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Adrenalin rush



 
 
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  #11  
Old September 19th 05, 06:20 PM
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Everett M. Greene wrote:
: Now, if there are any EEs present, perhaps they can explain
: why aircraft radios tend to fail in this manner whereas
: nothing much of anything else in the electronic world fails
: in a manner to produce heat and smoke. Are avionics units
: designed so close to the components' limits to cause this
: failure mode? I can understand a transmitter going up in
: smoke (while transmitting), but a receiver?

I'll take a stab at it... Probably a big reason why avionics fail like
that because they're older than most electronics. They're used for a longer period of
time so they can suffer individual component failures. "Normal" electronics tend to
get toss earlier, so their failures are more likely due to construction flaws.

They're also packaged very tightly, and cannot afford much overdesign that
would cause additional weight. Also, the environment they operate in is extremely
harsh... *huge* temperature/humidity swings, ridiculous vibration exposure, etc.

That's why I was singularly unimpressed with the internal build quality of the
Michel slide-in replacement radios. They're built with standard DIPs, through-hole
components, ribbon cables, and general run-of-the-mill consumer components. Minimal
strain relief and anti-chafing assembly. Makes for a less expensive unit, but I'm
sure they're more likely to wear/chafe than a well-built unit.

-Cory

--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

  #12  
Old September 19th 05, 06:28 PM
Dan Luke
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"Everett M. Greene" wrote:

Now, if there are any EEs present, perhaps they can explain
why aircraft radios tend to fail in this manner whereas
nothing much of anything else in the electronic world fails
in a manner to produce heat and smoke. Are avionics units
designed so close to the components' limits to cause this
failure mode? I can understand a transmitter going up in
smoke (while transmitting), but a receiver?


Receivers still contain amplifiers, power regulating transistors, resistors,
diodes, etc. in their circuitry. Failures at the discrete component level
can produce thermal events without increases in main power loads above
circuit breaker limits.

--
Dan
C-172RG at BFM


  #13  
Old September 19th 05, 06:40 PM
dlevy
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I had something very similar happen very recently.

On climbout, vfr (squaking 1200), I smelled something burning - a very
strong smell. I turned back to the airport and just a quickly as it came
the smell went away. No obvious panel problems - no breaker tripped - and
the smell stopped. I turned around again and continued on. As I got within
radar contact of home base, approach couldn't pick me up. The narco
transponder appeared to be working fine. A resister in the transponder
burned up.

Adding to the adrenalin rush was the fact that there was so much traffic at
the class D airport I couldn't even get a chance to let the tower know I had
smoke in the cockpit. This was in Houma, LA which is the closest open
airport to New Orleans. There were airplanes *everywhere*.



"Wizard of Draws" wrote in message
news:BF524628.32285%jeffbREMOVE@REMOVEwizardofdraw s.com...
September 17, 2004 1:00 1.3 hrs. (.2 actual)

It was an overcast morning that cleared somewhat to scattered clouds
around
5 and 6 thousand. Steve M. and I had plans to get a little actual on the
way
to Thompson-Mcduffie (KHQU), and possibly log an approach or two. After I
filed and pre-flighted, we hopped in and contacted Atlanta Approach to
open
our flight plan while we sat on the ground. As we sat there, Steve
discovered that we had power to our #2 radio, but no display. Not a flight
ending squawk, but annoying.

After getting our clearance direct HQU at 3000, expect 5000 after 10
minutes, void if not off in 10, we went wheels up from 22 and departed the
pattern from midfield on course 120. As soon as we reached 3000 they
cleared
us to 5000, where we began to run into the clouds. After I leveled off and
setup for cruise, we had a few minutes to enjoy looking at the inside of
the
clouds. When we reached the middle of Lake Lanier, the clouds gave way and
we had a pretty hazy view in front of us.

