Boeing Technical Journal A Century of Boeing Innovation in NDE

eing Technical Journal

A Century of Boeing Innovation in NDE

Gary

eorgeson

Abstract – This past year Boeing reached its 100 year birthday.

The author has been inspired by this significant milestone to

provide a review of the advancement of a specific technology

area—namely NDE (Nondestructive Evaluation)--that has been

an important part of Boeing’s success during its first century of

building airplanes. Boeing has been a world leader in NDE

innovation, developing technology and methods for ensuring the

structures with which it builds its many aerospace products are

safe and are performing as-designed. This paper introduces the

reader to the subject and purpose of NDE, and then goes on to

address important past, present, and future elements of NDE

development at Boeing.

Index Terms – Inspection, Nondestructive Evaluation. NDE,

NDT, NDI, Testing, Ultrasound, X-ray, Eddy Current, Bond

Strength, Composite, Laser Ultrasound, Backscatter, AUSS,

Blade Crawler, ROVER, Laser Bond Inspection

I. INTRODUCTION

As the Boeing Company enters its second century of flight,

it is worthwhile to review the advances that have been made

in an important technology area—namely Nondestructive

Evaluation (NDE)—that have paralleled and sometimes

enabled so many others. At times this core competency is

referred to NDI (Nondestructive Inspection) or NDT

(Nondestructive Testing), depending upon its particular

application or industry of use.

NDE can generally be defined as the evaluation of a

structure without harming or affecting its purpose. This

definition sets NDE apart from destructive or mechanical

testing of subscale or full-scale structures, which allows the

determination of properties or flaws, but which makes the part

unusable afterwards.

The specific goals of NDE (and NDI or NDT) have been

expressed very well by Robert McMaster in 1959 in the

American Society of Nondestructive Testing (ASNT)

Handbook [1]:

• Ensuring Reliability of the Product

• Preventing Accidents and Saving Lives

• Making a Profit for the User

o Ensuring Customer Satisfaction

o Aiding in Better Produ

ct Design

–Weight and Cost Savings

o Controlling Manufacturing Processes

o Maintaining Uniform Quality Level

o Providing Early Warning of

Impending Maintenance Issues

o New Products and Business

Opportunities

BOEING TECHNICAL JOURNAL

Ensurin

g reliability of the product and preventing accidents

and saving lives are important and obvious goals for

NDE. The goal of "making a profit for the user" is

often underappreciated, yet is essential to the effective use

of NDE for a manufacturer like Boeing. As aerospace

manufacturing platforms have grown more competitive in the

recent decades, NDE development as a cost and flow

time-reducer has become more critical to Boeing.

NDE research and development has been organized in

various forms and organizations over the last century. This

responsibility currently resides within the Advanced

Inspection Technology (AIT) group, under the Advanced

Production & Inspection group within Boeing Research and

Technology (BR&T). AIT’s mission is to be the provider

of NDE innovation and technology for all Boeing

products, services, and customers. This mission is

accomplished through NDE and measurement research,

NDE system development, analysis for advanced materials

and structures, and NDE/Measurement support to business

units and the enterprise as a whole.

NDE for aerospace industry covers two distinct but related

application areas: NDE during production, and NDE

during in-service usage. NDE for both these application

areas has evolved dramatically over the last 100 years. The

tremendous advancements in aerospace materials and

structural designs—from cloth bi-planes, to largely

aluminum structures, to composite primary structure—

have required aggressive and innovative advancements in

NDE.

II.

ISTORY OF AEROSPACE NDE

The early history of NDE emergence into aerospace is a

fascinating one. When the Boeing Company was founded in

1916, only three industrial NDE approaches existed at that

time: visual inspection, the “oil and whiting” method (which

would later become what we know as penetrant inspection),

and radiography. These methods were developed from non-

aerospace applications and applied to Boeing airplanes.

Visual inspection processes were developed in the mid-19th

century in response to boiler failures, including the famed

Sultana incident which killed almost 1900 POW’s returning

from the Civil War. This was the first maritime disaster in US

history. The oil and whiting method was developed in the mid-

19th century to support rail inspections for the railroad

industry due to a number of catastrophic failures. Wilhelm

Roentgen developed the first x-ray inspection process in 1895

and his first paper discusses the possibility of flaw detection

for industry [2].

Visual inspection was exclusively used in the early years of

aircraft up to the early 1930s, when the first all metal airplane,

the Boeing Model 247 was introduced. From an

NDE perspective, the 1920s saw the introduction of

industrial radiographic inspection processes for metals

developed by Horace Lester [2] and the first

magnetic induction/magnetic particle inspection

approach by DeForest and Doane [3].

These were applied on a limited basis fo

r inspection of Model

247 components as well as the more mass-produced

Douglas DC-3 that came along in 1936.

DC-World

War II saw the development of the first eddy

current instruments as well as the first ultrasonic testing

method developed by Floyd Firestone [4]. These

became the crux of aerospace NDE as Boeing entered the

jet age in the mid-1950s. As the space program came

along in the 1960s, Boeing (McDonnell) had a hand in the

development of the first sondicator to support inspection

of heat shield bonds on the Gemini spacecraft, probably

the most critical element of the vehicle. The early

sondicator led to development of more advanced

low frequency bond testing methods still used today for

inspection of adhesive bonds.

