1) The internship report summarizes the student's 2-month internship at AVIATEST, a testing center that performs non-destructive testing (NDT) on aircraft. 2) During the internship, the student investigated static NDT methods and applied NDT skills to aircraft testing, including strain gage measurement on a Ka-62 helicopter and analyzing different NDT techniques. 3) The report provides details on loading systems for aircraft structural testing, strain measurement, and applications of visual testing, penetrant testing, magnetic particle testing, and radiographic testing.

1. INSTITUTE OF AERONAUTICS
Faculty of Mechanical Engineering,
Transport and Aeronautics
Riga Technical University
INTERNSHIP REPORT
A report on the NDT oriented internship performed in the AVIATEST
company Riga
Student: __Egbenchong A. Romaric
(Name, surname)
_____01/04/2016_______
(Date)
Assistant company supervisor:
A.Nevky ___________________
(signature)
Academic supervisor: Company supervisor:
V.Shestakov ________________ V.Turko ___________________
(signature) (signature)
Riga, 2016

2. Preface and acknowledgement
For two months from February 22nd 2016 till April 1st 2016, I did an
internship at the AVIATEST research and testing centre which is
included in the team of the department of LNK Aerospace of the LNK
Group holding company in the Republic of Latvia.
AVIATEST core business involves in field rig testing of aerotechnics
(frames of airplanes, helicopters and their aggregates). The centre
also tests airport equipment (aircraft hydraulic jacks, torque
wrenches etc.) and various building constructions. This internship
project is a part of my 2nd year master program which I conduct at Riga
Technical University (RTU) Latvia.
I worked on an assignment project to investigate the static NDT
methods in aircraft control. The main content of the project is the
application of NDT skills necessary for aircraft testing. This topic
brings me to a very new and interesting area of applying NDT skills in
the aviation industry.
The tests carried out during this internship are related to other
similar tests carried out in this domain. For that reason, some data
used in this work will be similar or identical to some information and
data from the same topic. As a result, updates were made only if
necessary or available so as to maintain continuity of the research
topic.
Through the assignment, I did not only gain a lot of knowledge but
more importantly, I also had a great chance to sharpen my skills in a
professional working environment. Not less important than the
communication technologies that I have learnt, is the communication
skills that I have been trained and practiced through giving
presentations, discussing with the supervisors, experts and
translating for my fellow colleagues (Russian to English and vice
versa) in the field and other staffs within and outside the company.

3. Table of content:
1. Chapter 1. Introduction
1.1 Problematic and internship objectives
1.1.1 Problematic
1.1.2 Internship objectives
1.2 Organization of this report
2. Chapter 2. Loading systems during air craft structural static
testing
3. Chapter 3. Strain gage measurement
4. Chapter 4. Application of NDT skills necessary for aircraft
testing
5. Chapter 5. Testing and evaluating composite materials
Summary and Personal analysis
Conclusion and future work
References

4. Introduction
It is certain that aircraft NONDESTRUCTIVE TESTING (NDT) is the most
economical way of performing inspection and this is the only way of
discovering defects. In simple words we can say, NDT can detect cracks
or any other irregularities in the airframe structure and engine
components which are obviously not visible to the naked eye.
Structures & various aircraft assemblies are made from different
materials, such as aluminum alloy, steel, titanium and composite
materials. To dismantle the aircraft in pieces then examine each
component would be cumbersome and require too much time. Thus, making
use of NDT methods provides an efficient, reliable and economical
solution to the problem.
In AVIATEST, 70-80% of NDT is performed on the airframe structure,
landing gears and the rest carried out on engine & related components.
In order to maintain the aircraft defects free and ensure a high
degree of quality & reliability and as a part of the inspection
program, the following NDT methods are mostly used in the company
- Eddy current testing
- Magnetic particle testing
- Visual/Optical testing

