1. Structural Analysis

2. Structural Deterioration
Corrosion
Fatigue (cyclic loading)
Fabrication defects
Operation and Maintenance
Unforeseen loading (overloads)
Result into Failure or Fracture
As discussed in the beginning Corrosion, Fatigue (cyclic loading), Fabrication defects, Operation and Maintenance induced defects and Unforeseen loading (overloads) causes structure to deteriorate which could lead to failure or fracture

3. Inspection Levels General Visual Inspection (GVI)
During pre, tru or post flight
Detailed Visual Inspection (DET)
During periodic inspection
Special Detailed Inspection (SDET)
NDT of selected parts during periodic inspections
Typically, there are three Inspection Levels are in use in PAF:
General Visual Inspection (GVI)
A visual examination, performed in frame of the zonal inspection e.g. this is performed During pre, tru or post flight insp
Detailed Visual Inspection (DET)
An intensive visual examination of a specified detail or assembly searching for evidence of irregularity e.g. during periodic inspections
Special Detailed Inspection (SDET)
An intensive examination of a specific location similar to the detailed Inspection but requiring special techniques, mostly NDT e.g. NDT of selected parts during periodic inspections

4. Definition of NDT
Technique that allows a component to be inspected for serviceability, without impairing its usefulness
i.e. Inspect or measure without doing harm
NDT can be defined as
Technique that allows a component to be inspected for serviceability, without impairing its usefulness, in which noninvasive techniques are used to determine the integrity of a material, component or structure
i.e. Inspect or measure without doing harm

5. Uses of NDT Methods Flaw detection and evaluation Leak detection
Location determination
Dimensional measurements
In PAF NDT techniques are used for Flaw Detection and Evaluation, Leak Detection, Location Determination, Dimensional Measurements.

6. Uses of NDT Methods Structure and microstructure characterization
Material sorting and chemical composition determination
Mechanical and physical properties estimation
Stress (strain) and dynamic response measurements
Additionally they can also be used for Structure and Microstructure Characterization, Material Sorting and Chemical Composition Determination, Estimation of Mechanical and Physical Properties and Stress (Strain) and Dynamic Response Measurements,

7. Aircraft Inspection During manufacturing of aircraft
To detects damage during operation of the aircraft
A fatigue crack that started at the site of a lightning strike is shown below
Nondestructive testing is used extensively during the manufacturing of aircraft
NDT is also used to find cracks and corrosion damage during operation of the aircraft
The figure at the bottom shows A fatigue crack that started at the site of a lightning strike

8. Jet Engine Inspection During engine overhaul
Completely disassembly, cleaning, inspection and reassembly
Fluorescent penetrant inspection is shown to check engine parts
NDT techniques are extensively used during Aircraft engines overhauls in PAF
Engine parts are completely disassembled, cleaned, inspected and then reassembled
Fluorescent penetrant inspection is shown here to check many engine parts for cracks

9. Crash of United Flight 232
A defect that went undetected in an engine disk was responsible for the crash of United Flight 232
A typical case of NDT failure is the crash of United Flight 232, in Sioux City, Iowa, July 19, 1989.
A defect that went undetected in an engine disk was responsible for the disk failure
Investigation attributed the cause of the accident to a failure of maintenance processes to detect an existing fatigue crack.
Post-crash analysis of the crack surfaces showed the presence of a penetrating fluorescent dye used to detect cracks during maintenance. The presence of the dye indicated that the crack was present and should have been detected at prior inspection.

10. Airframe Loading : Critical Locations
This slide shows the non destructive testing applications for various loads on aircraft structure
The aircraft nose, wings and stablizers’ Leading edge may receive impact loads,
The fuselage bears hoop and longitudinal stresses due to pressurization.
The upper skin of wing is in compression and lower is in tension,
The wing , HT and VT also bears bending and torsional loads,
Very high stresses are produces at wings, tails, engine and LG attachemests
Therefore these all areas are to be inspected for any damage which using best avialble NDT techniques

11. Methods of NDT Magnetic Particle X-ray Liquid Penetrant Ultrasonic
Visual
Thermography
Microwave
Magnetic Particle
Tap Testing
X-ray
Acoustic Microscopy
Acoustic Emission
Liquid Penetrant
Magnetic Measurements
This slide shows the broad spectrum of NDT techniques (wait 10 s)
Ultrasonic
Replication
Laser Interferometry
Eddy Current
Flux Leakage

