Evolution of the Autopilot

Evolution of the Autopilot 

March 2018

ev·o·lu·tion

Noun: the gradual development of something, especially from a simple to a more complex form. 

I have written a number of “evolution” articles over the past few years, including features on the history of audio control, navcoms, mode S transponders and headsets (see “Resources” sidebar at the end of this article). In each of these cases, it was apparent that GA avionics technology evolves rather slowly between the time an initial version of a product or idea is introduced and the point at which the enhanced final version is made available.  Last month, I suggested that EFIS was going to be the hot topic in avionics for 2018 and that the autopilot would be a close second. That’s because autopilot technology made a giant leap in available features/benefits, safety and affordability in 2017. These products are now making their way into legacy airplanes.  Often, it is just one company that drives these types of improvements. In this case, however, there are four manufacturers driving this new, affordable autopilot market, and that is a very good thing for the GA aircraft owner.  It seems like I’ve been talking a lot about autopilots recently. Trio and TruTrak have been getting all the mileage as of late, but both Garmin and Genesys/STEC have also introduced new and better autopilots for GA – and they, too, are coming in at a significantly lower price point.  Let’s take a look at how the limited features and benefits found in earlier autopilots compare to what is now available from these four manufacturers.

Early Autopilots 

The first autopilot can be credited to Lawrence Sperry, who successfully test flew an autopilot in 1913, if you can imagine that. Sperry is also responsible for the invention of the gyro, a critical element in autopilots.

Lawrence Sperry

“Aerial Petting Ends in Wetting.”  

Lawrence Sperry, handsome, single and known to be a ladies’ man, also appears to be one of the earliest members of the Mile High Club. Yes, I said that!  On one memorable occasion, Lawrence took another man’s wife up for a “training” flight, turned on the autopilot and proceeded to … well, I’ll leave that part to your imagination. However, Sperry, in the cramped quarters of a small aircraft, managed to bump the gyro, and the aircraft ended up in the bay off Babylon, New York. Sperry and his “student” survived, but the tabloids succinctly described the incident with the now famous headline quoted above.

early AUTOFLITE Autopilot

In the 1950s, Don Mitchell (later Mitchell/Edo Air) began creating a GA autopilot and had six models by 1961. Piper first offered an autopilot in 1958 as an option on their Tri-Pacer, while Cessna/ARC first introduced an autopilot as an option in their 1962 172C model.  Early models were roll axis only. They kept the wings level, and when interfaced to the basic nav radios of the day, could track a nav signal but with limited accuracy and reliability.

NARCO OMNIGATOR

A few years later, if you added a DG or an HSI, you could also track a heading.  Two-axis models with basic altitude hold would follow, as would glideslope coupling. Over time, reliability got better, but any real bells and whistles were limited to just bells; whistles would come later.

Modern Autopilots a Decade Ago 

Avidyne introduced EFIS systems in 2003 for Cirrus aircraft (and later Piper) which included solid-state Attitude and Heading Reference Systems (AHRS). Cirrus models with the Avidyne Integra EFIS systems generally used the System 55X, STEC’s flagship model that required a gyro turn-coordinator for roll axis sensing.

Garmin G1000

In 2004, Garmin introduced their G1000 fully-integrated EFIS System and followed up a few years later with the GFC-700 autopilot, designed to interface with the G1000’s AHRS system. Now owners had “big glass” screens and the reliability of a solid-state AHRS driven autopilot. The combination was revolutionary but was only available as an OEM option.

Avidyne did something unusual in 2010. They introduced their DFC90 autopilot controller as a direct replacement for the STEC System 55X’s controller. Though only applicable to Cirrus aircraft at that time, the DFC90 offered a feature that we had never seen in an autopilot for GA. It was the first autopilot with a “Straight & Level” button, a safety feature that is really catching on today.