5. Chapter 1
Problematic andinternship objectives
I. Problematic
As briefly described, NDT is a technique used in controlling and
monitoring the life cycle and functionability of an aircraft without
altering its state.
Although destructive testing can be an effective and economical
solution for high-volume, low-cost components, it’s clearly
undesirable for larger, more expensive systems. If you want to test
the limits of a multi-million-euro jet engine, destroying it is a
drastic way to advance knowledge and/or science.
NDT is a very simple, efficient and finance friendly test method when
we look at the expensive and complex structure of aircrafts. During
the internship, aircrafts of the type Ka 62 helicopter Mi-26T and
Sukhoi Superjet 100 which are used mainly for experimental purposes
were present in the hangar.
NDT techniques are particularly useful for monitoring and testing the
kind of high-value, safety-critical components used in the aerospace
industry.
II. Internship objectives
Based on the observation that NDT is an efficient and economical
aircraft testing method, the main research objective of this
assignment is to study the application of NDT skills necessary for
aircraft testing.
The main objective above can be decomposed to 4 smaller objectives:
- Full-scale fuselage fatigue testing
- Wing fatigue testing
- Flap testing
- Horizontal tail testing
- Skin panel fatigue testing
- Landing gear attachment frame
- strain gage measurement
- Presentation of damage tolerance analysis software
- testing and evaluating composite materials
1.2 Organization of this report
The report is organized as follows:

6. - Chapter 2 will introduce a technical description of loading
systems during air craft structural static testing.
- Chapter 3 is about Strain gage measurement on the Ka 62
- Chapter 4 Application of NDT skills necessary for aircraft
testing
- Chapter 5.Testing and evaluating composite materials
- Personal analysis/summary
- conclusion

7. Chapter 2
Loading systems during air craft structural static testing
Fig1. Aircraft mounted and prepared for full scale tests in the
AVIATEST test hangar
Ultimate strength and fatigue tests are examples of static tests that
are critical for validating structural designs. Ultimate static
strength tests play a critical role in ensuring that a structure such
as an airplane wing can withstand extreme loads caused by nature such
as wind shear or other large transient forces.
Although these tests are an essential part of the testing phase, the
structures will only encounter a maximum of 67% stresses of this
magnitude in the real world. During static testing, the actual
strength of the structure is compared to simulations and design
specifications. Test data can reveal areas of concentrated stress that
were not well highlighted in the simulations. This data can also be
fed back into the models so that the simulations can be refined,
uncovering other areas to focus test efforts on. Once this iterative
process of determining absolute static strengths is well understood,
the next step is to validate the durability of the structure over

8. time. The aircraft on which the tests and experiments are carried on
is termed “Leader”.
TYPES OF LOADS
Basically, an aircraft is required to support two types of loads:
1. Ground Loads :Encountered by the aircraft during movement on the
ground; ie: taxying, landing, towing, etc
2. Air Loads: Loads exerted onto the structure during flight by the
manoeuvres carried out by the aircraft or by wind gusts (such as
wind shear).
Added to these, other role specific loads may also be generated by the
aircraft such as:
High Altitude Flying: Pressurized cabin,
Amphibious aircraft: Landing on water,
Military Aircraft: High Speed Maneuvers and resistance to considerable
damage.
Static Ground Condition
Fig2. Aircraft Static ground loads

9. Where:
RNose: Ground reaction at nose wheel
RMain: Main undercarriage ground loads
W : Mass of aircraft acting at centre of gravity (= Mg)
Aerodynamic Surface Loads
During flight, all aircrafts under steady flight maneuvers or gust
conditions experience pressure distributions on the surface of the
skin. The resultants of these pressures cause direct loads such as:
bending, shear and torsion in all parts of the structure.
A simple aircraft consists of: a fuselage, pair of wings, and a tail
(horizontal & vertical tail section).
The fuselage carries crew, payload, passengers, cargo, weapons, or
fuel. The wings provide lift and the tail contributes to directional
control.
As well, there are ailerons, elevators and a rudder which enable the
aircraft to be controlled, and flaps provide extra lift during take-
off and landing.
The force on an aerodynamic surface (wing, vertical & horizontal tail)
results from a differential pressure distribution caused by incidence,
camber or both.
For a typical wing, the chordwise pressure distribution is:
Fig3. Pressure distribution and resultant forces around airfoil

