private aircraft question: 1 engine or 2?

I know nothing about private aircraft but have always been curious.
I have 2 questions about some basic characteristics of private A/C.

Are 2 engine private A/C safer than 1 engine?
It seems obvious to me that it is, but the limited reading I have done indicates that the safety difference is minimal if it exists at all. So, all you private pilots out there, what is the straight dope?

Are 2 engine private A/C faster than single engine A/C?
According to the limited reading I have done, the answer is a) certainly in terms of “max cruise speed” and b) not really in terms of the actual typical flight times from point A to point B. The quote I remember is that at least for one type of A/C, the extra engine just about compensated for the increased weight and drag of the second engine. So, all you private pilots out there, what is the straight dope?


The answer to every version of those questions is “maybe”. It depends on the models in question and the application.

The short answer is that complete engine failures are extremely rare unless they are caused by fuel exhaustion (more engines won’t help you there). Dual-engine aircraft can be very hard to control with one engine completely out because of asymmetrical thrust that causes serious yawing problems. It takes skill and lots of training to fly, let alone land many of the common models with only one engine. Additionally, flying with one engine only during takeoff may have only barely manageable flight envelope performance even though that is one of the times an engine failure is most likely to occur.

Finally, there is the increased purchase and maintenance costs associated with two engines rather than one. This isn’t a trivial concern because it is aviation and even smaller twin-engine planes might as well just run on gold bars to cut out the middleman.

There are also some fairly large single engine aircraft available like the Pilatus PC-12 that roughly matches or even beats the popular twin engine King Air on most measures.

Twin engine private planes aren’t very much in vogue these days but that is mainly due to their high purchase and operating costs with marginal benefits. The best argument I have heard for them is extended over-water routes where the ability to maintain altitude after a catastrophic engine failure could mean the difference between life and death. Another popular application is to use them as a multi-engine trainer for prospective airline pilots because multi-engine time is required to gain the appropriate ratings to move up.

Most twin-engine general aviation aircraft require additional training on the part of the pilot in order for control to be maintained during single-engine operations. A small twin with an engine failure in one engine is usually far less forgiving than a single-engine airplane suddenly turned into a glider.

I’ve heard arguments that because of the greater demands on the human pilot during a stressful situation they are, in the real world, less safe than a single engine airplane.

In part, this is because in a small twin the airplane probably won’t be able to maintain altitude with just one working engine. All it does is extend the time you are in the air prior to a forced landing, it doesn’t allow you to continue flying. So, for such a twin, it’s sort of the same problem you’d have in a single with an engine failure (you are going to land soon, whether you want to or not) with the additional complication of having to maintain control of an airplane with uneven thrust.

How much money do you have?
Speed requires more money so how fast do you want/need to go?
Do you fly a lot and practice emergency procedures? (That money thing again.)

I have 10,000+ hrs in light aircraft. Most light twin engine aircraft do just fine on one engine if they are not at max weight, nor too high nor in high density altitude situations.* About 98% of the time.*

With over 5,000 of those hours in all kinds of light twins, from old Piper, many different Cessna’s, Aero Commanders, etc. Flying those were how I tried to make a living.

IMO, 98% of Pvt. pilots do not fly enough, train enough, know enough, think about it enough to be competent in any aircraft nor have the plans in place & practiced for most of the usual emergency situations that occur.

There are exceptions of course. :smiley:

I can’t afford a personal airplane anymore but when I could I had an 1946 85hp Swift.


Pretty much the inst panel I had

Very few are willing to try to fly one or even ride in one. ( It was said that a 85 Swift was behind the power curve in a vertical dive. :eek: ) Very accurate actually… :cool:

Machinery is seldom the problem, the human usually is/was the problem.

Flying is a right or wrong but right now kind of activity. You don’t often get to go home & think about it or get a lot of ‘do overs.’

Remember, speed takes money and the faster, bigger, you go the more training, practice is required.


Folks above have pretty well nailed it.

A factor you didn’t cover for is era of technology. Many factory-built light aircraft are 1950s or 1960s tech even if they were built into the early 1980s. Then there are more modern designs from both traditional and non-traditional manufacturers dating from the mid-late 1990s and forward.

Within any given generation of tech the twins will generally be a little faster and have more useful load and a higher service ceiling.

As to “safety” there are a couple of dimensions to that. Are you asking about likelihood of a mishap, severity of a mishap, or both? Within the earlier generations of tech, twins are slightly less likely to have accidents, but the accidents they have tend to be more violent. And since average seating capacity is higher, on average more people are involved in those more violent accidents.

As well there’s the issue of pilot skill / professionalism. The minimum level of cool needed to handle faster more complex aircraft when stuff happens is greater than needed for a slower simpler aircraft. A consequence is that light & medium twins developed a reputation as a “doctor killer” because of the number of high-income low-skilled pilots buying & flying them. Those same types of aircraft when operated by even low-level pros in charter service have a vastly better record.

The skill effect is not nearly so pronounced in simpler aircraft.

