What Happened to the Piston Twin?

Stepping from high-performance single to a twin was a natural pilot progression for decades, but no more.


The year 1979 was the last big year of aircraft shipments. Almost 18,000 were sold that year. About 3,000 of those airplanes were piston twins. Today, any single that sells 534 units a year is red hot. In 1979, that's how many Seneca twins Piper sold. If the piston single business looks lethargic when compared with the good old days, the piston twin is practically extinct. Beech builds a few Barons, and Piper some Senecas and Seminoles, mostly on special order. The Diamond Twin Star, which is a diesel twin, and the Adam 500 are just coming on line. In 1979 there were 33 different piston twins on the market.

So, what happened? Why did piston twins virtually go away? Will they come back? It is an interesting story.

New-design piston twins started coming to market in 1952 with the Twin Bonanza and Aero Commander. (The Beech 18 had been around but was in a different class.) The 310 and Apache followed shortly and then more models were added every year for the next 20 years.

Back in the 1950s and '60s, virtually all pilots who went beyond a private certificate also got a multiengine rating. The usual progression was private, commercial, multiengine, flight instructor and then a few would get an instrument rating, which was not a big thing at the time.

Twin training was available at almost every airport and was most often done in Cessna T-50s, Bamboo Bombers, surplus World War II airplanes powered by round 225 hp Jacobs engines. Almost every FBO had one and they were used primarily for training or rental. I'd add that the airplane had two engines because it needed them. There wasn't a best single-engine climb speed. Instead, there was a single-engine speed for minimum sink.

There were also legions of WWII pilots and those who had flown transports and bombers were both multiengine qualified and rated, and they liked airplanes with more than one engine. At the airports where I flew, many of the WWII pilots who were flying GA airplanes were transport/bomber guys; most fighter pilots seemed to have had enough.

So, when new piston twins came along there was a ready and eager market. I heard a lot of pilots say, after flying an Aero Commander or 310, that they had no intention of ever again flying a single-engine airplane.

Aviation was much into myths at the time. Two of them were that twins were far safer than singles, plus, that any red-blooded American pilot would "step up to a twin" as soon as he could afford to do that. It was a natural progression from a beginning airplane to a high-performance single to a twin (and later to a turboprop and then a jet).

The available information on accidents was sparse at that time and most opinions were formed based on what we saw and experienced around the local airport. Twins certainly seemed like they would be safer. The first tarnish that I saw on the reputation of the twin came in July 1958. I lost three friends when a Beech Travel Air flat spun to the ground on an FAA multiengine check ride. That accident was followed by many more like it, mainly in Travel Airs, Barons and Piper Twin Comanches.

The cause of all these similar accidents related more to an insane FAA requirement (do minimum engine-out control speed demonstrations as low as possible, but not below 500 feet above the ground) than to the airplanes. It was as if the FAA just wanted to certify survivors to fly twins. It took a long time and a lot of effort to bring sense and logic to the FAA on this subject.

These training accidents didn't discourage those who wanted a twin. The airplanes enjoyed continuing success and most pilots were still convinced they were safer. Twins had a bad record maybe in training, but much better after that.

The insurance companies were convinced, too. My father and I had been flying a 250 Comanche and switched to a Twin Comanche in 1964. I was astounded when I transferred the insurance. The twin's insurance was a lot less costly than the single's. Was that based on perception or reality?

Writing about safety was touchy at that time because information was more difficult to gather than it is today. Also, everyone was into things like "take a drive in the sky" and any suggestion that danger lurked was unwelcome. But I decided to give it a shot. I used all available information and wrote an article on the subject of singles v. twins, "Double Trouble," in the July 1965 issue of Air Facts magazine.

I found that, in total, the single fleet had a better accident record than the twin fleet. One twin was four times worse than the average of the singles. The single-engine retractables were better than the twins, too, with the record of the worst retractable more than twice as good as the record of the worst twin.

Another finding was that out of 81 fatal twin accidents, 15 were related to the fact that the airplane had two engines and one engine was not producing power; eight of those were on training flights. In 81 single-engine fatal accidents, only two were related to the fact that the airplane had only one engine and it quit; none occurred on a practice forced landing.

At the time we didn't name airplane names in accident reporting like we do today, but at least that study and that article brought the subject into the open. It was the first time anyone had suggested that twins were safer than singles only in perception. In reality, they were not safer. I'd hasten to add that with the better information that is available today, the conclusions are not that much different than they were 42 years ago.

To this day, many folks who were around then, and for the many things I've written since on the single v. twin subject, are convinced that I just hate piston twins. Nothing could be farther from the truth. All I ever wanted to do was convince pilots that if twins are properly flown, they will almost always give you a shot at landing on a runway after one engine fails. If they are not flown with a high degree of proficiency when the thrust is asymmetric, they'll kill you quick.

Something else I noted was that pilots tended to do things with twins that they wouldn't do with singles, such as fly IFR at night or in weather they wouldn't tackle in a single. There is no real difference between the capabilities of twins and singles until an (the) engine quits, and the only point I wanted to make there was that a pilot who flies trips in a twin that he wouldn't do in a single is looking for trouble. Mother Nature doesn't care how many engines are on the airplane, and the ground is just as hard for a twin as it is for a single.

