Wanttaja
Well-Known Member
Read the label on the graphic.Is that 104% chance of engine failure?
Ron Wanttaja
Read the label on the graphic.Is that 104% chance of engine failure?
So what if you have more chance of engine failure if you compensate adequately no big deal.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
Define "compensate adequately," and how this would be accomplished.So what if you have more chance of engine failure if you compensate adequately no big deal.
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%.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!
Compensate with an abundance of engines. Considering the rate they fail you just can't have to many.Define "compensate adequately," and how this would be accomplished.
Ron Wanttaja
About forty years ago (March 1990), Sport Aviation had an article about man who'd put four engines on a Lazair:Most will probably choose a lesser number, I encourage the number to be greater than 2.
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.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.
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.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 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.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.
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.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.