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Traveling with a twin engine 2 stroke airplane?

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blane.c

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Don't think "reliability" is the term you're looking for. Adding a second engine only doubles the chance of an engine failure.

You're undoubtedly looking at the ability to continue the flight to a safe destination, vs. having to perform an immediate power-off landing. One of the OWTs about flying is that you're actually MORE likely to get killed after engine failure on a twin-engine aircraft. The way the story goes, pilots fly "power-off" landings all the time, but the gymnastics needed to keep a twin going with a fan out is something practiced only BFRs. A VMC roll at low altitude is very likely to kill you.

Again, though, just a story...haven't seen any sort of statistics on it.

Light twin aircraft rarely have a surfeit of power. Do so research on the Champion Lancer, a twin-engine version of the Aeronca Champ. Thing couldn't get out of its way with one engine out.

To maximize safety, too, you're going to want to have featherable propellers on the engines...kind of rare, for two-stroke engines. That was the downfall of the Lancer, two O-200s with fixed props. If your plane can't climb on a single engine, you're just stretching the glide, which may or may not really be an advantage. Though maybe two-stroke engines don't windmill....

Two-stroke engine issues are a factor in homebuilt aircraft accidents about twice as often as certified aircraft engines. If safety is your goal, you'd be better off with a single, more reliable powerplant instead of two two-stroke engines.

Ron Wanttaja
So what if you have more chance of engine failure if you compensate adequately no big deal.
 

EzyBuildWing

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Twin-engined airplanes have twice the chance of an engine-failure, as single-engined airplanes, right?
OK.....so if Robinson s installed single-ignition Lycs in their R-22 and R-44 heli's they'd halve the chances of ignition-failure!
Rotax could go "single-ignition" too!
Would save weight everywhere!
Any pilots out there go for that?
 

TFF

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Oh come on now, that was funny.
It was a long time ago, but I believe Flying Magazine had a comparison of the Bonanza vs the Barron. Can’t get more even than that.
 

Wanttaja

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Twin-engined airplanes have twice the chance of an engine-failure, as single-engined airplanes, right?
OK.....so if Robinson s installed single-ignition Lycs in their R-22 and R-44 heli's they'd halve the chances of ignition-failure!
The difference is, losing an engine in a twin-engine airplane cuts the available power in half. But losing a magneto in a dual-magneto system means a power loss around 1-2%.

Aircraft engines have dual ignitions not for maximizing power, but due to the bad reliability of magnetos. They failed so much in the early days (still do, in fact) that regulatory authorities mandated dual magnetos.

About 8.8% of all homebuilt aircraft engine failures is due to the failure of an ignition system component (mags, coils, electronic controller, etc.). That rises to 10.4% for two-stroke engines, and 14.2% of auto-engine conversions.

Ironically, I've got a 1984 Nissan pickup truck with dual ignition. Two spark plugs per cylinder, two coils, but a single distributor.

Ron Wanttaja
 

EzyBuildWing

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Interesting numbers on the Pipistrel dashboard here: 90 kts cruise, 21 kW eMotor consumption, 1950 prop RPM. Pilot & passenger.
So just mount total 6 Cri Cri 2-strokes along the wing's LE, and the chance of a mechanical engine-failure bringing you down is about zilch!
 

blane.c

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27 is possibly ideal? 9 about the empennage and 9 each side about the wing. Then one can have relative comfort that the loss of a few won't really effect the outcome of the flight.
 

Wanttaja

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Most will probably choose a lesser number, I encourage the number to be greater than 2.
About forty years ago (March 1990), Sport Aviation had an article about man who'd put four engines on a Lazair:
1606667513823.png
The aircraft registration is listed as "Destroyed" about a year after this article came out.

Ron Wanttaja
 
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blane.c

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I've looked at this aircraft many times, it seems he moved the two original engines outboard and put two newer and larger engines in the inboard positions. I am not aware of what caused the aircraft to be destroyed.
 

Wanttaja

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I've looked at this aircraft many times, it seems he moved the two original engines outboard and put two newer and larger engines in the inboard positions. I am not aware of what caused the aircraft to be destroyed.
Didn't find an accident report, so the circumstances probably weren't too serious. May not have even been related to an crash; could have been a hangar collapse, discovery of a serious structural or handling issue, or even just a decision to permanently remove the aircraft from the registry to work on something else.

