REFLECTOR: CAD drawings of the XL

Mon Apr 23 07:30:25 CDT 2007

Hey Terry I have them some where. FG or RG.
Ricardo
  ----- Original Message ----- 
  From: Terry Miles 
  To: 'Velocity Aircraft Owners and Builders list' 
  Sent: Thursday, April 12, 2007 9:31 PM
  Subject: REFLECTOR: CAD drawings of the XL

  Hi,

  Does anybody have a TurboCad or Autocad   (TCW or DWG) type drawings of the XL?

  Thanks

  Terry

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  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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