However, the twins of that time had some good advantages over singles with dual charging systems and vacuum pumps, and items like ice protection and weather radar, and none of those capabilities were available on singles until many years later.

Most of the piston twins from their heyday were powered by two of the engines that were used in the largest singles. A Baron, for example, had two Bonanza engines. That made the math pretty simple. Engine overhauls and fuel per hour were double for the twin. The twin would climb faster and cruise faster but not at the ratio of the additional cost. The single/twin money relationships are the same today but, because of inflation, the actual dollar difference for flying a twin is a lot more. It is just more efficient to do the flying with one engine.

It took insurance underwriters a long while to realize that they were paying out proportionately more money on twin wrecks than single wrecks. Over the existing lifespan of the piston twins, the insurance folks have gone from giving very favorable treatment to twins to charging ever higher premiums and requiring annual training for twin pilots. In many cases, obtaining meaningful liability insurance for a twin could be difficult or impossible for a pilot of relatively low experience. It's standard advice to talk to your insurance person before considering a "step up" to anything, especially a twin.

Is this insurance paranoia justified? The simple fact today is that, using available numbers, there's little difference in accident rates of most high performance singles and piston twins. One can't be said to be safer than the other and there is no current justification for insurance discrimination against twins. That is somewhat different than my original study, but back then there were no numbers of hours flown by type and all you could look at was the percentage of the fleet that crashed. That gave an advantage to the singles because twins tend to fly more hours, and accident rates are generally considered to be so many per hundred thousand hours.

Today there are exceptions in the safety record picture, with the Piper PA-46 Malibu/Mirage, Cessna pressurized P210 and Aerostar twins on the high side. On the other hand, airplanes like the Cessna 172 and 182 have a lower involvement in serious accidents than other piston singles.

So many things have changed since the piston twin first came on the scene that it is hard to imagine how these airplanes can ever enjoy a second coming. The alignment of the stars will never again be like it was when the piston twin was the airplane lusted over by most pilots.

For a start, multiengine training is far from being as available today as it was 40 or 50 years ago. It is certainly done in the college and flight academy programs and that is where a lot of the twins that are being built today go to work. But not many FBOs have a twin for training.

Even into the 1980s we were able to rent twins to use for transportation or for photo missions. We didn't have to go to recurrent training to fly those airplanes. If walking into an FBO or flight school cold and renting a twin is possible today, I sure don't know about it. Maybe, just maybe, the Diamond Twin Star diesel twin will enable more FBOs to offer multiengine training and have a program to rent the airplanes. But that'll only happen if the insurance underwriters think it is a good idea.

But the real problem for growth in the piston twin market is that the people who are coming into general aviation today, learning to fly and buying new airplanes don't know that they are supposed to want to "step up to a twin." Nobody has told them, there are few twins to consider and the number of business/personal pilots flying twins is dwindling. If anything, a new pilot would explore the subject and decide that only professional pilots are supposed to fly twins.

I also suspect that most new pilots don't think in terms of engines quitting like pilots did 50 years ago. Most new singles have as much systems redundancy as did the twins of old, and while anyone is kidding himself if he thinks engines never quit, it is true that engines seldom quit as long as they are properly maintained and provided with adequate amounts of fuel. How long has it been since you had an engine failure in a car?

Then there is performance. The new Cirrus and Columbia airplanes climb almost as well as the twins of old and cruise almost as fast. They do it on one engine, an engine that when it gets full authority digital engine control (fadec) will be as advanced as a piston engine probably ever will be. They also have a feature that insurance companies like. The gear is always down and locked.

If anything, the Cirrus and Columbia almost guarantee there won't be a lot of new basic twins flooding the market. From an economic standpoint they would be tough competitors for any twin. With the Cirrus there is also the parachute answer to the old "what if" question about the engine failing at night while flying over ridges that are obscured.

Further, the twins used to be a step-up market, and still could be except for one thing. They have been replaced in the pecking order by the single-engine turboprop, and soon the single-engine jet. The single-engine jets are not here yet, but the most basic ones will probably cost about the same as a pressurized piston twin. They are also likely to get more favorable insurance treatment when flown by personal/business pilots.

Finally, the more advanced piston twins, such as the Cessna 421, have been replaced by turbine airplanes. The businesses that used to use 421s as corporate chariots are now using King Airs and Citations, and there is no way they are going back to piston engines.

Given the low rate of twin production and the age of the fleet, there will likely be ever less piston twins flying around. They will be missed, too. It was always satisfying to settle into a new twin, crank up a pair of Continentals or Lycomings, feel the surge of power on takeoff, watch the rocket-like climb, and experience the buzz of passing through the air at 200 knots. That might be only 10 knots faster than a Columbia but to some pilots it just feels a lot faster. There's more action. But the good old days aren't coming back.

There's one other fact that argues against a revival of the piston twin business. In 1979 Cessna offered 11 different twin models and sold about 1,000 of them. Today Cessna builds piston singles and jets. And where Cessna used to use the 300 and 400 numbers to designate twins, you can now count the number of engines on the Cessna 350 and the Cessna 400 on one finger.