10. - The vertical Lift Force component (L), perpendicular to the wind
direction.
- The horizontal Drag component (D), parallel to the wind
direction.
Increased downward load on horizontal tail, increases lift load
causing upward acceleration normal to the flight path.
Fig4.Aircraft load in pull out from a dive
This causes the load factor 'n' to be greater than 1. Therefore
creating inertia load on the structure to be nMg, where:
n = 1 + V2/Rg
R = Radius of curvature of the flight path.

11. Chapter 3
Simple illustrationofstraingage measurement onthe Ka 62
Fig5. Ka 62 Transport & Passenger Helicopter
As simple as its name, a strain gauge (or strain gage) is a device
used to measure strain on an object.
For the test, it was necessary to use the same loads that were used in
the calibration of the strain gauge array. As such, five cases were
considered:
- bending downward,
- bending upward,
- bending left,
- bending right,
- complex bending and torque caused by rear rotor thrust.
The value of the force applied in each load case was similar and close
to 2000 N. In the first cases the force was applied in the region
between tail boom and vertical stabilizer where strengthened ribs,
used to connect both elements by means of bolts, are applied. In the
last load case the belts were attached to the rear rotor shaft.
The same loads were introduced in the numerical model. The boundary
conditions were realized by constraining all degrees of freedom in the
nodes. The gravitational forces were not included in numerical
calculations, since the neutral state for strain gauges was determined
under influence of these forces.
The strain measurements of the tail boom and vertical stabilizer were
realized by means of foil strain gauges. Installation and calibration
of the measurement array was carried out by the AVIATEST engineers in

12. the test hangar.
Fig6. Localization of the measurement points
The installation on the helicopter's tail and vertical stabilizer
consisted of about 10 measurement points. First five were located just
after the first tail boom’s rib, where a greatest value of strain is
expected.
Points were aligned circumferentially to enable measuring strains
caused by different loads. The other five points were located at the
rear end of the tail boom on the upper and lower stringer.
The figure below shows an example strain gauge used in experiment
Fig7. A strain gauge used in the analysis
Since the stringers generally work in tension and compression, the
following strain gauge configuration was used.
This consists of four gauges and compensates both temperature changes
and strain caused by other loads that were not considered. The figure

13. below illustrates the location of the gauges on a stringer and how the
gauges are connected to create full Wheatstone bridge.
Fig8. Strain gauge placement and electrical scheme
For the configuration shown above, the output measured strain can be
defined by the formula as below:
(1)
Where:
E - Measured strain,
En - Normal (longitudinal) strain,
v - Poisson’s ratio,
k - Strain gauge constant (in this analysis equal 2.15),
Um - Output voltage,
Us - Source voltage.
To gather the strain measurements, a real time recorder and DTA
(Damage Tolerance Analysis) software created by HBM was used. It
enabled to gather real time coherent signals from all the sensors
simultaneously. Also, it was necessary to calibrate the whole system
to eliminate possible hysteresis in strain gauges indications.
The values indicated after this process was assumed to be
satisfactory.

