Long-EZ Bird Strike

On Thu, 30 Jun 2005 11:19:37 -0400, Kevin O'Brien
kevin@org-header-is-my-domain-name wrote:

But they have wood cores. I had thought he made all-compo ones. Guess not.

I'm not an aerodynamics engineer, or any kind of engineer, I just read
a lot and am cursed with this memory recall that can remember
portions of LOTS of stuff, but not necessarily the original source of
the recall.

I read somewhere that metal props can and do pick up certain
frequencies of vibration and can amplify the vibrations under the
right circumstances. When this happens, the vibrations can fracture a
portion of the prop blade and sometimes the entire blade.

Cutting down a metal prop can bring it into a resonant frequency that
the prop did not previously experience.

At the opposite end of the vibration spectrum is the wood prop which
actually dampens vibration.

Somewhere in the middle are composite props. Perhaps closer to the
wood end of the vibration spectrum would be the composite wood/carbon
fiber props, I'm guessing.

I did a little searching on Google about this subject and found
information that indicates Longs, Vari's, Velocities and Cozy's have
suffered a number of prop failures for a variety of reasons.

I don't have the information to know whether they suffer more prop
failures than tractor prop airplanes as a group. But having the prop
on an extension, which a number of the genre do, I would think would
make the prop more sensitive to turbulent air, regardless what it's
made of.

Corky Scott

Corky Scott wrote:

Lastly, as a Long EZ builder, owner, and flyer whose experience with
EZs dates back to the early Rutan days, my response to the scenario
and images depicted can be summed up in two words, Holy ****!

You weren't aware of why pusher props make more noise than tractor
props? See below for the scientific explanation.


Of course I am aware of why pusher props make more noise than tractor
props. My "Holy ****" comment was about the EZ pilot's harrowing
experience, not about anything you said in your post.

David Odum - email: David at AirplaneZone dot com

The prop in question is an old style Performance Prop. It does have
many laminations. About 24 I think, I have one hanging from the roof of
my study. Its safest there. They no longer wrap the out portion of the
blade as it has caused problems. If its gonna break it will right there.

Scott

Corky Scott wrote:
On Tue, 28 Jun 2005 18:52:56 -0700, Ron Wanttaja
wrote:


Hi Ron, I wonder what the evidence is that it was a bird strike? I don't
see any blood and guts anywhere.

I noticed that, too. Something else could have gone through the blade, but I
don't know if a bolt or nut would do this kind of damage. The guy may have
cleaned it off already....

Ron Wanttaja


Here's another couple of data points: The prop appears to be made
from a solid blank, not laminated from numerous strips.

I read a long time ago that the props on the EZ type aircraft run in
such turbulence that it's recommended they use wooden props only. The
turbulence is unavoidable in that it's the result of the prop passing
through the lift created by the trailing edge of the wing. There also
may be exhaust pulses to whap through as well. That's why the EZ's
have that characteristic buzz when they fly by. In fact all pushers
seem to sound that way.

Wooden props are supposed to **DAMPEN** vibration.

Interestingly, the only part of the information suggesting a bird
strike is the title. Nothing in the storyline claims that or suggests
it. It certainly isn't impossible for birds to be at 9,500, just a
lot less likely than closer to the ground. It isn't migration time...

Corky Scott

I am working off dim memories here, but ISTR that Klaus had vibration
problems with an experimental (in the deepest sense of the word)
3-bladed prop and that he recommended 2-blades only for the EZ series
aircraft.

Many pushers now use 3 bladed composite props. The most popular for the
180 HP and up crowd is the Catto Prop, maple laminate core with 25 to 36
layers of fiberglass over the wood with a 1/2" aluminum mounting plate
embedded on one side. He makes them for 100 to 600 HP engines. They
are known to be bullet proof.

The lower power pushers use 2 blades because they can get away with it
and they are much cheaper than 3 bladed fixed pitch props. The higher
the engine HP the more blade you need. A two bladed prop on a 200 HP
engine is just to long for a pusher, so 3 blades are required.

Scott

Richard Riley wrote:
On Sat, 02 Jul 2005 22:19:43 -0600, Scott Derrick
wrote:

: I am working off dim memories here, but ISTR that Klaus had vibration
: problems with an experimental (in the deepest sense of the word)
: 3-bladed prop and that he recommended 2-blades only for the EZ series
: aircraft.
:
:Many pushers now use 3 bladed composite props. The most popular for the
:180 HP and up crowd is the Catto Prop, maple laminate core with 25 to 36
: layers of fiberglass over the wood with a 1/2" aluminum mounting plate
:embedded on one side. He makes them for 100 to 600 HP engines. They
:are known to be bullet proof.
:
:The lower power pushers use 2 blades because they can get away with it
:and they are much cheaper than 3 bladed fixed pitch props. The higher
:the engine HP the more blade you need. A two bladed prop on a 200 HP
:engine is just to long for a pusher, so 3 blades are required.

I've had 2 blade props on 540 Berkuts from Props, Inc and Klaus.
They've worked fine. 3 blade Catto's are a little faster than the 2
blades from Props Inc, but slower than the ones from Klaus.

2 blade props are more effecient than 3. In fact, 1 blade is, in
theory, more effecient than 2, they're just hell on engine bearings
(the Germans tried them in WW2).

I saw a picture years ago of a one-blade prop and it had a counterweight
on the other side. This shouldn't be a lot harder on the bearings, but
you would have some aysmmetrical loading from the asymmetric thrust. It
sure looked ugly though!


Matt

Corky

The pusher prop/engine on the 0-2/337 didn't have any problems that I
was ever aware of. Nothing in Pilots Handbook. Aluminum props on both
front and rear engines.

Rear prop was in wing turblance, exhaust, etc.

Biggest problem was on gravel strips and nicks.

Big John
`````````````````````````````````````````````````` `````````````````````````````````````````````````` ````````

On Wed, 29 Jun 2005 10:50:48 -0400, Corky Scott
wrote:

On Tue, 28 Jun 2005 18:52:56 -0700, Ron Wanttaja
wrote:

Hi Ron, I wonder what the evidence is that it was a bird strike? I don't
see any blood and guts anywhere.

I noticed that, too. Something else could have gone through the blade, but I
don't know if a bolt or nut would do this kind of damage. The guy may have
cleaned it off already....

Ron Wanttaja

Here's another couple of data points: The prop appears to be made
from a solid blank, not laminated from numerous strips.

I read a long time ago that the props on the EZ type aircraft run in
such turbulence that it's recommended they use wooden props only. The
turbulence is unavoidable in that it's the result of the prop passing
through the lift created by the trailing edge of the wing. There also
may be exhaust pulses to whap through as well. That's why the EZ's
have that characteristic buzz when they fly by. In fact all pushers
seem to sound that way.

Wooden props are supposed to **DAMPEN** vibration.

Interestingly, the only part of the information suggesting a bird
strike is the title. Nothing in the storyline claims that or suggests
it. It certainly isn't impossible for birds to be at 9,500, just a
lot less likely than closer to the ground. It isn't migration time...

Corky Scott