May 2005 Additions to the rec.aviation "Rogues Gallery"...

May was an active month for the Gallery!

Click on http://www.alexisparkinn.com/rec_aviation.htm to see:

*- From Sacramento, CA, more pix of Jack Allison's beautiful Piper
Arrow...

*- From the United Kingdom, pix of Chris Blythe's French-built Wassmer
52...

*- From Manassas, VA, more pix of Bryan Chaisone's way cool Robinson
R22 helicopter...

*- From Chicago, IL, pix of Paul Hekman's fabulour Piper Arrow...

*- From St. Charles, MO, pix of Brian Larkin's awesome Piper Archer...

*- From Chetek, WY, pix of Scott Lifkin's slick Corben Junior Ace...

*- From Sandpoint, ID, pix of the new panel in Mike Rapoport's Helio
Courier...

What is this Rogues Gallery, you ask? It's a photo webpage created
exclusively for users of these rec.aviation newsgroups, designed and
maintained so that we can all have a better idea of who (and what) the
regular users of this group look like.

About to respond to a guy's post, and wondering what he flies? Take a
peek at the Gallery -- he's probably listed in there!

Want pix of YOUR pride & joy out there, for all of us to drool on?
Simply send me a few (4 - 8) pix of your bird, along with some
narrative about yourself (where you're based, how long you've been
flying, how long on the newsgroups, etc.), and I'll get 'em up ASAP!
Send 'em to

Blue skies!
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

Jack Allison: what happens when the rpm runs in the yellow band of the
tach? [you know, you can get rid of that pesky yellow segment by
installing a three-bladed prop :-)) ]

Mike R: How about a lesson on Courier fuel management?

john smith wrote:

Jack Allison: what happens when the rpm runs in the yellow band of the
tach? [you know, you can get rid of that pesky yellow segment by
installing a three-bladed prop :-)) ]

Um...nothing because the prop doesn't get run there. Three basic power
settings that I was taught: 1) Takeoff: Everything full forward 2)
1000 AGL: 25 squared for the climb 3) Cruise: 21-24 inches, 2400 RPM.

How does the 3-bladed prop get rid of the yellow arc?

--
Jack Allison
PP-ASEL-IA Student
Arrow N2104T

"When once you have tasted flight, you will forever walk the Earth
with your eyes turned skyward, for there you have been, and there
you will always long to return"
- Leonardo Da Vinci

(Remove the obvious from address to reply via e-mail)

Um...nothing because the prop doesn't get run there. Three basic power
settings that I was taught: 1) Takeoff: Everything full forward 2) 1000
AGL: 25 squared for the climb 3) Cruise: 21-24 inches, 2400 RPM.

Now that you've had some time to diddle around, what kind of speed are you
seeing at, say, 23 squared, Jack?

Also, are you and Jim Weir gonna "convoy" to Iowa City en route to OSH?

And you really need to get on Jav (Henderson) and get him to fly to OSH with
you guys this year, too! He appears to be coming up with excuses like
"family" and "work" that simply can't be allowed to interfere with essential
things like Oshkosh in July!

:-)
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

Jay Honeck wrote:

Now that you've had some time to diddle around, what kind of speed are you
seeing at, say, 23 squared, Jack?
Need more diddle time for this stuff. It's on my list though. For
flying instrument stuff like holds and approaches, I can tell you that
18 inches/2400 RPM works out to approx. 100 mph and gives my brain more
of a chance to keep up with the plane :-)


Also, are you and Jim Weir gonna "convoy" to Iowa City en route to OSH?
That's the plan. Jim and I have pinged each other a few times and I
need to actually fly the 20 minute hop to Grass Valley and meet
him...another "on the list" thing :-)

And you really need to get on Jav (Henderson) and get him to fly to OSH with
you guys this year, too! He appears to be coming up with excuses like
"family" and "work" that simply can't be allowed to interfere with essential
things like Oshkosh in July!
Ok, I'll take the challenge. Hey Jav H, be a man, come to Oshkosh this
year or Jay says he'll release several virus attacks against your
servers, he'll load up so many pictures in the Rogue's gallery that you
won't have any storage capacity, and we'll all create so much traffic
that your servers will explode in huge fireballs. Come on man, an Arrow
sandwiched between two straight leg Skylanes in a flight of three...the
poor newbie Piper owner will have girly man high wings all around him!

There, how'd I do Jay? :-) If Jav doesn't read this thread, perhaps we
can elevate the abuse to it's own thread.


--
Jack Allison
PP-ASEL-IA Student
Arrow N2104T

"When once you have tasted flight, you will forever walk the Earth
with your eyes turned skyward, for there you have been, and there
you will always long to return"
- Leonardo Da Vinci

(Remove the obvious from address to reply via e-mail)

Jack Allison wrote:
How does the 3-bladed prop get rid of the yellow arc?

The yellow arc in the middle of the green arcs is an area of
"resonance". That is, it can cause vibration in the airframe. With the
two blade prop operating in that rpm range, a frequency exists where the
whole airplane is in synch. Ever see the video of the Tacoma Narrows
bridge oscillating in the wind? The structure becomes "fluid-like" and
distorts in proportion to the amplitude/strength of the wave.
The three bladed prop has a resonant frequency outside that of the
airframe/engine/prop system.
This is the best answer I can give. I understand it, I may not be
explaining well.
I believe Jim Weir could probably give you a better expaination. He's a
teacher and very good at reducing technical things to simple english.

It isn't an airframe issue, it is an engine-prop combination issue. It
is a high frequency (about 220 Hz or a little below middle C on a
piano) torsional resonance involving the crankshaft and the propellor.


The mode of damaging vibration is such that a rotating observer sitting
on the also-rotating spinner would see the back of the crankshaft
rotationally deflecting to-and-fro while also seeing the propeller tips
going fro-and-two. The spinning observer gets a smooth ride.

Props are highl;y stressed. A spinning propeller (wood or metal) is
almost 1/8 of an inch larger in diameter than when standing still. The
prop blade leading and trailing edges accumulate the most fatigue
damage from this 220 Hz bending mode.

OK - the mode shape definition is a little honky but that is the best
way I know to describe it.

nrp wrote:
It isn't an airframe issue, it is an engine-prop combination issue. It
is a high frequency (about 220 Hz or a little below middle C on a
piano) torsional resonance involving the crankshaft and the propellor.


The mode of damaging vibration is such that a rotating observer sitting
on the also-rotating spinner would see the back of the crankshaft
rotationally deflecting to-and-fro while also seeing the propeller tips
going fro-and-two. The spinning observer gets a smooth ride.

Props are highl;y stressed. A spinning propeller (wood or metal) is
almost 1/8 of an inch larger in diameter than when standing still. The
prop blade leading and trailing edges accumulate the most fatigue
damage from this 220 Hz bending mode.

OK - the mode shape definition is a little honky but that is the best
way I know to describe it.

nrp, your posts on this topic are always illuminating.

I've heard the yellow-arc issue described as "detuning the crankshaft
counterweights" or some such.

If the counterweights are involved, and the the torsional vibration issue is a
propeller/cranskshaft phenomenon, do you change anything in the crankshaft
counterweights when you change the propeller?

Dave