III. PROGRESS IN AEROSPACE NDE

The first commercial Boeing airplane structures, like the

ne shown in Figure 1, were visually inspected during

manufacturing to verify proper wood frame assembly, fabric

attachment and adhesive application during fabrication. These

early airplanes were periodically visually inspected during in-

service use for damage such as fabric tearing, adhesive failure,

and wood frame damage or degradation. No instruments

beyond the human eye were used, except possibly

lighting aides or magnification to improve defect

detectability.

The rather rapid move from wood, cloth and glue to

aluminum aircraft structure (Figure 2) required the

development of NDE technology and methods that are still

used today in one form or another. New material systems

with new risks and uncertainties were often prevented from

finding widespread use on aircraft until NDE technology was

available to address the unknowns.

Figure 1. Early Boeing airplanes like this one were visually

inspected.

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Figure 2. Airplanes made o

f aluminum structure, like this

Boeing 707, increased the inspection challenges

and opportunities, and led to many applications for

emerging NDE methods.

Several major air catastrophes dro

ve the need for

better NDE. F-111 airplane crashes (late ‘60s and early

‘70

s) due to fatigue-induced cracking led to a ‘damage

tolerance’ strategy for design and inspection. The F-111

crashes led to the introduction of the fail safe /

damage tolerant design philosophy [5]. The first aircraft

designed in the damage to

lerance era was the Boeing

(McDonnell) F-15. Boeing, along with Pratt & Whitney

from the engine side, took the lead in addressing inspection

reliability in co

njunction with all NDE processes used to

support manufacturing. Boeing also was the first to utilize

structural analysis and NDE reliability assessments to

define in-service inspection intervals. The well-known

88 Aloha Airlines fuselage peeling led to an ‘aging

aircraft’ monitoring approach. The Aloha Airlines

explosive decompression incident in 1988 was caused

widespread fatigue damage. This incident, along with

the United Airlines DC-10 crash in 1989 (engine) and

corrosion failures associated with the KC-135 in the early

90s led the FAA to join with the DoD and NASA to

cooperatively address aging issues. This resulted in

significant funding going to aging aircraft research,

including NDE. Mu

ch of the funding that was applied to

development of new AUSS Mobile (page 4, and Figure 5b)

capabilities was derived from the aging aircraft initiative.

The Columbia STS-107

disaster, when the orbiter broke up

on re-entry, was also a driving force for new NDE. Boeing

ad a major role in NDE development associated

with the shuttle “return to flight,” including new inspection

processes for carbon-carbon ceramic materials, spray on

foam insulation, and thermal barrier systems. Boeing also

rought visual inspection to a new level during this time,

having a hand in development of a visual inspection process

performed in space.

Airp

lanes, like many other structures today, are designed

to be damage tolerant, so that NDE of detectable damage

occurs befo

re part failure. Inspections designed

specifically for monitorin

g aging mechanisms,

like corrosion, are used to p

revent failure of the structure.

In-service NDE would be used to identify damage while

it was within the designed tolerance and safety limits,

so that repair or replacement could be done before the

part fails. The result of a failure will depend upon whether it

is critical flight hardware or secondary (non-critical) structure.

While visual inspection continued to be the primary NDE

method, visual inspection could no longer address the

defect and damage detection needs, especially in-service.

Metal fatigue caused by the cyclic stresses of aircraft flight

produces small cracks that must be identified before they

grow to the point of structural failure. These fatigue

cracks, and cracks generated by excessive loads or

corrosion could be identified using an NDE method called

dye penetrant, which relies on a dye wicking into surface

cracks. Structural parts made with most steels could be

inspected with magnetic particle inspection. Both these

methods essentially enhanced visual inspection, and

continue to be used today for tubes, brackets, housings, etc.

Visual inspections require human reckoning that require

high skill interpretation and judgment. As the need for

inspection increased new instrumented methods had to be

developed to allow discovery with less judgment.

An electric current-based method called Eddy Current (EC)

testing, developed first in the industries making and

inspecting pipes and tubes, was the first significantly utilized

instrumented method of NDE in aerospace. With this method,

a changing electromagnetic field is generated by a coil

containing alternating or pulsed electric current. The field

produces corresponding electric (eddy) currents in the metal,

whose paths are modified by cracks. The same coil or a

separate receive coil senses the field change that the eddy

currents produce, thereby allowing detection of cracks using

electronic circuitry and (first) analog then (later) digital

display. Figure 3 is a photo on an inspector using an eddy

current instrument to find cracks in an airplane structure.

Magneto-Optical Imaging (MOI) was developed in the ‘80s to

enable 2-D EC-based imaging of cracks around fasteners in

fuselage lap joints and other structures. Linear EC arrays have

more recently been developed that can be swept along a lap

joint for in-service inspection for cracks around fasteners.

Film x-ray was the first radiographic NDE method used for

aerospace structure, to find cracks, voids, and foreign

material. It was also very effective with moisture detection in

metal honeycomb used for flight control surfaces, like flaps

and trim tabs. Boeing was involved in the development and

implementation of advanced radiographic inspection

processes in the 1990s, including Digital Radiography (DR)

and X-ray Computed Tomography. The film-to-digital

transition was driven by the advantages of digital data sets as

well as the cost reductions and environmental benefits of

eliminating film, processing chemicals and disposal. Digital

forms of X-ray like DR and CT have replaced film x-ray for

many aerospace applications in recent decades, due also to

the development and advancement of X-ray detector panels.

