Pilots -- General Aviation: For a long flight over water would you prefer a twin piston or single engine turboprop?

Usually with flights over water pilots prefer a twin (or more) engine plane. The reason being if there is nowhere to land having a second engine is a safety feature. That redundancy means if one engine goes kaput the other will get you to land. If you only have one engine over water and it craps out then you are going to have a really bad day.

But, the caveat here is turbine engines are considered much, much more reliable than a piston engine. Certainly they can fail too but they fail less often (although, from what I have read, a piston engine may limp along with some failure whereas a turbine is kinda all or nothing…it works or it doesn’t).

So, if someone said you had to fly from LA to Honolulu in a GA plane (assume it has the range…I know most GA planes under $10 million won’t but pretend you have the range for this…carrying a fuel bladder or just magic as you like) would you prefer a single engine turboprop or a twin engine piston plane?

(For the sake of argument assume all other performance specs are the same…speed, cruise altitude and whatnot.)

For those interested this question was prompted by this video:

More like a really bad couple of minutes.

Assuming the only problem is the engine died but the plane still has control it can glide. Most planes that are not gliders do not glide very well but they do it well enough. A competent pilot should be able to glide to a water landing. That’s not great but far better than just falling out of the sky and as the Miracle on the Hudson proved very survivable (they had a lot of advantages though compared to someone in the middle of the ocean but still…doable(ish)).

Single turbine over any recip combo. The substantial increase in turbine reliability is one reason ETOPS is in some cases 180 minutes. (I think this is correct, as my kiddo told me he’s flying ETOPS 180 routes now)

The company I’m on furlough from have B787s with 330 minutes EDTO (ETOPS).

To the OP, I wouldn’t be overly comfortable in a twin piston or a single turbine. I know mathematically I’d be better off in the turbine.

Not an expert in those sorts of airplanes, nor a multi-engine pilot myself, but with that caveat:

Single engine turboprop.

Both because of the turboprop’s reliability but also because a single-engine failure in a twin is NOT a trivial thing even with the most competent of pilots. You’d think having a “spare” engine would make things safer but the actual accident record sheds some doubt on that. Management of a twin suddenly made single is quite a juggling act, and not all twin pistons can maintain altitude with just one engine, much less climb, so really it’s a matter of delaying the unplanned landing rather than being able to continue the journey. Either way you’re ditching the airplane on the proposed route.

As @Broomstick said.

Any GA airplane flying from LA to Honolulu is going to be carrying a LOT of extra fuel. Which means that for most of the flight the airplane will be very heavy, perhaps even above the normal maximum legal weight and operating on a special flight permit.

In general light piston twins don’t fly very well on one engine. The good news is you only need to stay at about 50 feet above sea level; you’re not trying to also stay above a landmass that might be at 1000 or 5000 feet altitude. The bad news is even that low altitude may be impossible if one engine of a twin fails before you’ve burned off most of the fuel = weight.

Said another way, in a twin even with engines exactly as reliable as in the single, you don’t have half the chance of going swimming, you have double the chance of going swimming. At least for the 2/3rds of the flight where it won’t fly on just one.

There are people and businesses who specialize in ferrying light airplanes across oceans. They have plans & equipment for dealing with a mid-ocean landing. And make a point of not trying a crossing when the weather would make a water landing insufficiently survivable. Being dropped mid-ocean is nobody’s idea of a good day at work. But it’s also not a suicide mission.

Bottom-line: All the math says the single turbine is vastly safer.

I’d take a seaplane :slight_smile:


You’re flying across the ocean
When you hear your engine spit
You see the prop come to a stop
The goddamned engine’s quit
The ship won’t float, you cannot swim
The shore is miles behind
You’ll be a dish for happy fish
But you will never mind

I recall the Navy had a saying about that situation: 1 minute flying = 1 day swimming. And that was back in the piston days.

I’ve been in a twin engine glider before. The reason for 2 engines is a safety factor but that factor completely reverses on takeoff. And depending on the plane the 2nd engine is borderline at best and not sufficient for sustained flight. You really need to think about landing in the very near future with a twin that lost an engine. It’s not going to be much use for great distances.

