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Check WAAS Up!
It’s been just over a decade since the FAA commissioned WAAS for general aviation use. So these days I am so used to having WAAS that I don’t think twice about it, particularly when flying behind a Garmin G1000 panel. But if you are purchasing or renting an airplane that is a few years old, it is worth looking into whether the airplane is WAAS-equipped or not.
On a recent IFR flight, I was surprised to find that the LPV approach I wanted to fly into Camarillo, California (CMA) — the RNAV (GPS) Z RWY 26 approach — was unavailable in the G1000 system I was flying. With hundreds of hours of G1000 time in new airplanes in my previous job as a Cessna sales demonstration pilot, I had never seen this before. I didn’t realize that the 172 I had rented was delivered by Cessna in 2005, about one year before Garmin introduced WAAS into its highly popular glass panel. So while the G1000 appeared very familiar to me, it was missing an important component that limited its use. As you are probably aware, WAAS is needed to provide vertical guidance for instrument approaches such as LPVs. So because the system I flew behind was not WAAS equipped, the LPV approach I wanted to fly was unavailable.
The RNAV (GPS) Z RWY 26 LPV approach into CMA would have allowed me to go down to a decision altitude of 327 feet, 250 feet above the ground. The RNAV (GPS) Y has a minimum descent altitude of 620, nearly 300 feet higher than the LPV. Fortunately the clouds were at about 800 feet AGL, so they were high enough that I could safely fly the RNAV Y approach and get on the ground in Camarillo. But the experience was a good reminder that, while avionics often look universal and act in familiar ways, they don’t always provide the same capabilities.