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Magic stuff . . .

 
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nuckolls.bob(at)aeroelect
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PostPosted: Tue Apr 24, 2018 7:14 pm    Post subject: Magic stuff . . . Reply with quote

At 07:12 PM 4/24/2018, you wrote:
Quote:
--> AeroElectric-List message posted by: Alec Myers <alec(at)alecmyers.com>

I lost track of which Bob was recommending annual WD-40 as a switch failure preventive prophylactic, and which Bob wasn’t.
Can someone advise?

The short answer is "no".

The longer answer is, check the engineering
data on any line of switches or relays you
might be considering for your project. You
will find a constellation of styles and
ratings. It will be a rare switch or relay
that is rated for less than TENS OF THOUSANDS
of operations at rated load.

Now, consider how heavily you are going to load
this device . . . pushing the ratings? Probably
not. So from an ELECTRICAL perspective, the
service life of this devices will be some factor
greater than rated. Then we consider mechanical
service life . . . which logically exceeds the
rated electrical service life.

Now, how many operations are you going to put
on this device every year? Based on your
anticipated service demands, how many flight
hours will you put on the switch before it's
at risk for end of life? Trust me, it's a BIG
number . . . so big in fact that and end of
life failure is exceedingly tiny if not
zero. You cannot wear out that device during
your life experience with the airplane.

Hmmmm . . . switches and relays get replaced
all the time. Yup . . . and probably for
reasons unrelated to actual operating cycles
on the device. Okay, what's the reason
for premature failure? It's probably a combination
of serval things . . . most of which you'll
have no control over.

Hmmmm . . . what's a poor owner operator to do?
Can't tell you without going through the kinds
of failure analysis that dominated the last
10 years of my career in GA. The analysis
was expensive, time consuming and seldom
revealed a cheap and dirty resolution. Some
failures were one-of events usually based
on some fabrication error . . . it took
5-6 weeks of pushing one poor customer's
airplane up the chain of time, talent
and resources before I talked the pilots
into letting me tape a 37 conductor ribbon
cable to the fuselage and past gaskets in
the baggage and passenger doors. With this
rig I was able to watch a constellation
of parameters in the tail while we climbed
to 41000 feet . . . one more time . . . in
search of the elusive failure.

Found a crimp pin in a pressure bulkhead feed
through that was not seated. The wire bundles
had to get cold and shrink enough to pull the
pin back and cause the failure to manifest.

That 10-cent error cost tens of thousands
to chase down.

What's this have to do with switches on your
panel? It's but one example of how root cause
for a mis-behavior can run the range from
observable broken wires, dripping water or
hydraulic fluid, temperature cycles combined
with ozone concentrations, . . . all the way
up to failures that would only manifest
at altitude after consuming about as much fuel
in one flight as my wife's Saturn consumed in
a year.

Go back and look at the engineering data for
the device. I've never seen a manufacturer
recommend any form of periodic maintenance . . .
much less squirt 'magic stuff' into the device's
cracks with some notion of improving service
life or, worse yet, 'refurbishing' a misbehaving
switch.

Back in the day, we had several cans of cleaners,
lubes, sealers, etc. on the workbench where we
repaired radio and television sets. It was always
gratifying to drive the mischief out of a rotary
switch, noisy volume control or arcing flyback
transformer with a squirt of magic stuff.

But we're talking about airplanes now. We're
talking about devices that have obviously failed
to meet service life predictions. Okay, now what?
What forces in physics are responsible? Will
'magic stuff' mitigate those forces . . .
probably not. Will they 'repair' the effects
or simply squeeze a few more operations out of
a device that is close to gross failure? Finally,
how do you KNOW that you've squirted the magic
stuff into the RIGHT location and that it
doesn't present a new hazard to functionality
if it gets into the WRONG location.

Finally, how hard is it to replace a $5 switch that's
held on the panel with one nut and wired with a
couple or three fast-ons? I used to recommend
that my seminar attendees take a sunny afternoon
and $50 worth of switches and replace everything
on the panel . . . just for the hell of it.

System reliability benefits far more from
preventative maintenance than it does from
magic stuff applied to a device that's already
begging for help.

One more example. One day at Beech, a sales
rep came out to pitch a particular kind of
magic stuff. I think it was called "Stabilant 22."

It was reputed, nay, demonstrated to improve the
quality of metallic connection between pins and
sockets in our harness connectors. So, we
piled engineering data, test reports, user
testimonials, etc. etc. against field service
experience on a fleet of thousands of airplanes
gathered over 50+ years.

Yeah, Stabilant 22 was pretty whippy stuff . . .
but expensive and labor intensive with a risk
for waste due to spillage and getting it on
the wrong surfaces. I could just see the faces
of our line techs when we handed each one a bottle
of magic stuff with a requirement to properly apply
to each connector before it was mated up.

Then, there was the question, what's the return
on investment? After some consideration, we deduced
that it was a 'fix' for a problem we didn't have.

So there your have the long answer. If any combination
of components on your airplane is crying out for
help, then replace on condition is the
lowest risk and probably the lowest cost approach
to risk management. WD40 is good for the kid's
tricycle that might sit out and get rained on
from time to time.






Bob . . .


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alec(at)alecmyers.com
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PostPosted: Wed Apr 25, 2018 5:40 am    Post subject: Magic stuff . . . Reply with quote

Thanks Bob! I shall continue with my present practice of carefully NOT spraying WD40 into every switch annually.

On Apr 24, 2018, at 11:13 PM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com> wrote:

At 07:12 PM 4/24/2018, you wrote:
Quote:


I lost track of which Bob was recommending annual WD-40 as a switch failure preventive prophylactic, and which Bob wasn’t.
Can someone advise?

The short answer is "no".

