REFLECTOR: File Transfers

[Brian Michalk]

Looks like the permissions are not right to allow uploading.
Stand by.

Terry Miles wrote:
>
> Lar,
>
> It is nuts to send some of this stuff off line when the group might 
> benefit, but if the file is too large, it either chokes my dinky email 
> program, or the forum host rejects it for size.  Same for pics. 
>
>  
>
> Can somebody tell me how to transfer files to www.tvbf.org 
> <http://www.tvbf.org/>?  
>
>  
>
> Thanks,
>
> Terry
>
>  
>
> ------------------------------------------------------------------------
>
> *From:* reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] 
> *On Behalf Of *David Scharfenberg
> *Sent:* Monday, January 29, 2007 11:33 PM
> *To:* Velocity Aircraft Owners and Builders list
> *Subject:* Re: REFLECTOR: Using the starter supply(+) wire as a charge 
> wire
>
>  
>
> Hi
>
> My theory is that I can turn off the battery contactor (in the nose, 
> near the batteries) if the #2 wire should short to ground somewhere 
> between the battery and the starter.
>
> Dave Scharfenberg
>
>
> On Jan 29, 2007, at 10:37 AM, Scott Derrick wrote:
>
> Terry,
>
> This conversation about protecting the "big" wire that runs to the 
> rear of the plane to power the starter and to provide for the 
> alternators charge circuit got me interested in possibly protecting it 
> with a big fuse or breaker.  200 Amp or so... Starters draw a huge 
> current.  
>
> I'm not talking about protection for the alternator, this being the 
> short #10/8 or so wire that connects the alternators charge circuit(B 
> lead) to the supply side of the main starter relay(big wire from main 
> relay to starter relay).  That small wire should have a fuse or 
> resettable breaker. I think a fuse would be the right choice.
>
> I searched the Aero-Electric list and found this... Its not for a 
> canard but it is about a battery lead from the rear of a tractor style 
> airplane to the firewall.  Similar application..
>
> *>
> >Bob and everyone else ...
> >When considering a ground fault, what is best used to protect a #4 cable
> >run, from the rear battery, in an RV, while powering a bus?
> >
> >What is best used to protect this same #4 cable, when it is in 
> parallel with
> >the front battery and charging current is flowing to the rear batt?
> >Thanks ...
> >Jerry Grimmonpre'
>
> Fat wires in light aircraft are not, as a rule, "protected".
> If you study the wiring diagrams for light airplanes going
> back to the first generator and battery installations
> (mid 40's), things like fuses and circuit breakers do not
> appear in the fat feeders. Let's see what the certified guys
> design to by reading from FAR23.
>
> Sec. 23.1357 Circuit protective devices.
>
> First, keep in mind that I quote this document only as a means
> of illustrating thought processes for crafting the most trouble
> free system . . . and in no way am I suggesting that these
> words be treated as a "requirement" that should flow down into
> the OBAM aircraft community.
>
> (a) Protective devices, such as fuses or circuit breakers, must be
> installed in all electrical circuits other than--
>
> (1) Main circuits of starter motors used during starting only; and
>
> (2) Circuits in which no hazard is presented by their omission.
>
> I can tell you that these paragraphs describe the portion of the
> architecture you are asking about. Fat feeders in light aircraft
> are seldom if ever involved in a hard fault situation because of
> the extra care we take in securing such wires and thoughtfulness
> for installation to keep them clear of moving parts that might
> pose a threat.
>
> When a fat feeder suffers compromised insulation, it's generally
> against thin sheet metal and the fault tends to be "self clearing",
> i.e., it take a lot of force designed to drive the faulted conductor
> to ground such that the conductor is now at-risk for catastrophic
> failure due to high currents. Relatively light, passing contacts
> tend to burn open with little or no effect on the rest of the system.
>
> (b) A protective device for a circuit essential to flight safety may 
> not be
> used to protect any other circuit.
>
> Common sense. A fuse or breaker for every accessory. Don't stack
> multiple accessories on a single breaker/fuse whether "essential"
> or not. Of course, this begs for a definition of "essential" which
> is a topic for a who chapter. The government position on aviation
> is to build ever more goodies into the essential category . . .
>
> As I've described in Chapter 17 . . . it's up to YOU to decide
> what's "essential" based on your understanding of personal
> and mechanical limits based on proposed missions.
>
>
> (c) Each resettable circuit protective device ("trip free" device in which
> the tripping mechanism cannot be overridden by the operating control) 
> must be
> designed so that--
>
> (1) A manual operation is required to restore service after tripping; and
>
> (2) If an overload or circuit fault exists, the device will open the
> circuit regardless of the position of the operating control.
>
> Common sense.
>
> (d) If the ability to reset a circuit breaker or replace a fuse is
> essential to safety in flight, that circuit breaker or fuse must be so
> located and identified that it can be readily reset or replaced in flight.
>
> Yup, good thing to do. Now, I've suggested for years that there's
> no good reason for ANY single piece of equipment to become so
> "essential" that it qualifies for special treatment of access to
> fuses or breakers. There are hundreds more things that cause
> an accessory to fail that DOES NOT open a fuse compared to
> failures that DO open a fuse. Focusing on the ability to restore
> a fuse or breaker circuit is non-productive. These are
> a tiny proportion of all failures and likelihood of getting
> a system back by replacing the fuse is nil.
>
> It stands to reason then that if any one SYSTEM is so
> desirable, then there had better be a backup SYSTEM.
> Once this condition is achieved, there is no reason for
> making ANY fuse or breaker accessible in flight.
>
> (e) For fuses identified as replaceable in flight--
>
> (1) There must be one spare of each rating or 50 percent
> spare fuses of each rating, whichever is greater; and
>
> (2) The spare fuse(s) must be readily accessible to any
> required pilot.
>
> As thoughtful designers and users of OBAM aircraft, we're
> able to craft flight systems that completely negate any
> reason to observe this requirement . . . we can design
> so that there is no need to reach any fuse/breaker because
> there are no singular, "essential" systems likely to be
> resurrected by replacing a fuse or resetting a breaker.
>
> This is the general answer on circuit protection . . the
> short answer to your specific question is that experience
> and common sense have shown that there is no value in
> adding "protection" to long battery feeders (other than
> the locally situated battery contactor). This includes
> the generally smaller but still quite robust feeder from
> the cranking circuit to the main bus.
>
> Bob. . .*
>
>
>
>
> -- 
>
> -
> The only security of all is in a free press. The force of public 
> opinion cannot be resisted when permitted freely to be expressed. The 
> agitation it produces must be submitted to. It is necessary, to keep 
> the waters pure.
>
> Thomas Jefferson to Lafayette, 1823. ME 15:491
>
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