Autopilots Today 

The following are the basic features found in virtually all current autopilots in use: 

Single-Axis:

  • Wings Level
  • VOR/ILS and GPS Tracking
  • Tracking of Heading with optional DG, HSI or PFD
  • GPSS Roll-Steering with optional interface

Two-Axis:

The horizontal axis features listed above, plus …

  • Altitude Hold
  • Glideslope coupling (on some models)

Here are the premium features we find in many late models and virtually all new autopilots: *

  • Altitude Preselect: Set an altitude and the autopilot climbs or descends to that altitude and levels out. The pilot works the throttle(s).
  • Vertical Speed Control: Set a rate of climb or descent and the autopilot will maintain that speed. The pilot maintains the throttle settings.
  • Flight Director: The flight director serves as a visual indication of where the autopilot wants the plane to go. This has been a common feature on the more expensive autopilots for many years and a great tool for reducing pilot load in IFR.
  • Envelope Protection, Overspeed/Underspeed Protection: Thanks to marketing, each of the four manufacturers calls it something different, but it is essentially the same thing. Once the autopilot is programmed to the aircraft’s maximum and minimum speed, G-force limits and safe bank angle, it takes over when these parameters are exceeded. This is a significant step in the evolution of the autopilot!
  • Auto Trim: A step up from trim prompting. Most autopilots with altitude hold capability will alert you when too much force is being applied to the horizontal stabilizer, and you manually adjust. Auto Trim corrects the trim issue automatically.
  • Track Offset: One way to minimize traffic on the airways is to offset your track and run parallel to it. Today’s new autopilots have this feature.
  • Emergency Level Mode and Go Around: As mentioned, Avidyne introduced the “Straight and Level” button in their DFC-90 autopilot for the Cirrus back in 2010. Now, all of the new autopilots (listed below) feature a button that immediately takes the aircraft to straight and level flight. Garmin and STEC even provide a “Go Around” button for missed approaches – another significant improvement in the evolution of the GA autopilot.

*Note: almost all the newer features we find in modern autopilots are in the Pitch Axis!

Pre-2017 Autopilot Options 

Prior to the announcements made at AirVenture Oshkosh 2017, STEC has been the dominant player in autopilots, with Century Flight Systems a somewhat distant second and Avidyne making their small contribution. Here’s a peek at what was available prior to the Oshkosh announcements, along with the estimated price (installed) for each. I show this for perspective.

These are estimated installed prices.

Genesys/STEC:               

System 20: Basic Roll only with VOR/ILS/GPS Tracking……………..$11,500

System 30: Same with basic Altitude Hold…………………………………….$17,300

System 40: Same as the System 20 in 3 1/8ʺ configuration…..………$11,600

System 50: Same as the System 30 in 3 1/8ʺ configuration…………..$17,700

Note: GPSS and Electric trim are an option on the above systems. Heading track requires an optional DG or HSI.

GENESYS/STEC 55X

System 55X: This was the standard in GA for 2016! Full featured with GPSS (standard), Glideslope Coupling and Vertical Speed Command………$21,500

Note: Altitude Preselect and Auto Trim are an option on the 55X. STEC also offers a System 60-2 and System 65 for larger aircraft.

Century Flight Systems:

Century 4000 Autopilot

Century 1: Basic Roll Axis with VOR/ILS and GPS Tracking. Does not accept a DG or HSI for Heading Track…………………………………………………..………$11,900

Century 2000: Two-Axis with Full VOR/ILS/GPS Tracking, Glideslope Coupling, Trim Prompting, with DG……………………………………………..$24,500

Triden: Two-Axis in 3 1/8ʺconfiguration, Full Tracking, including heading (DG included), Auto Trim included…………………………………………………$21,000

Century 4000: Two-Axis, Full Tracking, Glideslope Coupling, GPSS, Vertical Speed Control, Voice Annunciation………………………………………………..$22,000

2018 Autopilot Options

(listed alphabetically)

Garmin GFC 500

 This is Garmin’s first digital, retrofit autopilot for GA aircraft weighing less than 6,000 pounds. The system includes all the basic features of a two-axis autopilot, including full VOR/ILS/GPS tracking* with GPSS roll-steering, Altitude Hold, Glideslope Coupling and Flight Director.  Garmin’s G5 EFIS PFD instrument with its internal AHRS will provide roll and pitch sensing for the GFC 500. Not to be outdone by Trio and TruTrak, the GFC 500 also adds Vertical Speed command and Altitude Preselect. Add the G5 DG or HSI and you add heading track.  The GFC also includes the safety features first introduced to GA by Trio and TruTrak. When engaged, the GFC 500 uses what Garmin calls ESP to raise or lower the nose when an overspeed or underspeed situation is present. Additionally, it also keeps the pilot from exceeding safe bank angles that could lead to a stall. Of course, the GFC 500 also comes with the aforementioned “Straight and Level” button.

