Trio Autopilot STC: Testing New FAA Policy

Trio Avionics joins the STC race with its Pro Pilot experimental autopilot. The initial focus is the Cessna 182/172 at a price thats below $10 grand.

The way we see it, if the Trio Avionics Pro Pilot autopilot is proven in experimentals like the Van’s RV series, it’s ready for duty in Cessna Skyhawks and Skylanes.

If the ongoing certification process falls into place, California-based Trio Avionics plans to bring an STC-approved version of the Pro Pilot to AirVenture 2017. With a post-installation price that’s targeted below $10,000, we think the market would embrace it as an alternative to an S-Tec system.

Can more sensible FAA policies and the right engineering approach make it happen? We think so.

Trio Pro Pilot autopilot control head

The Right Tech

At first blush, the Trio dual-axis Pro Pilot has the form and function we would expect in a modern retrofit autopilot. Not insignificant with any new autopilot is the installation complexity. To keep bottom-line costs down, a reasonable down-time might be less than one shop week, but we’re told the Pro Pilot can be installed in a Cessna Skyhawk in one day. Having had our hands in autopilot installs, we think that’s enthusiastic, frankly.

The backbone of any autopilot retrofit is the actuator installation, which is a sizable effort. The Pro Pilot has two servos: roll and pitch. Servo installation is traditional: attaching the pushrod to an aileron or elevator bell crank. In a Cessna 182/172 application, the roll servo is installed in the wing, while the pitch servo is in the tail.

However, in 182 applications, one of the goals is to mount the pitch servo behind the cockpit center pedestal, making it more accessible for installation and servicing. Earlier airframes have limited tail section access from the outside, which means you climb in and work while lying on the stomach. It’s not a task most techs look forward to.

Missing is a trim servo, but the system is smart enough to send signal commands to an existing pitch trim motor to balance the elevator forces when the altitude hold and climb/descent modes are engaged.

The Pro Pilot control head fits a 3-inch instrument cutout, weighs 12 ounces and houses all controls and sensors. This is a completely digital system that uses an internal solid-state inertial rate sensor, plus the inputs from an external GPS for navigation, including digital steering.

microprocessor-controlled Pro Pilot servo

The GPS monitors the inertial sensor’s performance, providing automatic corrections to the sensor data to correct for drift due to thermal shifts, inherent sensor drift and noise errors.

A fully digital interface is welcomed, but the reality of retrofits is having to deal with older analog equipment—including connection with the BendixKing KX155 and other vintage radios. Trio is engineering this analog-to-digital interface as it moves toward certification.

The Pro Pilot has what we think every new system should—airspeed capture and hold, plus lateral and vertical approach capturing. It also has altitude preselect, vertical climb and descents, plus stall and overspeed protection using servo feedback circuitry. There is also an automatic 180-degree turn feature to back away from inadvertent IMC. With a digital GPS input, the Pro Pilot’s display shows navigation status, including track, distance, estimated time enroute, plus fuel endurance data.

The kicker? The uncertified Pro Pilot currently sells for $2995.

Take It to the FAA

How do you keep autopilot technology like this from the panels of certified aircraft? Make the STC process so expensive and time-consuming that small companies like Trio Avionics want no part of the certified market. But when the effort includes an outside STC firm, aircraft owners and veteran aircraft engineers, it could be the most efficient way to work with an FAA that seems to be more forward thinking than ever. That’s where The STC Group—the company tasked with earning the initial STC, PMA and ISO 9000 certification for the system in the Cessna 182/172—comes in. The STC Group was founded by Paul Odum, an IT executive and aircraft owner from California.

We think Odum’s group has several feathers in its certification cap. First, it’s relying in part on new FAA policy, including Policy Statement PS-AIR-21.8-1602. The idea of the policy is to improve safety with a new approval process allowing the installation of NORSEE (non-required safety enhancing equipment) “that is determined to be a minor change to type design and whose failure condition is minor.” Previously, autopilot retrofits were considered major alterations. In the policy statement, the FAA specifically includes “stability and control (such as an autopilot or stability augmentation system)” in the NORSEE equipment category.

trutrak autopilot stc

It’s important to stress that NORSEE approval under this policy is not an approval for installation on the aircraft. The equipment becomes eligible for installation on the aircraft after approval. If the equipment is deemed to be a major change to the aircraft’s original type design, an STC must be pursued. But, experience counts.

The STC Group’s Mark Sullivan told us there is more than one Pro Pilot currently flying in Cessna 182 aircraft in the United States and in South America. The Trio installation in the U.S. registered aircraft was—get this—awarded an FAA field approval. While a field approval is a one-time STC, it is previously approved FAA data that might be useful.

The company isn’t only relying on seemingly more lenient FAA policy. In its pursuit of the Pro Pilot STC, it is utilizing engineering power that has extensive experience at Cessna Aircraft to construct the detailed technical drawings required for approval. In our view, these are the right people for the job because they understand how the autopilot installation hardware should adapt to a variety of Cessna airframes. Remember, Cessna at one time did autopilots in-house, using the Sperry/ARC line. The STC Group—which will own the STC—has also hired some of the best avionics field installation talent, and has gained AOPA lobbying efforts.

As for Trio Avionics, it started in the experimental market around the year 2000 and has close to 3000 autopilots flying in a variety of aircraft, including the Van’s RV and in EZ models.

The final price hasn’t been established and this will depend on the certification effort. There’s also the cost of product liability. The STC Group’s Sullivan—a longtime attorney and aircraft owner—isn’t concerned. He believes the goal of bringing an approved Pro Pilot to market just below the $10,000 mark, including installation, is achievable. We think it’s imperative.

Contact Trio Avionics.

Editor in Chief Larry Anglisano has been a staple at Aviation Consumer since 1995. An active land, sea and glider pilot, Larry has over 30 years’ experience as an avionics repairman and flight test pilot. He’s the editorial director overseeing sister publications Aviation Safety magazine, IFR magazine and is a regular contributor to KITPLANES magazine with his Avionics Bootcamp column.