AeroElectric-List Digest Archive

Sat 08/28/10


Total Messages Posted: 7



Today's Message Index:
----------------------
 
     1. 06:14 AM - Re: Re: GRT EIS-Fuel Sender (Robert L. Nuckolls, III)
     2. 06:26 AM - Re: Re: GRT EIS-Fuel Sender (Robert L. Nuckolls, III)
     3. 08:16 AM - Re: GPS outage in fiberglass plane (checkn6)
     4. 09:48 AM - Noise in the intercom . . . (Robert L. Nuckolls, III)
     5. 09:48 AM - Re: GRT EIS-Fuel Sender (jonlaury)
     6. 12:56 PM - Re: splicing wire? (Robert L. Nuckolls, III)
     7. 01:46 PM - Re: Re: splicing wire? (James Robinson)
 
 
 


Message 1


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    Time: 06:14:37 AM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
    Subject: Re: GRT EIS-Fuel Sender
    At 09:07 PM 8/27/2010, you wrote: > >Bob, you said: > > > That "unusable fuel" has two important functions. > > (1) provide a low-spot for moisture collection > > and (2) keep the vapor in the tank saturated. > > >I spent a lot of time and effort to make sure that every drop in my >fuel tanks was usable except for the debris sumps. The mains and >header can be pumped dry except for sump fuel (4-6 ounces). > >Is the small amount of fuel in the sumps enough to keep a 12' long >wing tank vapor-saturated? Are these 'sumps' part of the tank envelope or are they 'low spot' water separators plumbed to the tank through a fuel line? >I wasn't ever worried about this before, but now that it's out on >the line, just want to be sure I'm not committing a major oversight. I may have stubbed my toe on speaking of the "importance" of unusable fuel. I don't think that the designers deliberately shoot for a volume of unusable fuel just to meet some rule of thumb for reducing risk of explosion. I think it has just worked out that for most airplane tanks, the lowest spot in the tank was against the skin and that same spot becomes a good place to put a water drain. Obviously, plumbing a fuel line into the same location would look pretty ugly hanging out the bottom of the airplane. So fuel lines tend to tap through the tank wall at the lowest practical point . . . but obviously above the tank's low spot thus giving rise to "unusable fuel". I'm sure there are many instances of gasoline tanks on vehicles that are plumbed such that the total contents can be consumed by the engine. But unless the same tank is force-ventilated the vapor space mixture will remain very rich for long periods of time. But even after it becomes 'leaner', you still need an ignition source for the combination to become hazardous. I remember reading about WWII military fuel systems where a major consideration was taking a tracer through an empty fuel tank. At Cessna, we fitted some military airplane tanks with an open cell foam filler. While the foam reduced tank useful volume by about 5%, it had the effect of sucking the heat out of a flame front such that taking a tracer through a tank of stoichiometric mixture would not produce an explosion. It's hard to get an explosion to happen on purpose. I recall some conversations with a fellow who ran a test lab telling us about getting a mixture tuned up "just right" for the purposes of testing our motors for explosion proofing. He described a chamber with a hinged lid, foam gaskets all around the edges, and just enough weight to get a good seal. The chamber was fitted with mixing fans, a source of hydrocarbon (I think it was Butane), a source of ignition (spark plug through the wall), and equipment to allow us to run a motor inside. After putting what is believed to be the right amount of butane in the chamber, the motor run tests are conducted. When the prescribed tests are finished, he then sparks the mixture for the purpose of proving that the atmosphere was and is still hazardous. If things went right, the vapor lit off, the lid flies open and you get this fireball out the top. If things don't go right, nothing happens and the tests have to be repeated. Unless you plan to punch holes in your tanks and mount spark plugs in the holes, the practice of running the tanks dry offers no great hazard. If you're using fuel gaging systems that are shown to be intrinsically safe in a hazardous environment, you're good to go. Bob . . .