One of the issues today in FAA regulation of small aircraft in small miniature airline service is that the regs assume 1950s tech wherein twin engines provided increased redundancy. But with modern turboprop engines being hundreds of times more reliable and 2x to 4x as powerful than 1950s piston engines, a darn good argument can be made that this single is far safer than this roughly comparable twin Despite this, the regulations still place some obstacles in the way of using the safer aircraft. Just due to bureaucratic inertia. Although that’s slowly changing.

Again this is an example of comparing across tech generations, not within them.

I fly business jets now, and I’d be wary of getting back into a light piston twin.

It’s mostly been covered, so I’ll just say the important factor for me is climb rate in an engine failure scenario. It’s been a while, but as I recall light twins are not guaranteed to climb with an engine failed. Flying at blue line (Vyse) only assures you will fly straight. You may or may not get a climb depending on weight, density altitude, etc. And that assumes you’re handling the plane correctly and are hopefully feathering the engine.

If I were to get back into flying pistons, I’d feel better about single-engine aircraft. I was always good in dead-stick landing scenarios, and would rather do that than deal with a dead engine in a light twin.

'Zactly. As the old joke put it: The purpose of the second engine is to take you to the scene of the accident in style.

There are other systems failure scenarios where two is clearly better than one. Not so much for engine failure in light twins.

I’d rather be in a helicopter. :wink:

Not to derail this thread, but I’m curious Johnny…

I’ve taken a few lessons in helos, including some autorotations. Really enjoyed it, but from what I understand there’s no way it’s safer than a fixed-wing single. Helo guys have always told me the concern is the collective - it has a ton of moving parts, and if just one bolt or something lets go, the whole thing becomes unbalanced and shatters.

Saw the remains of one once. It had been hover-taxiing and the rotor clipped the side of a hangar. It was just a pile of rubble - you couldn’t tell it had been an aircraft. The pilot supposedly got out, but I was amazed by how complete the destruction was, and this was not high speed impact.

So I know you’re a rotory-wing enthusiast, but where would you actually rate the safety of a piston helicopter vs. piston single fixed-wing? Will have to see if the Nall report has anything on this, but what do you say?

Autorotations and catastrophic failures are different things. There are things that, if they come off, will have an adverse effect on your longevity. The big thing about autorotations is maintaining your rotor RPM and having enough energy at the bottom. Not a big deal.

People have crashed three of the helicopters I’ve rented. My instructor rolled the first one with the student before me (dynamic rollover). The second one was lost when a pilot making a ridge landing came in too shallow. He couldn’t climb out of the down-draft on the lee side of the ridge, and hit the side. He rolled (I think) 100 m down to the bottom. A guy was taking his dad for a ride in the third one when he got into a vortex ring state (settling with power). He failed to take corrective action. In all three cases the helicopters were destroyed. In all three cases there were no, or minor, injuries (bruises and abrasions).

As for safety, I’d rather be able to land in a parking lot, than have to find a long, straight, unobstructed ‘runway’. I heard once (quite a while ago) that the safest single-engine aircraft in the U.S. was the Bell JetRanger.

Are there many modern twin-engine designs, and are they as hard to fly with one engine out as the older ones? If that was such a problem with the older twins, seems like it’s a natural area for improvement and we have decades of knowledge and technology to bring to bear on it now. With a conventional twin layout, one engine on each wing, you’ll always have asymmetric thrust if one quits, but it seems like they could make it a bit more manageable.

Or has anyone tried to rethink the whole problem? The Cessna Skymaster seems like a great idea, but wasn’t hugely successful. (A link on that page goes to the Adam A500; similar configuration but only 7 were built.) Or instead of a twin, how 'about a triple? If one engine goes out you still have 2/3 thrust and not as far off center. Yeah, the cost just keeps going up, but the three engines could be smaller and simpler than the two they replaced.


The “problem” as you put it simply that piston twins work OK at large scale (think DC-3 and up) but they don’t scale down as far as 1950s tech tried to take them. The base problem is lack of power vs. weight. The engines are simply too weak to give adequate performance with one inop.

Among twins the Skymaster had truly pitiful performance; far worse than the contemporary Cessna 310 which used roughly the same engines and had broadly similar size, weight, etc. The Skymaster fuselage massively obstructs the airflow through the propellers reducing the effective power delivered. Engine cooling was also poor and produced a lot of drag.

Today conventional piston light aircraft are a technological dead-end, a stagnant backwater of installed base with no sales. The future is single turboprops or electric quadcopters or mini 4- and 6-seat bizjets or somesuch.

So this is a “problem” nobody is willing to invest money to solve.

Hmm, interesting thought. Are turboprops so reliable that we’ll abandon twin-engine designs?

The problem with turboprops is that they tend to cost an order of magnitude more than pistons. So saying pistons are ‘a stagnant backwater of installed base with no sales’ and that the future lies with turboprops is like saying General Aviation is dead.

Cough, cough!!!

