September-October 2022 - 19

manufacturer, " he said. " Nondestructive evaluation
(NDE) is the testing of materials and parts in
research and development to acquire engineering
information without being bound by specifications
or acceptance criteria. Nondestructive characterization
(NDC) is the determination of material properties,
often in a research environment. "
NDT is employed in the aerospace industry
beginning with the processing of raw materials
and extending through the lifecycle of the aircraft,
affirms Engelbart.
" NDT has evolved largely through improvements
in digital technology. In the transition from analog
to digital, instruments have become more compact,
rugged and reliable. Advances in digital imaging and
associated software have allowed improvements
in the quality of the acquired data and the ability
to extract more quantitative information, " he said.
" For example, digital radiography has overtaken
film radiography in many organizations; thereby
eliminating the need for chemical processing and
providing technicians with the ability to adjust and
optimize image parameters without reshooting has
resulted in significant cost savings. "
Newest NDT Technologies
According to Engelbart, in the aircraft and aerospace
industries, it is vital to detect damage to
materials and components at any point in their
operational life.
" Radiography is one such way to do so. This technology
is not new, but significant advancements
have been made in recent years to improve the timeliness
and quality of the finished product, " he said.
Digital radiography is an advanced form of X-ray
technology where radiation is emitted from the
source strikes a detector in place of the film, creating
an electronic image sent directly to a computer,
explains Engelbart.
" This can be adjusted for brightness, contrast and
other parameters, eliminating the need for expensive
and time-consuming re-shoots. As an example of
the use of this technology, ASTM International has
developed standardized digital reference radiographs
for aluminum and magnesium castings, " he said.
Computed radiography provides the advantage
of electronic imaging but with a flexible phosphor
imaging plate, highlights Engelbart.
" The plate is flexible and can be cut, bent and
placed similar to film. The plate is placed inside a
scanning unit where a laser picks up the image and
stores it, then wipes the plate for reuse, " he said.
Considerable innovations have also been made in
automated defect recognition, sometimes termed
" assisted defect recognition, " according to Engelbart.
" Using neural network learning, software has
been trained to make decisions on whether to
accept or reject inspected materials or components.
The program is not given authority to make final
decisions but makes the evaluator aware of data or
anomalies that can lead to a more informed decision, "
he said.
NDT Certification for MROs
The certification of an aviation MRO facility involves
a series of intensive audits of all phases of its NDT
operations, points out Engelbart.
" There are numerous ISO documents and ASTM
standards, guides and recommended practices that
may serve as guidelines to audits; an example of such
a document is ASTM E543, Standard Specification
for Agencies Performing Nondestructive Testing.
This specification in turn references several other
documents that cover a broad range of NDT methods
and applications, " he said
Items that might be targeted in an audit of an
NDT operation include the fitness of equipment,
personnel or a facility to perform each NDT method
for which certification is desired, equipment calibration
and traceability, and reference standard
traceability, according to Engelbart. Personnel
training and certification is also important, and
specifically formal training, the process of documenting
on-the-job training hours for method and
applications, training oversight, and the process of
advancing personnel through certification levels.
Other audit areas include the process for developing,
documenting and approving NDT procedures, and
record keeping and retention, he says.
Each potential customer of an MRO - be it an
aircraft manufacturer, an engine manufacturer
or aircraft operator - may have its own specific
requirements and is entitled to perform its own
audit on the NDT operations, emphasizes Engelbart.
" One approach to satisfying numerous customer
requirements is to obtain the National Aerospace
and Defense Contractors Accreditation Program
(NADCAP) certification. This is a governmentindustry
cooperative that has developed a standardized
and rigorous audit process; becoming a
certified supplier allows customers to select the
MRO without the added expense of their own audit
process, " he concluded.
www.AviationPros.com 19
http://www.AviationPros.com
September-October 2022

Table of Contents for the Digital Edition of September-October 2022