12. Six Common NDT Methods in PAF
Visual
Liquid Penetrant
Magnetic
Ultrasonic
Eddy Current
Radiography
Out of these six most common NDT techniques which are used in PAF are
Visual, Liquid Penetrant , Magnetic , Ultrasonic, Eddy Current, and X-ray

13. Visual Inspection - Types
Direct Visual Testing
Remote Visual Testing
Tools for remote inspection include fiberscope & borescope
The visual inspection can be classified in to Direct Visual Testing, Remote Visual Testing.
Here I’ll be focusing on a relatively modern technique called remote visual inspection
We generally use fiberscope, borescope, portable remote video inspection units for performing remote visual inspections
Portable video inspection unit with zoom allows inspection of large tanks and vessels

14. Remote Visual Testing –Borescopes
Flexible Borescopes
Contains a bundle of optical fibers
Also known as a fiberscope
Used for inaccessible cavities
Such as air inlets, combustion chamber, compressor, turbine blades, seals and other inaccessible aircraft parts
Good Image quality is required
A flexible borescope includes a bundle of optical fibers which divide the image into pixels. It is also known as a fiberscope and can be used to access cavities which are around a bend, such as air inlets, combustion chamber, compressor, turbine blades, seals and inaccessible aircraft parts.
So as to view the condition of the part without disassembling .

15. Remote Visual Testing – Borescopes
Video borescopes
Similar to the flexible borescope but uses a miniature video camera
A display shows the camera view
Much less costly and have potentially better resolution
Digital models have an integrated recorder and images / video can be saved
A video borescope or "inspection camera" is similar to the flexible borescope but uses a miniature video camera at the end of the flexible tube. A display shows the camera view.
As the complex optical waveguide is replaced with an inexpensive electrical cable, video borescopes are much less costly and has potentially better resolution, depending on the specifications of the camera.
Digital models often have an integrated recorder and can save images / videos in common digital formats.

16. Sensor Based Inspections : Principle
Excitation
Source
Signal / Image
Recognition
Display
Result
Input transducer
Almost all modern non destructive techniques are sensor based in which excitation source produces signal through a transducer which is captured by a measurement transducer. The signal or image processing techniques are used to improve the result quality. The input and output are analyzed in a computer and results are displayed on a screen.
Measurement
transducer
Signal / Image
Processing

17. Modern NDT Techniques Acoustic emission testing (AE or AT)
Electromagnetic testing (ET)
Alternating current field measurement (ACFM)
Alternating current potential drop measurement (ACPD)
Direct current potential drop measurement (DCPD)
Magnetic flux leakage testing (MFL)
Remote field testing (RFT)
Ellipsometry
Guided wave testing (GWT)
Impulse excitation technique (IET)
Infrared and thermal testing (IR)
The modern NDT techniques available today are as shown in this slide.

18. Modern NDT Techniques Laser testing Optical microscopy
Profilometry
Shearography
Optical microscopy
Radiographic testing (RT)
Computed radiography
Digital radiography (real-time)
Ultrasonic testing (UT)
Electro Magnetic Acoustic Transducer (EMAT)
Laser ultrasonics (LUT)
Phased array ultrasonics
Time of flight diffraction ultrasonics (TOFD)
The few more techniques are;
In subsequent slides I ll be discussing the modern techniques in relevance to potential application in PAF

19. Wire Rope Inspection
Electromagnetic devices and visual inspections are used to find broken wires and other damage to the wire rope
Wire rope are used in aircraft control cables, cranes, chairlifts, and other lifting devices
In PAF the wire rope inspection is a critical area,
conventionally the wire ropes are inspected visually or by moving a cloth along the wire.
However wire rope NDT allows the Electromagnetic devices to be used to detect broken wires and other damage to the wire rope

20. Wire Rope NDT Technology
Uses the magnetic properties of the steel wire rope
The principle of operation employs:
Measurements of EM fields near the surface to detect local defects
Measurements of changes in magnetic flux passing through the rope to evaluate cross section
Wire rope NDT is used extensively in the routine inspection of hoist ropes throughout the world. It is also used for inspecting wire ropes installed in crane ropes, mining eqpt, mountain installations, cable cars and ski lifts etc. This effective technology depends on the magnetic properties of the steel wire rope.
The principles of operation for electromagnetic wire rope NDT systems employ:
measurements of EM fields near the surface of the rope to detect local defects such as broken wires, corrosion pitting, and local wear.
measurements of changes in magnetic flux passing through a short length of rope to quantify changes in metallic cross section of the rope

