AeroElectric-List Digest Archive

Tue 04/14/15


Total Messages Posted: 6



Today's Message Index:
----------------------
 
     1. 05:13 AM - Re: OAT Probe Compatability (user9253)
     2. 06:43 AM - Re: OAT Probe Compatability (user9253)
     3. 07:38 AM - 14V alternator producing 28V? (Andy Elliott)
     4. 07:38 AM - Re: Do I Have a Problem? (Robert L. Nuckolls, III)
     5. 08:52 AM - Re: AeroElectric-List Digest: 26 Msgs - 04/13/15 (Christopher Ross)
     6. 04:12 PM - Re: 14V alternator producing 28V? (Robert L. Nuckolls, III)
 
 
 


Message 1


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    Time: 05:13:47 AM PST US
    Subject: Re: OAT Probe Compatability
    From: "user9253" <fransew@gmail.com>
    This paper talks about thermistors. http://ww1.microchip.com/downloads/en/AppNotes/00685b.pdf If the GRT and Dynon probe thermistors have different temperature coefficients, then the displayed temperature will not be accurate. The accuracy can be checked by exposing the probe to known temperatures like ice water and ambient air. Joe -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=440833#440833


    Message 2


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    Time: 06:43:35 AM PST US
    Subject: Re: OAT Probe Compatability
    From: "user9253" <fransew@gmail.com>
    > does anyone know if the oat probe for a dynon skyview is compatible with a grt mini? http://www.vansairforce.com/community/showpost.php?p=455620&postcount=3 Per Dynon Support: "Dynon's OAT's are a custom made part. It's a thermistor resistor between ground and the sense wire, with a 10K resistor from sense to +5V. The thermistor is 10Kohm @ 25C, with a .25% tolerance, -4.39%/C alpha @25C, and a 3892 0C/50C beta." When provided with the above information, GRT should be able to say if the Dynon OAT probe is compatible with the GRT mini or not. -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=440835#440835


    Message 3


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    Time: 07:38:01 AM PST US
    From: "Andy Elliott" <a.s.elliott@cox.net>
    Subject: 14V alternator producing 28V?
    In the airplane I just bought, there is a truly *arcane* mixed 12V/24V electrical system that I will need to rationalize in the coming months. But here is the first question: The plane has a 24V battery and a 24V starter. The alternator is clearly marked "14V" however. Now with my admittedly limited understanding of how alternators and regulators work together, I realized that an alternator can provide pretty much any voltage that the regulator asks for, up to maybe 150V or so. So my questions are: How are the voltage ratings and amperage ratings for alternators decided? And what are the issues with setting up a declared "14V" alternator to run with a 24V regulator? Is it nothing more than using higher capacity diodes? Thanks, Andy Elliott new owner of GP-4 N729LS


