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QinetiQ Aircraft Structural
Integrity Experience and Lessons
Learnt
Michael Houston
Fatigue 2014 Conference
March 2014
© Copyright QinetiQ Pty Ltd 2014
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Contents
1. Introduction
2. Our Role and Experiences in ASI
3. Establish the ASIP – Supporting the
Pakistan Air Force (PAF)
4. ASIP Fringe Dwellers – Undercarriage and
Mechanical Systems
5. ASIP in the Detail – Repairs and
Modifications
6. Conclusions
© Copyright QinetiQ Pty Ltd 2014
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1. Introduction
QinetiQ has been the primary engineering support contractor to the Australian
Defence Force Aircraft Structural Integrity section (ASI-DGTA) since 1996.
• Strategic initiatives in early 90’s included establishment of industry engineering
horsepower
• QinetiQ is an Authorised Engineering Organisation for structural
design and NDT for all platforms
• SPOs also access AEO services via ASI Services Contract
QinetiQ as the engineering services provider
acts in conjunction with the S&T organisation,
Defence Science and Technology
Organisation, in providing a full support
function to ASI-DGTA.
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2. Our Role and Experience in ASI
Initially the primary role was usage monitoring of a range of ADF aircraft fleets:
• Macchi, B707, Caribou, P-3, PC-9, F-111, F/A-18, C-130H, and then later,
• C-130J-30, Black Hawk, Chinook, Kiowa, Iroquois, Sea King, Seahawk, Squirrel, MRH90 and ARH
Engineering work for ASI-DGTA has been performed on all the aircraft types
listed above.
•
Routine ASIP activities – Fatigue Assessments, routine usage reports, Environmental
Degradation Assessments, Structural Life Assessments, AASA
•
Larger programs – “late life” and introduction to service support
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2. Our Role and Experience in ASI
Sustainment of existing capability and growth of new capabilities are constant
challenges – “use it or lose it”!
•
ASI engineering for RAF, RNZAF, RMAF and PAF: FT-5 (MiG-17), F-7 (MiG-21), A-5,
C-130B, F/A-18 C/D, A-109, JF-17, Mk-208 Hawk, Mirage III & V
•
Static and fatigue tests of a civil airliner
structures
•
Structural testing of a military land vehicle
•
Rail bogie structural integrity assurance
programs
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2. So what have we learned…?
Some management and technical themes common across all domains and
organisations
1. The Program: ASIP is a holistic, whole of life philosophy – therefore whole
of organisation as well
2. The Fringes: Where does the ASIP stop? What about mechanical systems?
3. The Detail: In-service changes to structure - modifications and repairs.
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3. Establish the ASIP – The PAF FT-5 Life Extension
Program
The FT-5 is used by the Pakistan Air Force (PAF) as their lead-in trainer following
basic training and prior to conversion to combat aircraft (eg. F-7, A-5)
•
Built in Chengdu, China, to a Russian Mig-17 design with 2800 hr “Safe Life”
•
25% fleet grounded – training capacity sustained (just) with overseas programs
•
Replacement program (K-8) delayed – introduction to service was not expected until 2010
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3. Establish the ASIP – The PAF FT-5 Life Extension
Program
Requirement: Provide limitations and instructions that enable PAF to operate
FT-5 to 3100hrs (approx. 10%).
