Wrong Worry in Twins Versus Singles

For three decades we have been at the forefront of the single versus twin debate. Our message is unambiguous. Why are we so misunderstood?


Piston twins are demonized by insurance companies and most general aviation pilots, and Flying magazine is responsible for the situation. Well, we are to blame for calling attention to the potential safety problems with twins, but our information has been misunderstood and certainly misapplied by many involved in general aviation. We have it right, and the insurance companies and most pilots have it wrong.

Dick Collins gets the credit for beginning and sustaining our crusade to inform pilots about the safety aspects of piston twins versus singles. Dick started his work on getting the facts out in the 1960s when the situation was reversed and commonly held attitudes about twins were wrong, but just the opposite of now. Back then the entire industry just knew that a piston twin was absolutely and automatically safer than a single.

So much safety attention in the post World War II era and on into the 1960s and '70s was focused on power loss that more engines was always believed to be safer than fewer in any airplane. Four engines were the norm for airliners, the military flew airplanes with eight or more, and pilots joked that you had enough engines when the copilot could say "number 12 just quit," and the captain could ask "on which side?"

General aviation pilots also bought into the many-engines-equals-safety concept. Nobody who could afford two engines flew with one. And certainly any serious transportation flying, especially at night or under IFR, would be done in a twin by the cautious pilot. Moving up to a twin was something every pilot dreamed of doing.

The belief in engine redundancy was so strong in those days that the insurance companies covered twins for a fraction of the premium charged for a single. Nobody bothered to look at accident statistics; it was so obvious to the industry that the ability to continue flying after loss of an engine was safer than making a forced landing.

But Dick started pointing out in Flying that twins were not safer than singles after either type of airplane lost an engine. His research clearly showed that twins were involved in more fatal accidents after an engine failure than were singles. He wasn't damning the twins, or defending singles, or even trying to cover for the obvious fact that the pilot of a single that loses an engine must survive a forced landing while the pilot of a twin shouldn't need to. He was calling attention to the reality that was different from the belief and demanding that the FAA and the industry do something to address the problem.

When Dick started his work, the safety situation in piston twins was abysmal, particularly in training. For many years the FAA flight test guides said that the VMC single-engine minimum safe airspeed demonstration should not be conducted below 500 feet agl. That seems like such an absurdly low altitude to practice such a critical maneuver that who could imagine such advice would be necessary? But the reality was worse than you can imagine, because flight instructors took the 500-foot advice to mean that VMC practice and demonstrations should be done at that altitude, not higher.

A reason to practice flight at VMC and demonstrate the onset of loss of directional control with an engine out at low altitude is because naturally aspirated engines make more of their full rated power down low. That means VMC loss of directional control is reached at the highest airspeed because there is more power from the operating engine, and the rudder forces and other control inputs are at their most demanding. In other words, you show the new multiengine pilot the worst case scenario when you practice VMC flight at a low altitude.

The worst case turned out to be many crashes during twin training because at such low altitudes there was no time for the instructor to take over and recover if the student botched the VMC demonstration. Dick was begging for the FAA and the flight training community to do something about this situation, but he was ignored for many years. Those who didn't ignore him wrote him off as a pilot who hates twins and is devoted to the promotion of singles, and that was totally wrong.

Eventually the tide turned and the FAA recognized the major flaws in twin training. The general aviation community began to recognize that Dick was right, that twins are not automatically safer than singles. The insurance industry began to demand more thorough and regular training for pilots of twins. There was probably a brief period in the late 1970s when general aviation understood what Dick was saying and had an accurate understanding of the issues of twin-engine safety. During that brief period, instructors, the insurance companies and pilots realized that a piston twin has excellent potential safety so long as the pilot is well trained and current in handling engine-failure procedures.

But then the pendulum passed through the center and continued on to its current position that is as wrong about twin engine safety as was the attitude in the 1960s. For the past several years insurance companies have typically charged much more to insure a twin, while at the same time demanding rigorous annual training and very high levels of time in type and total pilot experience. There is nothing wrong with that, except that the pilot flying a high-performance single is every bit as risky as the pilot of the twin. Why do the insurers demand so much of the multiengine pilot and so little of pilots of fast singles when the total risks are the same? Dick Collins is still pointing out that pilots of twins aren't doing the best possible job of handling every engine failure, but he also continues to write about how engine failure is a small part of the fatal accident picture in all airplanes, and that twins and high-performance singles have virtually the same overall accident rates when all factors are considered. Under actual IFR conditions, pilots of twins are doing better.

I'm happy that Flying and Dick Collins have had such success in calling attention to the safety issues of twins, but I'm frustrated that we can't get people to understand the true nature of the risk. Many, if not most, pilots, and certainly the insurance companies, now automatically assume the single is safer than the twin. And that is as wrong as the opposite assumption that prevailed 30 years ago.

Nobody believes twin-engine jets, or twin turboprops, are unsafe, even though pilots need skill and training to fly those airplanes after an engine failure. The same is true of the piston twins. And many competent pilots land twins uneventfully every year after an engine failure, but those incidents are never reported because they are not tracked by the FAA, NTSB or anybody else. A piston twin can't continue safely to a runway under every circumstance, but except for the moment or two during some takeoff conditions, a safe landing on a runway should almost always be possible.

Even more important than the continued flight after an engine failure is the fact that piston engines of sufficient power don't exist to propel the type of airplane many of us want. To get the climb rate, cruise speed, load carrying capability and cabin room to step up from a typical single you need more than the 300 or so horsepower that piston engines reliably deliver. Sure, a turboprop single is a very desirable airplane, but turbine power moves an airplane into a new, and much higher, price category.

So, please, insurers and pilots, read what Dick Collins writes in Flying, not what you think he writes. Piston twins are appropriate and desirable airplanes for any pilot with the budget and the willingness to learn to fly them. We need to stop punishing a whole category of airplanes because of a gross misunderstanding of its capabilities.