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Figure 3. An insp

ector is using a portable eddy current

instrument to inspect for cracks on an airplane structure.

Boeing R&D work under Air Force sponsorship in the early

to mid-1990s established standards for CT evaluation of

aerospace components and the resulting reports are still

referenced today [6]. CT provides 2-D and 3-D imaging of

material density, voids, porosity, and geometry, with very

high resolution capability for smaller parts. Boeing uses these

systems today mostly for structure and material system

analysis and manufacturing R&D. Today, CT is a key

technology in supporting qualification and certification of

metallic parts fabricated using additive manufacturing

processes.

Ultrasonic Testing (UT) is another important NDE

method for aerospace structure. UT uses high frequency

stress waves generated at the surface of a structure to

interrogate a structure for defects that reflect or attenuate

the signal. UT can be performed from one side of a part

with a single transducer that sends and receives an

ultrasonic signal, or in a through-transmission mode,

with a sensing transducer listening for losses in

transmission that is caused by flaws. UT has the benefit

of being able to see deeper flaws than EC, and will work

in non-electrically conductive media. UT’s use on

aluminum aircraft structure has grown over the years, in

particular with identifying in-service damage and

degradation [7][8].

As the complexity and design criticality have increased,

composites, as a percentage of an airplane structure, have

increased as well. Boeing (McDonnell, at the time)

pioneered the use of structural composites, starting with

the boron/epoxy rudder developed for the F-4 back in the

60s and then expanding dramatically with the

development of the F/A-18 and AV-8B Harrier II back in the

late 1970s. The AV-8B, 27% by weight composite, was the

first aircraft to employ an all-composite wing. These

accomplishments drove the development and

commercialization of automated ultrasonic systems in the

late 1970s and early 1980s.

While secondary structure on commercial aircraft,

like flaps or ailerons have been made for years with

composites, significant use is relatively recent. The Boeing

787 uses just over 50% by weight of composite materials

on its primary structure (Figure 4), and the 777X is being

developed to have composite wings and metal fuselage.

Composite materials are ideal for an airplane. Composites

are conducive to larger, more integrated designs.

Composites allow for tailored properties, such as

stiffness or tensile strength, they are fatigue and corrosion

resistant, enabling reduced maintenance costs and fewer

inspections. But the complexity of composite structure

has driven the need for innovation in NDE, directed at cost-

effective methods that will assure manufacturing

quality and safe in-service performance.

Figure 4.

Boeing 787 Dreamliner, whose structure is just

over

50% composite by weight.

Ultrasonic inspection of composites has benefited from

improvements over the years with electronics, automation and

computing power, so that 2-D and 3-D imaging and analysis

of UT data is now common place. Boeing has been a world-

leader in the development of automated ultrasonic

scanning systems, for production and in-service

inspection of composite structure. Boeing researchers

have developed and implemented many ultrasonic x-y-z

automated gantry, water tank UT, feed-through, and

(recently) robotic scanning systems that are used

internally and also sold world-wide under the Boeing

AUSS (Automated Ultrasonic Scanning System) moniker.

Composite aircraft wing and fuselage skins, spars, stiffeners,

floor beams, and other laminate structures are inspected

with a Boeing AUSS, with a single operating system that

enables elements such as inspection path planning, probe

signal activation and collection, and data display and

analysis. Two e

xamples of Boeing AUSS options are

shown in Figures 5a and 5b.

BOEING TECHNICAL JOURNAL

The current Boeing AUSS product line offers a

standard

user interface, modular hardware interfaces,

sensors and motion control systems, and is critical in

supporting current and future Boeing composite aircraft

manufacturing.

To date, over 70 AUSS gantry systems (such as shown in

Figure 5a) are used across the aerospace industry by OEMs,

composite part manufacturers, as well as Department

of Defense maintenance facilities. The AUSS Mobile

systems (Figure 5b) used for portable multi-modal (UT, EC,

etc.) on-aircraft scanning, have become standards for a

broader range of maintenance operations, including

corrosion detection, crack detection and disbond

detection in bonded structure. Over 130 systems have been

sold to industry, government and academia in support of

manufacturing, maintenance and research and

development. In total, the impact of Boeing’s advances in

automated systems have resulted in over a hundred

million dollars in equipment sales and billions of dollars

in cost savings, through reduced inspection time and

improvements in quality.

Figure 5a. Boein

g AUSS Tower, used for NDE of large

composite structure during manufacturing.

IV.

ECENT ADVANCEMENTS IN AEROSPACE NDE

There have been man

y innovations in NDE technology and

methods in the last several decades that have impacted

the aerospace industry. Increases in computed-based

data collection speeds and storage capacities have

transformed many industries, including NDE. One NDE

method that has benefitted has been ultrasound, with the

innovation of phased array ultrasound (PAUT), which was

originally developed in the medical field for looking into the

human body. With this technology, a linear set of

transducers can be activated in various time-phased or

simultaneous options that dramatically increase ultrasounds’

speed and capabilities over traditional single transducer

inspections. Boeing researchers have developed and

implemented many end effector innovations using

ultrasonic PAUT technology [9]. Most composites

structure fabricated by Boeing or its suppliers is now

inspected with PAUT-based inspection systems, and PAUT

is fully integrated into the Boeing AUSS family. Boeing

has also taken advantage of the development of

robotics to develop advanced NDE systems for the 777X.

