Why isn't the push/pull twin more popular ? What you say.

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With all the problems of pilots being proficient in handing a light twin on single engine, why isn't the push/pull twin design used more ?
Pro's and Con's
Indeed the Fuelie and Electric Combo is going to make a huge difference. Its a different matter whether the tech has arrived .... in time it will arrive and maybe a better option then an all electric with battery. A generator cum thrust engine is in my (verry basic) knowledge a good idea to move forward.
 

Tiger Tim

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I figure it’s a matter of design cost for a small twin and utility for a bigger twin.

For the small ones a Comanche became a Twin Comanche easily enough, just as a Cherokee Six became a Seneca. The Cessna 337 had to be from more or less a clean slate.

In bigger twins the engines eat up space that can be used to carry people and stuff. Look at how compact the footprint of a Navajo is for what it can do. To make it a push/pull you’d either be cutting seats or lengthening the airplane; one eats into your utility/profit and the other increases hangarage costs.
 

dog

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push pull is not,or almost,impossible in a jet
and is therfore not part of ,?what? 95%+ of the
tonage in the air or the minds of the designers
and builders
its a very large blind spot and what is left is therfore part of aviation I will call "also flown"
the persistance of 337's flying does in fact prove
that there is a use case ,and reading between the lines the 337 is regularly overloaded ,modified,
run past tbo and then semi abandoned only to
be resurected and flown again
other than that there were a whole raft of dornier
types that used push pull pairs on pylons,on the wings and for and aft on the fueselage,they olso
ran three engines on parasol ,strut braced wings
and other impossible to clasify aircraft
also other early flying boats and race planes
but nothing in comercial service other than the 337 now,I think
 

Vigilant1

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Several folks have made valid points about the drag of the aft fuselage of the 336/337. It's worth noting that the wing mounted engines on a "conventional" twin have their own drag bill. Yes, the nacelles look very smooth and swoopy, but they add frontal area that the 337 doesn't have. Also, while we (rightly) fret about the drag caused by the wing/fuselage intersection on our singles, these nacelles increase that intersection crease length by about 250%. Finally, while the fuselage on a typical utility aircraft isn't going to offer the hope of much laminar, or even clean, flow, there's a good shot of achieving relatively low-drag flow over the wing, or at least the leading 30% of it. The chances of that go down if we install propellers in the wing. The turbulent propwash on a convention twin covers about 40% of the wing area, and it's the hard-working inboard area that we count on for most of the lift.
I'm not saying that a 337 (struts and all) is necessarily cleaner than a "conventional" twin. But, it does fly faster and carry more useful load than a Seminole with the same installed HP. So...
Drag on the back if the rear engine quits? Yes, it goes up. But the rudder needed to keep a conventional twin flying straight when an engine quits also has a significant drag bill. If we don't attend to that rudder and don't pay that drag bill, bad things happen quickly.

 
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Vigilant1

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I think the 337 looks and sounds great in flight. I might feel a lot different about the sound if I ever get a chance to fly in one. :)
I have a friend who flew O-2s, he liked the airplane and the mission. It was sometimes a bitter pill for a young USAF pilot, especially since they'd finished in the top 30% of their pilot training class and could otherwise have gone to fighters.
 

Dana LaBounty

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Add simplicity with a single engine. Put the engineering effort into reliability of a single powerplant and the redundancy/expense of a twin become non-viable. Airframe technology can only advance when powerplant technology advances.
 

arj1

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Add simplicity with a single engine. Put the engineering effort into reliability of a single powerplant and the redundancy/expense of a twin become non-viable. Airframe technology can only advance when powerplant technology advances.
Hi Dana, sorry, agree to disagree - for me (as an IT guy) a single point of failure is still a single point of failure...
A single manufacturing defect could cause a problem with engine or prop, and that is it (over mountains at night or cold sea).
Although one the 337s went down due to double engine failure! I think it was due to very low temps? Flight in the north...

Going back to the OP's question - I think what people listed here sums it up: too many design problems. And both most known a/c in the class have failed to deliver (337 + Adam 500)
 

Vigilant1

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Add simplicity with a single engine. Put the engineering effort into reliability of a single powerplant and the redundancy/expense of a twin become non-viable. Airframe technology can only advance when powerplant technology advances.
Sure, everyone wants reliable engines. It's not like we aren't (as a group) trying to accomplish that, and a lot of progress has been made. At present, certified reciprocating powerplants have about 1 chance in 8000 of failing during a one hour mission. That's pretty darn good. It still means that if you spend a career flying behind single engined recips 35 hours per week, you are likely to experience a total loss of power on average about each 8 years. If that flying is mostly over the water or solid forest, then even this very good reliability may strike a person as insufficient.
IF we have two engines with this same reliability and IF the plane can maintain safe flight on just one and IF the engines are totally independent (share no failure points or issues, including crummy maintenance), then the expected time between total aircraft power loss due to mechanical engine issues would be about 1 in 64 million during one hour of flight. Heck, even the PT6 turbine has an hourly failure rate of about 1:200,000.
Now, in real life, recip twins (centerline thrust or "conventional") don't enjoy outstanding safety records compared to certified singles. There are several reasons for that, but it's not because the rate of total loss of engine power for mechanical reasons is the same between these groups.
I suppose someday electric propulsion may get pretty reliable, but it doesn't seem to be there yet. And the really low energy density of present batteries makes this a niche/novelty power option today.
 
