Loved by new and experienced pilots alike for its timelessness, the Cessna 172 predates many now-standard aviation technologies, so would it have an autopilot?
Being one of the most popular models with more than forty thousand in service. Few even date back to the 1950s. While many, especially the ones used in training environments do not have autopilots, all Cessna 172s can be retrofitted with an autopilot.
As an experienced corporate pilot, I find autopilots are necessary and rely on them to reduce cockpit workload, and increase accuracy, resulting in safer and more pleasant flights.
Purpose of Autopilots
The 172 is one of Cessna's highly successful models. Its airframe, tricycle landing gear, and high-wing configuration have given it more than just its iconic appearance but have also contributed to its robust and rugged longevity.
There is a common reason behind the question, is because most experienced pilots seek to reduce their workload when things get busy during IFR flights or on long hauls.
In the early days of the 172, circa the late fifties, IFR operations were less hectic due to the fewer aircraft sharing the skies. That is no longer the case today. The terminal area can get busy even under visual conditions, which becomes more hectic when it turns IMC.
Getting rerouted, put in a hold, or navigating complex step-down procedures are becoming more common today, drastically increasing the workload in the cockpit. Radio traffic is voluminous, requiring your full attention to catch the controller's instructions to you. Missing it can be catastrophic.
Then there is fatigue. The more tired you become, the less responsive, and the more disoriented you can get.
My instructor always drummed it into me, and I impressed it upon my students later, to always stay ahead of the aircraft.
To get above all these, the best thing to do is to become proficient with an autopilot.
Once free to turn your attention to navigation and communication, you can spend your time monitoring systems, communicating with ATC, and managing the aircraft better.
More Cessna 172s have wing-levelers than they previously did, while some high-end modifications even have full autopilots with three-axis control along with throttle control as well.
To answer the question, we should first break down the categories of autopilot before going on to discuss the kinds of autopilot pilots refer to when talking about the subject.
Single Axis Autopilot
A single-axis autopilot is an entry-level tool that can only control the roll of the aircraft about its longitudinal axis. In an emergency, it can right the plane to level its wings at the push of a button, or it can just maintain a wings-level flight.
If the single-axis autopilot is slaved to the directional gyro, you can turn the aircraft to a particular heading by changing the heading bug. If a gust of wind temporarily knocks you off your heading, a slaved single-axis autopilot will put you back on your heading.
It can keep the wings level, or bank at the standard rate but it can't track a course unless it is slaved to a GPS.
A two-axis autopilot can additionally control the pitch of the aircraft on its lateral axis.
In addition to controlling roll, a two-axis autopilot also controls pitch about the lateral axis. Unlike the roll control that controls the ailerons through its cables, the pitch control does not directly control the elevator. Instead, it controls the elevator trim.
In most cases, having a two-axis autopilot installed in a small aircraft like a Cessna 172 is more than adequate, especially if they are slaved to the DG, which is in turn slaved to the GPS. This would provide full navigational control based on a course entered into the system.
Three Axis Autopilot
The three-axis autopilot includes the yaw damper. The sensor in the system detects a slip or a slide (uncoordinated flight) and activates the rudder to compensate. It allows for better stability of the aircraft, increasing comfort and safety.
Auto throttles are exactly what you might expect from the name. A computer calculates how much thrust is needed to climb or descend and adjusts the power settings accordingly. I have personally not seen this type of autopilot installed in a C172 to date.
Should You Install an Autopilot in a C172?
Cessna 172s are one of the most stable and easy to fly small aircraft on the market. I typically trim the aircraft just before the middle marker and set the throttle to a specific RPM and the plane sticks the glideslope perfectly all the way down to the missed approach point.
But I still want an autopilot for all the reasons mentioned above. It is the responsible thing to do.
If so, there is no greater value to the money you will spend on upgrading your aircraft. Autopilots are not only a factor of convenience, reducing fatigue on long flights, but also make IFR flying, shooting approaches into busy terminals, and flying in IMC significantly safer.
For purists who believe that one should hand-fly every approach to keep yourself sharp, I can see that point. However, keeping sharp and reducing the workload are not mutually exclusive. You should do both. Continuously practice hand-flying your C172 and also practice flying it with the autopilot engaged.
The way I manage to get used to both is by having different mindsets for each. I invoke that mindset with a flow. When flying without the autopilot, I rely on one specific flow, and when I fly with an autopilot I rely on another.
So if you are still asking if you should install an autopilot on your C172, the answer in my humble opinion is, yes. Definitely.
Things to Consider When Deciding to Install an Autopilot
If you have to ask this question, it's probably because you now realize the importance and benefits of it and are in the market for one. There are several things you should consider before you make the final leap.
The first thing is to remember that autopilots are a necessity rather than a luxury. As such, look at the specs and the features as your primary concern. Bells and whistles are nice, but specs and features that get the job done take precedence.
Second, think about your budget and if you want a one, two, or three-axis system, and if you want it slaved to your nav equipment.
If you want it slaved to your nav equipment, now you have to consider if your nav equipment has the ability to command the autopilot. An old analog nav system is not going to interface with a digital autopilot. That would require upgrading your nav equipment, and possibly the DG.
This can start to add up. While some people decide to get what they can afford and slowly build it up from there, you may want to hold off on your purchase and have it all done in one go.
But if you want to jump right in, start with an unslaved two-axis autopilot.
You are still automating part of the three elements of flight - aviate, navigate, and communicate. The unslaved two-axis autopilot releases you from the burden of the first part. It can handle the 'aviate' part leaving you to navigate and communicate more effectively.
The benefit of a simple autopilot is that it gets you accustomed to a new flow in cockpit management in stages.
Each pilot is unique. Some folks like to jump in with the full spread while others want to take it slow and easy. If you are the latter, start with the two-axis. If you are the former, get the full upgrade.
You have to learn the operating handbook from cover to cover, just like you would study any system on the aircraft. Consider spending some time with a qualified CFII who knows the autopilot you have installed, and have him or her check you out on it.
With a robust autopilot system installed your Cessna 172 can be a frequent-use transport aircraft that is safe and reliable.
About THE AUTHOR
After spending years watching every video I could find about flying, I finally scratched the itch and got my pilots license. Now I fly every chance I get, and share the information I learn, here.Read More About Joe Haygood