21. Wire Rope NDT Readings compared with new wire “signature”
Monitoring the rate of degradation of a rope
A good rope will show a reproducible “signature” trace
The readings obtained during inspection of a wire rope are compared with a “signature” trace taken when the rope was first installed, and then subsequent traces, to assess more accurately any degradation which has developed in the rope.
Regular NDT inspections provide a powerful tool in monitoring the rate of degradation of a rope.
Under consistent conditions a rope in perfect conditions will show a trace that is a reproducible “signature” determined by its complex helical structure. The quality of a trace is improved by avoiding vibration and maintaining a steady speed.
LMA (loss of metalic cross sectional area)

22. Acoustic Emission (AE)
External stimuli, like mechanical loading, generate elastic waves in the material
As stress waves are generated when there is a rapid release of energy in a material, or on its surface
Used for part inspection, process monitoring etc
Acoustic Emission (AE) is a naturally occurring phenomenon whereby external stimuli, such as mechanical loading, generate sources of elastic waves due to small surface displacement of the material
This occurs due to stress waves generated when there is a rapid release of energy inside a material, or on its surface.
The wave generated by the AE is used in inspection, process monitoring ,quality control, system feedback,etc

23. Acoustic Emission Phenomena
Related to an irreversible release of energy
Can be generated from friction, cavitations and impact
Ranges from 1kHz, up to 100 MHz frequencies
AE is related to an irreversible release of energy, and can be generated from sources not involving material failure including friction, cavitations and impact.
Acoustic emissions can be detected in frequency ranges under 1 kHz, and can be detected to frequencies upto 100 MHz.
Which is due to Rapid stress-releasing events generating a spectrum of stress waves starting at 0 Hz and typically ranging upto several MHz.

24. Use in Non-destructive Testing
AE uses ultrasonic regime ( 100kHz and 1MHz)
Uses passive sensor which monitors acoustic emissions produced
Used to study the formation of cracks
Group of transducers record signals and locate area of defect origin
Applications in process monitoring
For non-destructive testing of materials AE normally uses the ultrasonic regime, typically between 100 kHz and 1 MHz.
Unlike conventional ultrasonic testing, AE sensors are passive devices which are designed for monitoring acoustic emissions produced within the material and then collecting them after they have traveled through the material, rather than actively transmitting waves
The technique is used, to study the formation of cracks during the welding process, a material under active stress as in case of an airplane during flight, transducers mounted in an area can detect the formation of a crack at the moment it begins propagating.
A group of transducers can be used to record signals then locate the precise area of their origin by measuring the time for the sound to reach different transducers.
In addition to non-destructive testing, acoustic emission monitoring has application in process or condition monitoring.

25. Phased Array (PA) Ultrasonics
Phased Array (PA) ultrasonics has applications in industrial nondestructive testing
The PA image shows the defects hidden inside a structure or weld
Phased Array (PA) ultrasonics is an advanced method of ultrasonic testing that has applications in industrial nondestructive testing and medicine.
the PA image shows defects hidden inside a structure or weld.

26. Phased Array (PA) Ultrasonics
PA probe consists of many small elements pulsed separately
Ultrasonic ripple are send as multiple waves to make a single wave front travelling at a set angle
Weld examination by phased array
The PA probe consists of many small elements, each of which can be pulsed separately.
In the figure the element on the right is pulsed first, and emits a pressure wave that spreads out like a ripple on a pond.
The second to right element is pulsed next, and emits a ripple that is slightly smaller than the first because it was started later. The process continues down the line until all the elements have been pulsed.
The multiple waves add up to one single wave front travelling at a set angle. In other words, the beam angle can be set just by programming the pulse timings.
The beam can be steered electronically. The beam is swept like a search-light through the object being examined, and the data from multiple beams are put together to make a visual image showing a slice through the object.
In TOP fig: The phased array probe emits a series of beams to flood the weld with sound.
In BOTTOM fig: The flaw in the weld appears as a red indication on the instrument screen.

