nuckollsr(at)cox.net
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 Posted: Thu Sep 07, 2006 7:44 am Post subject: An exercise in establishment of and compliance with design |
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At 10:11 AM 9/7/2006 -0400, you wrote:
| Quote: |
<echristley(at)nc.rr.com>
OK. The guy was/is a blowhard, with obviously way to much time on his
hands to be able to write long rambling dissertations with no
point; however....maybe there is a diamond or two amoungst all that
pig....stuff.
Bob wrote:
(1) He refused to acknowledge a modern alternator could experience a gross
OV failure in spite of demonstrations to the contrary. (2) He brushed
aside my oft stated design goals for providing seamless integration of his
favorite product (the IR alternator) into classic aircraft electrical systems.
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| Quote: | It irritated the snot out of me that he would never simply state an
alternative set of design goals. He did expound on the benefits that an
IVR has...temp compensation, slow start, etc. I think those are
desirable, but not if they don't fit in with the rest of the design
goals. Bob has clearly and succinctly stated that the design goal is that
the pilot have complete control of the charging system. It seems to me
that simply modifying one word would open the door for IVR systems and
maintain or increase the current level of safety. Do we really need
'complete' control, or will 'ultimate' control suffice?
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Not sure as to the distinction here. Let's reduce it to
the simplest terms: (1) The pilot should be able to operate
an alternator control switch at any time under any
conditions without concern for damage to the alternator
or other components of the system and (2) operation of
that switch is a sure bet - OFF means OFF and ON means ON.
| Quote: | That is, we allow the IVR to work it's magic was the IVR designers have
seen fit to have the magic performed,
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This has been an interesting study . . . at least for
internal regulation products wherein the manufacturer
offers to "tell all." See the data sheets for a
Freescale (Motorola) MC33032 . . .
http://www.aeroelectric.com/Mfgr_Data/Semiconductors/MC33092A.pdf
a little study of this document shows that while the
circuit overs "over voltage indication" there is
no provision for "over voltage shutdown". Further,
circuitry tasked with over voltage detection is
SHARED with circuitry for voltage control. This
violates aviation philosophies for separation of
annunciation and control.
An yes, there's a collection of bells-and-whistles
that look and sound good . . . but what has been
the cost of ownership to the aviation community
(or even the automotive community) for NOT having
those bells-and-whistles in the past?
Is there risk of lower reliability due to higher
parts count to acquire features with no demonstrable
benefits?
Now, how closely does the internal regulator of
any popular alternator mimic what we're privileged
to examine on the MC33092? I haven't a clue.
To date, nobody has come forward with clarifying
information on any other product.
The study is being conducted NOT to validate
the features of anyone's product but to illustrate
the depth to which data must be searched to validate
hardware suitability to the task of meeting
design goals.
Bottom line is that a study of the MC33092 is academically
satisfying but lends no insight to support any
claims anyone might make about other products.
My personal design philosophy (approved by
my employers) suggests we assume nothing. If you
have a device capable of dumping out LOTS of energy
in an uncontrollable mode, you put systems in place
to stand off and annunciate that event . . . unless
you can justify a failure rate of less than 1 per
billion flight hours.
| Quote: | but the pilot has "all rights reserved". (S)he can hit the kill switch
and take it out of the system at any time. Yes that might break the
alternator, but isn't it being taken offline because it's already broke?
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That was the philosophy behind the original publication
of Z-24. An unanticipated and unhappy consequence was
that Z-24 offered an ability to control the alternator
under conditions that did not meet design goal
(1) above.
Further, since anecdotal data from the field
says that failures greater than 1 per billion
flight hours have been observed, I accepted the task
of crafting a system consistent with the design
goals that assumes a OV runaway condition is
possible.
Now, a secondary design goal is to contrive an
arrangement that is easy to add to existing
installations. Further, cost of acquisition
and ownership should be equal to or lower than any
offering by any other manufacturer.
This was never intended to be a trashing of the
IR alternator . . . but simply an admission that I
didn't have a way to integrate a demonstrably
fine product into classical system design philosophies
we've adopted over the years. Now that I have an
idea and a means coming to validate it, proof
of the system is in the repeatable experiment.
It will happen.
Bob . . .
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