Mechanics of Elevator Trim. In Detail.

On Jun 19, 4:30 pm, Le Chaud Lapin wrote:
A CDROM drive is one of the most complex machines ever built if one
considers all what one needs to know to build it from basic
components, but it can easily be had for $25US.

That's the power of true commoditization.

Of course, if the vendor determines that you intend to mount the drive
in your Gulfstream, then adding a couple of 0's to the price would be
in order.

Those extra zeros reflect the cost of certification and the cost
of liability insurance to protect the maker when the drive quits and
the pilot loses control in IMC and crashes and the widows of his
highly-paid passengers sue everyone that ever had anything to do with
that airplane. Tell me how commoditization is going to fix that.
Common, "commoditized" hardware can't be used on aircraft, for
two reasons: There's way too much counterfeit junk on the market, and
the cost of ordinary hardware is almost as bad as the cost of aircraft
hardware. In the former instance, we are now sold SAE/AISI Grade 5
nuts and bolts in the hardware stores that could come from the US or
from China. It all has the same head markings, but the counterfeit
stuff won't make the grade and if one uses such stuff in an airplane
it will come apart under stress. Grade 5 bolts are supposed to have a
tensile strength of 125ksi but the cheap stuff might have half that
and would shear or snap during high loads, or it might be brittle and
have no margin between yield and ultimate. It might have no
anticorrosion properties at all, and so it fails after pitting
somewhat. That's the reason the Government aviation regulators demand
that certified aircraft use only the parts listed in the
manufacturer's parts manual, and the manufacturer will specify AN or
NAS or MS hardware becauase it is made to a hard specification and is
traceable all the way back to the manufacturer, who also has records
as to where the metal came from and what its composition was and what
heat treatment it received. This takes paperwork which costs money,
but it minimizes the occasional unfortunate incidents where unapproved
parts get into an airplane and it comes apart in flight like that
Convair 580 did over Finland a few years ago when the fin came off
because some crook sold the overhaul facility a counterfeit fitting
that failed under load. The paperwork system was ignored somehow. The
people who had those 40 relatives die in that accident would never
agree with "commoditization" that could lead to an enormous increase
in inflight structural failures.
And as far as the cost of that hardware, the universal AN/MS/NAS
hardware is not at all expensive since there are numerous companies
making it. When my son was into building RC model airplanes I got him
small AN hardware for less money than for the cheap junk that the
hobby shops sell. A few bolts (like the landing gear bolts on the
Citabria) cost around $35 for a 1/2" x 3" or so NAS bolt, but that
bolt has a tensile strength of about 190ksi, something no industrial
hardware reaches. Even at that those bolts get changed out every 500
hours and can be reused after NDI. A lesser bolt would fail,
guaranteed, and someone would get hurt. Besides, aircraft hardware is
made of nickel steel and other fancy alloys, not the plain carbon
steel used in common hardware. Huge difference, and when I, a
mechanic, am out flying and think about some of that critical hardware
that's hold me up, I'm glad we paid more for it than we could have by
using common stuff.
Numerous homebuilders have designed airplanes intended to cost
much less by using non-aviation parts, but they ALWAYS end up heavy
and more than a little questionable.
And as far as automating flight goes, flying will always
require both skill and awareness unless we turn the whole thing over
to computers like we did the telephone system. And I sure wouldn't
want to trust such a system, especially with opportunistic terrorists
around.

Dan