Found a 2009 obituary for someone who is probably the "Max Collin" who built the aircraft. Sounds like natural causes.

Ron Wanttaja
 

Toobuilder

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Obviously, having 50 independant fuel tanks of 1 gallon each are the ultimate in safety.
 

mwflyer

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Don't think "reliability" is the term you're looking for. Adding a second engine only doubles the chance of an engine failure.

You're undoubtedly looking at the ability to continue the flight to a safe destination, vs. having to perform an immediate power-off landing. One of the OWTs about flying is that you're actually MORE likely to get killed after engine failure on a twin-engine aircraft. The way the story goes, pilots fly "power-off" landings all the time, but the gymnastics needed to keep a twin going with a fan out is something practiced only BFRs. A VMC roll at low altitude is very likely to kill you.

Again, though, just a story...haven't seen any sort of statistics on it.

Light twin aircraft rarely have a surfeit of power. Do so research on the Champion Lancer, a twin-engine version of the Aeronca Champ. Thing couldn't get out of its way with one engine out.

To maximize safety, too, you're going to want to have featherable propellers on the engines...kind of rare, for two-stroke engines. That was the downfall of the Lancer, two O-200s with fixed props. If your plane can't climb on a single engine, you're just stretching the glide, which may or may not really be an advantage. Though maybe two-stroke engines don't windmill....

Two-stroke engine issues are a factor in homebuilt aircraft accidents about twice as often as certified aircraft engines. If safety is your goal, you'd be better off with a single, more reliable powerplant instead of two two-stroke engines.

Ron Wanttaja
This was Charles Lindberg's observation. The tri-motors others were trying to fly across the Atlantic required all three engines to fly when fully loaded, hence tripling the likelihood of a fatal engine out. That's why the Spirit of St. Louis was a single.

Instead of a featherable prop, what if you had a folding prop as some motorgliders use? If the engine stops the prop folds automatically. No prop control, or feathering the wrong prop. More workable on a pusher than a tractor.

'nother thought I had was overlapping the props so the thrust centerlines are closer to the centerline of the aircraft. I was looking at a Beech Starship when I thought of that. Extend one of the prop shafts and the distance between the prop centerlines can be reduced about 40%

But the big thing is the plane has to be able to fly on one engine. A plane that can fly on 100 hp can't necessarily fly on 50. The move from 100 hp single to twin may by that necessity become a 150 hp.
 

blane.c

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It is about performance with one engine out really whether twin or tri-motor because even with a tri-motor you are just talking glide slope with two engines out. Single engine designs rarely make good multi-engine platforms but like anything else there are exceptions. Like you said because with a twin you only have about 37% power in actuality after a engine loss the engines become larger to compensate this dominoes through the entire aircraft (change one thing change everything) and they are rarely anything like the single they may have sprouted from. The major exception is the center-line thrust twins which are to my knowledge designed as twins from the inception and have less drag losses with engine failure because they do not need to compensate for asymmetrical thrust. However no twin will have as much power available after an engine loss than a tri-motor considering they each started with the same amount of total hp.
 

Brünner

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This was Charles Lindberg's observation. The tri-motors others were trying to fly across the Atlantic required all three engines to fly when fully loaded, hence tripling the likelihood of a fatal engine out. That's why the Spirit of St. Louis was a single.
This is true, but let's not forget that 93 years ago piston engines in general were EXTREMELY unreliable. Lindbergh knew that his engine would work only for a limited amount of hours, pretty much irrespective of how much fuel he had or how carefully he managed it.

Instead of a featherable prop, what if you had a folding prop as some motorgliders use? If the engine stops the prop folds automatically. No prop control, or feathering the wrong prop. More workable on a pusher than a tractor.

'nother thought I had was overlapping the props so the thrust centerlines are closer to the centerline of the aircraft. I was looking at a Beech Starship when I thought of that. Extend one of the prop shafts and the distance between the prop centerlines can be reduced about 40%

But the big thing is the plane has to be able to fly on one engine. A plane that can fly on 100 hp can't necessarily fly on 50. The move from 100 hp single to twin may by that necessity become a 150 hp.
Correct, which is why an engine of a 777 is much more powerful that 2 engines of a 747 or 340, technological advances notwithstanding. Etops regs and such.
 
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