EAA Sport Aviation - October 2011

It is accurate to think of ESP as an “ electronic spring” in the control system. Many—actually most—airplanes have springs or weights in the control system to add stick force beyond what is available from air loads. ESP is a “smart” spring that adds stick force to alert the pilot to an unusual attitude, and to guide him back toward a normal attitude.

To see ESP in action, Garmin’s top test pilot, Tom Carr, and I flew the Cirrus SR22 that Garmin used to develop the system. When I rolled the Cirrus into a steep bank ESP kicked in so smoothly that I couldn’t feel it engaging, but could certainly feel the extra stick force resisting my roll control input. ESP felt totally natural, just as though the Cirrus had grown new stability that wanted it to bank less than 45 degrees. The 10 pounds of force was noticeable, but the full 20 pounds was really impressive, particularly when rolling left and trying to twist the side stick away from my body.

I had to zoom the Cirrus to get to the ESP pitch-attitude onset because a smooth pull-up would usually get to the low-speed ESP activation first. Obviously, ESP needs to do its best to help the pilot avoid a stall no matter what the attitude, and it does. At stall-warning onset ESP engages, adding nose-down stick force to turn the stall warning off. If you are near redline airspeed in a dive, ESP pulls back on the stick to help you slow the airplane.

Because ESP is part of the complete
Garmin system it’s possible for the auto-
pilot to jump in automatically if the
human pilot fails to recover to a more
normal attitude. If ESP is engaged for 50
percent of the previous 20 seconds—
meaning the airplane is in a very steep
bank, very nose high or low attitude—the
autopilot will engage automatically and
maintain a level attitude and maintain
altitude if there is enough available
engine power. This automatic autopilot
engagement is an option the airplane
maker can select, and Cirrus has.