Propellors vs Rotors

GET BACK IN THERE! 'YA DAMN WORMS!

Yea, rotor wash is real. I've been in it... under an AS Puma slow
orbiting just over wet pine trees, 100 ft. from a Bell 412, 212, 214,
206, 222, Boelkow 105C, AS AStar, AS Twinstar, Hughes 500C getting out
of a Bell 206-B3, Robinsin R44, Bell 206-L1, and numerous other
encounters that I can't quite remember over the years. My Dad was a
helicopter A&P.

Yea, a significant portion of the air surrounding a hovering helicopter
is moved downward, just as fixed-wing props throw back a pretty good
blast. So I guess it is possible that fixed wings do deflect some air
downward, though I've never felt it while flying hang-gliders. And
that's still not what makes wings work. Its one of the things that
makes them less efficient.

Wilbur Wright struggled with this very issue for months while
attempting to develop his propeller theory. And Wilbur's theory is that
propellers are not "screws", no or they fans. They're airfoils and not
rotating "aero planes". Not that you can't propel a plane or SkyCar
with a ducted fan, but thats reaction-thrust from my understanding. A
propeller is a wing traveling in a corkscrew path through air. Some of
the energy consumed by the prop makes lift and pulls the aircraft
forward. Some of the energy consumed by the prop pulls the air
backward. Developing a prop that puts enough energy into pulling the
plane forward and not just swishing the air around is the trick. Its
kinda like trying to turn a bolt with a wrench in space. Your arm can
turn the wrench in reference to you, or it can turn you in reference to
the wrench. In reality, space arms and propellers are pretty good at
doing some of both.

Wilbur and Orville used the largest props that would fit on their
airframe. In 1903 those were 8' 6" each and turned between 300 and 350
rpm depending on how hot the engine was. At an average of 8.56hp (the
engine only made 11.78hp for a few seconds dead cold), the twin props
produced an average of 96 lbs of thrust. or 11.22 lbs of thrust per hp.
Not bad on the first try.

Getting back to the original issue, here's another experiment. Hold a
peice of paper vertically. Grasp its lower edge with your thumb and
forefinger. Now let the paper drape over your wrist so that the free
edge hangs down and away from you. Now blow along the upper surface of
the paper. DO NOT let any part of your breath blow under the paper. See
what happens. Hmmmmmmm. What's holding that paper up? All of the air
that it, the sheet of paper, is throwing downward, all on its own,
because it instinctually "knows" that this is the correct behavior for
good little sheets of paper that get blown on? Hold your other hand
under the paper as you blow. Any air moving downward? And what's the
paper doing? Hmmm?

BTW, addressing my previous statement about AOA, some planes can
definately climb nose-down in upright flight. Amazing, but the B-52 is
one of them. I was reminded of this 2 days ago while watching the
Hitler Channel. Looks goofier than hell.

The original Wright 16" wind tunnel did not survive history. However,
the original balances and test airfoils did and are currently at the
Franklin Institute in Philly. Orville stored them in a box for years
and almost threw them out once. Thanks for shaking that box Orv. There
are numerous reproduction wind tunnels in museums. I'm planning to
build one myself. Nick Engler had blueprints for one on his website
http://first-to-fly.com/Adventure/Wo..._and_drift.htm

Harry "rotor-ramp-rat" Frey