27. Features of Phased Array
Produce a steerable, tightly focused, high-resolution beam
Produces an inside image of the object
PA instruments and probes are more complex and expensive
More experience and training than conventional technicians
Multiple probe elements produce a steerable, tightly focused, high-resolution beam.
Produces an image that shows a slice through the object.
Compared to conventional, single-element ultrasonic inspection systems, PA instruments and probes are more complex and expensive.
In industry, PA technicians require more experience and training than conventional technicians.

28. Phased Array Scan WWW.KAASHIFINFOTECH.COM
Shows the phased array scan of a metallic part

29. Ultrasonic Imaging
High resolution images can be produced by plotting signal strength or time-of-flight using a computer-controlled scanning system
Modern type of ultrasonic inspection is Ultrasonic Imaging this tech is similar to one used in medicine
In this technique High resolution images can be produced by plotting signal strength or time-of-flight using a computer-controlled scanning system
As shown in figure complete 3d inside picture of the object can be obtained
Gray scale image produced using the sound reflected from the front surface of the coin
Gray scale image produced using the sound reflected from the back surface of the coin (inspected from “head’s” side)

30. Infrared and Thermal Testing
Principle electromagnetic radiation emission as a function the temperature
Thermographic inspection NDT of parts through the surface imaging of the thermal patterns
Used for monitoring thermal changes
Infrared Thermography mapping of thermal patterns, on the surface of objects using infrared
Resolution few hundredths of a degree Celsius
Radiation is detected, processed and displayed on a computer display
Another modern Technique is Infrared or Thermal testing
The Principle is that All objects emit electromagnetic radiation of a wavelength dependent on the object’s temperature. The frequency of the radiation is inversely proportional to the temperature.
Thermographic inspection refers to the nondestructive testing of parts, materials or systems through the imaging of the thermal patterns at the object's surface
thermography refers to all thermographic inspection techniques used to monitor the thermal changes.
Infrared thermography is a nondestructive, nonintrusive, noncontact mapping of thermal patterns or "thermograms", on the surface of objects through the use of some kind of infrared detector.
An infrared thermographic scanning system can measure and view temperature patterns based upon temperature differences as small as a few hundredths of a degree Celsius.
In infrared thermography, the radiation is detected and measured with infrared imagers
The imagers contain an infrared detector that converts the emitting radiation into electrical signals that are displayed on a color or monochrome computer display monitor.

31. Thermographic Testing
Measures surface temperatures only
But surface temperatures are dependent upon the subsurface conditions
Energy flows can be slowed down by the insulating effects
Detect hidden thermal insulation faults and subsurface targets such as hot air leaks
An infrared thermographic scanning system measures surface temperatures only. But the surface temperatures are dependent upon the subsurface conditions.
The subsurface configuration effects are based upon the theory that energy cannot be stopped from flowing from warmer to cooler areas, it can only be slowed down by the insulating effects of the material through which it is flowing.
It can also be used to detect hidden thermal insulation faults and subsurface targets such as hot air leaks.
After the thermal data is processed, it can be displayed on a monitor in multiple shades of gray scale or color. The colors displayed on the thermogram are arbitrarily set by the Thermographer to best illustrate the infrared data being analyzed.

32. Thermographic Testing
Two methods are used :
Passive, in which the features of interest are naturally at a higher or lower temperature than the background
Active, in which an energy source is required to produce a thermal contrast
There are two approaches used in thermographic inspection:
passive, in which the features of interest are naturally at a higher or lower temperature than the background,
active, in which an energy source is required to produce a thermal contrast between the feature of interest and the background, for
The figure shows the thermogram of an aircraft panel the dark color shows the greater material thickness

33. Active Thermography Excitations
This slide shows the principle of operations and various excitation sources for active Thermography

34. Thermographic Testing
Energy sources induces a thermal contrast between defective and non-defective zones
Energy cannot pass through a flaw
External excitation
photographic flashes (for heat pulsed stimulation) or
halogen lamps (for periodic heating)
Internal excitation
Mechanical oscillations, with a sonic or ultrasonic transducer
Burst and amplitude modulated stimulations
A wide variety of energy sources can be used to induce a thermal contrast between defective and non-defective
if the energy is delivered to the surface it propagates through the material until it encounters a flaw; which can be detected in the thermogram
Typically, external excitation is performed with optical devices such as photographic flashes (for heat pulsed stimulation) or halogen lamps (for periodic heating),
whereas internal excitation can be achieved by means of mechanical oscillations, microwave etc with a sonic or ultrasonic transducer for both burst and amplitude modulated stimulation.