• Initial feasibility and options study conducted – supported transition to SBI
• Define and implement ASIP and enable establishment of supporting engineering and
S&T
Circumstances:
• Little design data and no data describing basis for
Safe Life or main spar bolt hole inspection
requirement
• Bolt hole defects found in-service
• No ASIP: no in-service monitoring of usage and little
recording of condition data; little knowledge of fatigue
critical locations
• No support from OEM
• Maintenance oriented airworthiness organisation
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3. Establish the ASIP – The PAF FT-5 Life Extension
Program
•
•
•
Pilot interviews
Syllabus review
Usage survey
and
measurement
Usage
Spectrum
Loads and
Stresses
•
•
•
•
•
Material
Properties
Critical
Locations
•
•
•
FE Model
Ground Strain Survey
Flight Load Survey
Aero Analysis
Flight Manual Limits
Fleet Condition
Teardown
Loads and stress
•
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OEM Data
Coupon tests
Evaluation for Instructions for
Continuing Airworthiness
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3. Establish the ASIP – The PAF FT-5 Life Extension
Program
Outputs
• Life extension of 300hrs provided subject to SBI
• SBI described in Supplemental Structural Inspections Document (SSID) accompanied
by NDT procedures
• Significant capability development and transfer via QinetiQ team in Pakistan and PAF
team in Melbourne
− Fatigue and stress, test and a pilot
• Program implemented with training for
maintenance, engineering and operations
personnel, and first of type trial
− Step change in structural airworthiness
management, methods and tools
• PAF capitalised on life extension – withdrew
type in early 2011 with K-8 introduction
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3. Establish the ASIP – The PAF FT-5 Life Extension
Program
Lessons on The Program
• Engage all stakeholders to communicate purpose, scope, approach and benefits
− Ownership of need and benefits
− Benefits can be difficult when one outcome may be a greater maintenance burden
• Close collaboration with operators and front line maintenance is required for successful
usage surveys and monitoring
− Characterisation of usage
− Data download and processing procedures
• Ensure instructions are developed in cooperation with sustainment – the supporting
infrastructure must be in place
− Repair and configuration
− Planning
− Logistics
• Training and support to maintainers
• Safe but simple
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4. ASIP Fringe Dwellers – Mechanical Systems
Several structures are often ASIP “fringe dwellers” – fly under the ASIP “radar”
• flight or maintenance critical structures with static and fatigue failure modes
• maintenance policies often set and frequently managed independent of structural
certification
Examples
• Control rods and gears (eg. Sea King, T-38, F/A-18)
• Supporting structures
• Control surface hinges
• Undercarriage
USAF Mechanical Systems Integrity Program USN Naval Aviation Sub Systems
Integrity Program in part a response to this
Undercarriage – F-111, C-130H
• Item tracking and configuration management
• Inspection and repair policies
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4. ASIP Fringe Dwellers – Mechanical Systems
Fatigue failure of C-130H NLG September 2008 due to growth of surface flaw
Subsequent investigation to review certification basis and fatigue management
strategy revealed several issues
• Typically Safe Life due to high loads, high strength materials – tolerance of damage in a
military environment? Inspection and repair policy?
• Much “grandfathering” to very early standards
(esp. C-130)
• LG often designed and manufactured by an
OEM supplier – access to certification data is more
difficult
• LG subject to civil certification – implications for
military operations?
• Life limited, moved between aircraft, but are they
tracked?
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4. ASIP Fringe Dwellers – Mechanical Systems
Lessons on The Fringes
Challenge is the same as any other sub-system: ensure certification basis is
appropriate for sub-system and that in-service management and maintenance
policy is consistent with this.
•
Criticality
•
Failure modes
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Certification basis and airworthiness instructions
•
Maintenance policy management and monitoring
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5. ASIP in the Detail – Repairs and Modifications
Fatigue Management and damage tolerance requirements for repairs has been
an structural airworthiness theme for a decade.
Basis for continuing airworthiness and management of the parent/underlying
structure can be overlooked altogether.
Example: QinetiQ reviewed prescribed, ongoing
inspection requirements for C-130 SBI locations
• Repair shown to be able to act as alternate load
paths in event of full severing of post
• Integrity of structure lost if new cracking occurs
at end fasteners in underlying structure due to the
changed load paths
• Specified inspections were visual and SSEC
• Acrit achieved before crack becomes
detectable at edge of post
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5. ASIP in the Detail – Repairs and Modifications
We found that only the integrity of the repair doubler addressed, not the integrity
of the underlying structure under the different loading caused by the changed
load paths.
• In-service cracking had occurred at end
fasteners in underlying structure
• BHEC inspection with appropriate
inspection intervals required to verify
integrity of underlying post.
Lessons in The Detail
•
Aircraft will be subject to many changes
over life – robust skills and attention to
detail required to preserve structural
integrity
•
Importance of engineering
judgement and intuition balancing
analytical skill.
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6. Conclusion
The Program: The ASIP is a whole of life program that requires high levels of
integration across multiple stakeholder organisations
• Lesson re-learned with PAF – communication, engagement and ownership is key
• Supporting infrastructure and organisational arrangements must be in place
The Fringe: Bring the fringe dwellers into the ASIP and ensure the integrity of
excluded sub-systems is adequately managed.
• Appropriate certification basis consistent with management strategy and maintenance
policy
• Configuration management and tracking
• Mechanical systems and MECSIPs
The Detail: Structure changes over the life of a vehicle. Disciplined configuration
control and careful consideration of interfaces and parent structure when
designing structural changes is required.
• An example of engineering judgement and intuition so important in developing structural
integrity engineers
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www.QinetiQ.com.au
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