props: tractor v pusher, q tip, ducted?

Tina wrote in news:1186370891.595213.170320
@w3g2000hsg.googlegroups.com:

The data I saw showed the 337 single engine pusher doing better, maybe
it is old data. The tractor prop is wasting energy blowing on the
windscreen and cowling, problems the pusher doesn't have. I know the
biggest gains the Mooney Exec had in going to the 201 had was because
of the cowling and windscreen redesign.


That's for the early airplanes regarding the Skymasters. the loss was in
cooling drag, which Cessna improved. After that the SE ceiling cruise
and climb were virtually identical, but the reputation the rear engine
had for better SE performance never went away..

I never heard that q tips did worse than straight bladed props, that
was an interesting observation.


Actaully, it was more than an observation. the Q tips were installed as
a noise requirement for Swiss registered airplanes. These airplanes had
a supplememt to the POH with degraded performance. Having said that they
also had "Swiss Mufflers" but they're supposed to have no effect on
performance.
Also flew a couple of Arrows similarly equipped as well as a Cessna 182
RG. Same deal for all of them IIRC. Some were German and I seem to
remember they had a different muffler assembly in Germany which deliverd
worse performance and made more noise.


Aren't Lakers configured as pushers? That is an interesting example.
because the engine is just hanging out there, you could put the prop
on either end.


Well, you're getting down to comparing apples with oranges. You'd have
to take two essentially identical aircraft and try both configurations
with it for a satisfacory answer based solely on observed performance,
but in reality, a real world airplane is going to throw so many other
variables, such as cooliing requirements, planform due to CG
considerations, disc availability due to fuselage cross section, whoch,
of course is down to cabin space, mission requirements yadda yadda
yadda. At the end of the day, when you look at similarly powered
aircraft with similar missions, or even better, if you look at the Cafe
racers, the evidence says it's al down to how clever the designer is,
and there's not a lot in any configuration, pusher, tractor tandem wing,
canard or conventional...



Bertie