How to stop chasing the needles

But when the syllabus moves on to flying approaches, the displays that show whether you’re tracking a localizer or GPS course and a glideslope or glidepath also demand your attention, and it’s common to watch students (or rusty instrument pilots) “chase the needles,” sometimes leading to a “sword fight,” where the vertical CDIs and horizontal glideslope/glidepath bars clash like swashbucklers’ sabers in an old pirate movie.

You can avoid chasing the needles by applying the fundamental principles of the control-performance method of instrument flying.

Use the control instruments—the attitude indicator to set or change pitch and bank and the tachometer or manifold pressure gauge to maintain or adjust airspeed and rate of climb or descent.

Check the performance instruments (airspeed, altimeter, heading indicator, rate-of-turn indicator, and so forth) only to confirm the results of your control inputs. In other words, to repeat a fundamental adage of flying: Set the pitch attitude, power, and configuration (flaps and/or landing gear), and predictable performance results.

Most discussions of the control and performance method, however, focus on the primary flight instruments, and many pilots don’t learn that the course and GS/GP indicators are also performance gauges. If you try to use the lateral and vertical deviation indicators as control instruments, you’ll chase the needles.

I use a simple technique to emphasize that key principle and to help pilots avoid fixating on the needles when they fly approaches. All you need is a Post-it note.

First in an aviation training device (ATD) or other simulation, and then in the airplane, set up to fly an ILS or RNAV approach with LPV guidance. As you intercept the lateral and vertical paths, establish the appropriate approach configuration for your aircraft. (In a typical Cessna 172, pitch at about –2.5 degrees, power at 1,900 to 2,100 rpm, and flaps at 10 degrees yields a descent of about 500 feet per minute at 90 KIAS, a good profile for a 3-degree descent path).

Wait about 15 seconds, then cover the HSI or other navigation indicator with the sticky note. You must now focus on flying the correct pitch and bank attitude to hold heading and maintain a stable descent. Reference the tachometer or manifold pressure gauge to confirm that power is steady and adjust the throttle to keep the VSI at about 500 fpm.

After flying 10 to 15 seconds using only the control instruments, briefly uncover the lateral and vertical guidance display to check how the aircraft is performing. Are you still on course and tracking the GS/GP? If not, note the discrepancy, cover the navigation display again, and use the attitude indicator to establish a brief, shallow bank to correct left or right and to adjust the pitch up or down. Check the rpm or manifold pressure gauge and add or reduce power as necessary to recapture the GS/GP.

Repeat that process every 10 to 15 seconds during the first one-half to two-thirds of the approach. As you get closer to the runway and the vertical and horizontal limits tighten, shorten the intervals between peeks at the navigation display.

In an ideal world, with no wind or turbulence, after capturing the horizontal and vertical paths, you could set the aircraft’s attitude, power, and configuration and the needles would never move off-center. But even in the real sky, with changing winds and vertical hiccups, the fundamental principle applies. Use the control instruments to set or correct back to the proper profile, and peek at the navigation displays only to confirm that you’re staying on centerline, and on glidepath. FT

Bruce Williams is a flight instructor in Seattle, Washington.