AeroElectric-List Digest Archive

Sun 10/04/09


Total Messages Posted: 13



Today's Message Index:
----------------------
 
     1. 09:31 AM - Re: Basic Electrical Architecture for review... (Steve Stearns)
     2. 12:13 PM - Re: 24V Heated Pitot (Robert L. Nuckolls, III)
     3. 01:11 PM - Re: Basic Electrical Architecture for review... (Robert L. Nuckolls, III)
     4. 01:54 PM - Re: 24V Heated Pitot (Chuck Jensen)
     5. 01:54 PM - Re: Basic Electrical Architecture for review... (Marvin Haught)
     6. 02:13 PM - Re: Re: Watons's RV-10 power distribution (Bill Mauledriver Watson)
     7. 02:25 PM - Re: Basic Electrical Architecture for review... (BobsV35B@aol.com)
     8. 04:02 PM - Re: Basic Electrical Architecture for review... (Robert L. Nuckolls, III)
     9. 04:05 PM - Re: Basic Electrical Architecture for review... (Robert L. Nuckolls, III)
    10. 08:32 PM - Re: 24V Heated Pitot (Robert Mitchell)
    11. 09:24 PM - Re: Watons's RV-10 power distribution (rckol)
    12. 10:51 PM - Re: 24V Heated Pitot (Joe Dubner)
    13. 11:13 PM - Re: Re: 24V Heated Pitot (Werner Schneider)
 
 
 


