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Jerry makes some interesting observations that
deserve comment.
<<< Because it is so expensive, and outside the budgets
of many of us,
Chelton produced a non-certified version. Contrary to what had been
inferred, this system does not use identical hardware to the certified
version.
>>>>
Jerry's incorrect inference is understandable. The
line between the certified and non certified Chelton systems is a
little blurry. There are three main elements to certification, hardware
testing per DO160, software testing per DO178 and manufacturing. There
are several components that make up a system including software,
Integrated Display Units (IDUs), sensors (GPS, AHRS, OAT, Air Data,
etc.) and accessory devices (Wx, traffic, AIU, etc.). The IDU and many
of the sensors are available in certified and non-certified versions.
The two fundamental elements of the system are the software and the
IDU, which contains the display, the processor and the interface. All
Chelton software configurations are based on the certified code base.
This makes practical sense when you realize that it would be more
(twice as) difficult to maintain two separate software databases.
The non-certified IDU, the IDU-I is the original IDU and has undergone
several upgrades (hardware, speed and memory) over the years. When the
decision to certify the system was made, work began to redesign the
system to use components that were rated down to -40 C and incorporate
additional communication ports and more memory. This was the IDU-II.
When the Capstone contract was awarded an additional requirement to fit
in a radio stack was added. This spawned the IDU-III, which was then
certified.
For certified systems, on the sensor side, Chelton supported Free
Flight and X-Bow to certify a WAAS GPS and AHRS respectively. An
already certified Shaden Air Data computer was used.
If your airplane is one of the 600+ aircraft models on the STC list and
if a qualified technician installs the STC specified components then
you can have a certified system. Because the Chelton IDUs and software
are designed to interface to a large assortment of sensors, an
experimental aircraft builder has the option to assemble a system from
certified and non-certified components as their preferences and budget
permit.
Chelton, by way of Direct-To, is the only company that provides this
wide a range of options, all based on certified core software. All
these options between certified and non-certified components gets
confusing, as Jerry points out, but those are the kinds of problems you
want to have.
<<<This would sound a lot more credible if we had not just
heard that the
Chelton non-certified version has been using an AHRS that has been
failing catastrophically on a regular basis.>>>
"Catastrophically" sounds like and explosion. Some
of the X-Bow 425s in some installations have occasionally reported
inaccurate attitude information. This is bad and potentially unsafe.
Direct-To, and Chelton, brought the problem to X-Bows attention which
resulted in the referenced letter. Give Direct-To and Chelton credit
for putting safety "front and center" and working with the vendor,
X-Bow, to fix the problem ASAP. Characterizing the problem as "
failing catastrophically on a regular basis." overstates the situation
and discourages future disclosures by others.
<<<If you can afford the certified Chelton system, you
are lucky, and it will probably be very reliable. >>>
If you can afford a certified Chelton system
I would assume that hard work, not luck, put you in that position.
<<<If you cannot, the
Chelton non-certified system has proven to be no different from the
others.
>>>>
This is only correct in limited cases. In the
context of the X-Bow 425 (and likely the 420) issue, it is true that a
third party sensor problem will effect any manufacturer's EFIS. GIGO.
In this case Chelton is no different than the others. What is different
is that Chelton was the first to identify the problem, the first to put
pressure on X-Bow to fix the problem and the first to notify users.
Kirk at Direct-To said it best "Sales aren't
everything…safety
is!" and he is a
salesman.
There are many other obvious differences in reliability, functions,
features, performance and customer service. Some are outlined above.
Of course you could make the claim that all EFIS systems, like all
cars, are basically the same four wheels and an engine, be they Yugo or
Mercedes. This view may be popular with Yugo dealers, but which would
you rather drive?
Before making a decision on avionics you MUST do your homework and,
preferably, get a flight demonstration prior to purchase.
Merry Christmas.
Brent Regan
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