35. Thermographic Testing : Features
Thermographic inspection is safe, nonintrusive and noncontact, allowing the detection of relatively shallow subsurface defects
Large area can be inspected
Fast and time saving
Friction in moving parts like control links, cables, surfaces hinges etc.
Hidden hydraulic, hot /cold air, fuel leak can be detected
Thermographic inspection is safe, nonintrusive and noncontact, allowing the detection of relatively shallow subsurface defects (a few millimeters in depth) under large surfaces (typically 30x30 cm2 at once, although inspection of larger surfaces is possible) and in a fast manner (from a fraction of a second to a few minutes depending in the configuration)
Friction in moving parts like control links, cables, surfaces hinges etc.
Hidden hydraulic, hot /cold air, fuel leak can be detected by their thermal signature

36. Thermographic Testing : Features
Looks for “hot spots” in electrical equipment, showing high resistance areas
Inspecting composite or honeycomb aircraft structural components
This method is reliable and cost effective
A typical application for regularly available IR Thermographic equipment is looking for “hot spots” (40 °C to 150 °C ) in electrical equipment, which illustrates high resistance areas in electrical circuits.
Widely used for inspecting composite or honeycomb aircraft structural components
This method is reliable and cost effective.
This thermogram shows a fault with an industrial electrical fuse block
This thermogram shows a fault with an industrial electrical fuse block.

37. Fuselage inspection of Boeing 737
Fuselage inspection of a Boeing 737 aircraft using thermography shows the skin lap joints, stringers, doublers, and rivets. This image shows no defects part. The frame station and the frame of the window appear in a darker color, an indication that they are made out of thicker material.
The bottom picture shows the thermograph of 737 hull and debonding defect in composite

38. Digital Radiography
Digital X-ray sensors are used instead of traditional photographic film
Time efficient due to through bypassing chemical processing
Digital processing and transferable enhance images
Also less radiation required
Typically there are two variants of digital image capture devices
Flat Panel detectors (FPDs)
High Density Line Scan Solid State detectors
Digital Radiography is essentially filmless x-ray imaging, where digital X-ray sensors are used instead of traditional photographic film. Advantages include time efficiency through bypassing chemical processing and the ability to digitally transfer and enhance images. Also less radiation can be used to produce an image of similar contrast to conventional radiography.
The advantages of DR over film include immediate image preview and availability, a wider dynamic range which makes it more forgiving for over- and under-exposure as well as the ability to apply special image processing techniques that enhance overall display of the image.
Typically there are two variants of digital image capture devices.
Flat Panel detectors (FPDs), and
High Density Line Scan Solid State detectors.

39. Digital Radiography WWW.KAASHIFINFOTECH.COM
This slide shows the Radiographic Setup and image results for a typical Flat Panel Xray detectors (FPDs)

40. Pulsed Eddy Current Inspection
Step function voltage is used to excite the probe instead of sinusoidal AC current
A step function voltage contains a continuum of frequencies
The electromagnetic response to different frequencies can be measured
Depth information can be obtained
Conventional eddy current inspection techniques use sinusoidal alternating electrical current of a particular frequency to excite the probe. The pulsed eddy current technique uses a step function voltage to excite the probe.
A step function voltage contains a continuum of frequencies.
As a result, the electromagnetic response to several different frequencies can be measured with just a single step.
Since the depth of penetration is dependent on the frequency of excitation, information from a range of depths can also be obtained. Since, the measurements are made in the time domain, indications produced by flaws or other features near the inspection coil will be seen first and more distant features will be seen later in time.

41. Pulsed Eddy Current Inspection
Received and reference signals are compared
Flaws, conductivity, and dimensional changes can be measured
Depth of a part can be measured
To improve the strength and ease of interpretation of the signal, a reference signal is usually collected, to which all other signals are compared this is similar to nulling the probe in conventional eddy current inspection
Flaws, conductivity, and dimensional changes produce a change in the measured signal. The difference between the reference signal and the measurement signal is displayed on the screen
The distance of the flaw and other features relative to the probe will cause the signal to shift in time. Therefore, time gating techniques like in ultrasonic inspection can be used to gain information about the depth of a feature of interest.

