March 25, 2013
By Ian J. Twombly
They’re often an overlooked item in general aviation airplanes. They act as a solid workhorse in the background of new, technologically advanced avionics. But if someone asked you to trade your multifunction display or second radio for it, you’d never even consider it. That’s especially true if you fly for long periods of time on each trip. Yes, the modern autopilot is the panel’s sleeper. It’s a required piece of equipment for a fully integrated cockpit, and it does more to increase safety and reduce workload than almost anything else in the airplane.
AOPA’s Get Your Glass Sweepstakes Piper Archer has one of the best units available for GA airplanes today—the S-Tec System Fifty Five X. The System Fifty Five X is a two-axis autopilot, meaning it controls pitch and roll. An optional yaw dampener would make it a fully three-axis system. Like most units, the System Fifty Five X has heading, navigation, and approach mode for roll and lateral navigation functions, and altitude hold and vertical speed selections for vertical navigation. Most of those functions are self-explanatory, but it’s worth mentioning that when activated in the approach mode with the altitude hold selected, the System Fifty Five X will also fly the glideslope.
One great feature of the System Fifty Five X that won’t be found integrated into a lot of other units is GPS steering, or GPSS. Pilots who learned to fly on Century III autopilots or another similar unit will remember what it’s like to not have GPSS. The trick was always to make sure the needles were centered and the airplane was on the same heading as the HSI. Then it was engage the autopilot and hope it held. With GPSS autopilot navigation is much more precise. Because the autopilot is obtaining navigation information from the GPS, and not the HSI, lateral inputs happen almost instantly, and are slow and progressive. There’s no more turning left three degrees, then left three more five seconds later. It’s a smooth, accurate motion.
The sweepstakes airplane has another nice feature from S-Tec as an add-on, the SA200 altitude preselect. All the pilot has to do to change altitude is dial in the desired altitude, push the “alt” and “vs” buttons simultaneously, and sit back and watch. The autopilot will automatically capture the altitude and level the airplane. It’s impossible to describe how much this one device reduces workload, especially in the terminal environment when things are happening fast.
As with the other avionics work on N208GG, Penn Avionics in West Chester, Penn., installed the S-Tec and its associated components. Autopilots are complex tools, requiring many different parts to work in harmony. There’s the unit itself in the panel, the associated roll and pitch guidance instruments, and the servos. Like some other autopilots, the System Fifty Five X requires a turn coordinator, although it can be behind the panel. It also needs to steal information from the altimeter. For the Archer, servos went under the rear seats in the spar carry through, the same location as the old ones.
Integrated the unit to the Aspen Avionics EFD1000 primary flight display was probably one of the more difficult parts of the install, mainly because Penn had never done it before. The System Fifty Five X is analog, like most GA autopilots, so the Aspen ACU had to be used. Each function has a different wire, which obviously takes time and careful work.
The best thing about the System Fifty Five X is that it’s easy to use. Sure, you could do the smart thing and read the manual. But why? The display is intuitive and the functions will be recognizable to anyone who has flown with an autopilot before. The SA200 is also quite simple. After all, to the pilot it’s just a knob to select the altitude. I did have to pull out the book once so far. I couldn’t figure out the procedure described previously to capture altitude with the SA200. I figure one reference for a sophisticated unit like this is pretty good.
What can’t be stressed enough is how much the autopilot and SA200 reduce workload. One drawback of the System Fifty Five X is that you have to keep yourself honest. It’s easy to get into a routine of punching it on after takeoff and turning it off on short final on every flight. Altitude change? Just turn the knob. Course change? Program it in the GPS and you’re on your way. With such a fully integrated cockpit, I wonder if the pilot needs to be there at all!
Next week: Rigging issues
E-mail the author at [email protected]
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