The Glideslope

When you see what you expect to see

- ALEN HEWITT

It was 2001, and an IFR-approved panel-mounted GPS had just been installed in my airplane, a Cessna 180. I was anxious to see it in action with its moving map, a multitude of functions, and the information it provided. A short 20-minute flight to a nearby airport for breakfast with a friend and some hands-on use of the new equipment was in order. The weather at the breakfast airport that morning was not VFR because there was a low marine stratus layer. The AWOS reported instrument conditions, with a 300-foot overcast but reasonable visibility of 4 miles below the cloud deck. Because I pride myself by staying instrument current, this would help me stay that way.

The airport is served by an ILS (with 200-foot and half-mile minimums), and the local approach controller can give vectors for the approach, though they lose radar coverage around the final approach fix.

I asked the controller for the approach using a pop-up clearance, and I quickly received one with assigned altitudes and headings. As I entered the clouds, the GPS provided course information to the airport. I completed the before-landing checklist; verified the settings on the radios, knobs, and switches for the approach; and listened to the Morse-code identifier for the ILS to verify that the approach frequency was properly identified. I reviewed the approach plate one more time.

I loaded the approach into the GPS—albeit this would be a backup to the primary navigation instrument, an HSI that would be presenting localizer and glideslope information from the ILS transmitter. The only new piece of equipment installed was the GPS; the rest of the radios had been in place for years and worked well. I enjoyed the tracking of the flight on the GPS’s moving-map display, and I wondered how I had managed to fly 40 years without one.