Piston Power Series: Cessna 421C vs. King Air C90

Piston Power Series: Cessna 421C vs. King Air C90

Piston Power Series: Cessna 421C vs. King Air C90

Let’s say you’ve got a family of six, and the kids are barely kids anymore. You used to be able to haul everyone around in a Piper Malibu, a Cessna 210 or a Cherokee 6, but the kids keep growing and waists keeps growing. Suffice it to say that your family is not what it used to be in terms of weight, and you want to be able to carry everyone when you go on family trips. 

Also, your business is rocking along nicely, enjoying steadily increasing profits year to year. And while you used to just fly yourself around to business meetings, you now find yourself flying passengers more and more. A bigger airplane would sure be nice. 

Bottom line, you are ready to move up. What is the next logical step? 

Any of the “big fuselage” King Airs just seem like too much airplane, both in cost and size. The MU2’s performance looks cool, but you plan to fly 100 hours per year and self-admittedly, you know you are not Chuck Yeager’s protege. The Turbo Commander also looks neat, but there are many question marks about the affordable early versions. A TBM would do the trick, but dang, seven digits are required to enter that world.

The bottom line is you have $300,000 to $450,000 for a budget, and you don’t want to make a mistake. Can you really afford to purchase and feed a cabin-class twin? A cabin-class turbine twin? The answer is maybe, and your search will likely result in the King Air C90 and the Cessna 421C on your shortlist of prospective airplanes.


When looking at either a King Air C90 or a Cessna 421C, the first thing you’ll notice is their impressive size. Stepping into either cabin reveals seats that are wide apart and comfortable for all sizes of people, even the tall and wide. It’s a long hunched-over hike for the pilot up the aisle between the seats, but that pilot is welcomed to a large cockpit with plenty of panel for the latest gadgets, lots of legroom and large comfy seats. In both airplanes, the pilot sits high off the ground with a “grand appearance” view noticeably different from any piston single.

Both have solid all-engine operating performance numbers, with the C90 climbing a bit better and cruising a bit faster. The C90 will average about 220 KTAS while the 421C averages about 205 KTAS. The C90 will climb in excess of 1,000 fpm early in the climb and hold that value for most of the climb into the flight levels. The 421C will hold 1,000 fpm early in the climb, but the engine temps will require a cruise climb airspeed that will net about 600 fpm when leveling off in the flight levels. With cabin size and performance so similar, what are the true differences for the discriminating buyer?

King Air C90

The King Air 90 came out in the late 1960s and quickly developed a reputation as a great airplane. Before long, the A90, B90 and C90 became available. Of course, there are E90s and F90s and a whole lot of modifications to make the C90 like the newer and faster versions, but the C90 is the most prolific version of the King Air 90. Why? The C90 is the version that holds true to the unofficial design mantra of the entire King Air fleet: “In no single aspect of consideration is it the best, but in every category, it is really good.” 

The C90 is not the fastest, most powerful, nor will it go the farthest, but you get a lot for your money, both in airplane and performance. The C90 is sneered at by the pro pilots for being a slow turbine, but those who really know best will testify that the C90 shows up just a little later on most trips than some other sleek airplanes, and the owner doesn’t have to empty the bank account to buy it or fly it. 

In the King Air C90, there is a potty system that actually works, giving passengers comfort. The belted potty is so nice that if all the seats are full, a wise passenger might even select the potty for the long ride as opposed to the main cabin seats. Plenty of legroom and plenty of privacy exists. There is also ample luggage space in the C90. You can really carry six people, all of their bags, and still leave room for enough fuel to go a long way. It is a comfortable cross country cruiser that is still a rugged, strong Beechcraft King Air.

But, the best part about the C90 is the PT6 engines. The PT6-21 engine came standard on many of the C90s, and I think it is one of the best engines ever. There are literally thousands of -21 engines flying around the planet, so finding a maintenance provider with experience is easy. Like the C90, it is not the “sexy” big engine found on some other airplanes, but it is a rugged and smooth engine that hums along without a whimper. Once you get it started, it likely won’t fail unexpectedly unless you run the fuel tank empty. Bulletproof. That’s the PT6-21.