42. Pulsed Eddy Current Inspection
This slide shows a typical pulsed eddy current equipment and driving voltage and the coil current

43. Shearography Shearography is an optical nondestructive testing method
Uses include aerospace, space, wind rotor blades, automotive and materials
Advantages include the large area testing capabilities, non- contact properties and its good performance on composites and honey-comb materials
Shearography is an optical nondestructive testing method that provides information about the inside quality of different materials.
Shearography is extensively used in production and development within aerospace, space, wind rotor blades, automotive and materials research areas.
Main advantages of shearography are the large area testing capabilities (up to 1 m² per minute), non-contact characteristics and good performance on composites and honey-comb materials, which is a big challenge for traditional NDT methods.

44. Principle of Operation
An interferometric image of the surface is taken and stored it in a computer
Image is a unique footprint of the surface
The material is then stressed with a small amount of thermal load
The material tries to expand when heated up, and weak spots will expand more
Second interferometric image is taken
In this technique the images of a test specimen's surface is taken with a special Shearography camera.
The camera acquires an interferometric image of the surface and stores it in a computer.
This image can be thought of as a unique footprint of this surface, including surface roughness and shape.
The material is then stressed with a small amount of load (thermal).
The material tries to expand when heated up, and if it has weak spots it will expand more.
At the loaded state one more interferometric image is taken.

45. Principle of Operation
By subtracting the two images a shearogram is created
The defects will be seen as fringe patterns resembling a pair of “hills” or a pair of "bulls-eyes"
The size of the defects can be quantified by measuring how large this fringe pattern is
Using an appropriate software, a shearogram is created. By subtracting the two images. The defects will be seen as fringe patterns resembling a pair of “hills” or a pair of "bulls-eyes" superimposed on the surface's image.
The size of the defects (in plane) can be quantified by measuring how large this fringe pattern is.

46. Shearography
A primitive shearography setup; Two physical points on test object will be projected on to one point on the CCD chip to record a interferometric footprint. The tested surface is illuminated with a monochromatic light, typical 650 nm.
The primitive shearography principle. A shearography image is recorded at unloaded state and one image is recorded in the loaded state. Thereafter they are subtracted and in the result defects can be detected.
This slide A primitive shearography setup; Two physical points on test object will be projected on to one point on the CCD chip to record a interferometric footprint. The tested surface is illuminated with a monochromatic light, typical 650 nm.
The primitive shearography principle. A shearography image is recorded at unloaded state and one image is recorded in the loaded state. Thereafter they are subtracted and in the result defects can be detected.

47. Structural Health Monitoring
This bring me to a slightly newer concept in aviation maintenance called Structural Health Monitoring. This methodology is analogous to real time monitoring of pain receptors in humans replaced by on board sensors monitoring aircraft structural health

48. What is SHM
Continuous monitoring of structures using integrated or applied sensors
Aimed at assuring structural integrity of the aircraft, by detecting damages resulting from fatigue, corrosion, excessive loads, impact ...
This does not imply knowing the status of the structure in real- time
Structural Health Monitoring is the continuous monitoring of structures/components using integrated or applied sensors.
Aimed at assuring structural integrity of the aircraft, replacing on-event and periodic inspections to detect damages resulting from fatigue, corrosion, excessive loads, impact ...
Monitoring of structures does not necessarily mean knowing the status of the structure in real-time.

49. What is SHM
After normal or exceptional events, maintenance can be planned at next appropriate inspection
Systems are available for aircraft condition monitoring - mostly for loads (accelerations, flight parameters, etc.) and enable decisions to be made based on actual flight load levels
Structures are designed with acceptable margins such that, after normal or exceptional events, maintenance tasks can be planned at next appropriate inspection.
Systems are available for aircraft condition monitoring - mostly for loads (accelerations, flight parameters, etc.) and enable decisions to be made based on actual flight load levels.

50. SHM Advantage
In terms of life cycle cost, a US DoD study attributed that
27% of the total cost of an aircraft being maintenance related with structural inspection being a significant driver of this cost suggesting
SHM could save up to 44% of current inspection time on modern fighter aircraft
SHM will improve reliability since structures are monitored directly, measuring the effect of damage
In terms of life cycle cost, a US DoD study attributed that
27% of the total cost of an aircraft being maintenance related with structural inspection being a significant driver of this cost suggesting
SHM could save up to 44% of current inspection time on modern fighter aircraft
SHM will improve reliability since structures are monitored directly, measuring the effect of damage

