Light twins not using contra-rotating propellers

Mark Levin writes:

As was pointed out to me the Beechcraft Baron does not use contra-rotating
propellers. A bit of research showed me that most U.S. built light twins do
not use them either.

My question is why?

My guess is that the market for mirror-image engines (the most
straightforward implementation) is too small. If you don't use mirror
images, you have asymmetries in the powerplant engineering.

I do wish that things were different. I consider the effects of
P-factor and torque to be design defects.

--
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Recently, Mxsmanic posted:

Mark Levin writes:

As was pointed out to me the Beechcraft Baron does not use
contra-rotating propellers. A bit of research showed me that most
U.S. built light twins do not use them either.

My question is why?

My guess is that the market for mirror-image engines (the most
straightforward implementation) is too small. If you don't use mirror
images, you have asymmetries in the powerplant engineering.

Probably not the market, but the cost of maintenance, quantity of
available parts, and other things mentioned in this thread are reason
enough to warrant the practice.

I do wish that things were different. I consider the effects of
P-factor and torque to be design defects.

A design defect is a problem caused by some aspect of the design. I don't
know why you would consider the effects of propeller propulsion to be
"design defects". They are simply aspects of that type of propulsion.

Neil

Mxsmanic wrote:
I do wish that things were different. I consider the effects of
P-factor and torque to be design defects.

You can't design out P-factor or torque, but I don't think they're that
critical anyway in flight for most low-powered GA craft. The propeller
slipstream has more effect on both the rudder and elevator, and that
can be reduced with canted tailfin, and more or less fixed with dual
booms and T-tail.

There are centerline push-pull twins, like the Cessna Skymaster or the
current Adam A500. They eliminate the engine-out yaw problem. As
long as both are running, torque etc should cancel out since the
engines essentially counter-rotate because of their facing fore and
aft.

Kev

Mxsmanic wrote:

I do wish that things were different. I consider the effects of
P-factor and torque to be design defects.


Christ your an idiot. Until you change the laws of physics you're stuck
with those 'design defects'.

Neil Gould writes:

A design defect is a problem caused by some aspect of the design. I don't
know why you would consider the effects of propeller propulsion to be
"design defects". They are simply aspects of that type of propulsion.

An aspect of propulsion that constantly pulls the aircraft to one side
sounds like a defect to me.

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Newps writes:

Christ your an idiot. Until you change the laws of physics you're stuck
with those 'design defects'.

Then twins with propellers that turn in opposite directions would seem
to have already violated the laws of physics.

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On Fri, 01 Dec 2006 07:40:00 +0100, Mxsmanic wrote:

Neil Gould writes:

A design defect is a problem caused by some aspect of the design. I don't
know why you would consider the effects of propeller propulsion to be
"design defects". They are simply aspects of that type of propulsion.

An aspect of propulsion that constantly pulls the aircraft to one side
sounds like a defect to me.

No more than the fact that you can't pull the nose of a General Aviation up to a
90 degree angle and keep climbing. Designers *can* build airplanes that will do
this, but the cost/benefit tradeoffs usually preclude it. Similarly, the
P-factor effect is accepted in some cases in order to minimize the production
cost. A design defect is something unexpected that becomes apparent AFTER the
aircraft flies, not something that is known and recognized while the plane is
still on the drawing board.

Ron Wanttaja

Recently, Mxsmanic posted:

Neil Gould writes:

A design defect is a problem caused by some aspect of the design. I
don't know why you would consider the effects of propeller
propulsion to be "design defects". They are simply aspects of that
type of propulsion.

An aspect of propulsion that constantly pulls the aircraft to one side
sounds like a defect to me.

It is a simple matter accounted for by Newtonian physics. Apparently, the
"designer" of that aspect of the real world doesn't see a problem with it,
as "real world version 2.0 has yet to be released, AFAIK. BTW, pilots of
propeller-driven aircraft don't see a problem with it either.

TANSTAAFL.

Neil

Recently, Mxsmanic posted:

Newps writes:

Christ your an idiot. Until you change the laws of physics you're
stuck with those 'design defects'.

Then twins with propellers that turn in opposite directions would seem
to have already violated the laws of physics.

There is no violation at all. Such twins are designed to take advantage of
the laws of physics.

Neil

"Mxsmanic" wrote in message
...
I consider the effects of
P-factor and torque to be design defects.

By your standards, are bicycles poorly designed because they are unstable at
slow speeds?