Cessna 421C

The Cessna 421C was Cessna’s flagship of the multi-engine piston world and arguably still is—except that they aren’t being made anymore. Few manufacturers today have a multi-engine piston flagship, but don’t let that fool you into thinking that the Cessna 421 is not a good airplane. There are a lot of Cessna 421s in the world, and they make remarkable purchases for the savvy buyer.

The Cessna 421 first became available in the late 1960s, quickly gaining popularity as an airplane with a big cabin, solid performance and sexy looks. It was a great step up from a Cessna 310, Cessna 210, or even an unpressurized Cessna 300-series. Sales were solid and improvements soon came along. The pick of the litter is the latest model, the Cessna 421C. The C-model has the best fuel system, trailing link landing gear and the newest year model. Clearly, the C-model is the most desirable in the marketplace today.

However, the Cessna 421C gained the reputation for having engines that were particular – and that is not a good thing. The geared Continental engine requires a knowledgeable, well-trained pilot. Simply put, power management is critical to the long life of the engine. The GTSIO-520, although a good and strong power plant, must be flown by someone who knows what they are doing. It doesn’t suffer neglect, abuse or disrespect well. Treat it well and it’ll provide years of solid performance. Treat it in any other fashion and it’ll eat you out of house and home and hangar.

And oh my, does it require maintenance. Any piston engine requires more maintenance than a turbine, but the Cessna 421 is nearing 50 years old, and anything 50 years old with lots of moving parts will go to the maintenance hangar frequently. With the big twins, there’s double the power available and double the number of things that can go wrong. 

 Match Your Need

So, at the end of the analysis, both a C90 and a 421C will accomplish your mission, and both will be much more expensive to operate than any single-engine piston. But, which do you select? My advice is to make sure you match your need to the airplane you are going to buy.

The big-piston Cessna 421C could be the exact answer to your traveling needs, and if your budget is $350,000 to $450,000, you can get one of the nicest Cessna 421Cs on the planet. You should be able to buy a 421C with super nice paint and interior, a well-stocked panel of avionics, low engine and airframe times and an example with no damage history. 

That $450,000 will also buy you a C90, but that C90 will be an older 1970s version, may not have the latest avionics, may have tired paint and interior, and the engines may be mid-life. But, it’ll be a turbine, and that is scary for the uninitiated.

If you go for a Cessna 421C, make sure you place a high value on the maintenance pedigree. Maintenance in any airplane is a “pay me now or pay me later” situation. If the present owner has been skimping on maintenance, you don’t want to pay anywhere near retail. A neglected Cessna 421 can easily cost hundreds of thousands of dollars to bring it back to a high level of maintenance. And there are lots of Cessna 421s languishing outside in the weather on ramps all over the United States. But if you can find that cherry Cessna 421C, and you don’t mind paying to keep the maintenance at a very high level, it could be the perfect airplane for your mission. You can buy a lot of airplane for the money.

But, if I can afford to fly behind a PT6, I’m going to fly behind a PT6. To me, the engines are the critical factor and this is where the C90 shines. I can handle tired paint and less-than-stellar interior. I don’t mind steam gauges if they are being pushed by a nice GPS unit and a good autopilot. So, if you can find a “good bones” C90 with good engines, you’ve got something worth pursuing. 


Ready to enter the turbine world? If so, the C90 is a great way to get into the game. But, I advise buyers to consider their cash reserves and their appetite for the big expenses. If a $200,000 hit would throw your company out of business or force you to sell the airplane, stay in the piston world and buy a Cessna 421. Just accept the mosquito bite maintenance requirements that come along with owning a big piston airplane. But, if you are cash-solvent with income that you can predict far into the future, and have a mission that regularly requires four to seven people, then go for the King Air C90. I have a lot of flight time in both, and would gladly own and pilot either if it fit my mission. 

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    Stepgen Halford November 14, 2020 at 3:41 am

    I owned a 1976 C421C in the 90s did around 750hrs (350 at night) across UK and Europe in all weathers. Solid and trustworthy machine but manage engines by the book. Remarkable it still has its niche and remember there is the C425 as a turbine option albeit more expensive to purchase it has oerformance and advantages.

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