G3X Touch Experimental Lean Assist

Overview

Lean assist is a way to achieve top performance from an aircraft engine. By adjusting the fuel/air mixture, the pilot can manage fuel flow for best performance at a given pressure altitude. Richer mixtures cause the Exhaust Gas Temperature (EGT) to decrease, while leaner mixtures cause the EGT to increase. The G3X Touch™ glass cockpit suite lean assist system is used to determine peak temperatures that indicate the best engine performance at a given altitude. At a certain point in the fuel adjustment, the pilot will discover the peak temperature, the point at which the engine will not run more efficiently.

The G3X Touch Lean Assist is a feature that monitors and detects peak temperatures for EGT or Turbine Inlet Temperature (TIT) as the pilot leans the engine's fuel/air mixture. When configuring EGT or TIT inputs, Lean Assist can be enabled or disabled. If Lean Assist is enabled, the LEAN soft key will appear on the engine page in normal mode. Lean Assist should be disabled for engines that do not have pilot-controllable fuel / air mixtures, including Full Authority Engine Control (FADEC) systems. 

Keep in mind, the G3X Touch does not make a distinction between engine types or pilot operating preferences to run the engine. Different engines will run more efficiently at different settings, and the best place to find that information is either through the engine or kit manufacturer.

Usage

A Lean Assist button is displayed on the engine page when Lean Assist Mode is enabled and at least one EGT or TIT input is configured. Refer to the G3X Touch Installation Manual for more information.  Note: This instruction is only for experimental models of the G3X. If you have a Certified G3X, see a Garmin Dealer for adjustments to configuration settings.

1. From the MAIN tab of the engine page, touch LEAN ASSIST.
2. As the mixture is leaned, one of the cylinders 'EGT' values will peak.
3. Continuing to lean the mixture will cause each additional cylinder to peak (if applicable) until the last of the cylinders peaks.
4. To cancel Lean Assist mode, touch LEAN ASSIST again.

When LEAN ASSIST is selected, the Lean Assist mode waits for the cylinder's EGT to reach a peak temperature and decrease by at least 7^oF. To prevent the detection of false peaks, the system waits for a cylinder's EGT to increase by at least 15^oF before detecting a peak. In addition, if the cylinder temperature rises above the previously detected peak by more than 100^oF, the previous peak is considered false. 

The following bar graph is displayed when four or more EGT cylinders are configured and the same number of EGT and CHT probes are configured. When each cylinder peaks, its bar changes from green to blue, and the white EGT number changes to a blue delta number. The blue delta number is the difference between current EGT and peak EGT for each cylinder. The first cylinder to peak is identified with a solid blue box around the delta number, and the last cylinder to peak is identified with a hollow blue box. The outline and gray number above each bar display is the actual peak EGT value. 

The following graph is displayed if EGT data is configured on less than four cylinders and a different number of EGT and CHT probes are configured. The temperature deviation between the current temperature and the peak temperature for the cylinder currently closest to its peak is displayed in cyan. A cyan hollow triangle appears on the EGT gauge at the temperature where the first cylinder peaked. 

The following dual-pointer gauge is displayed when exactly two cylinders of EGT are configured. Each cylinder has its own peak temperature triangle.

The following gauge is displayed when TIT is configured instead of EGT.

Note: A "+"  delta EGT value indicates the current temperature is greater than the previously detected peak.

If a fuel flow sensor is configured, the fuel flow value detected as the first cylinder peaks is saved. The fuel flow corresponding to the peak EGT is drawn on the fuel flow gauge as a hollow blue pointer. This can be used to determine if you are on the rich side of the peak or the lean side of the peak. Rich of Peak (ROP) if the fuel flow pointer is above the blue triangle, or Lean of Peak (LOP) if the fuel flow pointer is below the blue triangle. 

The EIS displays the cylinder whose temperature is currently close to its own peak value (when Lean Assist Mode is active) as a white pointer with the cylinder number. The peak temperature is depicted by a hollow blue pointer, and the temperature deviation from the peak is displayed in place of the normal temperature number in cyan text. 

For more detailed guidance, please see your G3X Touch Pilots Guide.