One excellent example is the 777X wing spar inspection

cell that uses multiple robots to handle the spar and

move out of the way when the inspection robot moves past

to collect PAUT data (Figure 6).

Figure 6. 777X Wing spar Robotic NDE Cell.

The row of

robots on the left hold and spar, while the robot on the right

inspects it.

New NDE approaches are also needed to support in-service

commercial and military aircraft and space systems.

Improved in-service NDE sensors and methods are being

developed to rapidly conduct fleet inspections with less

disassembly. These sensors generally fall into three

categories: 1) limited access inspection tools that enable

inspection of interior structure without disassembly, 2)

structural health monitoring or In-Situ NDI sensors, systems,

and 3) sensors with speed, defect sensitivity, cost, simplicity

of use, or networkability improvements.

The goal of Boeing in-service NDE R&D is ultimately to

increase business revenue through the development, and

implementation of in-service NDI equipment and procedures.

There has always been an important role for NDE support to

the Boeing business units, and Enterprise as a whole. This

support includes in-service FAA responsiveness (fleet

inspection procedures, airworthiness directives), supplier 911

Figure 5b. Boein

g AUSS Mobile, used for on-aircraft in-

service NDE applications.

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calls, service bulletins, personnel certification requirements,

NDE inspector roles, NDE equipment qualifications at Boeing

and its suppliers, NDE standards, and rapid support for

unplanned event needs across the world.

Business-related NDE benefits Boeing has enabled and

passed on to its customers include: reduction of inspection

time and cost, increased inspection intervals, reduction of

tear-down and re-assembly costs, and critical structure/system

implementation. We have delivered improved NDE

technologies and methods to depot and field-level personnel,

and provided high-value NDE support services to our

commercial and military customers. Several examples are

described below.

A ‘Surgical NDE’ tool is any device, whether hand held or

fully automated (or anything in between) that allows an NDE

sensor to be guided through an access hole of a closed space,

and placed on or near a region to be inspected. The primary

purpose for Surgical NDE tools is assessment without

disassembly. When the 787 program needed a means for

customers to inspect the center section of the horizontal

stabilizer through multiple bulkheads, a Boeing NDE team

applied what they learned building and testing a tool for the

Air Force [10] shown in Figure 7 to a more advanced next

generation motorized ‘Extended Reach Tool.’ The ‘Extended

Reach Tool' is baselined for use on up-coming 787

maintenance D-checks and is expected to cut Boeing and

customer inspection cost and time by more than 50% by

eliminating disassembly and re-assembly shown in Figure 8.

gure 7. USAF Surgical N

DE Tool developed under

contract to Boeing.

Figure 8. The Boeing Extended Reach NDE Tool was

developed for surgical inspection applications, including

the inspection of fastener areas in the interior bay of the

787 horizontal stabilizer center box. The tool contains

multiple rotating motorized joints, a telescoping end

joint, and a camera for situational awareness.

‘In-Situ NDE’ is the name for the general application

of NDE sensors directly on a structure structural testing or

in-service use. In the structural test application, multiple

NDE sensors are mounted using various methods at locations

where failure is expected to initiate or grow under load. In-

Situ NDE enables precise correlation of loading conditions

and levels to specific composite damage, thereby allowing the

validation of designs and failure models/predictions.

Boeing NDE researchers developed and patented the

sensor attachment and data collection method, which is now

used on virtually all Boeing composite structural testing.

In-Situ NDE provided critical location damage monitoring

on the 787 sub-scale and full-scale tests used to validate

structural performance. In-Situ NDE is now implemented

on all 787 and 777X composite structural tests. An

estimated $2-4M per year is avoided by replacing a

percentage of costly tests with advanced analysis methods

enabled and validated by In-Situ NDE. A $1M/yr

estimated additional value comes from improved

damage monitoring of more than 100 tests per year. In

2015 a costly 787 side-of-body repair was avoided with the

help of In-Situ NDE data. Figure 9 is a photograph of In-Situ

NDE ultrasonic transducers attached in various means to

structures under test.

Figure 9 (left). Photographs of various In-Situ NDE

sensors attached to test structure. The left photo is of a

patented spring-loaded mount for ultrasonic

transducers that maintains a well-coupled contact with

the surface. The right photo shows an array of mounted

sensors to track damage initiation and growth. The center

photos are a bottom and top view of an alternative

mounting for In-Situ NDE.

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In-Situ NDE for inspecting in-service aircraft is also being

developed by Boeing and the aerospace industry in

general (In the in-service contex

t, In-Situ NDE is often

referred to as Structural Health Monitoring or SHM). The

method involves the application of ultrasonic, eddy

current, comparative vacuum, or other kinds of sensors

directly to a specific structure that has limited access, is

critical, or is known to be subject to damage. A reliable In-

Situ NDE method can reduce the high cost and time of

disassembly, NDE activities, and re-assembly that would

otherwise be required [11].