Message 1


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    Time: 09:31:43 AM PST US
    From: Steve Stearns <steve@tomasara.com>
    Subject: Re: Basic Electrical Architecture for review...
    Hi Bob, Thanks for taking a look at my architecture drawing. As to why it differs from the recommendations in the Z-figures. Good question. I hope my answers are as good (I have no inherent desire to be "different"). The project at hand is the "repair" of a LongEZ that already has 1000 hrs on it by the previous owners (mostly by the original builder). My objective is to return the aircraft to what I consider flight-worthy shape. "Return" might not be the right word here as there were many details (electrical and otherwise) on the aircraft that have never been in what I would consider (by my standards today) flight worthy, though they may have been by some standards 30 years ago... And then put a year or two of flying on it (day VFR) while I become opinionated about what I want in it and what I don't. Then, the next project will be to add the enhancements I think are appropriate. I'm expecting the desired enhancements to include night & IFR support, eliminate the vacuum system etc. This project description flows down to the electrical subsystem as the constraint to keep it as simple as possible to meet the objective (and, specifically, avoid the temptation to grow the scope of the project). One other bit of background that may be relevant to my particular choices: Almost all of my flying since my license (1988) is in my no-electrical system Taylorcraft. For day VFR missions, a total electrical system failure, as long as the failure didn't make fire or smoke, would not give me sweaty palms. I would, however, be mindful of the loss of ignition redundancy and might choose to shorten the leg... Note: All of my explanations below (many), are intended solely as explanation and not a "defense". Although I believe I have thought everything through, I might have missed stuff and I could easily have misunderstood why some things were the way they were. PLEASE feel free to express any disagreement. I am seeking out things that I still need to fix. Given the above, this is what I did relative to Z11 and why: - Removed the starter and associated support. (As I also removed it from the aircraft. I saved the parts as I might want to reinstall it (more appropriately wired) later. - Removed the primer (As I also removed it from the aircraft. This might also be added back later in a more appropriately wired and plumbed manner) - Replaced the ignition switches with SPST as part of the removal of the starter support features. If/when I re-install the starter I intend to revisit the latest recommendations regarding connections here and anticipate I will be replacing these with the progress transfers as shown in Z11. - Rearranged the ground buses to match a pusher configuration rather than the tractor configuration. - Redefined the avionics ground bus to be an audio ground bus. My Nav/Com uses a differential audio path allowing separate audio/power grounds. All the avionics power grounds, with the exception of the low-power intercom return, terminate at the PNL Gnd bus. All audio grounds (including the intercom power ground) terminate at the Audio Gnd bus. - Reduced the number of connections tying the PNL ground to the Audio ground as it no longer carries any significant current. - Replaced the regulator shown on Z11 with the one existent on the aircraft. - Added a stand alone low-voltage indicator as the existent regulator (to my knowledge) does not support the feature. - Replaced the ANL with one sized to the existent alternator. - Replaced the shunt with one sized to match the existent Ampmeter. - Used a 20Amp blade fuse instead of a fuse-link for the regulator power for reasons that are lost to history. I will be using the fuse-link rather than 20A fuse approach. (I suspect that, back when I did this, the recommendation for a fuse-link wasn't as obvious but who knows... My book is years old.) - Combined the endurance bus and main battery bus as the only items on the main bus that have significant load are the position, landing, and strobe lights and, if I end up with a (currently not shown) backup path for the bus feed, the check list will list specific loads to drop (e.g. turn off these lights) before enabling the backup power path. - Removed the bus alternate feed as I haven't (yet) justified it as a worthy exception to the project guidelines (repair, not enhance as this stage). - Removed the Battery Bus as I have nothing that would attach to it. - Adjusted wire gauges as seemed appropriate for my actual loads. - I put each engine instrument on it's own fuse as I couldn't think of a good enough reason not to. It would have been the only exception to the one-fuse-per-end device approach. - I changed the "6 inches or less" to "24 inches or less" (turns out to be about 18 inches at the longest) due to the LongEZ's configuration constraints. The battery is in the nose. The contactor, shunt and ANL current limiter (with the regulator mounted on the closest fuselage side) are all mounted on the canard bulkhead (about as close as you can get them to the battery but the required wire length is still longer than 6 inches) and the fuse panel is on the right fuselage side between the canard bulkhead and the panel. This is also about as close as you can get it but is still requires wire lengths longer than 6 inches. Fortunately, with a non-metal airframe, it's a little easier to ensure appropriate protection for these runs. - I changed the fuse values to match either that recommended by the manufacturer of the end device, or, if not stated, to an appropriate value less than or equal to that required to protect the wire. Let me know if I missed any changes. It occurs to me now that the cleanest way to add an alternate power path (I don't like the approach I pondered on the schematic) may be to (conceptually, relative to Z11) move everything except the regulator power path from the main bus to the endurance bus (thus the main bus effectively becomes the output contact on the contactor). And then replace the battery bus and the alternate feed switch with a fuse-link to a panel mounted breaker switch. (Ideally a fuse link appropriate for 7-10 Amps, assuming such a thing exists) My justification for the breaker switch in this application that I want this resettable in flight given that I will be required to manually load shed (i.e. turn off the lights) and, if I neglect the check list and leave the lights on, I want to have a reasonable recovery option. I'm also still seriously considering leaving the alternate feed path off until I revisit the electrical system during the "enhancement" project to follow in a couple of years. For my current project, I think the alternate feeds greatest value is, in the event of a contactor failure, allowing my to keep my redundant source of ignition (but it also allows me to keep my primary nav/com etc. which is also nice :-) All comments welcome but I am particularly interested in discussion of failure mode for which I don't have appropriate fault tolerance. Thanks in advance, Steve Stearns Boulder/Longmont, Colorado CSA,EAA,IAC,AOPA,PE,ARRL,BARC (but ignorant none-the-less) Restoring (since 1/07): N45FC O235 Longeze Cothern/Friling CF1 (~1000 Hrs) Flying (since 9/86): N43732 A65 Taylorcraft BC12D


    Message 2


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    Time: 12:13:20 PM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
    Subject: Re: 24V Heated Pitot
    At 09:46 PM 10/3/2009, you wrote: >I have a chromed AN 5812-1 14V heated pitot tube from Aero >Instrument Co. and need the exact equivalent in a 12V model. Anyone >care to trade? > >Anticipating some responses that lead to thread drift: I don't want >to change the heating element. It's physically impossible to retrofit these devices. The heating elements are stainless tubes about 12-15" long with spiral wound segments tailored to deliver specific amounts of heat to various portions of the tube assembly. Emacs! Here you can see the heater tube as it loops twice through the labyrinth chamber and around the nose piece. I had to cut the tube apart just to SEE the heater . . . replacing it as a maintenance operation is not an option. > And yes, it gets hot on 12V but not hot enough to suit me. I > rather just swap with someone who has a 12V model and a 24V airplane. What defines "hot enough to suit"? Know that the crafting of a practical heated pitot tube involves a careful study of ice accretion characteristics under worst case conditions. The goal is to prevent liquid ice (super-cooled water droplets) from becoming solid ice on contact . . . this requires MUCH more energy than that required to maintain the surface at above freezing temperatures. As I alluded earlier, it's also not a function of simply installing a heater . . . the heater is a long, linear, un-even liberator of heat crafted to the task. Here's some data I took on an identical pitot tube in flight (clear air). http://www.aeroelectric.com/Pictures/Curves/Pitot_tube_temps_at_altitude.pdf The upper curve shows that while RAT was sometimes below -35C, the pitot tube was over 100C in cruising flight at 41K feet. An THIS was on a tube that was being studied for potentially deficient ability to avoid freezing under some conditions. Heated pitot tubes have been installed on tens of thousands of light aircraft not certified for flight into know icing conditions. I wouldn't discourage anyone from adding this feature to their airplane . . . it just MIGHT save your bacon one day. But know too that the icing conditions that would render your airspeed (and perhaps static instruments) useless are similarly destructive of the airplane's ability to fly. But then, it might be interesting to know how high you are and how fast you're going down . . . Bob . . . --------------------------------------- ( . . . a long habit of not thinking ) ( a thing wrong, gives it a superficial ) ( appearance of being right . . . ) ( ) ( -Thomas Paine 1776- ) ---------------------------------------