14. Fig9. Captured signals during the experiment. Complex bending and torque
load case
The read values of force, from the experiment were then used as loads
in numerical model.
Values obtained from calculations were compared with those from the
experiment and after some necessary modifications to the model, a
reasonable accuracy was obtained.
The crucial points noted were B01, B02 and B09. The ratio was no lower
than 75% which is considered to be a satisfying result.
Values of B03 and B04, which are in a neutral bending plane, are low
both in the experiment and computer simulation. Values of B02 and B09
which are symmetrically aligned on sides of hole in the lower part of
tail boom show identical levels of strain both in experiment and
simulation.
Rear rotor thrust causes a combined bending and torque state in the
tail boom. The direction of bending moment is sideways hence points
B03 and B04 are considered to be the most crucial.
Since B02 and B09 are offset from the vertical plane of symmetry of
the tail boom, they also show sufficiently high signal to be taken
into consideration. One can see that the ratio for both these points
is sufficiently high, not lower than 90%.
Based on these results a chart showing the module of differences in
results from experiment and numerical calculations is shown in a
figure below.

15. Fig10. Module of differences of results for each point
As a conclusion from the studies above realized on the Mi-26T, it is
possible to pull out similar conclusions for the Ka 62. As such,
Fig11 Mi-26T ready for NDT testing at the AVIATEST
- it can be stated that, the presented numerical model represents
the real structure with sufficient accuracy, and the
simplifications didn’t have any significant influence on the
reliability of the global model,

16. - the presented model, after necessary modifications, can be
applied in further numerical analysis of the Mi-24 and Ka 62
helicopter structures
- validation processes presented within this article can permit us
to significantly increase reliability of the numerical model and
to verify the boundary conditions
- Strain gauge measurement is a relatively fast and exact method
for validation of a mechanical structure.

17. Chapter 4
Application ofNDT skills necessary for aircraft testing
Fig12. Performing NDT testing on an aircraft part
The research and testing centre AVIATEST provides nondestructive
testing and diagnostics.
At the centre, a full spectrum of modern methods of non-destructive
testing, including ultrasonic, capillary, magnetic powder, x-ray and
other diagnostic methods to reach tasks such as control of the welded
joints’ quality, definition of geometric deviations, measurement of
the residual voltage and identification of high voltage locations,
development of the constructions’ monitoring methods are utilized.
Table1. A brief analysis of the different NDT methods
Method Principles Application Advantages Limitations
Visual
Testing
(VT)
Uses
reflected or
transmitted
light from
test object
that is
imaged with
Many
applications
in many
industries
ranging from
raw material
to finished
Can be
inexpensive
and simple
with minimal
training
required.
Broad scope
Only surface
testing
conditions
can be
evaluated.
Effective
source of

18. the human eye
or other
light sensing
device
products and
in service
inspection
of uses and
benefits
illumination
required.
Requires
access
Penetrant
testing
(PT)
A liquid
containing
visible or
fluorescent
dye is
applied o the
surface and
enters
discontinuiti
es by
capillary
action
Virtually any
solid non
absorbent
material
having
uncoated
surfaces that
are not
contaminated
Relatively
easy and
materials are
inexpensive.
Extremely
sensitive,
very
versatile.
Minimal
training
Discontinuiti
es open to
the surface
only. Surface
condition
must be
relatively
smooth and
free of
contaminants
Magnetic
particle
testing
(MT)
Test part is
magnetized
and fine
ferromagnetic
particles
applied to
the surface,
aligning at
discontinuity
All
ferromagnetic
materials,
for surface
and slightly
subsurface
discontinuiti
es; applied
in large or
small parts
Relatively
easy to use.
Equipment/mat
erial usually
inexpensive.
Highly
sensitive and
fast compared
to PT
Only surface
and a few
subsurface
discontinuiti
es can be
detected.
Ferromagnetic
materials
only
Radiographic
testing
(RT)
Radiographic
film is
exposed when
radiation
passes
through the
test object.
Discontinuiti
es affect
exposure
Most
materials,
shapes, and
structures.
Examples
include
welds,
castings,
composites,
etc as
manufactured
or in
service.
Provides a
permanent
record and
high
sensitivity.
Most widely
used and
accepted
volumetric
examination
Limited
thickness
based on
material
density.
Orientation
of planar
discontinuiti
es is
critical.
Radiation
hazard is
possible
Ultrasonic
testing
(UT)
High
frequency
sound pulses
from a
transducer
propagate
through the
test
material,
reflecting at
interfaces
Most
materials can
be examined
if sound
transmission
and surface
finish are
good and
shape is not
complex
Quickly
provides
precise, high
sensitivity
results.
Thickness
information,
depth, and
type of flaw
can be
obtained from
one side of
No permanent
record
(usually).
Material
attenuation,
surface
finish and
contour.
Requires
couplant