The benefits of NDE automation for in-service applications

include process speed improvements, data

consistency improvements, reduced labor cost, and

increased personnel safety. Boeing has taken the

initiative to develop various automated tools for NDE that

can extend or supplement the important AUSS product

line, particularly for in-service inspections, and provide

for greater personnel safety by eliminating the

requirement to be on or adjacent to the aircraft under

inspection. Two recent innovations are the ROVER

(Remotely Operated Vacuum Enabled Robot) for aircraft

exterior structural inspection, and the Boeing ‘Blade Crawler’

for rotorcraft rotorblade NDE. The Boeing ROVER system

(Figure 10) was developed to reduce the manual labor and

inspection time associated with in-service aircraft wing

and fuselage inspections [12]. The Boeing ROVER system

uses a crawling robot with specially designed floating

vacuum heads that hold the crawler to the surface while

still allowing it to move over laps, gaps, and minor

surface perturbations. Holonomic (or Mechanum)

wheels allow movement of the crawler in any direction or any

rotation, independently or simultaneously. This feature

optimizes scanning capability and area coverage. Crawler

guidance and locating is done using one of two off-board

positioning systems: the low cost portable Boeing-developed

Local Positioning System (LPS) (shown in Figure 10), or the

higher resolution Motion Capture (MoCap) technology that

enables the tracking of multiple crawlers at the same time.

Current efforts are underway to assess ROVER

implementation opportunities with military and commercial

aircraft customers. There has also been interest in a modified

ROVER for oil tank inspection, using magnetic attachment

instead of vacuum.

The Boeing Blade Crawler (Figure 11) is a spin-off

technology from the ROVER development. It is a self-

propelled automated inspection system that scans one or more

NDE probes or arrays over the surface of a helicopter

rotorblade, as it crawls from one end of the blade to the other.

Because the Blade Crawler can operate on rotorblades in-

place, in-service blades can be inspected faster and without

costly and time-consuming removal, reinstallation, and re-

balancing. In additional, the automated data collection

improves the quality and consistency of the information over

hand-held methods, and enables damage trend analysis and

improved repair planning. Boeing recently licensed the Blade

Crawler technology to NDT Solutions, which will enable

Boeing to offer this innovation to rotorcraft customers, like

the U.S. Navy.

Other Boeing developed NDE technology innovations are

changing the way the industry assesses aerospace structures.

One example is the Boeing-developed X-ray Backscatter

system, that creates an image of the interior of a structure by

scanning an x-ray pencil beam across it and collecting the x-

rays that scatter back (X-ray Backscatter was originally

proposed by Boeing as a method of NDE in the 1970s, but

then set aside due to the cost and speed limitations of legacy

technology. Because of terrorism and border security

concerns of the 1990s, the security industry rapidly evolved

the technology to decrease the cost and size and increase its

capability, therefore, making it more attractive to develop as

an NDE tool). X-ray Backscatter does not require access to

both sides of a structure in order to do an inspection, which is

an advantage for NDE of both large and in-service structures.

It also selectively scatters from and discriminates between

materials. The method is particularly sensitive to adhesives,

moisture ingress, density changes, voids and foreign object

debris. It has recently been shown to be able to characterize

Figure 11. The Boeing Blade Crawler is shown

traversing a helicopter rotorblade

during an inspection.

Figure 10.

Boeing ROVER (Remotely Operated Vacuum

Enabled Robot) for aircraft (and other) exterior structural

NDE. In the left photo the system is shown during an

inspection demonstration, with the mobile automated

boom that provides fall protection, power, and

communication to the crawler, which is shown in the lower

left photo. The LPS (shown in the upper right photo) is

one method that is used for guidance and tracking of the

crawler.

BOEING TECHNICAL JOURNAL

composite heat damage and detect wrinkles in composites.

More research is needed to quantify these new capabilities.

Figure 12 is a photo of the Boeing X-ray Backscatter

system and several imaging examples. The inspection head

can run on a track during data collection, or be mounted on

the end of a robotic arm.

Figure 12. Boeing X-ra

y Backscatter system photograph

(left), imaged hat stringer with a crack due to a blunt

impact (middle), and water in a honeycomb panel (right).

Laser Ultrasonic Testing (LUT) is an alternative

approach to traditional UT that has been developed for

application to composite aircraft structure. Ultrasonic

stress waves are generated by a laser pulse (instead of a

piezoelectric element) and detected (after interacting with

the structure) with a second laser interferometry system.

The benefits include non-contact (no couplant), no

perpendicularity required with the surface, and broader

frequency content that provides improved flaw

characterization. LUT systems, manufactured by companies

such as iPhoton (Fig. 13), PaR, and Technatom, have shown

cost benefit usage for certain complex parts built by

Lockheed Martin (F-35 production) and Airbus (in

development). But these systems are high enough cost ($3-

$7M) that the cost-benefit trades haven’t yet worked for

Boeing applications.

Figure 13. The iPhoton Robo

t Mounted System is

commercially available off-the-shelf, but has proven

too expensive for any Boeing applications.

Fortunately, Boeing has been working with the University

of Washington to invent a lower cost LUT alternative, called

the PULSAR (Pulsed Ultrasonic Laser Scanner And

Receiver). The Pulsar is a Laser UT system that uses a low

cost, lower energy fiber-based laser that is pulsed at a high

repetition rate. While it shows much promise, the PULSAR

still requires modificatio

ns and development before it can be

used for production use. Lab prototypes in Seattle

and Charleston will be used for this purpose (Figure 14).