    Message 3


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    Time: 01:11:28 PM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
    Subject: Re: Basic Electrical Architecture for review...
    At 04:47 PM 10/3/2009, you wrote: ><handainc@madisoncounty.net> > >Bob - Sent this earlier but did not get a reply. Thought I would >send it again. I found my reply in the out-box. Here it is again: ------------------------------------------------------------- At 10:17 AM 10/2/2009, you wrote: ><handainc@madisoncounty.net> > >Bob - > >I'm a lurker on this site, but am in progress on a Pa22-20 project >(certified). How difficult would it be to use Z-11 in a certified >aircraft and get a 337 for that purpose? Has anyone done that >recently? Looks perfect for the project. >M. Haught I have often fantasized about taking a nice ol' rag-wing piper and updating the electrical system with something like Z-13/8, all new lightweight hardware and an RG battery. I'm aware of no projects flying where one has successfully run the gauntlet for permission to do a good thing to an ageing aircraft. Several folks have proposed such upgrades and have received tentative blessings on things like the forest of tabs ground bus and fuse blocks. But those systems have yet to be completed and signed off for flight. Bob . . .


    Message 4


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    Time: 01:54:35 PM PST US
    Subject: 24V Heated Pitot
    From: "Chuck Jensen" <cjensen@dts9000.com>
    Joe, As Bob said: "The goal is to prevent liquid ice (super-cooled water droplets) from becoming solid ice on contact . . . this requires MUCH more energy than that required to maintain the surface at above freezing temperatures. As I alluded earlier, it's also not a function of simply installing a heater . . . the heater is a long, linear, un-even liberator of heat crafted to the task." >From a qualitative perspective, it takes very little pitot heat to keep the pitot clear of rime and clear icing that we occassionally bump into at the altitudes that most GA flies. If we accidently run into SCD icing, we'll likely have far bigger and faster problems, long before the pitot heating is overcome by the super-cooled droplets. But, as always, each should do that that gives the greatest level of comfort. Chuck -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com]On Behalf Of Joe Dubner Sent: Saturday, October 03, 2009 10:47 PM Subject: AeroElectric-List: 24V Heated Pitot I have a chromed AN 5812-1 14V heated pitot tube from Aero Instrument Co. and need the exact equivalent in a 12V model. Anyone care to trade? Anticipating some responses that lead to thread drift: I don't want to change the heating element. And yes, it gets hot on 12V but not hot enough to suit me. I rather just swap with someone who has a 12V model and a 24V airplane. Thanks, Joe Independence, OR http://www.mail2600.com/position


