Emergency Landing in a COZY MKIV

"Robert M. Gary" wrote:
Marc J. Zeitlin wrote:
Folks:

For those interested, we had an experience this weekend in our COZY
MKIV when the propeller decided to proceed along a different path than
the rest of the airplane. You can read the details at:

http://www.cozybuilders.org/Desert_Center/

I didn't see the cause of the failure (I'm sure it was there but there
was a lot to read through). Could this have been one of the Hartzell
recalled hubs?

-Robert

No cause identified yet. Catto three blade (composite?). Possible
blade separation or torque issue due to change in climate. Unknown at
this time. Pusher configuration.

Ron Lee

Marc J. Zeitlin wrote:
For those interested, we had an experience this weekend in our COZY
MKIV when the propeller decided to proceed along a different path than
the rest of the airplane.

First, glad to hear you came out of it OK.

Second, after looking at some satellite pictures, I agree that your prop
probably landed 0.7854 km east of the exact middle of nowhere. But it
still might be worth mentioning to one of the rangers at Joshua Tree.
He or she may well confirm that nobody actually goes to that area, but
you never know. That might be the location of the secret air-conditioned
cabin where the rangers go to drink beer when they are tired of dealing
with tourists. Or maybe they know of a group planning to hike through
that area and could ask them to keep an eye out. The hikers may not be
able to schlep the prop back out, but they might be able to provide co-
ordinates and maybe a digital photo of the hub.

Also, on the satellite photos, there appears to be a large strip mine
just southeast of the red square you put on the map, outside the park
boundary. It looks somewhat disused in the photos, and a little
Googling says it was an iron mine run by Kaiser and shut down in the
early 1980s. There is now apparently a privately-run prison there.
It may be too far southeast, but that might be another place to ask
about your prop.

I realize that both of these ideas are long shots, but you never know.
It might help answer the question of why your prop left.

Matt Roberds

Ron Lee wrote:

Congrats on a safe landing. Do keep us informed on actual cause.

I don't think that it will ever be possible to say absolutely, but
after a day of discussions on the COZY and canard-aviators mailing
list, and a ton of email from many experts (Burt Rutan and Mike
Melvill, both of whom I work for, included), the consensus (with which
I agree) is that the prop bolt torque was low, causing bolt failure.

For Mike Regish, yes, the bolts were safety wired, but as Bob Moore
points out, with a wood core prop that doesn't necessarily mean diddly
:-).

.... I also have a Catto three blade prop on an RV-6A. The
"undertorqued" option seems unlikely since you no doubt can
properly torque bolts.

You know, however smart, qualified, and wonderful a person may or may
not be, mistakes can be made. I know that I make them at least my
fair share. I might have screwed up in my torqueing technique; I
might have had one or two bolts that were bottomed out; I might have
had them loosen due to temperature/humidity changes; or who knows what.

Is there a chance that a change in humidity from your normal
location caused a change in torque?

Well, I've been out here in the desert for over a year now, but it's
possible that even when I THOUGHT I was testing the REAL torque, I
wasn't, since I didn't loosen them and retighten them - I just pushed
on the torque wrench.

I will heretofore be checking torque at every oil change, rather than
only at the condition inspection.

Finding the prop could answer a lot of questions.

It could, but this is the classic needle in the haystack. No roads
nearby at all. To me, it's not even remotely worth the effort to find.

--
Marc J. Zeitlin
http://www.cozybuilders.org/
Copyright (c) 2006

Richard Riley wrote:

When you opened the throttle with the prop missing, did the engine go
to really, really high RPM's (like redline plus) on partial throttle?

A number of folks have asked this question privately, and the answer
is (as far as I know) no, it did not. The throttle setting was low
already and I brought it back almost to idle as soon as I heard the
"BANG". I don't believe that the RPM's ever went above standard
cruise levels - about 2600-2700 RPM.

Here's where an engine analyzer with recording capability would be
useful, eh? I was thinking of getting the Dynon......

--
Marc J. Zeitlin
http://www.cozybuilders.org/
Copyright (c) 2006

"Richard Riley" wrote in message
...
On Sun, 17 Dec 2006 06:00:58 GMT, "Marc J. Zeitlin"
wrote:

Marc - if you happen to remember...

When you opened the throttle with the prop missing, did the engine go
to really, really high RPM's (like redline plus) on partial throttle?

That was my first thought. You would have thought the revs hit the moon!

------------------------------------------------
DW