IFR Fix: Nonprecision, not imprecision

July 15, 2014

It only takes two panels on a government-issue instrument approach plate to illustrate the missed approach for the VOR RWY 28 approach to Pennsylvania’s St. Mary’s Municipal Airport.

The entire approach is uncomplicated, but it’s easy to see how it could become a challenge in weather, with limited navigational equipment or systems issues, say loss of DME.

Consider pilot workload during that two-step missed approach. There’s a climbing right turn followed by navigating to EMPOR via Slate Run’s 264-degree radial. In that turn, you’d rotate the omni-bearing selector to the 084-degree inbound course, intercept, and track it, identifying EMPOR when the right-deflected needle of your No. 2 nav—previously set to the Keating 333-degree radial—centers. Then enter the racetrack holding pattern, rotate the No. 1 OBS back to Slate Run’s 264-degree radial, and hold. All this—don’t forget to level at 3,900 feet, as published—during six nautical miles' flying from the missed approach point to the holding fix.

A back-seat passenger monitoring the briefing for this operation might glaze over at the technicalities—but would perk up at hearing it mentioned that this is a "nonprecision" procedure, and that mastering nonprecision approaches is a more highly prized skill in an instrument pilot than flying more technologically evolved approaches, especially when things are going wrong. (Think back to early IFR training: You may recall surprise that your first ILS approach, though all bells and whistles, was easier to fly than local VOR or NSB approaches with their erratic step-downs and those imprecisely timed final approach segments.)

In the satellite age, it’s still true that the less precision exists for navigation, the more precise the flying must be; instrument checkrides still include two nonprecision approaches and "demonstrations of a nonprecision instrument approach without the use of the primary flight instruments or electronic flight instrument display."

"A nonprecision approach without the use of the primary flight instruments/electronic flight instrument display is considered one of the most demanding situations that could be encountered," says the practical test standards. "If applicants can master this situation, they can successfully complete a less difficult precision approach."

But don’t let checkride success go to your head.

"If an actual approach in IMC becomes necessary without the aid of the primary flight instruments/electronic flight instrument display, a less difficult precision approach should be requested, if available," the PTS states, adding that "sound judgment would normally dictate such requests."

Dan Namowitz

Dan Namowitz | Aviation Writer

Dan Namowitz is an aviation writer and flight instructor. He has been a pilot since 1985 and an instructor since 1990.