    Message 5


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    Time: 01:54:55 PM PST US
    From: Marvin Haught <handainc@madisoncounty.net>
    Subject: Re: Basic Electrical Architecture for review...
    Well, I was afraid that was what you would say, as I had no seen any discussion of such a project while I have been on here. I guess I'm stuck with the original. Looking at my fuselage, the wiring harness is intact and actually, all of the wiring looks really good with no frayed covering or corrosion on the attachment points. But it will not support much in the way of avionics, etc. Thanks, Bob - M. Haught Robert L. Nuckolls, III wrote: > <nuckolls.bob@aeroelectric.com> > > At 04:47 PM 10/3/2009, you wrote: >> <handainc@madisoncounty.net> >> >> Bob - Sent this earlier but did not get a reply. Thought I would >> send it again. > > I found my reply in the out-box. Here it is again: > ------------------------------------------------------------- > At 10:17 AM 10/2/2009, you wrote: >> <handainc@madisoncounty.net> >> >> Bob - >> >> I'm a lurker on this site, but am in progress on a Pa22-20 project >> (certified). How difficult would it be to use Z-11 in a certified >> aircraft and get a 337 for that purpose? Has anyone done that >> recently? Looks perfect for the project. >> M. Haught > > I have often fantasized about taking a nice > ol' rag-wing piper and updating the electrical > system with something like Z-13/8, all > new lightweight hardware and an RG battery. > > I'm aware of no projects flying where one > has successfully run the gauntlet for > permission to do a good thing to an ageing > aircraft. Several folks have proposed such > upgrades and have received tentative blessings > on things like the forest of tabs ground bus > and fuse blocks. But those systems have yet > to be completed and signed off for flight. > > > Bob . . . > >


    Message 6


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    Time: 02:13:54 PM PST US
    From: Bill Mauledriver Watson <MauleDriver@nc.rr.com>
    Subject: Re: Watons's RV-10 power distribution
    Robert L. Nuckolls, III wrote: > <nuckolls.bob@aeroelectric.com> >> My thinking was the fuse is just protecting the wire to the pullable >> breaker. The wire is 16AWG and the fuse a 15amp. Then the breaker >> is a 5amp. But I think what you are telling me is that the fuse >> could defeat the whole purpose of having the pullable breaker. And >> that either a fusible link is needed to protect the wire or a direct >> connection to the buss. Is that correct? > Fuses are so much faster than breakers that > you may pop a 15A fuse trying to open a 5A > breaker. There's a reason for the fusible > link depicted in the Z-figures. I must be back level on my printed out Z figs. The one I have has that circuit connected directly to buss but in either case I get the point. I'm going to add 2 fusible links (22AWG based) to the circuit and take the power directly from the power feeds. >> It's an RV10 with both batteries in the rear. So I used 2AWG for the >> run to the starter and for the interbattery connections. The other >> battery has a (previously unmarked) 8AWG wire for the other run to >> the front. >> My analysis suggested that the 8AWG is enough for the 20amp Alt side >> of the circuit even in a crossfeed situation. > > Do you intend to load the aux battery for cranking? > If batteries are in the rear, then contactors are > in the rear and crossfeed contactor is on firewall > to give you a fat-terminal, power distribution point > at the cross-feed contactor. > > Use 4AWG welding cable off each battery terminal > to contactors and ground. 2AWG for run forward to > the starter contactor. > I did this a little different. I have all 3 contactors back with the batteries. Then a 2AWG running forward for the starter circuit and fuse board 1 with the majority of the load. Then a 8AWG line running forward to the other fuse board. The batteries are twin PC680s (pic attached). I can crank with both batteries or with 1. The plan is to generally just use 1. All of this was done over a year ago so it's all installed at this point. - Why a Z14? In the end, I fell for the simple symmetry of the whole thing over an E-bus solution. A bit irrational with some extra cost but it's working for me so far. It is an all electric a/c with my dream IFR panel (3 GRTs, G430w). No electronic ignition though. One of the things I found myself doing when IFR in my Maule, is sitting on the ramp getting a clearance, programming the G300XL, and more recently watching the Nexrad on the G396. For example, a year after Katrina I was sitting at the GA New Orlean's airport waiting to get past a line of buildups. The FBO was operational but their weather terminal was down so I spent 2 or 3 hours running out to the Maule checking the 396 for a hole and otherwise figuring out when and how to escape. I started to worry about having enough juice to start (I've never figured out what kind of time I would have in such a situation). Then when things opened up a bit, I shut everything down because I was keeping to the practice of not starting with the avionics online. Then I had to load a plan and wait for the 396 to get it's Nexrad back. All the time trying not to rush to get thru the hole. Since then based on your writings, I've started turning on my Maule avionics stack when needed, and keeping it on when starting. No problems ever encountered of course. But the doc for the GRTs suggest that it might reduce the life of the screeens if this is done frequently, so... Two things I wanted to have with my Z14. 1) I wanted the ability to run most of my stack without worrying about having enough energy for the start. I've always found that time spent on the ground prepping for an IFR flight, especially a single pilot departure into IMC, can be the most valuable in the flight. 2) I wanted to feel totally comfortable running the stack during the start - given the manufacturer's warning and a lifetime of perhaps worrying about something I didn't need to. An un-rushed, guilt-free panel setup before the start is a very nice thing to have. And then I have this dual electric system that can put 2 batteries on the starter if ever needed and can backup just about any electrical failure without much concern. And I don't think I can get too much weight back there in the battery compartment - the RV10 seems to benefit from it. Thanks for the review and the resources. Bill "this thing is going to fly in 2010" Watson > > Bob . . . > > --------------------------------------- > ( . . . a long habit of not thinking ) > ( a thing wrong, gives it a superficial ) > ( appearance of being right . . . ) > ( ) > ( -Thomas Paine 1776- ) > --------------------------------------- > >