    Message 2


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    Time: 06:26:07 AM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
    Subject: Re: GRT EIS-Fuel Sender
    At 09:21 PM 8/27/2010, you wrote: > >You don't have to run the tanks dry. True . . . but if one intends to leave a specific volume of fuel in the tank, an accurate means of gaging is indicated. I just checked out my copy of part 23 where I found: ------------------------------ Sec. 23.971 Fuel tank sump. (a) Each fuel tank must have a drainable sump with an effective capacity, in the normal ground and flight attitudes, of 0.25 percent of the tank capacity, or 1/16 gallon, whichever is greater. (b) Each fuel tank must allow drainage of any hazardous quantity of water from any part of the tank to its sump with the airplane in the normal ground attitude. (c) Each reciprocating engine fuel system must have a sediment bowl or chamber that is accessible for drainage; has a capacity of 1 ounce for every 20 gallons of fuel tank capacity; and each fuel tank outlet is located so that, in the normal flight attitude, water will drain from all parts of the tank except the sump to the sediment bowl or chamber. (d) Each sump, sediment bowl, and sediment chamber drain required by paragraphs (a), (b), and (c) of this section must comply with the drain provisions of Sec. 23.999 (b)(1) and (b)(2). ------------------------------- So in TC airplanes, it would be a violation to design a tank with zero unusable fuel. This section gives us some insight into the existence of one or more drains in each tank plus a low spot drain (usually the gascolator) at the bottom of the fire wall. Bob . . .


    Message 3


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    Time: 08:16:47 AM PST US
    Subject: Re: GPS outage in fiberglass plane
    From: "checkn6" <checkn6@yahoo.com>
    I agree, but I am going to go one small step further and do the frequency test while on the ground the next time I go to the airport. I too have had GPS drop-out for brief periods and just thought that I had gotten a bum deal on EBAY on my little hand held Garmin 196. I still have a plan A and plan B since my little GPS is more for informational purposes only and is really a plan C. Thanks for starting this thread. My wife thinks I'm nuts for reading this "boring stuff" but I love learning new things and once again I found a little gem to check on. Chris [quote="james(at)etravel.org"]Interesting stuff. That's worth everyone with a GPS tucking away in the "for future reference" part of the brain. Thanks for taking the time to report this info. James While on the tiedown, with engine and everything running, I started to tune in the various com frequencies I use in my area. With the GPS screen set to show the sat reception bars, I quickly found that the bars would quickly pulse down to nothing when the frequency was set between 119.200 to 119.5. This was even without transmitting and it was dramatic. As it turns out, I am usually tuned within this frequency range when flying the routes I had associated with GPS loss. Read this topic online here: http://forums.matronics.com/viewtopic.php?p=310382#310382


    Message 4


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    Time: 09:48:24 AM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
    Subject: Noise in the intercom . . .
    >Comments/Questions: I have alternator noise in my Sigtronics >intercom. I re-wired and re-routed the harness out of the tunnel >(Glasair III) to around the cockpit - no help. > >I get alternator noise with the intercom on, quiet with it off, and >/or the ALT CB pulled. I also get aditional noise when the fuel >pump or flap motor are run (but not always). I'm kinda stumped. > >I've [now] been told that pulling the CB can hurt the alternator...true? No >Also that a bad diode in the alternator can cause this noise? Sometimes . . . but if you have other accessories that cause noise too . . . then the problem is most likely more general and involves how the intercom was installed. >I had the alternator rebuilt to no effect, so I thought that had >eliminated the alternator, but I could be wrong. I also have >replaced the (B&C) voltage regulator. > >Suggestions and/or help would be appreciated. I'm sorry to hear that you've tried so many hopeful and expensive fixes without positive result. I note that you are not currently subscribed to the AeroElectric-List. Early on (after reading your symptoms) I and others on the list would have steered you toward an evaluation of your ground system. The problems you've described are almost certainly a function of shared pathways in the ground system for both victim (intercom) and antagonists (alternator, flaps, etc). These issues are also addressed in the chapters on Grounding and Noise found in the AeroElectric Connection. If you do not have a copy of the Connection you can download it here: http://www.aeroelectric.com/Book/AEC12A_PDF.zip I'll suggest also that you join us on the List for expanded support of your quest for solving this problem. Never met a noise dragon that couldn't be slain. Bob . . .