Then we smelled it. A sharp electrical smell that told us something was
burning and not quite right. Steve quickly turned off the misbehaving #2
radio. The smell got stronger, but there was no visible smoke. A moment
later, when the realization hit home that we might have a serious problem,
I
keyed the mike to tell Atlanta Center that we smelled smoke, may have a
developing issue with our #2 radio, and that we wanted to divert to Athens
as a precaution. He answered immediately that Gainesville was our nearest
airport, and asked if we were declaring an emergency, can we maintain our
current altitude. I replied affirmative on the altitude but we didn't have
an emergency yet, so we just wanted vectors to Gainesville. "OK, turn left
heading 050, and it will be 11 miles at your 12 o'clock." Then he gave us
the pertinent airport info and handed us off to Atlanta Center on 134.8,
telling us that they were aware of our situation. They instructed us to
descend and maintain 3700. Shortly after we arrived there, he cleared us
to
land on the runway of our choice.

By now we were directly over the airport, so we canceled IFR, alerted GVL
UNICOM of our situation and dropped into the pattern where another plane
on
base leg terminated his approach to get out of our way. A pretty gusty
crosswind made for a roller coaster style approach, but we made it down
without bending any metal.

After we parked, we tried to pull the #2 radio to confirm our suspicions
that it was the source of our problem, but we didn't have an Allen wrench
and the shops on the field were all closed. So we called Randall and he
sent
Steve's son Ryan in a 172 with a set that turned out to be too short to be
any good. So we climbed in anyway and didn't turn on the #2 on the way
home
while Ryan flew back in loose formation with us. When Steve pulled out the
radio after we landed at 47A, it was very apparent from the strong smell
coming out of the box that something had burnt inside. Thankfully, it
didn't
develop into anything more serious, whether by luck or turning it off as
quickly as we did.
--
Jeff 'The Wizard of Draws' Bucchino

Cartoons with a Touch of Magic
http://www.wizardofdraws.com

More Cartoons with a Touch of Magic
http://www.cartoonclipart.com



  #14  
Old September 19th 05, 06:57 PM
Peter R.
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dlevy wrote:

Adding to the adrenalin rush was the fact that there was so much traffic at
the class D airport I couldn't even get a chance to let the tower know I had
smoke in the cockpit.


I would imagine that a few "Maydays," regardless of the fact that when you
begin you might step on someone else's broadcast, will get you a quiet
frequency.

--
Peter
























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  #15  
Old September 19th 05, 08:43 PM
Marco Leon
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Hmmm, maybe they're on to something. When was the last time you had a
"general run-of-the-mill" consumer product start smoking on you?? ;-)

Seriously, another question for you EE folks: are more modern components of
a better quality in that they don't need a robust surrounding support
structure to prevent catastrophic failures?

Marco Leon


wrote in message
...
Everett M. Greene wrote:
: Now, if there are any EEs present, perhaps they can explain
: why aircraft radios tend to fail in this manner whereas
: nothing much of anything else in the electronic world fails
: in a manner to produce heat and smoke. Are avionics units
: designed so close to the components' limits to cause this
: failure mode? I can understand a transmitter going up in
: smoke (while transmitting), but a receiver?

I'll take a stab at it... Probably a big reason why avionics fail like
that because they're older than most electronics. They're used for a

longer period of
time so they can suffer individual component failures. "Normal"

electronics tend to
get toss earlier, so their failures are more likely due to construction

flaws.

They're also packaged very tightly, and cannot afford much overdesign that
would cause additional weight. Also, the environment they operate in is

extremely
harsh... *huge* temperature/humidity swings, ridiculous vibration

exposure, etc.

That's why I was singularly unimpressed with the internal build quality of

the
Michel slide-in replacement radios. They're built with standard DIPs,

through-hole
components, ribbon cables, and general run-of-the-mill consumer

components. Minimal
strain relief and anti-chafing assembly. Makes for a less expensive unit,

but I'm
sure they're more likely to wear/chafe than a well-built unit.

-Cory

--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************




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  #16  
Old September 20th 05, 12:38 AM
Wizard of Draws
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On 9/19/05 1:40 PM, in article ,
"dlevy" wrote:

I had something very similar happen very recently.

On climbout, vfr (squaking 1200), I smelled something burning - a very
strong smell. I turned back to the airport and just a quickly as it came
the smell went away. No obvious panel problems - no breaker tripped - and
the smell stopped. I turned around again and continued on. As I got within
radar contact of home base, approach couldn't pick me up. The narco
transponder appeared to be working fine. A resister in the transponder
burned up.

