Avionics News May 2021 - 60

DUNCAN AVIATION

Continued from page 59

Aviation actually found a Legacy owner located near
its satellite facility in Houston, Texas. Ultimately, as
the STC program evolved over the ensuing years, this
turned out to be quite a benefit for the program.
For the initial STC, the Legacy was moved to Duncan
Aviation's facility in Lincoln, Nebraska. Because the
installation teams based in Lincoln were busy with
other projects, technicians from the Houston facility
were brought in to do the installation and testing.
As it turned out, this requirement was fortuitus for
the project: 18 months after the original STC was
granted, Duncan Aviation and Honeywell needed to
update the STC (there are more details later in the
story), but the aircraft's owner wasn't able to relocate
the airplane to Lincoln a second time. So they moved
the program to the Houston satellite facility to complete
the amendment.
" We're fortunate to have a large network of satellite
facilities around the country, so we did the STC
amendment out of the Houston location, " Carraher
said. " It required a bit more coordination and travel but
wasn't a deal breaker by any stretch. We just flew our
people in for the engineering, inspections, witnessed
testing, and test flights - things of that nature. It wasn't
difficult. "
Duncan Aviation's
three-for-one STC program
Now back to the STC program itself. As we left off,
finalizing the agreement's business side was the green
flag to start the STC process. And what a process it was.
" We actually were asked to do three separate STCs for
the Legacy, " stated Russ Kromberg, Duncan Aviation's
certification coordinator. " The first was to replace the
old DU-870 CRT displays. The Legacy actually has five
displays - two for the PFDs, two MFDs, and one, centerlocated engine instrument display. "
While developing an FAA STC to replace all five
displays would be a handful, this one came with the
added steps to allow a Legacy owner/operator to change
any one, or combination, of the CRT displays at any time.
" The flexibility of the STC helps reduce the cost
and downtime to change individual displays as they go
bad, " Kromberg said. " The second STC is to upgrade
the Honeywell FMZ-2000 FMS to the new-generation
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2021

FMZ-2010, which provides localizer performance
with vertical guidance and wide-area augmentation
capabilities. That STC also included new GPS antennas
and updated integrated avionics computers.
" The third STC installs the new Honeywell Mark III
communications management unit, which is FANS-1A
Plus (Future Air Navigation System-1A Plus) capable.
That STC also includes the Honeywell VHF datalink
radio, FMS, cockpit voice recorder, and Iridium Satcom
transceiver for the datalink. "
" One of the nice things about the entire package is
rather than just upgrading the old CRT displays, once
it's down for the CRT installation, why not upgrade the
FMSs and have a really compliant airplane? " Carraher
added. " It will be current with all the FANS-1A
mandates and be a much more capable airplane. "
While the three-part STC seems to cover everything,
it didn't include an ADS-B compliance solution.
" These STCs did not include an ADS-B solution,
but they would need to upgrade the GPSs for ADS-B
anyway, " Kromberg said. " So if it wasn't already
ADS-B Out compliant when it comes in the shop, we
would do that upgrade at the same time. "
The ABCs of an STC
Of course, if you've ever been involved with
developing an FAA STC, you know that understanding
what you want to accomplish is just a small piece of the
puzzle. Now that the Duncan Aviation and Honeywell
avionics teams had a goal, the next step was developing
the plan.
" After Shawn and his team got all the contracts
signed, the project comes over to my desk as a valid
STC program, " Kromberg explained. " The next step was
to write a project-specific certification plan. Once that
is done, we submit it through our ODA (organization
designation authorization) to the FAA - that process
alone needs its own article - but once it's accepted by the
FAA's ACO (Aircraft Certification Office), we can then
start the design and engineering work. "
As Kromberg explained, the next step is to complete
substantiation reports, including the structural reports
for the new antennas, and hardware. Also included were
the antenna icing reports and other safety substantiation
reports, which covered the ground-test and flight-test
plans.
" Concurrently with all this, our technicians in
the shop were doing the actual installation on the

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