Hi Dale,
Did the 123's windmilling engine have the blades at flat pitch?
I did engine off testing in my RV6A 160 lyc with 80 inch pitch metal
sensenich prop. The glide slope was not measured to be any difference whether I
windmilled the prop at best L/D speed or whether I pulled up slowed enough to
stop the prop turning and then returned to same speed.
Bernie Kerr, 6A sold, 9A rotary getting close
----- Original Message -----
Sent: Saturday, February 28, 2004 12:45
PM
Subject: [FlyRotary] Re: FW: [VAF Mailing
List] Engine Choice
Jim Sower wrote:
Yeah. Also, I
believe Tracy has answered all of his "questions" around tortionals and
props and dynos. Additionally, if there were problems, Tracy would
have encountered one in 1500 hrs.
The guy's statement around "... sprag clutches cause the prop to
freewheel in the event of engine failure putting the equivalent of a barn
door (HUGE drag compared to stopped prop) behind the airplane ..." is so
preposterous that it calls ALL of his other engineering into question.
Not so fast, Jim ....
A widmilling prop DOES have hugh
drag compared to a stopped one. An unfeatherable, windmilling prop
almost had me swimming in the Pacific Ocean near Wake Island many years
ago. The fact that the engine seized when a piston could no longer
reciprocate inside a missing cylinder ...was what saved my bacon. Once
it stopped, even though the props' blade angle was nowhere near feathered, the
drag reduction was so dramatic that we were able to level off from a forced
descent and keep the ship (a C-123B) in the air long enough to make it to
destination on the other engine.
When you think windmilling drag ...
think prop circle area, not just the blades cross section themselves. Square
yards of drag, not square ft.
His article sounds authoritative, but has all the intellectual allure of
Lamar's rantings that NACA ducts and Electric Water Pumps "... cannot
possibly work ...". Stick with Tracy. He has something
flying. This guy has nada.
I tend to like Tracy's
solution also. His hours in the air give him a lot of credibility.
Just a theory .... Jim S.
David Leonard wrote:
Dale
Smith