Using VNAV on an Approach at KBVS

Pilots of GA piston singles don’t typically fly STARs, and usually ATC vectors us to join approaches that don’t require many step-downs as we intercept the final approach course. Instead, we tend to use the VNAV features in our avionics to manage the descent from cruise to an initial altitude for an approach or to help us arrive near an airport at the appropriate traffic pattern altitude.
But when connected to a GPS navigator, such as a Garmin GTN 750 or 650, that supports vertical navigation, new digital autopilots like the Garmin GFC 500 and GFC 600 can automatically descend as you fly the initial legs of an instrument approach, reducing your workload and helping you spend more time monitoring your progress.
To see VNAV fly a series of published step-downs, join me as I fly the RNAV (GPS) RWY 29 approach at the Skagit Regional airport north of Seattle, an approach that shows the value of using VNAV. I’m in my Beechcraft A36 equipped with the GFC 600 autopilot, a GTN 750Xi, and G500 TXi.

[@waltermengden8927]

👍

[@wheelerdavea]

Thanks again for the ride along. When you reduce power on a coupled approach, does the trim automatically engage, or is glide path maintained solely by elevator pressure?

[@BruceAirFlying]

My GFC 600 (and many GFC 500 installations) autopilot has a trim servo, so it adjusts elevator trim as airspeed varies and when you change configuration, such as extending flaps and landing gear. My autopilot also has a yaw damper that handles that axis.

[@wheelerdavea]

@@BruceAirFlying That's awesome. The last "real" autopilot I flew was our old KFC200, that would fly a coupled ILS or GPS approach but you still had to manually keep the trim up to date.

[@christophvz]

Nice job slowing down to maintain separation from the landing traffic. I’ve noticed that you maintained over 1nm separation at all times. Is 1nm your personal rule (where you’d break off the approach if you got any closer) or a coincident? If not, do you have a minimum or does it depend on factors such whether you’re converging ? 11:46

[@BruceAirFlying]

I am acutely aware of recent accidents, such as the mid-air at Watsonville (KWVI), where a twin continued a straight-in approach at high speed and collided with a Cessna which was in the pattern ahead. That's why I slowed down and made additional position reports and confirmed on the CTAF that I had the aircraft on base in sight. I didn't have a specific distance (e.g., 1 nm) in mind. I just kept the airplane ahead in sight and adjusted speed early to allow safe spacing as I got to short final. I also make position reports relative to the airport, not to fixes on an approach. Those fixes may not be familiar to non-IFR pilots and pilots who don't have the approach chart available.

[@tammaramma]

Hey Bruce, could you do a tutorial on a non-precision approach using the GFC autopilot. I haven't seen one of those yet.

[@BruceAirFlying]

I suspect that most pilots flying with a GFC autopilot have a WAAS-capable GPS navigator. And if they do, they will see an advisory glidepath (+V) when flying most 2D (nee non-precision) approaches. Newer GTN Xi variants provide +V guidance even when you fly a VOR approach (bruceair.wordpress.com/2021/05/14/vor-approaches-with-lnavv/). My practice and recommendation is to follow the advisory glidepath and use the point at which that +V guidance takes you to 50-100 ft above the MDA as the decision point--i.e., where you begin the missed approach. I'll try to get fresh video of a 2D approach one of these days. In the meantime: kzbin.info/www/bejne/p4iUdWiXiNKMfqM

[@greymarck]

In the beginning of this video you appear to be utilizing a PC simulation of the GFC 600. I've been unable to find one that ideally works with the Garmin PC Trainer, or even with a flight simulation that accurately simulates all of the modes and functionality available. What software are you using in this video? Thanks!

[@BruceAirFlying]

I am not aware of any simulation of the GFC 600 or GFC 500 autopilots. To help explain the features I was using, I captured images from the free Garmin PC Trainer Suite for Windows and photos of the GFC 600 controller. www8.garmin.com/support/download_details.jsp?id=12373