    Message 5


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    Time: 09:48:25 AM PST US
    Subject: Re: GRT EIS-Fuel Sender
    From: "jonlaury" <jonlaury@impulse.net>
    > > You don't have to run the tanks dry. > True and I probably won't 99% of the time. But I designed this multi-tank fuel system to be bullet proof if it is just ON. I don't want to inadvertently build in a gotcha if there's a need or a screw-up that runs a tank dry. Re Bob's Part 23 quote, by coincidence, my wing and header tanks (with integral, drainable debris sumps within the tank envelope) are configured in conformance, as they drain into a 32 oz. sump tank (w/drain) that feeds the pumps. So now all I have to do is remove the fuel tank spark plugs. :D Read this topic online here: http://forums.matronics.com/viewtopic.php?p=310391#310391


    Message 6


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    Time: 12:56:07 PM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
    Subject: Re: splicing wire?
    At 01:57 PM 8/28/2010, you wrote: >Good afternoon Bob >I have a question on splicing wire. I need to lengthen the wires to >my headset plugs from the intercom. ( NAT intercom). They currently >go to plugs in the center console. I was originally going to run >new wires all the way to the intercom. This is proving to be a >major undertaking. Everything is bundled and nicely tied and very >difficult to get to. Can I add a length of wire to the existing >without creating problems? Would there be any considerations I >would need to address? Sure. the big guys do it all the time. They use a product called solder-sleeves. You don't need to get THAT fancy. I've illustrated a poor-man's solder sleeve technique here: http://aeroelectric.com/Pictures/Wiring_Technique/Wire_treatment_3.jpg and a comic book on the technique here: http://aeroelectric.com/articles/Solder_Lap_Splicing/Solder_Lap_Splices.html If you have some shields to deal with, just bring their pigtails together as if they were individual wires. This technique offers a minimum-bulk methodology for jointing wires and insulating the splice. If practical, you might want to trim the lengths of the existing wires so that the splices don't all bunch up next to each other in the finished bundle. Bob . . .


    Message 7


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    Time: 01:46:49 PM PST US
    From: James Robinson <jbr79r@yahoo.com>
    Subject: Re: splicing wire?
    Thank you Bob!! James Robinson Glasair lll N79R Spanish Fork UT U77 ________________________________ From: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com> Sent: Sat, August 28, 2010 1:26:30 PM Subject: AeroElectric-List: Re: splicing wire? At 01:57 PM 8/28/2010, you wrote: Good afternoon Bob >I have a question on splicing wire. I need to lengthen the wires to my headset >plugs from the intercom. ( NAT intercom). They currently go to plugs in the >center console. I was originally going to run new wires all the way to the >intercom. This is proving to be a major undertaking. Everything is bundled and >nicely tied and very difficult to get to. Can I add a length of wire to the >existing without creating problems? Would there be any considerations I would >need to address? Sure. the big guys do it all the time. They use a product called solder-sleeves. You don't need to get THAT fancy. I've illustrated a poor-man's solder sleeve technique here: http://aeroelectric.com/Pictures/Wiring_Technique/Wire_treatment_3.jpg and a comic book on the technique here: http://aeroelectric.com/articles/Solder_Lap_Splicing/Solder_Lap_Splices.html If you have some shields to deal with, just bring their pigtails together as if they were individual wires. This technique offers a minimum-bulk methodology for jointing wires and insulating the splice. If practical, you might want to trim the lengths of the existing wires so that the splices don't all bunch up next to each other in the finished bundle. Bob . . .




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