Light twins not using contra-rotating propellers

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'.

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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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

Neil Gould writes:

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

Then the design defect of propellers that rotate in the same direction
is not a violation of the laws of physics, QED.

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Recently, Mxsmanic posted:

Neil Gould writes:

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

Then the design defect of propellers that rotate in the same direction
is not a violation of the laws of physics, QED.

Your paraphrase is incorrect. It should be, "The design using propellers
that rotate in the same direction is not a defect".

Neil

Newps schrieb:

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'.

Be extra careful before calling names! Even when you don't like the poster.

Of course the effects of the P-factor can be overcome by appropriate
design. The most simple solution would be the possibility to trim all
three axis. As this seems to be a pretty straight forward and cheap
solution, I've never understood why this isn't offered in all airplaes.
Sure would make flying a light single more enjoyably. Yes, I even agree
that this avoidance could be called a design defect.

On the more expensive level (much more expensive, I would guess), you
can overcome the P-factor effects by using two contra-rotating coaxial
propellors. This would not only overcome the effects of the P-factor,
but also those caused by torque. Kamov helicopters are an example of
such a design.

Contra-rotating coaxial propellors not only solve the P-factor and
torque, but they make the propellor more efficient, too. Probably too
little effect compared to the additional cost and complexity, so it has
been realized only rarely. Tupolev 114 is an example. (In marine
applications, you find contra-rotating coaxial propellors more often.)

Stefan

Stefan wrote:

Of course the effects of the P-factor can be overcome by appropriate
design. The most simple solution would be the possibility to trim all
three axis.

Yaw damping does wonders in the Pilatus. Of course your typical GA
aircraft doesn't have 1200hp - and doesn't cost $3.5M.

On the more expensive level (much more expensive, I would guess), you
can overcome the P-factor effects by using two contra-rotating coaxial
propellors. This would not only overcome the effects of the P-factor,
but also those caused by torque. Kamov helicopters are an example of
such a design.

Effective, yes, but very complex, heavy and expensive. I recall seeing
an ad for Breitling watches that had a P-51 with contra-rotating props.
I think it was a one-off aircraft with a RR Griffon engine?

Contra-rotating coaxial propellors not only solve the P-factor and
torque, but they make the propellor more efficient, too. Probably too
little effect compared to the additional cost and complexity, so it has
been realized only rarely. Tupolev 114 is an example.

IIRC Tu-95/114 was the fastest prop aircraft of its category. I think
the cruise speed was near 500mph? I think that was a combination of
high-shp Kuznetsov turboshafts and the efficiency of the contra props.
Pretty amazing aircraft IMO.

"Kingfish" wrote in message
Effective, yes, but very complex, heavy and expensive. I recall seeing
an ad for Breitling watches that had a P-51 with contra-rotating props.
I think it was a one-off aircraft with a RR Griffon engine?

That aircraft was modified for Unlimited racing at Reno. It also had the
bobbed canopy and clipped wings.

D.

Recently, Stefan posted:

Newps schrieb:

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'.

Be extra careful before calling names! Even when you don't like the
poster.

Of course the effects of the P-factor can be overcome by appropriate
design. The most simple solution would be the possibility to trim all
three axis. As this seems to be a pretty straight forward and cheap
solution, I've never understood why this isn't offered in all
airplaes. Sure would make flying a light single more enjoyably. Yes,
I even agree that this avoidance could be called a design defect.

I think it would be a good idea to distinguish between design defects and
design _trade-offs_ in this kind of discussion. Many GA planes have 3-axis
trim, but, as in other areas, this option comes at a cost. The question
becomes which options a buyer might find more attractive, for example
would you prefer 3-axis trim or better avionics and moving map GPS?

Neil

Neil Gould schrieb:

distinguish between design defects and design _trade-offs_

Agreed.

for example would you prefer 3-axis trim or better avionics and
moving map GPS?

Personally, I'd choose the trim without having to contemplate one
second. That's why I actually think that the lack of a three axis trim
is a defect. But then, I also think that an engine which has a
dispacement of 360 cubic inch and burns 10 US gallons per hour only to
produce a mere 180 hp (actually much less in cruse) should be called
defect in the 21th century. But I'm getting OT.

Stefan