GOD how I love common sense ! Need a days worth of conversation! Thanks Mark
Sent from my iPhone > On Nov 18, 2021, at 10:43, Mark Langford <m...@n56ml.com> wrote: > > Here's another argument against header tanks that occurred to me yesterday > as I was struggling to access some wiring on a plane with a header tank. All > of the space that a header tank (mounted in the "forward deck") occupies > gobbles up a lot of valuable space that could otherwise be used for battery, > coils, voltage regulator, system electrical bus, and most > importantly.....easy access to all of this stuff. Future additions, > alterations, repairs, panel upgrades, electrical bus connections, > troubleshooting....all of that stuff is a lot easier to access, with that > space available if the fuel is out in the wings instead, in low vertical CG > voids that are normally empty anyway! And if you make the front deck easily > removable with piano hinges like I did, access is about 30 seconds away from > the decision to open it. > > The unattractive alternative is often to put some of this engine-related > stuff on the engine side of the firewall, which really starts crowding > things out there, and subjects the components to constant heat (requiring > cooling) and perhaps oil contamination....and will likely result in much more > difficult access, and perhaps less opportunity for inspection and > troubleshooting. > > See the photo at http://www.n56ml.com/electrical/index.html for what all I > had under the front deck, long before I ever even flew the plane. At first > flight it had a lot more out there, like the EIS static/pitot sensor, > transponder altitude encoder, fuel pumps and regulator fastened to the aft > side of the firewall, etc, and nowadays it could have all the ADS B stuff > under there....with very easy access. > > I've said this before and I'll say it again, I'm not a big fan of "gravity > feed" fuel systems. The head pressure (and therefore fuel pressure supplied > to the carburetor) varies depending on the level of fuel in the tank, how > well the tank is vented (plugged by an insect), and even on what kind of > maneuvers the plane is doing (stick back or forward). Some carbs are more > sensitive than others to these pressure changes. A fuel pump and regulator > solves this problem by providing constant pressure and flow rate, and also > adds the potential for an electric primer without introducing a potential > fuel leak (a mechanical primer) into the panel. A backup battery and a > double-pole double throw switch adds redundancy to a level that I consider to > be quite adequate....it swaps out both ignition system and fuel pumps to a > backup battery that is always fully charged by the alternator, and isolated > (one-way) with a 40A diode. > > And most of all, if I were to tear a plane up in an off-airport landing > (although I'm sure that would never happen to me......), I'd much rather have > the wings on fire than the cockpit, especially surrounded by a hundred "hot" > electrical wires right in front of me! > > See http://www.n56ml.com/electrical/index.html > > Mark Langford > m...@n56ml.com > http://www.n56ml.com > Huntsville, AL > ________________________________ > -Please see LIST RULES and KRnet info at http://www.krnet.org/info.html > -Change list delivery options at > https://list.krnet.org/list/krnet.list.krnet.org/ Affinity List Info Board > -Search recent KRnet Archives at > https://list.krnet.org/empathy/list/krnet.list.krnet.org/ > -Search John Bouyea's decades of archive at > https://www.mail-archive.com/krnet@list.krnet.org/ ________________________________ -Please see LIST RULES and KRnet info at http://www.krnet.org/info.html -Change list delivery options at https://list.krnet.org/list/krnet.list.krnet.org/ Affinity List Info Board -Search recent KRnet Archives at https://list.krnet.org/empathy/list/krnet.list.krnet.org/ -Search John Bouyea's decades of archive at https://www.mail-archive.com/krnet@list.krnet.org/