Complex geometry and edge inspection of Boeing

composites (including the 777X wing skin edge trim)

are under consideration, among other applications for

LUT. A 2015 invention called ISAFE (Integrated

Shielding Apparatus for Factory Environment) that enables

Laser UT to be used safely in a manufacturing environment

is slated to be developed in 2017 under a NASA-funded

program.

Figure 14. Boeing PULSAR

(Pulsed Ultrasonic Laser

Scanner And Receiver) lab set-up.

Because of the manufacturing cost and weight benefits,

all-bonded structures are being considered for

replacement of fastened composites. However, design of

bonded structure assumes that there is full adhesion, and

that bonds will not weaken over time. NDE techniques can

measure parameters or features such a void fraction, wave

speed, bulk modulus, thickness, etc., but not strength.

Validation of the strength of bonded primary structure

currently requires proof testing, but proof testing of bonded

structure can be very expensive and difficult.

Test Part

Excite Head

Receive Head

Figure 15. Laser

Bond Inspection methodology for

measuring bond strength.

BOEING TECHNICAL JOURNAL

Former Boeing Senior Technical Fellow Dr. Richard Bossi

and his team invented an alternative method using stress

waves generated by a high energy pulsed laser to provide

localized proof testing. The approach is nondestructive to

nominal strength bonds, but fails weak bonds and acts as an

indicator of bond strength. The way Laser Bond Inspection

(LBI) works is shown below in Figure 15.

The LBI device actually measures bond strength. A

photograph of the test panel with three levels of bond strength

is shown in the upper left of the Figure 16. The ultrasonic C-

Scan image of the panel revealing no difference in the

attenuation due to the various levels is shown in the upper

right of the figure. The included table compares the LBI

results with various mechanical tests, showing the

effectiveness of the method.

Figure 16. A panel with a range of bond strengths,

traditional NDE (through-transmission ultrasound) revealing

no differences, and the LBI Device results that show

bond strength differences.

Figure 17 shows a photograph of the LBI Device and its

application to testing composite structure. LBI works well on

composite to composites, though there are limitations due to

thickness and quality of materials. Over the last few years, the

USAF has been funding Boeing, together with other

aerospace companies, to conduct research to quantify

LBI capability for a certified bond strength

measurement. Automation of LBI, using robotics, is also

being assessed at Boeing, for potential manufacturing

verification of bonded structure [13]. It is worth noting

that the NDE technologies developed and matured by the

Boeing team have found valuable applications beyond

characterizing defects during inspection. Imaging

technology and methodologies like photogrammetry

and profilometry that were originally developed to

characterize defects in the shape or finish of a surface, are

now being used for reverse engineering applications

to support 3D modeling of legacy aircraft during

modification and upgrade efforts. Past NDE related radio

frequency research has now been spun to create RFI

technology used to track products and inventories in our

factories.

Figure 17. A photograph of the LBI Device (left) and its

use testing composite structure (right) The LBI Device was

developed by Boeing, with funding from the USAF, and

built and sold by LSP Technologies Inc, Dublin, Ohio.

Dr. Al Stewart conducts the test while Marc Piehl looks on.

IV.

OEING’S NDE FUTURE

Probably the best question to ask as we approach the

conclusion of this paper is this: What are key NDE development

areas that we can expect to see within Boeing ask we look into

the future [14]? Below are some preliminary answers to that

question:

NDE in the future will include automated data analysis

(ADA) that increases throughput by reducing time-consuming

human-based data analysis. Lower cost pedestal and modular

NDE robots will replace the current higher cost, large footprint,

stationary scanning systems [15].

Factory flow will be optimized for speed and cost with

automated crawling NDE platforms. NDE sensors will see

significant technology innovation. Waterless stand-off NDE

sensors, such as Laser Ultrasound Arrays, will inspect complex

shapes and edges faster, without having to touch the part or deal

with water collection and recirculation issues. Thinner

laminates, like the 787 barrel skin, could soon be inspected with

faster, large area NDE methods, such as Infrared Thermography

(IRT), with UT used only for characterization of flaws (Boeing

has previously advanced IRT for inspection of SPF/DB titanium

parts and moisture detection in radomes, and we are exploring

IRT for inspection of non-critical composite parts).

The value of utilizing NDE and other measurement data as a

process control tool is only now being fully appreciated. The

goal is to move inspection (such as UT, IRT, CT, etc.) back up

the manufacturing chain so it becomes transparent to the

fabrication process. This approach will drive quality

improvements through trend analysis, and reductions in process

variations. In-process sensor feedback during manufacturing

will be expanded to newer manufacturing methods, like additive

manufacturing [16].

Ultimately this approach will tie the NDE and measurement

data into a "digital thread" that supports cost-effective

implementation and maintenance during the entire life cycle of

the aircraft. Better NDE during the design process reduces the

uncertainty of new manufacturing capability and allow design

teams to have confidence to optimize the design and not add

BOEING TECHNICAL JOURNAL

costly overdesign to account for uncertainty. Better NDE

during development optimizes production, resulting in

fewer requirements for NDE in perpetuity.