The longer answer is, check the engineering
data on any line of switches or relays you
might be considering for your project. You
will find a constellation of styles and
ratings. It will be a rare switch or relay
that is rated for less than TENS OF THOUSANDS
of operations at rated load.

Now, consider how heavily you are going to load
this device . . . pushing the ratings? Probably
not. So from an ELECTRICAL perspective, the
service life of this devices will be some factor
greater than rated. Then we consider mechanical
service life . . . which logically exceeds the
rated electrical service life.

Now, how many operations are you going to put
on this device every year? Based on your
anticipated service demands, how many flight
hours will you put on the switch before it's
at risk for end of life? Trust me, it's a BIG
number . . . so big in fact that and end of
life failure is exceedingly tiny if not
zero. You cannot wear out that device during
your life experience with the airplane.

Hmmmm . . . switches and relays get replaced
all the time. Yup . . . and probably for
reasons unrelated to actual operating cycles
on the device. Okay, what's the reason
for premature failure? It's probably a combination
of serval things . . . most of which you'll
have no control over.

Hmmmm . . . what's a poor owner operator to do?
Can't tell you without going through the kinds
of failure analysis that dominated the last
10 years of my career in GA. The analysis
was expensive, time consuming and seldom
revealed a cheap and dirty resolution. Some
failures were one-of events usually based
on some fabrication error . . . it took
5-6 weeks of pushing one poor customer's
airplane up the chain of time, talent
and resources before I talked the pilots
into letting me tape a 37 conductor ribbon
cable to the fuselage and past gaskets in
the baggage and passenger doors. With this
rig I was able to watch a constellation
of parameters in the tail while we climbed
to 41000 feet . . . one more time . . . in
search of the elusive failure.

Found a crimp pin in a pressure bulkhead feed
through that was not seated. The wire bundles
had to get cold and shrink enough to pull the
pin back and cause the failure to manifest.

That 10-cent error cost tens of thousands
to chase down.

What's this have to do with switches on your
panel? It's but one example of how root cause
for a mis-behavior can run the range from
observable broken wires, dripping water or
hydraulic fluid, temperature cycles combined
with ozone concentrations, . . . all the way
up to failures that would only manifest
at altitude after consuming about as much fuel
in one flight as my wife's Saturn consumed in
a year.

Go back and look at the engineering data for
the device. I've never seen a manufacturer
recommend any form of periodic maintenance . . .
much less squirt 'magic stuff' into the device's
cracks with some notion of improving service
life or, worse yet, 'refurbishing' a misbehaving
switch.

Back in the day, we had several cans of cleaners,
lubes, sealers, etc. on the workbench where we
repaired radio and television sets. It was always
gratifying to drive the mischief out of a rotary
switch, noisy volume control or arcing flyback
transformer with a squirt of magic stuff.

But we're talking about airplanes now. We're
talking about devices that have obviously failed
to meet service life predictions. Okay, now what?
What forces in physics are responsible? Will
'magic stuff' mitigate those forces . . .
probably not. Will they 'repair' the effects
or simply squeeze a few more operations out of
a device that is close to gross failure? Finally,
how do you KNOW that you've squirted the magic
stuff into the RIGHT location and that it
doesn't present a new hazard to functionality
if it gets into the WRONG location.

Finally, how hard is it to replace a $5 switch that's
held on the panel with one nut and wired with a
couple or three fast-ons? I used to recommend
that my seminar attendees take a sunny afternoon
and $50 worth of switches and replace everything
on the panel . . . just for the hell of it.

System reliability benefits far more from
preventative maintenance than it does from
magic stuff applied to a device that's already
begging for help.

One more example. One day at Beech, a sales
rep came out to pitch a particular kind of
magic stuff. I think it was called "Stabilant 22."

It was reputed, nay, demonstrated to improve the
quality of metallic connection between pins and
sockets in our harness connectors. So, we
piled engineering data, test reports, user
testimonials, etc. etc. against field service
experience on a fleet of thousands of airplanes
gathered over 50+ years.

Yeah, Stabilant 22 was pretty whippy stuff . . .
but expensive and labor intensive with a risk
for waste due to spillage and getting it on
the wrong surfaces. I could just see the faces
of our line techs when we handed each one a bottle
of magic stuff with a requirement to properly apply
to each connector before it was mated up.

Then, there was the question, what's the return
on investment? After some consideration, we deduced
that it was a 'fix' for a problem we didn't have.

So there your have the long answer. If any combination
of components on your airplane is crying out for
help, then replace on condition is the
lowest risk and probably the lowest cost approach
to risk management. WD40 is good for the kid's
tricycle that might sit out and get rained on
from time to time.



Bob . . .


- The Matronics AeroElectric-List Email Forum -
 

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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Kellym



Joined: 10 Jan 2006
Posts: 1548
Location: Sun Lakes AZ

PostPosted: Wed Apr 25, 2018 5:53 am    Post subject: Magic stuff . . . Reply with quote

Another side to the issue. WD-40 is essentially fish oil or a synthetic
clone of fish oil. It dries up over time and leaves a very sticky mess,
as well as attracting dirt.
If you insist on lubricating connections, ACF-50 or Corrosion X or just
contact cleaner are better alternatives.
The only use I have found for WD-40 around an airplane that doesn't
cause future problems is to use it as a belly cleaning solution.

Kelly

On 4/25/2018 6:38 AM, Alec Myers wrote:
Quote:


Thanks Bob! I shall continue with my present practice of carefully NOT spraying WD40 into every switch annually.


Quote:
> I lost track of which Bob was recommending annual WD-40 as a switch failure preventive prophylactic, and which Bob wasn’t.
> Can someone advise?

The short answer is "no".


- The Matronics AeroElectric-List Email Forum -
 

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

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Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD
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