---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Wed 07/30/14: 3 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 04:27 AM - Fw: Re: Garmin 430W - Comm & Nav Power from Separate Busses (Buckley William) 2. 07:32 AM - Re: Fw: Re: Garmin 430W - Comm & Nav Power from Separate Busses (Robert L. Nuckolls, III) 3. 08:16 AM - Re: Ni-Cad? (Robert L. Nuckolls, III) ________________________________ Message 1 _____________________________________ Time: 04:27:44 AM PST US From: Buckley William Subject: Fw: Re: AeroElectric-List: Garmin 430W - Comm & Nav Power from Separate Busses Bob, To your question: As currently designed, the equipment list in my panel has the comm side of the 430 as comm#2 and the nav functions of the 430 as the primary navigation source. With an alternator failure, I want comm#2 to be among the equipment that gets dropped while keeping the navigation functio ns. The comm functions will be handled by a different transceiver as comm#1 . And why not make the 430 the primary comm and nav source? ...Budget. I'd li ke to have the full compliment of panel equipment on day one but its likely that the 430 will be added later. Starting out with only VFR capability an d I'm planning for the full enchilada later. Thanks, William B. --- On Tue, 7/29/14, Robert L. Nuckolls, III wrote: > From: Robert L. Nuckolls, III > Subject: Re: AeroElectric-List: Garmin 430W - Comm & Nav Power from Sep arate Busses > To: aeroelectric-list@matronics.com > Date: Tuesday, July 29, 2014, 1:17 PM > > > To: aeroelectric-list@matronics.com > > Subject: Re: AeroElectric-List: Garmin 430W - Comm & Nav > Power from > Separate Busses > > - How did your ENDURANCE load analysis come to suggest > > - that Com functions need not be part of an extended > > - battery-only ops scenario? > > - Bob . . . > > ________________________________ Message 2 _____________________________________ Time: 07:32:31 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: Fw: Re: AeroElectric-List: Garmin 430W - Comm & Nav Power from Separate Busses At 06:26 AM 7/30/2014, you wrote: >Bob, >To your question: As currently designed, the equipment list in my >panel has the comm side of the 430 as comm#2 and the nav functions >of the 430 as the primary navigation source. With an alternator >failure, I want comm#2 to be among the equipment that gets dropped >while keeping the navigation functions. The comm functions will be >handled by a different transceiver as comm#1. But comm#2 doesn't draw any significant power unless you talk on it . . . so what is the ENDURANCE advantage for shutting it down and making comm#2 unavailable except by bringing the main bus back up? >And why not make the 430 the primary comm and nav source? ...Budget. >I'd like to have the full compliment of panel equipment on day one >but its likely that the 430 will be added later. Starting out with >only VFR capability and I'm planning for the full enchilada later. Okay, you're planning ahead . . . good show. Do you have an battery-only endurance target? Is your engine electrically dependent? Have you run the numbers on battery-only flight at end of battery life? Bob . . . ________________________________ Message 3 _____________________________________ Time: 08:16:25 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Ni-Cad? At 02:10 PM 7/29/2014, you wrote: >Pengilly > >Back in the early 90s the Royal Navy fleet of >SeaKing helicopters (S-61 derivative) used NiCad >batteries. We were pretty much banned from using >them to start and made sure ground power was >always available. They didn't turn the engine >over quickly enough to get a reliable start - >usually too much fuel and not enough rpm >resulted in a hot start with sheets of flame out >the exhaust - and potentially an overheated >turbine. The batteries were a lot of trouble, I >remember several being float tested after >aircraft landed back on-board with over heating >or smoking battery compartments (now not an >option as nothing is allowed over the side). We >could also swap out individual cells if a >battery went down. I guess the technology has >moved on in 20 years, but I still would not be rushing to fit one. The hot-start phenomenon would not have root cause in the chemistry of the batteries, only the sizing- to-task irrespective of chemistry. The volumetric and power density numbers for ni-cad are superior to lead-acid . . . i.e. a PROPERLY SIZED ni-cad will be smaller and lighter than the lead-acid capable of the same starting performance. But as others have noted, ni-cads are not very friendly to the cost of ownership. Their alkaline electrolyte is antagonistic to lead-aced which prompts maintenance operators to have separate shops for dealing with the two technologies . . . which could probably be dispensed with today . . . nobody has to 'maintain' electrolyte in a lead-acid battery any more. The thermal runaway thing was the byproduct of some rather un-creative design decisions. The smaller, lighter cells were very capable of cranking engines but when those engines started, generators rated at hundreds of amps would stuff energy back into the little batteries causing them to warm up. Ni-Cad temperature coefficient of voltage causing them to draw more current from a fixed voltage bus as their temperature rises . . . which causes them to warm up still faster . . . you get the picture. Quoting from Wikipedia at: http://tinyurl.com/7zm7xee "One of the biggest disadvantages is that the battery exhibits a very marked negative temperature coefficient. This means that as the cell temperature rises, the internal resistance falls. This can pose considerable charging problems, particularly with the relatively simple charging systems employed for lead'acid type batteries. Whilst lead'acid batteries can be charged by simply connecting a dynamo to them, with a simple electromagnetic cut-out system for when the dynamo is stationary or an over-current occurs, the Ni'Cd battery under a similar charging scheme would exhibit thermal runaway, where the charging current would continue to rise until the over-current cut-out operated or the battery destroyed itself." People who understood batteries published reams of data on how to get the best performance from Ni-Cads . . . data which said "constant current charge" . . . but those- who-know-more-about-airplanes-than-we-do decided that it would be too much to expect an air-framer to install ni-cad friendly starter-generator controllers. They decreed that thermometers be added to ni-cads with displays on the panel along with warning lights for battery overheat. Instead of crafting a battery management system totally transparent to the pilots . . . the pilots were burdened with rudimentary system management duties to offset poor regulatory judgement. Hence, the ni-cad gets this bad rap for being higher risk . . . risks driven by inelegant design. As a chemical energy storage system, ni-cads have a lot going for them. But as we've discussed here on the List . . . there is no such creature as an alternative chemistry, drop-in lead-acid replacement. THERE ARE DIFFERENCES that beg understanding and deference in design, fabrication, installation, operation and maintenance. Whether lead-acid, ni-cad or lithium-ion . . . failure to pay homage to the physics gods is at best just expensive . . . at worst it sets airplanes on fire. Every technology comes with its own constellation of challenges. http://tinyurl.com/kxu3s6j Bob . . . ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message aeroelectric-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/AeroElectric-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/aeroelectric-list Browse Digests http://www.matronics.com/digest/aeroelectric-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.