It seems that hardly a week passes without a new GPS navigator appearing, but the world of autopilots progresses at a relatively glacial pace. But progress it does. Although the field of players hasnt changed a great deal, there are new entrants into the world of computer-aided piloting.
Notably, AlliedSignal recently rolled out its new KFC 225, a premium George aimed at the high performance market. Meanwhile, S-TEC continues to impress buyers with its modular approach to autopilot design and marketing.
The company has introduced some new stuff since we last examined autopilots and were told more developments are in the works.Heres our point-in-time assessment of whats out there now:King Radio started making autopilots 30 years ago and under AlliedSignal, Bendix/King has carried the flag forward. The company has some of the most successful systems, including the KFC 200 and the now 20-year-old digital autopilot, the KFC 150.
We mention the age of the KFC150 and variants (KAP100, KAP150), because only in the last three years have there been new general aviation autopilots from AlliedSignal (King Radios purchaser and absorber).
The KAP 140 debuted with the new crop of single-engine Cessnas and for all intents and purposes, its a Cessna-only autopilot for the time being. The latest entrant from Bendix/King, the KFC225, is tailored to high-performance aircraft such as Barons, the Piper Mirage and, we suspect, other high-performance singles to come.Starting with the basics, KAP140 is a rate-based one- or two-axis system with a radio rack-mounted computer-controller unit, the KC140. No remote boxes here so its a relatively simple install.
It uses the typical Bendix/King servos, but the system relies on conventional DGs and turn coordinators provided by other manufacturers, not the specialized attitude gyros found in higher-priced Bendix/King autopilots.
The KAP 140 offers roll modes of heading select, nav and approach, as well as back course. If you have a two-axis system, you get vertical speed hold as well as altitude capture and hold.
In approach mode, the KAP 140 will track glideslope. One feature in the KAP 140 and in the newer KFC 225 that tickles us are the vocal alerts. Instead of the ubiquitous elevator chimes, these systems will announce, Autopilot disconnect.
Although certified only for the Cessna at the moment, we suspect the KAP 140 will eventually find its way into the general light aircraft GA market. However, it will have to muscle aside S-TEC products in the mid-range and that wont be easy.
AlliedSignals KFC225 is the latest in high-performance autopilots. To date it has been certified in Piper Malibu/Mirage (in lieu of KFC150) and the Raytheon Bonanza and Barons where it will take over from the popular KFC 200.Bendix/King says many more certifications are planned, with the Mooney Ovation and Bravo due in the short term.
The KFC 200, although still supported, has been effectively discontinued and since its in the general price range of the 225 anyway, we cant make an argument to buy the 200 over the 225, even if you can find a new unit.
In a move that diverges from Bendix/Kings policy of only certifying autopilots in airplanes that are in production, AlliedSignal is pursuing a KFC 225 STC for the Aerostar. Thats great news for those who want a high performance autopilot to match the aircraft capability.
Like the KFC 150-series, the KFC 225 is a digital autopilot, not because it has numbers, like a digital watch, but because it uses microprocessors to compute and control the autopilots actions. This serves to make the units smaller, because a processor takes the place of dozens of discrete parts.
It also makes the certification and the aircraft specific programming easier, because it can all be done with a computer. Connect a laptop to the autopilot and teach it how to fly the airplane its installed in.
On the downside, a digital computer sees things in steps, which can be coarse, like a low resolution picture. Airplanes are purely analog devices, with infinite movement in all planes so an autopilot thinking in binary mode tends not to be a smooth stick. But Bendix/King solved these problems in the early days of the KAP 150, with software that smoothes the bumps.
The KFC225 is a rack mounted autopilot, similar to the KFC 150, so although its a major install, everything goes into the panel in a single box. Gone are the old discrete altitude preselect panel and yaw damper controls. Its all incorporated into a single unit that looks about like a KLN 89B GPS.
Installation wise, the KFC 225 is meant to be a panel mount replacement for the 150/200 systems, which means that it uses the KI 256 flight command indicator and existing KCS 55A and KCS 305 HSI and compass slave system, so if youve got all that stuff, youll spend less. This autopilot does use Bendix/Kings new KS 27CX servos, however.