    Message 7


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    Time: 02:25:04 PM PST US
    From: BobsV35B@aol.com
    Subject: Re: Basic Electrical Architecture for review...
    Good Afternoon Marvin, I would never qualify as an expert on electrical systems, but I did recently make a few changes which I feel are improvements to our 1955 PA-22-20. I replaced every piece of wiring that could be reached without cutting the aircraft's fabric covering with nice new Tefzel wiring of the appropriate gauge. I replaced all of the original Circuit Breakers and most switches with new production substitutes. I removed the original CB panel and replaced it with a hunk of angle aluminum that extends left to right all the way across the bottom of the instrument panel. I also made new busses for all switches and CBs. 'Lectric Bob won't care for this next item, but I did add a radio master switch to feed an electronics buss. I performed all functions in accordance with AC 43.13-1B citing appropriate paragraphs for documentation of suitability. All work was noted on a 337 and filed with the FAA. No local approval required as AC43.13-1B provides adequate documentation for an IA to determine whether or not the installation is in conformance with those provisions. Our Pacer is now a very nice full WAAS equipped IFR platform! Any help at all? Happy Skies, Old Bob In a message dated 10/4/2009 3:55:58 P.M. Central Daylight Time, handainc@madisoncounty.net writes: --> AeroElectric-List message posted by: Marvin Haught <handainc@madisoncounty.net> Well, I was afraid that was what you would say, as I had no seen any discussion of such a project while I have been on here. I guess I'm stuck with the original. Looking at my fuselage, the wiring harness is intact and actually, all of the wiring looks really good with no frayed covering or corrosion on the attachment points. But it will not support much in the way of avionics, etc. Thanks, Bob - M. Haught