So, if you can’t, don’t know how, or got to a place that the aircraft simply can not fly on one of 2 engines, why would you not take the first available, reasonable, within your skill set, emergency landing spot? Faulty thinking about how it should fly and you do not know the aircraft as well as you should to be PIC is usually the reason you die in style. :smack:
Just pull the plug on the other engine and do your simple aircraft emergency landing. Apparently that seems unacceptable to you all. Don’t know how it reacts to 2 windmilling engines or how it glides with both feathered or any other configuration? Nothing wrong with the airplane. The so called pilot is ::: cough, cough… :::: I thought you guys were/are pilots, not god complex doctors in too much aircraft… :eek:

And still spouting the old small twins can’t fly on one or can’t climb, or will kill you in the mountains, etc. Old wives tales.:rolleyes:

Old Piper Apache with 150hp engines at max weight is a single engine aircraft that needs 2 engines to do much of anything. The pilots made all the mistakes in every crash of those that I ever knew anything about.

Lancer, fixed pitch props. If were smart you never tried to fly with just one producing power. Lancer

And other of that ilk. Yepper, not big preformers.

Had the C-310 turbo I worked in to 31,000 feet. It was snowing inside. Not at max weight of course.

IMO, way too much wrong info being repeated about light twins in the world today…

If flown with malice of forethought, knowledge, skill, and no god complex, it can be just as safe or safer than the multi million dollar single turbo-prop with the safer, more powerful engine.

I do not agree that the type, cost, power or other goodies on board in anyway compensates for bad, insufficient, and stupid thinking which causes so much of the small aircraft accidents.

Come on guys, don’t spout the non-sense. It makes me think you all started as Continental co-pilots… :stuck_out_tongue:

Bawahahahaha That is so bad. Sorry. he he he :smiley:

I owned a Twin Comanche for a few years. Flew it fairly often. Yes, assuming you started from cruise it would fly on one engine. What it would *not *do is climb out from an engine failure shortly after liftoff on a summer day in Vegas where I had it based. Unless you were solo with less than half-full tanks.

I also flew a 337 for almost a thousand hours. Another example of an aircraft that can lose an engine in cruise and more or less maintain level flight. Unless hot or heavy or high. And that does very poorly in low altitude failures.

So yes, the pilot thing to do in case of an engine failure near the ground or in adverse conditions is to make the best forced landing you can. Mostly straight ahead and as stylishly as possible.

But seen with modern, not 1950s, sensitivities that’s an example of failing to use your superior pilot judgment causing you to need to use your superior pilot skill.

I readily admit to being spoiled here in my current role. But I’m not sure there’s any peacetime mission so important that takeoffs should be attempted with passengers on board where safe climb-out and control is not assured after engine failure given your actual conditions of weight, temp, altitude, etc. Light twins by and large do not meet those standards except under rather benign conditions. Nor are they required by FAR to do so. Legal ain’t always smart.

In addition to changing attitudes to risk since the 1950s another thing that has changed since then is the availability of flat open ground near airports to make forced landings into. Admittedly a light twin force-landed skillfully isn’t going to slide very far. But far more airports are utterly surrounded by dense suburbia with a forest of overhead wires than was the case when I was first learning to fly in the early 1970s. There certainly are still some country airfields. But not nearly the percentage of the total that they represented back then.

Knew that my post was going to irritate you a bit. :smiley:

How can a poor PVt pilot fly if he has to have a plane that meets your requirements?

There were flocks of birds in the area, why did the big iron take off? Immense power did not overcome the birds. Only place to go was a river. So big iron get a pass on those judgement calls?

No one except those with large disposable incomes who can afford very expensive aircraft that have safety margins equal to modern airline aircraft should ever take a passenger in any older tech aircraft? I know you did not mean that but how did you get than much time in a 337 using your self imposed safety judgement?

Why did you buy a Twin Comanche? Unsafe in any useful way or condition using your recommendations on what is sane & safe.

What airport is safe for any single engine aircraft that loses it’s engine at the wrong time? Cessna Caravan is just as helpless as the 1940 J-3 Cub.

No criteria is too expensive for those who do not have to pay it. You said your own personal aircraft did not meet your requirements… :stuck_out_tongue:

We come to the pilot world from two very different backgrounds, time frames, education backgrounds and you are by far the better informed on current flying, have more PIC time than me I would think, info about all things ‘big iron,’ a military fighter background, etc., the ability to communicate for the non-pilot readers, etc. Love to listen/read to what you know & I respect your opinions on many things you post about.

( Nuff apologizing & sucking up from me.) :cool:

IMO, totally safe flight decisions limit pilots to very few flights. Same goes for the aircraft, all aircraft.

Look to Lockheed for design.
Look to Douglas for engineering.
Look to Boeing for damn fine airplanes.

And never forget the Grumman Iron & Foundry Works.

Yeah, I’m old. Bawahahaha

In general, a twin-engine plane has twice the probability of engine failure that a single-engine plane has.

Twice the probability of single engine failure, but the probability of total engine failure is the square root of an otherwise equivalent single.

The issue is, in terms of the assessment of the severity of possible outcomes and the respective risk thereof, is it better to have the reduced chance of having no thrust (which happens with the twin) or the reduced chance of having less than full thrust (which happens with the single)–and that balance depends on the weight and aerodynamic characteristics of the single vs. twin airframe.

My father was a private pilot. When I was growing up, the belief was that single-engine planes were safer. That’s because you made damn sure the engine was working perfectly.