Fully bonded composite aircraft are an important part of

the future for Boeing, because they can be made lighter, and

will cost less to build, fly, and maintain. While the LBI

device discussed above is a good initial solution for bond

strength verification, lower cost alternatives will be

discovered and developed.

For in-service NDE, some new capabilities that are likely

to b

e implemented to reduce NDE costs include

nanotechn

ology, self-sensing structures and surfaces, robotic

surgical NDE, and

fully networked remote expert (tele-

erational) NDE that extends the reach of the expert to

virtually any place in the world. New advan

ced NDE sensors

will impro

ve damage characterization capability and extend

the time required between in

spections. For example,

Magnetoresistive and Millimeter Wave Sensors (for crack

detection, and Frequency Selective Resonance (FSR) methods

(for honeycomb

/sandwich structure) are being developed at

Boeing today, for future implementation on in-service

aircraft. Advances in radiographic method

s, including

Computed Tomography, X-ray Backscatter, and Neutron

Radiography are also part of Boeing long-term R&D plan to

provide the best possible NDE tools when new critical,

difficult, o

r time-sensitive challenges arise [17][18].

ACKNOWLEDGMENT

The author wishes to acknowledge the many Boeing

engineers, scientists, and technicians who have contributed to

the development of NDE technology and methods over the

past 100 years. Their innovative ideas, unique designs, and

tireless efforts aimed at solving challenging inspection

problems have made Boeing today’s world leader in

aerospace NDE. Unfortunately, there are too many to

mention by name here. However, several of these

deserve specific mention for their significant contribution to

key developments described in this paper: Dr. Richard Bossi

and Dr. Al Stewart (CT, LBI, LUT); Dr. Don Palmer (AUSS

Mobile, in-service NDE, SHM); Morteza Safai, Talion

Edwards, and Jim Engel (X-ray Backscatter); Jeff

Thompson (IR Thermography) Tyler Holmes (IRT,

Remote Expert NDE); Dr. Jill Bingham, Jim Kennedy, Bill

Motzer, Dennis Sarr, Chris Vaccaro (UT advancements for

composites, LUT and UT ADA), Paul Rutherford, Jeff

Kollgaard and Nate Smith (Surgical NDE, Remote Expert

NDE, in-service NDE and EC advancements), Nancy Wood,

Scott Black, Barry Fetzer (AUSS and Robotic UT), Dr. Jim

Troy, Karl Nelson, Scott Lea, and Dan Wright (ROVER,

LPS), Mike Fogarty, Bill Tapia (In-Situ NDE), Bill Meade

(X-ray ADA); Martin Freet (general NDE advancements)

and Joe Hafenrichter (Blade Crawler). Sincere apologies are

offered to those deserving mention whose names or

technology developments the author has failed to include in

this survey paper.

Wayne Woodmansee (Boeing), Don Hagemeier (Douglas),

and Bob Roehrs (McDonnell) deserve special mention as

fathers of modern aerospace NDE, who were about a

generation ahead of those of us acknowledged above.

Hagemaier did more than anyone in developing in-service

inspection approaches, primarily eddy current, to support

commercial airlines. Much of his work led to established

standards used by ASTM, ASM and SAE. Roehrs was the key

driver in bringing an aerospace flavor to the American Society

for Nondestructive Testing, which had its beginnings in

industrial radiography. He was also instrumental in

establishing standards for NDT system and personnel

qualification, and in the early years of the damage tolerance

era, defining protocol for probability of detection.

Woodmansee had some pioneering work back in the 1960s

relative to automated UT systems development and signal

processing, well before automated systems became accepted

standards for large area inspection.

DEDICATION

Of course,

the future is impossible to fully predict. Many

factors will determine the direction of technology

development in any field. However, we can point to the fact

that Boeing has been a leader in NDE innovation this past

century. We should make every effort to continue that

passion for innovation that includes minimizing non-value-

added costs of inspection and maximizes the discovery and

utilization of the important NDE data. NDE researchers need

to work closely with NDE practitioners, as well as designers,

and manufacturers of our structures. If we do so, Boeing NDE

R&D will continue to play a key role in Boeing’s future as the

world’s premiere aerospace company.

VI. C

ONCLUSION

NDE is a critical technology area for Boeing, that has

grown and developed along with the company these past

100 years. A brief overview of the highlights of NDE

development at Boeing has been provided in this present

paper. As we move into our second century as a company,

the future of Boeing will continue to rely on NDE

innovation. If the past is any indicator of the future, many of

these innovations will come from Boeing personnel

working diligently to overcome the technical barriers to

new structure verification, while keeping an eye on

Boeing’s current and future business needs.

The author would like to dedicate this Boeing Technical

Journal article on NDE innovation to Mahender Reddy, the

Advanced Inspection Technology (AIT) Senior Manager

who retired this past year from Boeing after a long and

highly respected career. His consistent leadership and

strategic vision—supported by the entire AIT

management team—have produced a fruitful environment

for high impact NDE development, advancement, and

implementation at Boeing.

BOEING TECHNICAL JOURNAL

BIBLIOGRAPHY

[1]. McMaster, R., American Society of Nondestructive

Testing (ASNT) Handbook, 1959.

[2]. Jones, T.E., ed., From Vision to Mission: ASNT 1941

to 2016, pp. 8-21, ASNT, Columbus, OH, 2016.