19. the component
Eddy current
testing
(ET)
Localized
electrical
fields are
induced into
a conductive
test specimen
by
electromagnet
ic induction
Virtually all
conductive
materials can
be examined
for flaws,
metallurgical
conditions,
thinning and
conductivity
Quick
versatile,
sensitive;
can be non
contacting;
easily
adaptable to
automation
and in-situ
examination
Variables
must be
understood
and
controlled.
Shallow-depth
of
penetration,
lift-off
effects and
surface
conditions
Thermal
infrared
testing
(TIR)
Temperature
variations at
the test
surface are
measured/dete
cted using
thermal
sensors/detec
tor
instruments/c
ameras
Most
materials and
components
where
temperature
changes are
related to
part
conditions/th
ermal
conductivity
Extremely
sensitive to
slight
temperature
changes in
small parts
or large
areas.
Provides
permanent
record
Not effective
for detection
of flaws in
thick parts.
Surface only
is evaluated.
Evaluation
requires high
skill level
Acoustic
emission
testing
(AE)
As
discontinuiti
es propagate,
energy is
released and
travels as
stress waves
through
material.
These are
detected by
means of
sensors
Welds,
pressure
vessels,
rotating
equipment,
some
composites
and other
structures
subject to
stress or
loading
Large areas
can be
monitored to
detect
deteriorating
conditions.
Can possibly
predict
failure
Sensors must
contact test
surface.
Multiple
sensors
required or
flaw
location.
Signal
interpretatio
n is
required.
For convenience, it is also possible to regroup these NDT methods of
control under the following three features:
a) Interaction characteristics of the study part with other
substances which is based on the reaction or change in attitude
when the study part is subjected to certain given conditions or
test substances.
For example; the presence of a discontinuity (crack, porosity,
inclusion of a foreign object) in a test object will cause a
change of the radiation passing through it, or the spread of a
test substance.
b) Primary informative parameter – which is the specific field
parameter (amplitude of the field, time taken by the control

20. substance to spread, quantity of the substance used etc) or
matter which is used to change the characteristics of the
controlled object.
c) Methods of obtaining the studied data being the specific type of
sensor(s) or substance(s) used for measuring and recording the
information of the selected parameter.

21. Chapter 5
Testing and evaluating composite materials
Fig13. Strength test evaluation equipment (MTS 319.10)
The research and testing centre AVIATEST is equipped with modern test
machines and climatic chambers which allows tests of different
material elementary samples to be performed at a wide range of loads
and temperatures.
Together with the Centre Composite Enterprise of the LNK Group holding
company, AVIATEST performs sample tests to define the physical-and-
mechanical properties of the laminated composite materials in static
and high-speed power load conditions with respect to temperature
effects, humidity, time factor, and also performs the computational-
and-analytical backup of the industrial hub and composite material
aggregate field testing.

