HPC-2 from ASA (yes, the airline pilot needed a visual aid). It’s a hand-held card depicting left and right holding patterns with a clear rotating compass card. Remember the letters T-D-P in that order and that standard turns are to the right and non-standard to the left. For standard, right turn holding, picture an HSI divided in half with the line starting 70 degrees RIGHT from your heading. If your heading is 360, the line starts at 070 and slices over to 250.
You put the T in the 70-degree wedge, you put the D below it in the bigger 180-degree wedge and finally, the P in the remaining small wedge. Now, put the holding radial on the HSI and see which wedge it is in. For non-standard, LEFT turns, the line dividing the HSI in half starts at 70 degrees LEFT of your heading. Which, if headed 360, is 290 and slices over to 110. The T goes in the 70-degree wedge again, the D below it in the bigger 180-degree wedge again and finally, the P in the remaining small wedge. Put in the holding radial and, voilà! Don’t forget to slow down if needed and report entering the hold. I know, it’s painful. I hate holding problems too.
Loading a holding fix and pattern into the MD-80’s GFMS takes about ten seconds if the hold is at a published fix and, because of proficiency, it takes about thirty years if it’s a radial/DME fix holding pattern. If ATC gives you a short-notice hold, one that is close, you may wish you were flying something slow. But flying your jet at 250 kts ground, or faster, makes things happen fast. When we were issued the nearby holding fix by RDU approach, I quickly recognized our time-crunch dilemma and instinctively fell back to the old-school, tried-and-true method. I switched my NAV from GPS to VOR, set in the radial and checked the DME. I did a quick fix-to-fix calculation the way they taught us in the Air Force, using DME and the VOR bearing pointer on the RMI (Radio Magnetic Indicator). The holding pattern was close: twenty degrees to the right and four miles away – too close to load the GFMS.
We were at 6,000 feet and 250 kts, so I called for slats, pulled the throttles to idle, slowed to about 200 kts and turned a bit to the right. I pictured the hold using T-D-P on the HSI, and at 35 DME, entered the hold via a parallel entry and watched the DME increase. My FO created a GPS waypoint at the radial/DME clearance fix, used that point as the holding fix, and built the holding pattern in the GFMS. At 45 DME I turned right onto the protected side of the radial and headed back to the radial at a 40-degree intercept. I tracked the radial inbound and at 35 DME turned left into the hold – just the way the picture appeared on the NAV display a couple seconds later. Whew, we got it right. After just two turns in the hold, and after the autopilot failed during the approach, I hand-flew the ILS through the rain, wipers at medium speed to a 400/2 landing. Once parked at the gate we looked at each other and chuckled as we had a moment of “holy cow” about the holding pattern and the ILS. It was work … but fun!
Another Sticky Note
Holding is a part of instrument procedures, just as much as an approach, but the frequency of a holding event is extremely low. And lack of frequency causes lack of proficiency. The same is true of non-ILS approaches: RNAV, GPS, VOR, ADF and LOC BC. In the Part-121 world, we fly an ILS 99% of the time and we are very proficient. A non-ILS, not so much. And we are issued holding perhaps two or three times per year and are probably not so proficient at that either – especially if referenced to a VOR, NDB or clothes-line pole. I’m moving from the MD-80 to the 737 soon with all of its modern avionics, a HUD and other magical approach and holding capabilities. But, I bet it doesn’t have an RMI – guess there’ll be another sticky note on my forehead.