For some reason, many articles suggest you buy the most plane you can afford. This is the sort of dangerous advice that’s pithy enough to have the ring of truth, and does seem fairly plausible. Most people would agree that if you’re deciding between a 1974 Skylane with the original velour interior and one with a beautiful restored interior, you’ll be better off the the restored interior. However, this glosses over the critical fact that you should never buy a plane that doesn’t fit your mission. If the most plane you can afford is an early 172, and your mission is flying a family of 4 people 500 miles to visit family, then you should not buy a plane. Maybe down the line when your financial situation improves you can reevaluate, or you can figure out something creative with a partnership, or you can wait for a market hiccup to bring something larger within reach. But at that moment, buying the most plane you can afford is a huge mistake: what’s the point of owning a plane that doesn’t do what you want?

Once you know your mission, you need to find the cheapest plane that will satisfy your mission. The broad strokes of the used Cessna market are pretty simple, but the individual features of an aircraft can have a big impact on whether it suits your mission. Here are some features and modifications you’re likely to see on your search:

Bladders vs wet wings: Early Cessnas used rubber bladders to store fuel. Unfortunately, some bladders tended to develop small ridges that trapped water. This trapped water couldn’t be drained during preflight, but it would work its way into the fuel system and cause fuel starvation. Cessna solved the problem through a series of airworthiness directives that involved changing the fuel bladders and replacing the fuel caps with a better design less likely to allow water to enter the tanks. Combined, these changes make it almost impossible for water to get into the tanks and prevent the water from being trapped if it does manage to sneak in. Of course, you still need to draw a fuel sample from every drain but you can be confident that there won’t be trapped water you can’t drain.

Despite having fixed the problem, Cessna eventually switched to a “wet wing” design, where the fuel is stored in a sealed cell within the wing. These have not been found to trap water. However, after many years of service they can develop leaks. These are expensive to fix, because at a minimum a mechanic will have to partially disassemble the wing to find and repair the leak.

The bottom line is that both are safe if all ADs are complied with.

Two vs three bladed prop: A three bladed prop can take a much bigger bite of air with each rotation. This means that you can set a lower RPM (thus enjoying a lower noise level in the cabin) and get comparable performance. You also gain a few hundred feet/min of climb. The downside is that you’ll give up a few knots of speed in cruise. If you’ll fly in mountains or with heavy loads, it’s worth considering since the added climb will make you safer. On the other hand, if you stay in the flatlands and travel light it’s probaby not worth losing a few knots of cruise.

Turbocharger/Turbonormalizer: A turbocharger is a big air compressor that allows the engine to develop full power in thin air. This allows you to climb up near or even in the flight levels to take advantage of the strong winds, and to enjoy good performance even on hot days. Of course, maintenance will be more expensive. You also have to be more careful with the engine; in the case of a turbocharger (as opposed to a turbonormalizer) it’s possible to overboost the engine and severely damage it by requesting too much power. Despite those caveats, if your missing involves long flights, flights over mountains, or visits to mountain airports a turbo will come in handy.

Retractable gear: Looks neat and adds a few knots in cruise. However, expect to pay a substantial premium in maintenance and insurance. The damage will depend on your experience, but if you only have a few hours of complex time your insurance will be at least $2,000 more per year. As you build complex time without any incidents, this will go down. The retractable gear is also less sturdy than the conventional gear.

STCs: The FAA allows planes to be modified by applying a Supplemental Type Certificate, or STC. Different companies will develop a modification, perhaps to improve speed or handling. After sufficient testing, the FAA will certify the modification and allow the company to start selling it. Applying an STC legally changes the type of plane you have; it will come with a fancy looking certificate and a series of POH supplements. Some also have instructions for continued airworthiness. Make sure to scrutinize these; you don’t want to buy a plane with STCs that’s missing some of the materials or hasn’t been maintained in accordance with the STC. Doing this is just as bad as buying a plane out of annual or without a valid airworthiness certificate.

Speed mods: STC-happy owners like to slather their planes in all manner of seals, fiberglass bits, and racing stripes. The results will not be game-changing; in practice you can expect a few knots better than book numbers. Also, wheel pants are prone to damage in hard landings or rough fields, and they prevent you from inspecting or filling the tires or breaks.

Strikefinder / Stormscope: At first glance, these seem almost as good as weather radar. After all, they display real-time information about weather surrounding the aircraft. But they’re really more like “pretend weather radar”. They work by detecting lightning strikes (Strikefinder) or areas of severe turbulence (Stormscope) and averaging them over a brief time window to present a stable display. In theory, those areas will be well correlated with thunderstorms. However, it’s important to note that these are not weather radar: they are less accurate and update less frequently. They are certainly fun toys and provide slightly increased situational awareness, but they do not increase your ability to navigate thunderstorms.

Pressurization: Envious of Piper’s success with the pressurized Piper Malibu, Cessna tried their hands at a similar line with the pressurized Cessna P206. The P206 is a neat concept, but it suffers from two major handicaps. Firstly, it’s built on a modified 206 airframe which has never intended to be pressurized. It also uses a single engine, and it’s tough for a single engine to produce enough energy to fly the plane and pressurize it. As a result, the cabin tends to leak and the pressurization isn’t that strong, leading to a fairly weak pressure differential. You’ll also give up substantial payload and money to maintain the system.

Continental vs Lycoming Engines: They’re the same. The plane’s maintenance history is vastly more important than the engine manufacturer. If it’s been well looked after, you’ll probably be fine. If the previous owner skipped oil changes and stretched it well past TBO, it won’t matter who made the engine.

Mogas STC: Many Cessnas have a popular STC that allows running the engine on automotive gas, or “mogas”. In theory this lets you save money by using cheaper gas, but in practice you’d never want to use this. You can only use automotive gas without ethanol, which is hard to find. Even if you find approved gas, it will cause the engine to wear more quickly and reduce the odds you’ll reach TBO. Even if the impact is small, why use a fuel that will reduce your performance and might damage your engine just to save a little bit of money? Better play it safe and use 100LL.

Hail damage: Many old planes are running around with at least light hail damage. It’s unsightly and largely unrepairable, but doesn’t compromise the plane’s handling.

KAP 140 autopilot: A great little autopilot that supports flying a heading, flying an RNAV flight plan, and flying coupled approaches. It can also climb to a set altitude at a set rate. The only downside is that it tends to induce a slight altitude oscillation when in altitude hold mode.

STEC 55x autopilot: Similar to the KAP140, but only supports holding a pressure altitude or maintaining a vertical speed. It doesn’t have the altitude oscillation problem of the KAP140, but it has a much slower response to sudden attitude changes. This means that in practice you can’t really use it in turbulence, unless you’re confident all your passengers will tolerate sudden altitude changes and rolls of ~30 degress.

Engine monitor: Many pre-G1000 Cessnas come with only a single cylinder head temperature gauge. This doesn’t do much to help you lean the engine or spot engine trouble. To remedy this, many owners install a dedicated engine monitor. This instrument tells indicates the EGT and CHT for each cylinder. This lets you lean far more precisely (which saves you money on gas) and can provide advance warning of engine trouble (which saves you a bad day).

Fuel totalizer: These are great; you tell it how much fuel you have at the start of the flight, and it measures the fuel flow to track consumption. If initialized correctly, it will provide you with a very accurate fuel level and endurance remaining throughout the flight.