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#11
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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
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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
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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
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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 ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
#15
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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 * ************************************************** *********************** Posted Via Usenet.com Premium Usenet Newsgroup Services ---------------------------------------------------------- ** SPEED ** RETENTION ** COMPLETION ** ANONYMITY ** ---------------------------------------------------------- http://www.usenet.com |
#16
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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
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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
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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
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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
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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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