[3]. Jones, T.E., Ibid., pp. 24-26.

[4]. Jones, T.E., Ibid., pp. 62.

[5]. Negard, Gordon, The History of the Aircraft Structural

Integrity Program, ASAIC Report 680.1B, San Carlos,

CA: Aerospace Structures Information and Analysis Center,

June 1980.

[6]. Georgeson, G. and R. Bossi, X-ray computed

tomography for advanced materials and processes,

USAF Report, ADA259828, 1992

[7]. Kennedy, J. C. and Bledsoe, P., Lean and efficient NDI

scanning technologies, models 737, 747, 757, 767,

777, Boeing Research and Technology collection, MDR

R-00403, 2001.

[8]. Kennedy, J. C., FA-18 NDI support, Boeing Research

and Technology collection, MDR R-00040, 2001.

[9]. Palmer-Jr., D., Rapid large area inspection

using ultrasonic phased arrays, Boeing Technical

Excellence Conference, 9th, 2005, Saint Louis,

Missouri, Report BTEC09 C07

[10]. Georgeson, G., Motzer, W. and Rutherford, P., Surgical

Nondestructive Evaluation (SuNDE), USAF

Report ADA549006, 2011.

[11]. Fogarty, M. and Georgeson, G., In-Situ NDI for real time

monitoring of aircraft structures during mechanical

testing, Boeing Technical Excellence Conference

20th, 2013, Lynnwood, Washington, Report BTEC20

STR30.

[12]. Nelson, K., Remotely operated vacuum enabled

robot (ROVER), BR&T Block Report BR7-14481-01, 2013.

[13]. Safai, M., Robotic integration high energy

pulse optimization and NDE correlation, BR&T Block

Report, BR9-16597-01, 2014.

[14]. Georgeson, G., NDT – A Continuing Responsibility

in the Future of aerospace, 10th Asia-Pacific Conference

on Non-Destructive Testing, 17-21 September 2001,

Brisbane, Australia,

http://www.ndt.net/article/apcndt01/papers/1205/1205.htm

[15].

Kennedy, J.C., Rapid inspection data analysis,

BR&T

Block Report, BR11-11528-03, 2016.

[16]. Bossi, R., Palmer-Jr., D., and Hudson, J., Nondestructive

Evaluation Vision to Meet Production Demands,

Boeing Technical Excellence Conference 18th, 2011, St.

Louis, Missouri, Report BTEC18 B06

[17]. Georgeson, G., Trends in R&D for

Nondestructive Evaluation of In-Service Aircraft,

5th International Symposium on NDT in Aerospace, 13-15

November 2013, Singapore.

[18]. G. Georgeson, Nondestructive Inspection for Composite

Aerospace Structures, 6th International Symposium on NDT

in Aerospace, 12-14 November 2014, Madrid, Spain

NDE Resources:

An extensive list of books on NDE techniques can be found

on the ASNT.org site on the ‘NDE Method References’ page:

https://asnt.org/Store/Browse?category=NDT%20Method%2

0References

Boeing Nondestructive Evaluation Technology Forum

Archive Server (Contact author for access.)

\\NW\data\NDETechForumArchive\

Boeing Enterprise Composite Handbook

http://catalog.web.boeing.com/search/i?

SEARCH=D950-11193&SORT=DX&searchscope=22

ISU CNDE NDT Resource Center web site –

http://www.nde-ed.org/index_flash.htm

ASNT Industry Handbook: Aerospace NDT, R. Bossi, Ed.

2014

ASM Handbook, Volume 21 Composites, “Nondestructive

Testing,” pp 699-725

Additional articles and presentations can be obtained on the

subject of NDE by searching the author’s name in the Boeing

Library:

http://catalog.web.boeing.com/search/a?SEARCH=george

son+g&searchscope=22

BIOGRAPHY

Gary Georgeson is the Boeing Senior Technical Fellow in

NDE. He holds a Ph.D. in Materials Science from the

University of California at Santa Barbara, and has worked for

Boeing in the Puget Sound area since 1988. In his current

role, Gary provides technical leadership aimed at advancing

NDE for aerospace structures, particularly composites, during

manufacturing and aircraft service.

Gary is a prolific inventor of NDE systems or methods. His

innovations have supported various Boeing platforms, and

helped Boeing win contract R&D programs from the USAF,

USN, NASA, and the FAA. He is often called upon by the

U.S. government and industry for advisory roles regarding

NDE. He has published or presented over 130 technical

articles, government reports, journal articles, as well as a

section of the ASNT NDE Handbook.

Gary has received five Boeing Breakthrough Technology

Awards, four Boeing Special Invention Awards, and holds

nearly 200 patents worldwide. He also received the ASNT

2016 Research Award for Innovation and the 2016 Robert C.

McMaster Gold Medal Award for NDE industry impact, the

2015 Mentoring Award from the American Society of

Nondestructive Testing, and the 2015 Jud Hall Composites

Manufacturing Award from the Society of Manufacturing

Engineers.

Gary is the currently Chairman of the Research Council of

ASNT, where he is a Fellow. His professional affiliations

include ASNT, SAMPE, SME and SPIE.

He also holds a master's in Theology, and is the founding

pastor of a local church, with a focus on serving the poor and

disenfranchised, and making a difference in people’s lives.