What does it do, exactly, that older models cant do? In addition to combining all the controls into a single unit, the KFC 225 is smarter and more talented with regard to talking to navigators and, especially, EFIS displays.
As we mentioned, this system is capable of nagging you. For instance, when you deviate from your assigned altitude, it gives you a little tone song and then says, leaving altitude. Better the autopilot than ATC.
One feature thats unique in the Bonanza and Mirage market is roll steering. Not just a nav track, roll steering takes a complete navigation output from the GPS, for instance, and uses it for more precise control.
On a GPS approach, for example, the roll steering can provide complete turn anticipation throughout the procedure turn, instead of chasing the needle, you get to anticipate the course, and flow smoothly through the maneuvers.
The bad news is this function is only available with certain high-dollar navigation systems which have a data bus output with steering commands, such as the KLN 90B.Nex-gen GPS navigators are more likely to have that but a mid-market box wont, which is why only airplanes with relatively sophisticated supporting equipment will get the most out of the KFC 225.
With the mid-range well served by S-TEC and no meaningful movement toward making the 140 available on more airplanes, AlliedSignal is once again giving ground in a field it had dominated for years.
Then theres the price: Bendix/King has always occupied the high rent district and the KFC 225 doesnt change that. Baseline price for the hardware is $28,883, less the HSI and yaw damper.
The fact that Bendix/King has staked out the autopilot high ground has stimulated a lively market in the mid- and low-priced autopilot arena which S-TEC has aggressively claimed as its own.
S-TEC split off in 1978 from Century Flight Systems over a difference in opinion for the basic operating premise of autopilots. S-TEC believed that the rate-based principles in the very basic Century I could be applied, in true building block form, to all autopilots.
We can safely say that history has proved S-TEC correct. Yes, there are other factors at work beyond the pure technical issues, such as marketing, support and pure product value, but the concept has proven so sound that AlliedSignal borrowed a page from the S-TECs book by selecting a rate-based digital scheme for the KFC 225.
S-TEC has achieved solid market acceptance and even the OEMs are taking notice: Both Piper and Mooney offer S-TEC systems as factory equipment. The latest and greatest from S-TEC is the System Twenty (Ya gotta spell it out, kid.). Its a basic roll-axis autopilot but whats special about it is its compact packaging. It requires zero panel space because the controls are built into the turn coordinator.
Weve all got one of those-or some variation thereof-so out with the old and in with the new (TC, that is) and youre halfway toward having a new autopilot. The System Twenty has a suggested list price of only $4495. For that price, you get roll stabilization, plus commanded turns and nav tracking for your VOR and GPS. This is the entry-level system for tracking your GPS navigator.Lets count the parts we need for the complete Twenty: a TC autopilot controller, a roll servo and a switch to turn it on and off. Thats it. Want to add altitude hold and other features? Thanks to S-TECs modular approach, you can.
The entry level autopilot that will maintain your GPS course and hold your altitude is the System 30, which sells for $6995, a remarkably good value in the world of autopilots. Like the Twenty, this system requires very little panel space because many of the controls are in the turn coordinator.
Next up the price and capability ladder is the System 55, (this ones numerical, kid) which places all the functions of the previous generation System 60-1 into a standard rack mounted computer/programmer. It may have a list price thats $200 more, but its easier to install and lighter, too. The LCD display in the radio stack may not be in the most convenient spot, but S-TEC makes a remote annunciation to put in your primary scan.The System 65 is S-TECs top of the line autopilot, which also has a flight director system integrated into it. You dont have to use the FD but if you do, it requires an optional FD steering horizon. But the upgrade path is far easier than the Bendix/King alternative. With a list price of $14,995, its still less than the KFC 225 or even the KFC 200, if they were still available.
The System 65 is a panel-mounted programmer thats smaller than the System 60-1 and not a rack width of the System 55, but a 1/3 ATI size programmer designed for the pedestal of the kerosene burners. A remote mounted indicator places the critical information in the scan.
The system still weighs less than the System 60-2, for more features and capability.Although this system has bells and whistles for the high performance airplanes, thanks to S-TEC flexible certification and consistent practices, you can have a System 65 in your American General (Grumman) AA-5, or your E90 King Air.