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Radicaldude1234

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This airplane seemed to have the single engine reliability, was fast, and had looks that killed (literally for its intended victims and its pilots):

Do335.jpg


All kidding aside, I think the answer to Pop's question is more fundamental to anything technical:

People who own twins want speed, carrying capacity, and roominess. An extreme example, but with the exception of its single seat cockpit, the Dornier above was packed from spinner to spinner with either fuel or engine systems.

The Cessna Skymaster has the same issues with useful load and cabin space. The cabin space and useful load is very similar to a Centurion...and is in fact slower! I guess the interference from all those tail booms and struts really did a number on its drag coefficient.

That, and that the target audience for twins being more well-to-do individuals who want to take 2 of their best buddies and their spouses (who are probably leery of flying and will bring lots of luggage), they're going to want something that's fast, roomy, and looks like an "airplane".

I think the Adams A500 had the best chance to break the mold, but they just never attained the critical mass to make it happen.
 

arj1

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I think the Adams A500 had the best chance to break the mold, but they just never attained the critical mass to make it happen.
@Radicaldude1234, if I remember rightly, they've done it alright but underestimated the weight! In the end it was too high. From Wikipedia: "With the 230 US gal (870 l) fuel tanks full, the available payload for crew, passengers and baggage is 160 lb (73 kg), down from a projected 720 lb (327 kg). This means that the A500 cannot carry full fuel and one standard weight adult male or female pilot."
Ouch!
Otherwise - nice aircraft. Pressurised twin, with 220kts cruise etc.
 

challenger_II

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I think the 337 looks and sounds great in flight. I might feel a lot different about the sound if I ever get a chance to fly in one. :)
I have a friend who flew O-2s, he liked the airplane and the mission. It was sometimes a bitter pill for a young USAF pilot, especially since they'd finished in the top 30% of their pilot training class and could otherwise have gone to fighters.
Meh. Fighters have appeal, but One sucks a big hole and falls into it! Lobs a missile from time to time. The O birds got down and into the scrap. I had two uncles that flew O-2's and were upset when they were reassigned to Hoovers.
 

Pops

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Model of Steve Weaver's Cessna 337 that he used in his aerobatic routine . " Bodacious "
 

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Pops

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Did I here someone say the word " BeetleMaster" ?

 

Vigilant1

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I love the idea of a mini 337.
You aren't the only one, brother!
Of course there were real, in-the-flesh tiny 2 stroke push-pull aircraft including the Powers-Bashforth Minimaster and the Toucan.

We've had a lot of fun batting around the idea of a " Beetlemaster " a two (+?) seat design to be powered by two VW Type 1 engines. Pops had the idea in his head before we started thrashing it out here It looked like a useful airplane could be designed and built that would fly and perform well and still climb and fly safely on one engine. Some rough 'back of the envelope" performance WAGs for three variants of the Beetlemaster. It could be a lot of fun.

Going smaller still, we looked at a single place plane design (MicroMaster) powered by two 28-30 HP industrial engines It also appeared possible to end up with a fun plane with safe single engine performance.

The critical thing driving the design in the last two cases is achieving safe single engine climb. It requires a not-too-heavy plane and adequate wingspan. Rutan's Defiant and several other designs show it's possible to use fixed pitch props on a twin and still get good single engine performance and acceptable cruise speeds. It ain't optimal, but it can be done.
 
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Pops

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You aren't the only one, brother!
Of course there were real, in-the-flesh tiny 2 stroke push-pull aircraft including the Powers-Bashforth Minimaster and the Toucan.

We've had a lot of fun batting around the idea of a " Beetlemaster " a two (?+?) seat design powered by two VW Type 1 engines. Pops had the idea in his head before we started thrashing it out here It looked like a useful airplane could be designed and built that would fly and perform well and still climb and fly safely on one engine.

Going smaller still, we looked at a single place plane design (MicroMaster) powered by two 28-30 HP industrial engines It also appeared possible to end up with a fun plane with safe single engine performance.

The critical thing driving the design in the last two cases is achieving safe single engine climb. It requires a not-too-heavy plane and adequate wingspan. But it does seem to be possible.
I'm just waiting for you or someone to start construction of a BeetleMaster.
Tired of holding my breath. :)
 
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