Adding to the adrenalin rush was the fact that there was so much traffic at
the class D airport I couldn't even get a chance to let the tower know I had
smoke in the cockpit. This was in Houma, LA which is the closest open
airport to New Orleans. There were airplanes *everywhere*.


I wouldn't have continued on if I were you. Obviously it worked out for you,
but we know that something had to create that smell, and it might have been
the first link in the chain of events that led to an unhappy ending.
Breaking that chain may not be possible after you've had that first chance.
--
Jeff 'The Wizard of Draws' Bucchino

Cartoons with a Touch of Magic
http://www.wizardofdraws.com

More Cartoons with a Touch of Magic
http://www.cartoonclipart.com

  #17  
Old September 20th 05, 10:04 AM
David Cartwright
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"Marco Leon" mmleon(at)yahoo.com wrote in message
...
Hmmm, maybe they're on to something. When was the last time you had a
"general run-of-the-mill" consumer product start smoking on you?? ;-)


Oh, I've had a couple recently. My dad bought an electric light that
contained a transformer, which did the blue smoke thing, and the CD-ROM
drive in my sister's PC did the same the other week (I've had them fail, but
never in a combusting kind of way!). And I've lost count of the number of
power supplies in computer equipment that have exuded smoke over the years.

D.


  #18  
Old September 20th 05, 07:07 PM
Everett M. Greene
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"David Cartwright" writes:
"Marco Leon" mmleon(at)yahoo.com wrote
Hmmm, maybe they're on to something. When was the last time you had a
"general run-of-the-mill" consumer product start smoking on you?? ;-)


Oh, I've had a couple recently. My dad bought an electric light that
contained a transformer, which did the blue smoke thing, and the CD-ROM
drive in my sister's PC did the same the other week (I've had them fail, but
never in a combusting kind of way!). And I've lost count of the number of
power supplies in computer equipment that have exuded smoke over the years.


I've had numerous power supply failures in (ground-based)
devices over the years and have never had any smoke from
any of them. They just quit working...

There is a difference between linear and switching power
supplies. The latter are most likely going to fail
quietly whereas the former can very well smoke something
when they fail.

A thought occurs to me regarding avionics failures: The
confined environment of small airplane cabins and the
close proximity to the avionics devices may cause the
even a miniscule amount of odor to be noticed whereas
on the ground nobody may be close at the time of failure
and any odor goes unnoticed.
  #19  
Old September 23rd 05, 10:47 PM
Rob
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Wizard of Draws wrote:
"dlevy" wrote:
I had something very similar happen very recently.

I wouldn't have continued on if I were you. Obviously it worked out for you,
but we know that something had to create that smell, and it might have been
the first link in the chain of events that led to an unhappy ending.
Breaking that chain may not be possible after you've had that first chance.


Not meant to criticize, but isn't dlevy's story the same as yours? You
continued flying your aircraft without finding the allen wrench
necessary to verify the source of your similar problem, right?

-R

  #20  
Old September 23rd 05, 11:06 PM
Rob
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Everett M. Greene wrote:
Now, if there are any EEs present, perhaps they can explain
why aircraft radios tend to fail in this manner whereas
nothing much of anything else in the electronic world fails
in a manner to produce heat and smoke. Are avionics units
designed so close to the components' limits to cause this
failure mode? I can understand a transmitter going up in
smoke (while transmitting), but a receiver?


I'm an EE. In my day job I design guitar amplifiers. Let me tell you,
I've made a LOT of unintentional smoke at my workbench. When I was
in school a fellow student explained to me that the smoke contained
inside those little electronic components is what makes them work.
It's magic smoke. If you let out the magic smoke, the electrons stop
doing whatever it is they're designed to do.

Seriously though, maybe the propensity of aircraft radios to fail in
this manner has to do with the fact that on average they're pretty old,
and constructed mostly of discrete components. Modern electronics are
more highly integrated into power- and space- miserly "chips", or ICs
(integrated circuits). ICs also allow for more circuitry in a smaller
space, so thermal protection, over-current protection, and other
similar support circuitry can be incorporated into a design without the
weight and space penalties that made them impractical for aircraft
radios "back in the day". It's a theory, anyway.

-R

 




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