Declared first emergency last week

Morgans wrote:

"brian whatcott" wrote

There's one element that is very troubling: the cable break in the
middle. I am supposing that the bowden has triple internal helical
wires as low friction standoffs - and that repeated motion against a
wire cut the cable.

That shouldn't happen....

Unless the run is perfectly straight, any bend will flex the internal
cable each time it moves. Metal fatigue still happens, given enough time.

If a plane is flown twice a week for thirty years, there could be
30 X 52 X 2 X 5 cycles on the throttle - and that's a highball estimate.
16000 cycles should not fatigue a wire, should it?

Brian W

On Sep 9, 7:35*am, brian whatcott wrote:
Morgans wrote:

"brian whatcott" wrote

There's one element that is very troubling: the cable break in the
middle. I am supposing that the bowden has triple internal helical
wires as low friction standoffs - and that repeated motion against a
wire cut the cable.

That shouldn't happen....

Unless the run is perfectly straight, any bend will flex the internal
cable each time it moves. *Metal fatigue still happens, given enough time.

If a plane is flown twice a week for thirty years, there could be
30 X 52 X 2 X 5 cycles on the throttle - and that's a highball estimate.
16000 cycles should not fatigue a wire, should it?

Brian W

The cable failure I had was to carb heat on an old Mooney Ranger, and
the failure was right at the carb. Finding a serious rubbing point
within the cable run itself seems unlikely, but that is what happened
to the OP.

If a plane is flown twice a week for thirty years, there could be
30 X 52 X 2 X 5 cycles on the throttle - and that's a highball estimate.
16000 cycles should not fatigue a wire, should it?

We replaced our prop adjustment cable in the Pathfinder this year. It was
probably the original cable from 1974. It was getting stiffer and stiffer
over time.

Upon removal it was obvious that a few strands of the sheathing had broken,
and were scraping on the cable every time we moved the blue lever. How
this happened is a mystery, but after 25 years we figured it didn't owe us
anything. (Although it is a real SOB to change...)

The OP did a great job getting the plane down safely.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
Ercoupe N94856
www.AlexisParkInn.com
"Your Aviation Destination"

"Jay Honeck" wrote

We replaced our prop adjustment cable in the Pathfinder this year. It was
probably the original cable from 1974. It was getting stiffer and stiffer
over time.

Upon removal it was obvious that a few strands of the sheathing had
broken, and were scraping on the cable every time we moved the blue lever.
How this happened is a mystery, but after 25 years we figured it didn't
owe us anything. (Although it is a real SOB to change...)

Yep. Some things will not last forever, and cables are one of them. Once
they get enough age and use and age on them, switch them out, as part of a
good preventative maintenance program. After all, what good is keeping fuel
in the tank, airspeed under the wings, and a good running engine and
airframe, if you can't control the damn thing! g That is one important
piece of twisted up steel, going from your hand to the engine and prop.

The OP did a great job getting the plane down safely.

No argument from me on that point!
--
Jim in NC

Some things will not last forever, and cables are one of them. Once they
get enough age and use and age on them, switch them out, as part of a good
preventative maintenance program.

I always wonder how to implement something like this, and with which items.

Control cables, for example, are obviously critical -- yet I don't recall
ever hearing about them being changed on condition, let alone preemptively,
even on our 61 year old Ercoupe. Sure, they're inspected every year, and
occasionally adjusted, but apparently they never wear out? Yet surely they
must, someday.

Just another one of those things you think about when you're flying an
antique aircraft. Right up there with "golly, that wing is only held on
with two bolts", and "gee, I wonder how many bouts of turbulence a
six-decade-old wing spar can withstand?"

:-)
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
Ercoupe N94856
www.AlexisParkInn.com
"Your Aviation Destination"

In article pQ_pm.36760$5n1.23712@attbi_s21,
"Jay Honeck" wrote:

Some things will not last forever, and cables are one of them. Once they
get enough age and use and age on them, switch them out, as part of a good
preventative maintenance program.

I always wonder how to implement something like this, and with which items.

Control cables, for example, are obviously critical -- yet I don't recall
ever hearing about them being changed on condition, let alone preemptively,
even on our 61 year old Ercoupe. Sure, they're inspected every year, and
occasionally adjusted, but apparently they never wear out? Yet surely they
must, someday.

Just another one of those things you think about when you're flying an
antique aircraft. Right up there with "golly, that wing is only held on
with two bolts", and "gee, I wonder how many bouts of turbulence a
six-decade-old wing spar can withstand?"

:-)

How about, "Those wings are only held on with two pins *which I just
installed myself an hour ago*."

Or, "Gee, those pins that hold the body to the wings are smaller than my
thumb, and there's only two on each side."

Flying an aircraft you assemble yourself each time you fly it is much
like flying an antique aircraft in that respect. (Flying an antique you
assemble each time you fly is even better yet.)

--
Mike Ash
Radio Free Earth
Broadcasting from our climate-controlled studios deep inside the Moon

Jay Honeck wrote:
/snip/
Control cables, for example, are obviously critical -- yet I don't
recall ever hearing about them being changed on condition, let alone
preemptively, even on our 61 year old Ercoupe. Sure, they're inspected
every year, and occasionally adjusted, but apparently they never wear
out? Yet surely they must, someday.
/snip/

Jay,

Control cables are absolutely changed out on condition. They will tend
to fray where they pass over pulleys, especially if the cable tension is
a bit loose (it will tend to "bounce" against the pulley), or the pulley
doesn't turn as freely as it should. During maintenance checks, a
mechanic will run their fingers over all cables at these locations, and
any broken strands will be felt, as they tend to stick out. Not super
common on light GA aircraft, but not at all unheard of. Corrosion can
also be a problem. Advisory Circular 43.13 has an entire section
devoted to cable inspection and condition.

Happy Flying!
Scott Skylane

On 2009-09-10, Jay Honeck wrote:
Just another one of those things you think about when you're flying an
antique aircraft. Right up there with "golly, that wing is only held on
with two bolts", and "gee, I wonder how many bouts of turbulence a
six-decade-old wing spar can withstand?"

Or... "Good grief, the wing is only held together by 64 year old glue!"

The joys of worrying about wood wings :-)

Thanks Jay!

"Jay Honeck" wrote in
news:QUOpm.43737$la3.10515@attbi_s22:

If a plane is flown twice a week for thirty years, there could be
30 X 52 X 2 X 5 cycles on the throttle - and that's a highball
estimate. 16000 cycles should not fatigue a wire, should it?

We replaced our prop adjustment cable in the Pathfinder this year. It
was probably the original cable from 1974. It was getting stiffer and
stiffer over time.

Upon removal it was obvious that a few strands of the sheathing had
broken, and were scraping on the cable every time we moved the blue
lever. How this happened is a mystery, but after 25 years we figured
it didn't owe us anything. (Although it is a real SOB to change...)

The OP did a great job getting the plane down safely.