Thanks to Bill Ziesenitz (DPE >40 years) for his text this week motivating this blog. It seems many pilots are still unaware of the auto-on "envelope protection" built into Garmin autopilots 😳
Unlike older autopilots that a pilot manually turns on (usually >400 ft), the newer Garmin 500/600 series comes alive on its own at 200 feet agl. in Electronic Stability Protection(ESP)™ mode. In training, holding an extreme nose-up attitude in a plane equipped with the Garmin (ESP)™ will engage a “full nose down” autopilot command (> 10 seconds >15° up). The more you pull, the more it trims. It is critical that every CFI or DPE training in a plane equipped with ESP™ understand this feature and manually disable it for maneuvering.
Electronic Stability & Protection (ESP)™ — The ESP function provides a soft barrier to keep the aircraft within the desired operating envelope when the autopilot is not engaged. When the GFC 600 senses the aircraft is near the defined operating limit in pitch attitude, roll attitude, high airspeed, or low airspeed, the ESP function will automatically engage one or more servos to nudge it back to the nominal operating envelope.GFC 600™ Pilot Guide
After 10 seconds the full autopilot engages (and annunciates) forcing the plane into the “Level Mode.” At this point, all the servos are actively working to restore that level flight attitude.
If an unprepared CFI initiates a power-on stall with a high nose attitude, the full autopilot will engage and trim full nose down to correct the unusually high pitch (restoring “level mode”). This could make a stall recovery pretty radical if you are unprepared. Additionally, if a pilot stalled with ESP™ not disabled and a roll ensued on recovery, this autopilot will aggressively roll in aileron control to lift the low wing (creating more drag and a perfect spin set-up). Disconnect ESP™ before maneuvering (a five-second press on the red button will turn it off):
So I (30 hr student pilot) was practicing power-on stalls with my CFI in a plane newly equipped with a Garmin autopilot – which was turned off. At 80% power or so in a 180HP 172, the nose is waaay up there (at least to my low-time nerves.) So I’m pulling back further, waiting for the stall to break, dutifully holding the nose with rudders and definitely not ailerons, having experienced one near-spin already and not caring to repeat that experience.
All of a sudden I hear “Autopilot Engaged” on comms and Mr. Garmin decides to put in heavy aileron input. Immediately a wing drops and we are most of the way into a spin which my CFI recovers.
This shakes me up pretty well – we pulled some G’s getting back to level flight and overall, I was really not into it. Redit
Garmin ESP™ is passively watching every flight all the time, and is designed to maintain a “normal flight envelope” within limited parameters, usually 45° bank, 15° pitch up and 12° pitch down (this varies with airframe). First, it nudges, then after 10 seconds (cumulative operation), the full autopilot engages and forces the plane back into that envelope (which will interfere with training and could even make it dangerous). You will feel ESP™ fighting your bank on commercial steep turns. Every CFI or DPE flying with these units should be aware of this feature and disable it in the pre-maneuver set-up. (below)
If flight maneuvers exceeding the normal ESP envelope are intended, the feature can be disabled on the Aux – System Setup Page on the MFD
Enabling/Disabling ESP (Garmin G1000 NXi
1) Turn the large FMS Knob to select the Aux Page Group.
2) Turn the small FMS Knob to select the ‘Aux – System Setup’ Page.
3) If necessary, press the SETUP 2 Softkey to display the ‘Aux-System Setup 2’ Page.
4) Push the FMS Knob to activate the cursor.
S) Turn the large FMS Knob to place the cursor in the Stability & Protection field.
6) Turn the small FMS Knob to select ‘Enabled’ or ‘Disabled’.
7) Push the FMS Knob to remove the cursor.
(ESP will be automatically enabled on the next system power up)
On twin-engine aircraft, this autopilot is also equipped with “Smart Rudder Bias” that will “assist the pilot in maintaining bank control by lowering the roll
attitude ESP thresholds in the direction of the failed engine and pitch to maintain Vmc.” This feature is also continuously active in the Garmin autopilot and might need to be disabled for training. Again for quick disconnect: hold down the red disconnect button for > 5 seconds. Happy holidays to all who celebrate 🎉🎅🎄 Fly safely out there (and often)!
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I have a client with the 500 . In Appr mode it captures the GS and starts down. At 500’ it disconnects the GS (AP remains on) and will pitch up in a climb if a higher altitude if it’s preselected (ex MA altitude). I suggested he contact the avionics shop. An Arrow I fly at the flight school also has the 500, another PA 32 too, and both maintain the GS.
We’ve had issues with the ESP on landing so much that it’s policy to turn it off before every landing.
According to the manual, the ESP™ system *should* disable itself at 200 agl. If it didn’t that certainly could be a big problem! The PC-12 I used to fly (Honeywell Apex avionics) had an active pusher system everyone feared on landing. You do start to wonder if sometimes “protection” might become a problem.
Training for ESP like systems also needs to consider failure modes. I was using a DFC-90 (has its own ESP) to track the glideslope down. Probably due to icing in the pitot tube, my indicated airspeed dropped in spite of proper performance and track. Recognizing the problem, I ignored the false indication and low speed warning. Unfortunately, the DFC-90 did not understand the wrong airspeed indication, trimmed down, and disabled the level off. Without pilot recognition, the autopilot would have flown into the ground.
Good catch on your part. I have been flying a “Jurassic jet” with a not-so-wonderful autopilot. We watch it’s every move, ready to take over!