    Message 8


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    Time: 04:02:23 PM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
    Subject: Re: Basic Electrical Architecture for review...
    At 11:28 AM 10/4/2009, you wrote: > >Hi Bob, > >Thanks for taking a look at my architecture drawing. As to why it >differs from the recommendations in the Z-figures. Good >question. I hope my answers are as good (I have no inherent desire >to be "different"). > >- Removed the starter and associated support. (As I also removed it >from the aircraft. I saved the parts as I might want to reinstall >it (more appropriately wired) later. Okay >- Removed the primer (As I also removed it from the aircraft. This >might also be added back later in a more appropriately wired and >plumbed manner) Hmmmm . . . must be a REALLY easy-to-prop engine . . . >- Replaced the ignition switches with SPST as part of the removal of >the starter support features. If/when I re-install the starter I >intend to revisit the latest recommendations regarding connections >here and anticipate I will be replacing these with the progress >transfers as shown in Z11. Okay >- Rearranged the ground buses to match a pusher >configuration rather than the tractor configuration. Okay >- Redefined the avionics ground bus to be an audio ground bus. My >Nav/Com uses a differential audio path allowing separate audio/power >grounds. All the avionics power grounds, with the exception of the >low-power intercom return, terminate at the PNL Gnd bus. All audio >grounds (including the intercom power ground) terminate at the Audio Gnd bus. >- Reduced the number of connections tying the PNL ground to the >Audio ground as it no longer carries any significant current. Can't comment on this without having understood/crafted the system . . . >- Replaced the regulator shown on Z11 with the one existent on the aircraft. good >- Added a stand alone low-voltage indicator as the existent >regulator (to my knowledge) does not support the feature. always good >- Replaced the ANL with one sized to the existent alternator. okay . . . recall too that ANLs are VERY robust . . . you can go as small as ANL30 with plenty of headroom for 50A alternator. >- Replaced the shunt with one sized to match the existent Ampmeter. You have a 50A alternator? >- Used a 20Amp blade fuse instead of a fuse-link for the regulator >power for reasons that are lost to history. I will be using the >fuse-link rather than 20A fuse approach. (I suspect that, back when >I did this, the recommendation for a fuse-link wasn't as obvious but >who knows... >My book is years old.) . . . you can always download the latest Appendix Z from the websit along with the change-pages from the last revision. It's easy to keep your book up to date. >- Combined the endurance bus and main battery bus as the only items >on the main bus that have significant load are the position, >landing, and strobe lights and, if I end up with a (currently not >shown) backup path for the bus feed, the check list will list >specific loads to drop (e.g. turn off these lights) before enabling >the backup power path. >- Removed the bus alternate feed as I haven't (yet) justified it as >a worthy exception to the project guidelines (repair, not enhance as >this stage). Re-read the explanation for an E-bus in Appendix Z notes and chapter 17 on reliability. The E-bus is for maximizing a limited resource (battery energy stored) during alternator-out operations. It's also a plan-B during battery contactor failure. Highly recommended. >- Removed the Battery Bus as I have nothing that would attach to it. Okay <snip> >It occurs to me now that the cleanest way to add an alternate power >path (I don't like the approach I pondered on the schematic) may be >to (conceptually, relative to Z11) move everything except the >regulator power path from the main bus to the endurance bus (thus >the main bus effectively becomes the output contact on the >contactor). And then replace the battery bus and the alternate feed >switch with a fuse-link to a panel mounted breaker switch. (Ideally >a fuse link appropriate for 7-10 Amps, assuming such a thing >exists) My justification for the breaker switch in this application >that I want this resettable in flight given that I will be required >to manually load shed (i.e. turn off the lights) and, if I neglect >the check list and leave the lights on, I want to have a reasonable >recovery option. > I'm also still seriously considering leaving the alternate feed path off until I revisit the electrical system during the "enhancement" project to follow in a couple of years. For my current project, I think the alternate feeds greatest value is, in the event of a contactor failure, allowing my to keep my redundant source of ignition (but it also allows me to keep my primary nav/com etc. which is also nice :-) Your e-bus should supply power to goodies especially useful for continued flight to airport of intended destination without an alternator. This usually amounts to a handful of electro-whizzies for a battery only endurance that exceeds hours of fuel aboard Bob . . .


    Message 9


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    Time: 04:05:07 PM PST US
    From: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
    Subject: Re: Basic Electrical Architecture for review...
    At 11:28 AM 10/4/2009, you wrote: > >Hi Bob, > >Thanks for taking a look at my architecture drawing. As to why it >differs from the recommendations in the Z-figures. Good >question. I hope my answers are as good (I have no inherent desire >to be "different"). >- Removed the Battery Bus as I have nothing that would attach to it. Correction, how about the electronic ignition. It has its own power switch and is an excellent candidate for battery bus power. If you got bad smells in the cockpit you can power down the whole electrical system without reducing engine support. Fuel pump might run from battery bus too. Bob . . .


    Message 10


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    Time: 08:32:00 PM PST US
    From: "Robert Mitchell" <rmitch1@hughes.net>
    Subject: 24V Heated Pitot
    On the data plate it says 24V? You didn't really mean 14V? Bob Mitchell L-320 -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Joe Dubner Sent: Saturday, October 03, 2009 21:47 Subject: AeroElectric-List: 24V Heated Pitot I have a chromed AN 5812-1 14V heated pitot tube from Aero Instrument Co. and need the exact equivalent in a 12V model. Anyone care to trade? Anticipating some responses that lead to thread drift: I don't want to change the heating element. And yes, it gets hot on 12V but not hot enough to suit me. I rather just swap with someone who has a 12V model and a 24V airplane. Thanks, Joe Independence, OR http://www.mail2600.com/position


    Message 11


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    Time: 09:24:37 PM PST US
    Subject: Re: Watons's RV-10 power distribution
    From: "rckol" <rckol@kaehlers.com>
    Hi Bill, Just curious: Why have you wired SW01 and SW02 to disconnect both the alternator and battery at the same time instead of using the progressive transfer scheme in most of the Z diagrams? -------- rck Read this topic online here: http://forums.matronics.com/viewtopic.php?p=266525#266525