51. SHM Advantage SHM has many advantages:
No access to the inspection area necessary
Safe inspection of hazardous areas
Eliminating time consuming setup
Sensors used in the inspection are integral to the structure
Automated process - no human factors influence on inspection POD
Interrogating many locations or wide field at once - significant time saving
Compared to conventional NDT based maintenance, SHM has many advantages:
No access to the inspection area necessary – fewer access panels & component removal requirements
No physical operation in the area - safe inspection of hazardous areas
No use of scanners necessary – eliminating time consuming setup
Sensors used in the inspection are integral to the structure
Automated process - no human factors influence on inspection Probability Of Detection
Interrogating many locations or wide field at once - significant time saving

52. Structural Health Monitoring
With SHM new possibilities exist which can be used to ensure the structure integrity:
Damages
Loads/Strains
Flight parameters and conditions
Environmental conditions
Production parameters
Additional to conventional NDI with SHM new possibilities exist which can be used to ensure the structure integrity:
Damages
Loads/Strains
Flight parameters and conditions
Environmental conditions
Production parameters

53. Possibilities for NDT Visual Inspection (VI)
More than 95% of all NDI inspection are done visually
Non-Destructive Testing (NDT)
Performed where VI is not sensitive enough or damages are not visible on the surface
Structural Health Monitoring/Management
Sensor permanently attached / embedded in the structure
Information on structural events or states to arbitrary times available
Automated assessment and prognostic of the health of aircraft structures
SHM has verey large potential for NDT
Visual Inspection (VI)
More than 95% of all NDI inspection are done visually
Non-Destructive Testing (NDT)
Performed where VI is not sensitive enough or damages are not visible on the surface
Structural Health Monitoring/Management
Sensor permanently attached / embedded in the structure
Information on structural events or states to arbitrary times available
Automated assessment and prognostic of the health of aircraft structures

54. NDT in PAF
From visual inspections to more detailed technique based on penetrant inspection, eddy currents, ultrasonics, x-rays, etc…
Inspection intervals are generally OEM specified or self experience based
These Inspections result in downtime and significant effort
Monitoring activity comes at a considerable cost and accounts a large maintenance man-hours for commercial aircraft
In PAF NDT is mainly applied from visual inspections followed by for more detailed technique for hidden flaws, procedures are defined based on penetrant inspection, eddy currents, ultrasonics, x-rays, etc…
Inspection intervals are generally OEM specificied or experience based derived from knowledge of the structure residual strength, operating environment, applied loads, damage growth rate and failure consequences.
These Inspections result in downtime and inaccessible areas of structure often require significant effort to remove equipment or strip protective coatings for access, which then must be restored after the inspection.
Monitoring activity comes at a considerable cost and accounts for an average of 44% internationally of all on-aircraft maintenance man-hours for commercial aircraft (Andresen, 2006).

55. Conclusions
NDT plays key role in safe operation and especially in damage tolerant design / operations of aircraft structures
Furthermore NDT is “enabler” for reliable introduction of new materials, technologies and design concepts
We have to realize that adopting new NDT techniques and more focus on training can improve flight safety
NDT plays key role in safe operation and especially in damage tolerant design / operations of aircraft structures
Furthermore NDT is “enabler” for reliable introduction of new materials, technologies and design concepts
We have to realize that adopting new NDT techniques and more focus on training we improve flight safety
However we need to emphasize more on NDT

56. Conclusions Enhanced training On job expertise
Developing NDT trade or screening NDT trained specialists
Developing and managing NDT pool through sub NDT classifications
Acquiring latest and modern equipment
Education everyone about NDT Advantages and Hazards
As NDT is highly skill based inspection we have to accord due importance to it by
More training
On job experience
Developing NDT trade or screening NDT trained specialists
Developing and managing NDT pool through sub NDT classifications
Acquiring latest and modern equipment
Education everyone about NDT advantages and Hazards

57. Conclusions Including introductory NDT course in PPT curriculum
Thorough scrutiny of inspection procedures from NDT Perspective
Ensuring availability of personnel protecting equipment especially in RT and PT
Making a PAF level certifying, training and regulation body
Including introductory NDT course PPT curriculum for young engineering officers
Thorough scrutiny of inspection procedures from NDT Perspective
Ensuring availability of personnel protecting eqpt especially in RT and PT
Making a PAF level certifying, training and regulation body monitoring all NDT related activities in PAF

58. Thankyou