22. Composite material testing can be grouped under the following
techniques or principles:
- Non-destructive composite material testing and
- Destructive composite material testing
- Contactless testing
Non-destructive composite material testing which includes:
a) The strength analysis performance with a visualization of the
sections that facilitates stress state assessment in relation to
the tested elements
b) The preparation of spatial maps to facilitate the evaluation of
load influence on the stability of composite elements
Destructive composite material testing which includes:
a) The determination of strength allowing the evaluation of
exploitation parameters that influence the validation of product
usefulness in practical applications
b) Tests performed on the MTS 319.10 machine while making use of all
the necessary equipment and accessories (handles, adapters,
temperature chamber, extensometers and relevant software);
additionally tests can be performed in relation to different
groups of construction materials such as plastics, elastomers,
wood, fabric, metals and composites
c) The analysis of simulating different types of loads i.e.
possibility to apply loads corresponding to compression, bending,
shearing, stretching (as included in the typical tests for
conventional construction materials) separating and stripping
(for composite material testing methods)
d) The possibility of conducting tests in a temperature range of
between -130 to 315 degrees. It is also possible to run
diagnostic tests using the NDT acoustic emission (AMSY-6 devices)
technique or a quick camera allowing a diagnostic documentation
for the evaluation of fracture propagation

23. Fig14. Sound emission analysis system AMSY-6
e) The deformation measurement of composite structures using
composite fibers in the function of a sensor network that allows
for temperature measurement, displacement, deformation,
acceleration, stresses or measuring the level of acoustic waves;
the tests permits identification of early stages of composite
element wear (including fracture and delamination)
Contactless testing
This technique is based on the capacities of a 3-dimensional confocal
microscope that enables determination of a chemical composition
(recreation of the material form of a detail and defining porosity
parameters of the objects, including fine-grained structures);
additionally it is possible to perform defectoscope tests
(defectoscopy), define abrasion, determine friction parameters and
identify wear
At the labs, it is also possible to process the test results, optimize
constructions and redesign the tested elements so as to obtain the
optimum state of stresses connected with increasing the reliability of
the designed industrial object.

24. Summary and Personal analysis
As a personal analysis, I noted that NDT techniques as used in the
AVIATEST labs are the core of an aircraft's functioning. The process
of testing the parts beyond their limits is actually exciting as it
puts the engineer at the tip of new discoveries and therefore, a
scientific.

25. Conclusionand future work
NDT is an extensible technique to support a growing demand in
different domains. As the name properly defines, it does not
permanently alter the inspected part, it is a highly valuable
technique that can save both money and time in product evaluation,
troubleshooting, and research.
The main research objective of this assignment is to study the
application of NDT skills necessary for aircraft testing.
As outlined in chapter 4, the different types of NDT and their
principles are pointed out. In the course of this work, these
techniques were utilized at the AVIATEST labs to monitor and test the
limits of aircraft parts.
During the internship, aircrafts of the type Ka 62 helicopter Mi-26T
and Sukhoi Superjet 100 which are used mainly for experimental
purposes were present in the hangar.
This research work contributes in the better understanding of the
application of NDT techniques alongside loading systems and strain
gage measurements as performed on the Ka 62 helicopter during the
internship.
There is much more work to be done to assure even more safety in the
manufacturing of aircraft. Most of this work relies in the quality
testing of construction material for better aerodynamics and
durability or strength.
For future works, it is important to focalize on even better materials
(cheaper, lighter and more resistant). The success of the aviation
industry relies on its efficiency which in turn relies on the forth
sight of NDT techniques.

26. References
1. http://www.aero.jaxa.jp/eng/facilities/composite/
2. http://www.aviatest.lv/
3. http://www.russianhelicopters.aero/en/helicopters/civil/ka-
62.html
4. http://www.ndt.net/article/ecndt98/aero/031/031.htm
5. https://www.theengineer.co.uk/non-destructive-testing-in-the-
aerospace-industry/
6. http://emt-systems.com/composite-testing.html
7. http://www.ni.com/white-paper/12648/en/
8. CHINESE JOURNAL OF AERONAUTICS Vol. 18 No. 2 “Digital Simulation
of Full Scale Static Test of Aircraft”
9. Journal of KONES Powertrain and Transport, Vol. 18, No. 2 2011
“VALIDATION OF THE FEM MODE OF THE Mi-24 TAIL BOOM AND VERTICAL
STABILIZER”