    Message 12


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    Time: 10:51:51 PM PST US
    From: Joe Dubner <jdubner@yahoo.com>
    Subject: Re: 24V Heated Pitot
    In spite of my best efforts to avoid thread drift ... All I want to do is have a reliable source of dynamic pressure at all times. It's not a secret but neither is it well known: the Dynon EFIS requires a working pitot system for reliable attitude information. *Attitude*. Not just airspeed. I don't want to turn an inadvertent icing encounter into an emergency (and I consider flying needle-ball-and-airspeed with failed airspeed in IMC an emergency). I'm 100% positive an AN 5812 12V heated pitot operating with a 12V electrical system will provide enough heat in an RV at RV altitudes and airspeeds. I'm not sure a 24V heater running on 12V will. It might, but I won't be performing a "careful study of ice accretion characteristics under worst case conditions". I just want to swap this 24V model with someone (perhaps a Lancair builder?) who could use it and has an equivalent 12V model lying around. We both agree: I'm not going to be changing the heating element :-) Anyone want to trade? -- Joe Robert L. Nuckolls, III wrote: > At 09:46 PM 10/3/2009, you wrote: >> I have a chromed AN 5812-1 14V heated pitot tube from Aero Instrument >> Co. and need the exact equivalent in a 12V model. Anyone care to trade? >> >> Anticipating some responses that lead to thread drift: I don't want to >> change the heating element. > > It's physically impossible to retrofit these devices. The > heating elements are stainless tubes about 12-15" long > with spiral wound segments tailored to deliver specific > amounts of heat to various portions of the tube assembly. > > Emacs! > > > Here you can see the heater tube as it loops twice through > the labyrinth chamber and around the nose piece. I had to > cut the tube apart just to SEE the heater . . . replacing > it as a maintenance operation is not an option. > >> And yes, it gets hot on 12V but not hot enough to suit me. I rather >> just swap with someone who has a 12V model and a 24V airplane. > > > What defines "hot enough to suit"? Know that the > crafting of a practical heated pitot tube involves > a careful study of ice accretion characteristics > under worst case conditions. The goal is to prevent > liquid ice (super-cooled water droplets) from becoming > solid ice on contact . . . this requires MUCH more energy > than that required to maintain the surface at above > freezing temperatures. As I alluded earlier, it's also > not a function of simply installing a heater . . . the > heater is a long, linear, un-even liberator of heat > crafted to the task. > > Here's some data I took on an identical pitot tube in > flight (clear air). > > http://www.aeroelectric.com/Pictures/Curves/Pitot_tube_temps_at_altitude.pdf > > > The upper curve shows that while RAT was sometimes > below -35C, the pitot tube was over 100C in cruising > flight at 41K feet. An THIS was on a tube that was > being studied for potentially deficient ability to > avoid freezing under some conditions. > > Heated pitot tubes have been installed on tens of > thousands of light aircraft not certified for flight > into know icing conditions. I wouldn't discourage > anyone from adding this feature to their airplane . . . > it just MIGHT save your bacon one day. But know > too that the icing conditions that would render your > airspeed (and perhaps static instruments) useless > are similarly destructive of the airplane's ability > to fly. But then, it might be interesting to know > how high you are and how fast you're going down . . . > > > Bob . . . > > --------------------------------------- > ( . . . a long habit of not thinking ) > ( a thing wrong, gives it a superficial ) > ( appearance of being right . . . ) > ( ) > ( -Thomas Paine 1776- ) > --------------------------------------- > >


    Message 13


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    Time: 11:13:25 PM PST US
    From: Werner Schneider <glastar@gmx.net>
    Subject: Re: 24V Heated Pitot
    Joe, get yourself the newest 5.1.1 version of the software and hook up a GPS that will give you additional comfort as with that version the attitude is, in case of dyn. press. lost backed up with GPS speed. (Interesting to see on takeoff roll when a message tells you that before the pitot comes live. Werner > > All I want to do is have a reliable source of dynamic pressure at all > times. It's not a secret but neither is it well known: the Dynon EFIS > requires a working pitot system for reliable attitude information. > *Attitude*. Not just airspeed. I don't want to turn an inadvertent > icing encounter into an emergency (and I consider flying > needle-ball-and-airspeed with failed airspeed in IMC an emergency). > >




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