GRT Autopilot Servos

With no clutches and a single gear reduction, GRT servos are the epitome of simplicity and reliability. There are practically no mechanisms to fail. Safety features are abundant, including an shear-able output arm that remains captive to prevent jamming, and a safety-wired case. Limited authority means you can take over, even if you forget to disconnect the autopilot. Motor temperature sensing prevents motor damage without sacrificing torque. Pitch servos include an optical force sensing mechanism, that will never wear out, to keep the pilot aware of trim required. Even the drive electronics protects themselves from extreme conditions.


Autopilot/Flight Director

Designed to a higher standard…to fly the plane as you would.
Every GRT Avionics display unit, from the first WS, through our Horizon 10.1 flagship, as well as the Mini-EFIS, is capable of performing as an autopilot control head. Just connect one or two servos and we will fly you from just after takeoff, to just before touchdown. We will couple you to your approach and fly you to your selected altitude…and much more!*

No servos? No problem! The flight director makes you the autopilot, combining attitude and navigation targets into a single cue that even a non-pilot can follow.

*Vertical autopilot functions are optional with some display units.

Smooth and Accurate – Exceptional in Turbulence

All autopilots are not created equal. More than many other aspects of an EFIS, the autopilot depends on the mathematics and logic that drive the servos to deliver the performance you expect. Our engineering background includes autopilot experience with commercial and military aircraft. The result is a smooth and accurate autopilot that with ride quality in turbulence superior to hand flying. Our claims are exceptional, but they are met by our autopilot performance.

But the autopilot isn’t just about flying the airplane with servos. It is also about working with the pilot.

Simple to Engage

A single press of the autopilot engage button and you are free! The autopilot instantly holds pitch attitude and heading. Simultaneously, the autopilot shortcut menu appears, making coupling to your selected targets only one more button push away. It is the job of autopilot to make your life easy, and we did not forget this.

Simple to Command

Want to change your selected altitude? Couple the autopilot to fly to any runway in the database? A single push of the right knob brings up the full autopilot menu. A twist of the knob sets your selected altitude. One click of the “SAP” (Synthetic Approach) softkey and we prompt you with the available runways and winds. Climbs and descents can be made at a selected vertical speed, or IAS. The autopilot provides automatic capture of ILS and synthetic approaches. It is always that simple, yet always that sophisticated.

Yes, We Couple to That…

Lateral and vertical coupling is only limited by the navigation sources connected to the EFIS, such as GPS, VOR, ILS, LOC, and even lateral and/or vertical steering commands from an external GPS. Coupling to the synthetic approach is also provided, and may be used with all approaches, visual or instrument.

Pitch Trim Sensing

The pitch servo must work against pitch trim changes due to speed, flap position, fuel burn, etc. If these forces become too high, an autopilot may gradually lose control of the airplane and no longer fly accurately, or may suddenly slip, resulting very abrupt pitch changes. In VFR flight this is at best a nuisance. It can result in a very uncomfortable experience and can be hazardous. In IFR flight this is dangerous, and can result in failure to hold altitude, follow the glideslope or a disorienting sudden pitch change. This is why the GRT pitch servo senses its force output and shows a clear indication of direction and amount of trim required. When trimming becomes more urgent, the need is annunciated with color coding and an audio alert of “trim up” or “trim down”.

Providing Awareness

What is it doing? This should never be a question when it comes to an autopilot, and it won’t be with a GRT autopilot. Lateral and vertical modes and targets are color coded and displayed prominently in the upper corners of the display. If an autopilot mode change is pending, such as when an approach has been armed, the pending mode is shown next to the active mode, and will “jump the fence” (move to the outer column) when it becomes active.

Here the autopilot was coupled to GPS1, but it is unable to provide navigation guidance because it lacked a flight plan or lost GPS position lock. The EFIS autopilot reverted to heading hold until GPS1 is restored. The heading hold mode, and its target is clearly displayed in yellow, and GPS1 shown pending. On the right, the vertical mode is currently in IAS climb mode at 125 knots, and will level off at 8,000’. No vertical modes are pending.