The pricing for the GFC 500 looks like this:

  • G5 EFIS PFD……………………………………………………………..………..$2,149
  • GFC 500 Autopilot…………………………………………………………….$6,995

(Pitch Trim is an option at $1,500 additional)

  • G5 DG or HSI/ with GAD29 * (for Tracking and Heading)…$2,995

Total list price (excluding labor):                                             $12,139

*GFC 500 with the optional G5/GAD29 adapter appears to be compatible with Garmin GTN and 400/500 series navigators only. You’ll already need to have made a significant commitment to Garmin (or plan to) to use this autopilot.

Garmin GFC 600

Initially, I thought the GFC 600 was designed for aircraft weighing more than 6,000 pounds. That is incorrect.  Unlike the GFC 500, the 600 includes an internal AHRS system and can link to the G500/600TXi PFD/MFD and although targeted to more sophisticated aircraft than the GFC 500, the 600 is already STCd for 182’s and Bonanzas with other  aircraft STCs in the works.

Pricing for the GFC 600 starts at $19,995.

Genesys/STEC 3100 Digital Flight Control System

S-TEC has been the dominant manufacturer of GA retrofit autopilots for years.  The Digital S-TEC 3100, unlike the GFC 500, is self-contained with internal AHRS and requires no external sensors. It is full-featured by 2018 standards with all the basic features plus Vertical Speed Control, Altitude Preselect, Envelope Protection/Alerting and Level Flight button.I have limited information on the S-TEC 3100 right now, but it appears the pricing starts at about $16,200 (plus installation).

Trio Avionics Pro Pilot

 Like I said, Trio and TruTrak have been getting a lot of attention lately – from the industry and from me! I have covered both the Trio and TruTrak systems in recent issues so I’m not going to get too specific here (see “Resources” to reference previous articles). Let’s just say that like the Prego pasta sauce commercial of old, the phrase “It’s in There” applies equally well to the Trio Pro Pilot!  All of the basic and most of the premium features are there: full tracking (including GPSS IFR approaches when coupled to a WAAS GPS), Altitude Hold and PreSelect, Vertical Speed Control, Auto Trim, Track Offset, Envelope Protection and the Straight and Level button. The Pro Pilot does not support a flight director, but Trio has thousands of quality autopilots in the air and their technology is well proven.

The Trio Pro Pilot (including the required STC and install kit) runs $6,000* for most Piper and Cessna singles. The final installed price is likely under $10,000.

*Note: New lower price! The Cessna 180/195 Series and the Piper PA32 series install kits are a little higher, but the worst (or is it the best?) scenario is $6,500 complete, plus installation.

TruTrak Vizion Autopilot

TruTrak, like Trio, is not a new player in the autopilot business. Yes, their market has been the Experimental/Light Sport market for the last 15 years, but without the FAA breathing heavy over their shoulders, TruTrak (and Trio and Dynon) have been able to advance their technology faster than the certified market.  While the legacy aircraft owner is just now getting Envelope Protection, Straight and Level buttons and other affordable features like Altitude Preselect and Vertical Speed, TruTrak customers have had these options available to them for years. It’s all in there, minus the Flight Director and Go-Around button!

Pricing for the TruTrak Vizion is $5,000 (excluding the required $200 STC available through EAA). The final installed price should be less than $9,000.

Conclusion 

I believe that any pilot who flies IFR should have an autopilot on their equipment list, especially if they are a low-time pilot with a fresh IFR ticket! However, as an avionics advisor, I have been hard pressed to suggest that a legacy aircraft owner invest, especially in the more desirable 2-axis autopilot unless he or she has a very long-term plan for the aircraft. Even a basic, two-axis unit (like a STEC System 30) represents a big chunk of change to an aircraft owner who has tired avionics and an ADS-B mandate to meet.  Thankfully, that has all changed. It’s great that Garmin has entered the market and STEC now offers a more affordable alternative, but if you’re looking for someone to thank, look to Trio and TruTrak. It was they who brought this affordable technology to pilots years ago, and it was the FAA who recognized it.  If you feel that you need a flight director or a Go-Around button, the big guys may be right for you and your budget. But if not, I think the choice is obvious and I hope that you will support the little guys too!

Until next time, I wish you Safe and Happy Flying!

Bob Hart – www.AvionixHelp.com