I would take the single turbine because it’s more reliable and if things get really bad then I’d rather try to land a single than a twin in water.

You and others saying that a second engine is of little use for safety prompts the question…why would anyone want a twin engine piston GA plane? If the second engine is more burden than benefit why add the extra cost? Is it performance? It seems there are single engine planes that perform as well as a twin so…?

Having the engines on the wings allows for better visibility forward for the pilot. There did come a point where bigger and bigger single engines started to become problems due to sheer size.

Adding on more engines allows for larger payloads/speeds without needing to develop bigger and bigger engines.

People thought they would be safer… even if it turns out the response to that is “not as much as you would think.”

The rest I’ll leave to those authorities here that know more about twins than I do.

The practical factors certainly override the theoretical ones, but I’d like to point out that the chance of complete failure should go down by much more than half with two engines. If there’s a 0.1% chance of failure (picking round numbers) on any given flight with one engine, then assuming independence there’s a 0.0001% chance of failure with two.

In the other direction, you’re clearly right: given 99.9% success with one engine, there’s 99.8001% chance of success with two, so basically double the failure rate.

And of course failure events are not independent, so even if you only need one out of two engines, your odds aren’t improving that dramatically.

The thing that’s hard for newbies to understand about piston GA is it’s essentially in a technological stasis from the 1950s/1960s. Yup 60+ years ago.

Originally, light twins were about performance, not safety.

Back in the 1950s the designers had a choice of one 180 HP engine or 2 180HP engines. If you wanted to carry more load than one engine could move, you used 2. The fact it didn’t really fly on just one was OK enough.

Slowly engines got more powerful and by the late 1960s, the heyday of piston GA, the biggest turbocharged engines put out 350HP. Again if the designers wanted more load or speed than one engine could carry, they used two.

There became enough performance headroom with those larger engines that a light twin could fly on one engine. But only with much les than full fuel and/or much less than full payload and even then only at low altitude on a cool day. Which depending on where and how the airplane was used, that might be 5% or might be 95% of its operating life. In the latter case the second engine did provide a real safety benefit. Not so much in the first.

Now fast forward in to the 1980s and suddenly turbine engines that start at 500HP and go up to 1,500HP are available. The need for 2 engines to break 350HP is gone. So a whole new type of aircraft, the turboprop single came into being.

With eyewatering performance compared to a piston airplane, and an eye-watering price-tag to match.

The phrase “GA” is really a grab bag of a lot of very different machines for very different missions. It’s an error to look across sub-types that are too different and think of them as “all just GA”. An ultralight and a G-550 are both “GA”. Sharing those two initials is about the extent of their similarity as air vehicles.

FWIW I use “GA” to mean a single pilot plane as opposed to a plane that requires two pilots to fly. I do not know if that is a fair line to draw but that’s what I am thinking (and to me, two pilot planes are generally commercial or super-swank business jets…and I know small planes can be commercial too).

Would you consider a Mustang bought in 1950 a GA plane? :slight_smile:

Yes (assuming it was not used in a military role anymore but just for flying around).

I would imagine that would be a fun plane to fly but minus its guns it is pretty much useless as a plane except for the fun of flying (which for some is all they want and that’s fine). Kinda like a super expensive two-seat sports car. It’s not of much practical use but fun as hell to drive.

You may be interested in the Otto Aviation Celera 500L. It’s still a long way from production but a flying prototype has been built and so far seems to be progressing towards production. If it lives up to the promise it has truly astounding performance numbers for any light plane, not to mention a piston plane. It might be a real game changer for light aircraft (consider a 4,500 nm range for starters).

That’s not standard usage, but not insane either. The standard term closest to that is probably “private plane”, a plane where the pilot owns it, or could at least afford to buy it.

Even so, that covers a lot of ground. This is a Cessna private plane selling for about $30,000. This is a TBM private plane selling about for $4M new, just 150x as much.

For comparison, here’s a $30K used boat and here’s a $4M used boat.

I think you’d agree that the two boats are very different and have very different features. The same is equally true about the two planes. Despite the fact they’re not all that different in gross size. Not nearly like the boats are.