The Same Approach- IFR or VFR

Traditional coupling to lateral and vertical navigation sources for IFR approaches is included and augmented with the automatic capture feature. Similarly, VFR approaches can be flown coupled to any runway in the database also by coupling to the synthetic approach. We took it one step further. Recognizing the benefit of making every approach the same, so we allow you to fly the approach the same, IFR or VFR. IFR requires only that you tune the ILS. The EFIS will take it from there. Highway-in-the-sky guidance will supplement the raw data ILS display and autopilot coupling will function the same as a synthetic approach.

A Backup to the Nav Radio

Our synthetic approach normally defaults to extended runway centerline, and your default setting for the glideslope angle. This is great for VFR, but is provides no assurance of obstacle clearance. However, when the EFIS sees (via its database) that the runway you have selected includes an Loc or ILS approach, it will construct its synthetic approach to emulate the actual approach. This provides greater assurance of obstacle clearance and is a last-chance backup to an ILS receiver.


A well-designed autopilot is driven more by safety than its primary job of flying the airplane. Safety must consider much more than mechanical failures, but also its role when working with the pilot. Some of our safety features include:

  • Pitch servo torque sensing with out-of-trim annunciation and alerting
  • Clear and unambiguous annunciation of the current and pending modes
  • Continuous self-test of servo electronics and communication
  • Under-speed/over-speed/g-limiting
  • Unusual attitude recovery
  • Driven by high-integrity attitude data
  • Annunciation of autopilot disconnect
  • Safe mechanical design and its mounting
  • Attention to these issues reflects our engineering experience with commercial, military and experimental aircraft. Like our AHRS, our autopilot is designed to a higher standard.

System Architecture

GRT servos can be wired to all display units. AHRS attitude/air data is used to drive the autopilot, and is displayed to the pilot. Want redundancy? Upgrade to a dual AHRS, and you get redundant, cross-checked, attitude/air data not just to your displays, but also for your autopilot.

Easy to Maintain!

No regular maintenance is required, and like all GRT equipment, servo software can be updated without removing it from the airplane.

Mounting Kits

Factory approved mounting kits are available for all popular kitplanes. Order your servo with your EFIS, or add it later for the same low price at anytime.


Servo Torque Specifications Max Holding Torque (oz-in) Max Starting Torque (oz-in)
Standard Torque Servo 690 348
High Torque Servo 1176 720
Servos are over-temperature protected. Torque is automatically reduced if servo reaches maximum operating temperature. This would normally only occur if heat was directed onto the servo, or the servo had minimal cooling via airframe mounting/air circulation, which is unusual, as typical servo mounting provides significant heat conduction to the airframe.

Manuals Revision Release Date
Autopilot Mode Control Panel (touchscreen models) A 11/14/2018
GRT Autopilot Pilot’s Guide A 5/23/2014
GRT Autopilot Installation and Setup Guide B 07/18/2018
Autopilot Modes C 4/2011
Wiring Diagrams    
Single Display Unit Autopilot Wiring  H 11/07/2013
Dual Display Unit Autopilot Wiring  H 11/07/2013
Dimmensional Drawings    
Autopilot Servo Dimensional Drawing A 2/03/2017


Autopilot interface software is part of the display unit software. However, the servos may need to be updated from time to time as the display unit software changes. The software in each servo is updated with a USB stick using the same procedure as the display unit. Use the Software Update function on the A/P Maintenance page to send the new software to the servos.

SoftwareVersionRelease Date
Current Servo Software
*Note on V. 13/14 – Versions 13 and 14 are both current. Version 14 is functionally the same as Version 13 and was created to adapt to the newer style PIC chip. If an update to servo software is required, the system will automatically detect the chip type and install the version appropriate for the servo. The March 21st software release only reflects this combination, and is not a routine software update for autopilot operation. (In other words, if your servo software is Version 13, it IS current and it will not update to Version 14 because Version 14 does not apply to it.)
Beta Software

This section contains software in the development or testing stage for customers interested in testing new features before a final release. The software below may be incomplete or have unexpected behavior. Never use in instrument conditions or other situations where EFIS failure or unexpected behavior will affect safety of flight.

VersionRelease Date
No beta software available at this time.

Roll Servo

Roll Servo Mounting Kit

Pitch Servo

Pitch Servo Mounting Kit


Add-ons total:


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