    Message 4


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    Time: 07:38:44 AM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
    Subject: Re: Do I Have a Problem?
    On a flight a couple of months ago I noticed my endurance bus voltage lower than usual. It was showing 12.5-12.9 volts, where I usually see 12.9-13.3 volts. Since it was time for my annual, and I have 5 years and 460 hours on the plane (and the voltage regulator), I 'threw' on a new Standard VR166 regulator without any diagnosis. At subsequent start-up, I noticed what looked like a healthier 13.5-13.8 volts, so I thought I guessed right, and also thought maybe my previous 13.0 volts had been a bit low for the entire 5 yrs. I've been flying! (I get about a 0.5 voltage drop from my 4-diode bridge rectifier). Expected readings . . . A couple of days ago, 35 minutes into a 1 hour flight, I got my very first low voltage alarm (which is set at 12.4v). Voltage was 11.2-11.9. My GRT EIS records engine info each second. The log showed the low voltage lasted only 6 seconds. At 40 minutes, it tripped again, lasted 17 seconds, showed 11.2-11.6 volts. It alarmed a third time at 54 minutes into the flight, lasted 13 seconds, and again showed 11.2-11.9 volts. I later checked the EIS log, and noted that each time the bus voltage went down, the field voltage went down, and the total load ammeter also went down. Any clues there? Wow! Symptoms quantified with numbers . . . and field voltge too? Be still my beating heart . . . I think I have an issue that deserves more diagnosis, but then again, maybe it's just an artifact of having an EIS that just provides too much information. After all, we're talking about only 36 seconds out of a 1 hour flight. What do you think? And where should I start looking? I'd certainly rather investigate now, and not wait for a total failure while away from home. You cannot have too much information. It's possible to mis-interpret data and having lots of it might be distracting . . . but ALL of my most challenging failure studies began with getting the data acquision systems installed with a hope that the problem would repeat and be captured on hard-drive. One test involved routing a long piece of 30 conductor ribbon cable from the hell-hole on a Beechjet, out the baggage compartment door under the seal, tapped to the side of the fuselage and thence into the cabin through the main door seal. Only then was I able to watch and record a library of events surrounding a problem that would only repeat after 30 minutes or so at 41K feet. Turned out to be a pushed back pin in a pressure bulkhead connector. The airplane had been out of service for several weeks at killobux per day while un-informed studies were conducted. Only after I got them to put the airplane in 'experimental license' and convinced the pilots that we weren't going to suck the tape and wire into the engines did we GET THE NUMBERS. The airplane was back in service the next day. Background and a couple more questions: Wired Figure Z-11, with the B&C OV protection module. In addition to the externally-regulated (40A, B&C) alternator, the field wire goes to both a sub-panel connector (per Z23 and note 8); and also to an aux input on the EIS. (I WONDER NOW IF THIS WAS OK). A load test on the battery showed it still 'in the green', but only barely so. At 3.5 years old, I'm replacing it now. Can the Crowbar OV module go bad and cause the regulator to perceive lower bus voltage? No . . . the CBOVM will OPEN the field breaker to effect a permanet shutdown of the alternator. It is incapable of intermittent operation you describe. My Crowbar OV module ground is connected first to the Master Switch, then from there goes to the common firewall ground tabs. I note this because I looked at the current Z11 figure and see that there the module ground is shown going directly to ground. But electrically, this should be the same, right? The CBOVM can be grounded to any sturdy location. If field voltage drops coincident with drop in bus voltage, there is a DISCONNECT between the bus and the alternator field terminal. It can be anywhere along that path INCLUDING a bad alternator switch, misbehaving regulator, even a bad breaker, or perhaps a poorly crafted joint. This has the 'smell' of a poor connection . . . so if you've not already done so, check the tightness of screw terminals, tug firmly on crimped terminal joints, the usual suspects. Given that the gross failures of alternator output occured after you changed the regulator, I'd pay particular attention to the terminals and crimps associated with that device. The next time the symptoms manifest, cycle the breaker and the alternator control to see if the action immediately clears the symptoms. Bob . . .


    Message 5


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    Time: 08:52:39 AM PST US
    Subject: Re: AeroElectric-List Digest: 26 Msgs - 04/13/15
    From: Christopher Ross <crav8r@gmail.com>
    Apologies if someone has already referenced this site. I haven't actually used one of these, but they are built by an aviation enthusiast, and there is lots(!) of USB information on the site..... http://www.commitlift.com/usbchargers.html Chris Chicago > > Time: 08:19:30 AM PST US > Subject: Re: AeroElectric-List: Re: USB Charger > From: "H. Marvin Haught Jr" <handainc@madisoncounty.net> > > > And none of the panel mounts are in stock. > > M. Haught > > Sent from my iPad > > > On Apr 12, 2015, at 2:32 PM, John Tipton <jmtipton@btopenworld.com> > wrote: > > > > > > Yes: nice quality items, but for us this side of the pond expensive, > starting > at 99.00 that's about $150.00 > > > > John > > > > Sent from my iPad > > > > ----x--O--x---- > > >


    Message 6


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    Time: 04:12:48 PM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
    Subject: Re: 14V alternator producing 28V?
    At 09:36 2015-04-14, you wrote: > In the airplane I just bought, there is a truly *arcane* mixed > 12V/24V electrical system that I will need to rationalize in the > coming months. But here is the first question: > The plane has a 24V battery and a 24V starter. The alternator is > clearly marked "14V" however. Now with my admittedly limited > understanding of how alternators and regulators work together, I > realized that an alternator can provide pretty much any voltage > that the regulator asks for, up to maybe 150V or so. > So my questions are: How are the voltage ratings and amperage > ratings for alternators decided? And what are the issues with > setting up a declared "14V" alternator to run with a 24V > regulator? Is it nothing more than using higher capacity diodes? The B&C SD-20 series OBAM and TC aviation alternators are 14v devices. Using the standard line of 14v alternator controllers, this device produces 20+ amps at 14v. It can be used in a 28V system but only with a special regulator designed to limit field voltage to 15 volts. You're correct, an alternator is capable of a wide range of voltages depending on RPM, field voltage and loads. It may be characterized at some voltage like 14 or 28v . . . but it's not necessarily limited to working in the one system. Where is your alternator mounted? Belt or pad driven? What is the make and model number of the alternator regulator. My suspicions are that you have a 28v system . . . not a mixture of two systems. Bob . . .




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