Aerospace & Defense Technology - August 2022 - 24

Test and Simulation
ed four mainframes, two LAN-XI 11-slot
mainframes near the nose of the airplane,
where the main GVT control station
was located, and two LAN-XI 5-slot
mainframes at the rear of the airplane.
The mainframes were daisy-chained
together via a network switch.
Key components of the GVT data acquisition
system included:
* Type 3660 Mainframes. This test system
used both five-slot and eleven-slot mainframes.
The 3660 mainframes provide
both power and connectivity, as well as
protection, for LAN-XI modules.
* Type 3053 12-Channel Input Module.
This module was chosen because it provided
a compact and cost-efficient solution
for this application.
Two of the LAN-XI Mainframes in Position for Testing.
* Type 3160 Generator Module. This module
was used because this application
required system excitation. It is available
with either two inputs and two outputs
or four inputs and two outputs. All input
and output channels have a frequency
range of DC to 51.2 kHz.
Vertical Tail Lateral Excitation Location.
tions, they installed two uniaxial accelerometers
or a triaxial accelerometer.
The accelerometers around the motors
were very difficult to install because of the
limited access and real estate around the
electric motors. In addition to the GVT
external accelerometers, they acquired
data from the flight accelerometers using
the airplane's instrumentation system and
compared this to data gathered from the
nearest GVT accelerometers.
24
To acquire data from these accelerometers,
the NASA team used a
300+-channel LAN-XI data acquisition
system from HBK. The LAN-XI is a
modular data acquisition system and
analyzer platform capable of acquiring
sound and vibration data from more
than 1,000 channels, with a wide
dynamic input range, used in many
demanding measurement applications.
The NASA AFRC LAN-XI system includmobilityengineeringtech.com
14
Test Configurations, 191 Test Runs
NASA performed 191 test runs using
14 different test configurations. There
were 11 different configurations that
used the soft-support setup, two that
used the on-tires setup, and one additional
configuration that excited directly
on the A-Frame lifting device that
was part of the nose soft support system.
The last configuration was added
to characterize the A-Frame and ensure
there was no coupling with the airplane
modes of interest. The airplane
remained suspended on soft supports
for this A-Frame test.
To keep track of the process, a test
configuration matrix was created that
included the target modes, excitation
locations and directions, number of
shakers, and which locking devices
were used as constraints in either the
cockpi t or
the control
surfaces .
Throughout the testing, the test engineers
relied heavily on this configuration
matrix to ensure both primary and
secondary test objectives were
achieved. When running these tests,
they used either one or two shakers
appropriately placed for the test. Shaker
locations are typically determined
by the FE model.
Aerospace & Defense Technology, August 2022
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Aerospace & Defense Technology - August 2022

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