System Thirty ALT
The System 30 ALT is one of those products that you wonder aloud if it has a purpose and then instantly imagine a dozen special applications where it makes perfect sense. The System Thirty is a $3295 altitude hold system that can be added to many existing roll axis autopilots, or as a stand alone pitch-axis autopilot.
All it does is hold altitude. It has a servo, a button, a remote mounted computer and pressure sensor. Three grand and four pounds will add value to older, yet functional roll-axis autopilots, even an old Century that still works as good as new.
Speaking of Century, theyre still out there. During our last autopilot roundup some five years ago, we found that the Century 2000 series was among the most affordable and desirable autopilots available. Unfortunately, since then, Century Flight Systems has done virtually nothing to advance their lines or promote the products. The Century autopilots, such as the Century I through Century III, are reliable and proven in the vast number of installations. But they are as dated in design and construction as a 64 Plymouth Fury, in our view.
As we reach the end of this century, Century Flight System appears destined to be left behind by the new, fresh designs from S-TEC and even AlliedSignal.
The Century I is an excellent wing leveler, but the S-TEC System Twenty costs only $400 more and does much more in terms of nav functions. The top of the line Century 2000, a top pick five years ago, has added nearly $2000 to the price and sales have lost momentum.
The Century 2000 is notable because it is a truly upgradeable rack-mounted autopilot. The computer/controller stands about two and a quarter inches high, and contains card slots like a PC.
Want to add pitch? Slip in a pitch card and add a servo. Flight director?Add a card and change the ADI. Prices start at $10,000 for a single-axis system and extend to more than $25,000 for a flight director/autopilot with HSI. That would be comparable to the $28,000 S-TEC System 55 with HSI.Most good avionics shops know how to fix Century autopilots. Thats a double-edged sword if ever there were one. The servo design has been around a long time and most shops have dealt with a Century system or two over these many years.
Its not fair to say Century systems are repair prone but on the other hand, old designs and old parts sometime arent as reliable. One of the most interesting comments weve heard was from the manager of a midwestern avionics shop that specializes in autopilot repairs. Last year, he said, We fixed more than 500 autopilots. Of those, five were S-TEC.
Your autopilot decision is not as simple as picking the system you can afford and has all of the features you want. It depends on whether the autopilot you want is certified for your particular airplane. And its not just a question of Is it STCd for a Cessna 172? The STC can be as specific as a serial number range for Cessna 172G models.
The latest autopilots from AlliedSignal are the most limited, because the company seems to spend much effort in improving and reproving the installations and servos.
S-TEC re-uses much of the same servo and installation technology, only improving on the functions and packaging. As a result, they have a huge array of STC kits available even for the most recent autopilot systems.
In addition, this commonality means that the autopilot muscles are proven and reliable and many shops are capable of repairing the components. The sophisticated products developed by AlliedSignal sometimes require more TLC and engineering support inthe early years, then smooth out as they mature.
In the past few years, we have seen S-TEC dominate the marketplace. This is because they have a comprehensive product line, a reputation for customer support that breeds loyal owners and an almost bulletproof reliability record. AlliedSignal has some exciting new products, but they also have a tremendous amount of marketing, sales and service inertia to overcome. And their limited selection of airframes means they will be playing catch-up for a long time to come.
How about Century? The 41 and 2000 are fine autopilots in their own right but measured against the sophistication of AlliedSignal products and rock bottom prices of S-TEC they are, sadly, nothing special. On the service and support front, S-TEC gets higher marks from the customers ans shops we have talked to.
We wouldnt steer you clear of considering any Century product or buying an airplane with one installed, but valuewise, for new autopilots, S-TEC systems are the ones to beat and probably will be for the foreseeable future.
Also With This Article
Click here to view the Autopilot Checklist.
Click here to view “Autopilot 101: A Golf Analogy.”
Click here to view Autopilot Contacts & Addresses.
Click here to view “What Features?”
Click here to view the Autopilot Specifications.
-by Gary Picou
Gary Picou is Aviation Consumers avionics editor. He is VP of marketing at PS Engineering, an intercom maker.