NOTE: For a more up-to-date discussion, see Understanding RNAV Approaches.
Continuing my series on the simulating RNAV approaches with the new Garmin 400/500W Trainer software, here are some preliminary results of experiments flying an LPV approach.
I chose the KOAK RNAV 27L approach, which has published LNAV, LNAV/VNAV, and LPV minima.
I initialized my position over TRACY intersection (northeast of the Livermore airport) at 6000 feet, clicked the direct button, and selected KOAK as my destination. Clicking the PROC button, I scrolled down and selected RNAV 27L from the list of choices, and selected SUNOL as the initial approach fix. Since you often get vectored to a fix inside the IAF on approaches into Oakland, I clicked the FLP (flight plan) button, clicked on the small knob on the lower right to enter cursor mode, scrolled to the HEDER waypoint with the big knob, and clicked on the direct button. By the way, loading an approach procedure and then proceeding directly to a fix on that approach effectively activates the approach.
Approaching HEDER, I used the Trainer's throttle slider switch to reduce my airspeed to about 120 knots and the countdown message appears, providing a 10 second warning for the turn to join the intermediate approach course. It's harder to see in this example, but there is a small arc showing the path to fly-by HEDER and become established on the approach. Note that the course sensitivity annunciation is still TERM (terminal mode), meaning a full scale deflection represents a course deviation of 1 nautical mile. Once past HEDER and established, it will be time to descend to cross VODSY at or above 1600 feet. Notice that there is still no clue as to whether the unit will provide LPV, LNAV/VNAV or plain old LNAV sensitivity, so it's best to be prepared for the worst - a non-precision descent to 420 feet and a minimum 5000 foot RVR. Just in case there is going to be vertical descent guidance, it would be best to be at 1600 feet a mile or so before VODSY.
After passing HEDER and joining the approach course, the course sensitivity annunciation changes to LPV, meaning the 530W has the required GPS accuracy to provide vertical guidance and I can use the lowest (LPV) minima shown on the approach chart - 259 feet and a 4000 foot RVR (runway visual range). I just hit the jackpot - the lowest minima - though there won't be a flood of nickels pouring out of the 530W. Descending on the glideslope with the trainer is a bit tricky since you aren't really flying a plane, you're just clicking on an altitude button to descend or climb 100 feet at a time. Descend too quickly when using a 530W that has TAWS and you'll get a terrain warning, even with the Trainer software.
The next installment will investigate flying RNAV departure procedures with the 400/500W Trainer.