1. No category

Bundesamt für Zivilluftfahrt BAZL
Lightning
Protection
in Aviation
Markus Farner, 14. October 2011
Content
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Introduction
Direct effects
Indirect effects
Aircraft certification in general
Protection and certification direct effects
Protection and certification indirect effects
Lightning Protection in Aviation
Markus Farner, 14. 10.2011
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Introduction
Once in 3000 flight hours in average a commercial transport
aircraft is hit by a lightning strike.
•They can have adverse effects on aircrafts
•Electronic and electric systems are susceptible
•New materials and technologies is a challenge for
Aircraft certification should prevent adverse lightning
effects by aircraft design
Lightning Protection in Aviation
Markus Farner, 14. 10.2011
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ISOKERAUNIC MAP OF THE WORLD
Lightning Protection in Aviation
Markus Farner, 14. 10.2011
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INCIDENTS VERSUS ALTITUDE,
WHERE IS THE DANGER
Above 10’000 ft intracloud.
mmmmmmmmmmmmmm
Below 10’000
mmmmmmmmmmmmmm
ft cloud to ground
90% aircraft triggered
10% aircraft intercepted
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Swept Channel Effect
The aircraft moves fast
The lightning channel is stationary
Continuous sweep only possible on unpainted surfaces of
the same material
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Lightning Effects on Aircrafts
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Lightning Effects on Aircrafts
Direct effects
Lightning Protection in Aviation
Markus Farner, 14. 10.2011
Indirect effects
8
Direct Effects of Lightning
•Thermal Effects
•Sparking
•Mechanical Effects
•Puncture
•Disruptive Forces
•Shockwaves
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Aircraft Structure
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Lighting current between the entry and the exit point
tend to spread out over the entire airframe as a
conductor.
All conductive part becomes as part of the
conductive part of the lightning current.
Metal structures normally prevents physical damage.
Physical damage due to a poor bonding is not as
sever, except they in a fuel tank.
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Specific for Carbon Structure (CFRP)
and other Conductive Composites
•50% CFRP
•Conductive, but less than aluminium
•Material break down may end catastrophic!!!
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Indirect Effects of Lightning
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Hidden Failures
Soft Failures
Visible or invisible
Hard Failures
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Lightning Protection and Certification
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Aircraft Certification in general
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Comply with the regulations
Extend driven by regulation
Certification by use of AMC & GM
Certification = acceptance =
approval
Does not mean 100% is checked
Organisations have privileges
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Markus Farner, 14. 10.2011
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Aircraft Certification in general cont.
EASA = European Aviation Safety Agency
FAA = Federal Aviation Authority
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CS-22 for Gliders and powered Sailplanes
CS-23 for small Aircraft’s up to 5670 kg (8618 kg)
CS-25 for large Aircraft above 5670 kg
CS-27 for small Rotorcraft up to 3175 kg
CS-29 for large Rotorcraft above 2450 kg
CS-E/FAR-33 for all Engines
More Specification available
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Aircraft Certification in general cont.
Part
CS-23
Lightning protection
CS-25
CS-27
CS-29
§.581
Electrical bonding and
protection against static
electricity
§.867
§.899
§.610
§.610
Fuel system lightning
protection
§.954
§.954
§.954
§.954
Equipment, systems and
installation
§.1309
§.1309
§.1309
§.1309
§.865
§.865
System lightning
protection
External loads
Lightning Protection in Aviation
Markus Farner, 14. 10.2011
§.1316
16
Main objectives, direct effects
•
Prevent catastrophic structural damage.
•
Prevent hazardous electrical shocks to
occupants.
•
Prevent loss of aircraft flight control
capability.
•
Prevent ignition of fuel vapors.
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Fuel system lightning protection
CS 25.954
The fuel system must be designed and arranged to prevent the
ignition of fuel vapor within the system by –
(a) Direct lightning strikes to areas having a high probability of
stroke attachment;
(b) Swept lightning strokes to areas where swept strokes are
highly probable; and
(c) Corona and streamering at fuel vent outlets.
Lightning Protection in Aviation
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Steps in Protection Design and
Certification
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Certification plans
Establish the Lightning Zone Locations
Identify Systems and Components that are Performing
Flight Critical or Essential Functions
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Establish Protection Criteria and Design Protection
Verification of the Protection
Demonstrate compliance to the Authority
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Lightning Zones for Biz Jets
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Zone 1A - First return stroke
zone
Zone 1B - First return stroke
zone with long hang on
Zone 1C - Transition zone for
first return stroke
Zone 2A - Swept stroke zone
Zone 2B - Swept stroke zone
with long hang on
Zone 3 - Surfaces not in Zones
1A, 1B, 1C, 2A, or 2B
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Critical Functions, Protection
Criteria, Design and Verification
•Improved electrical conductivity
•Arc root dispersion
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Composite Fuel Cells
a
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Composite Fuel Cells
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Antennas / Radome
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Externally mounted Hardware
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Standardized Lightning Environment
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Radome verification by Test
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Pitot-Static Probe verification by Test
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Certification
Convince the agency it is safe!!!
You need to submit a Certification plan.
• Description of the airframe and systems to be addressed.
• Description of the protection.
• Acceptance Criteria.
Submit a Testplan if you plan to test, which descibes.
• purpose of the test
• test article description and configuration
• test setup to simulate the electrical aspects of the
production installation.
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Externally mounted electrical and
electronic Equipment
Equipment as:
• External Lights
•
Antennas
•
External sensors
•
Electrically heated anti-ice boots
•
Fuel quantity probes
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Zoning definition, Equipment
Categories and Current Components
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Certification
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Submit a Certification plan.
Submit a Testplan.
Perform testing
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Main objectives, indirect effects
MMMMMMMMMMMMM
MMMMMMMMMMMMM
MMMMMMMMMMMMM
MMMMMMMMMMMMM
MMMMMMMMMMMMM
MMMMMMMMMMMMM
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Approach to Compliance
1. Performance of a Functional Hazard Assessment on
Aircraft and on System Level.
2. Determination of the lightning strike zones.
3. Establishment of the lightning environment in relation to the
lightning strike zones.
4. Determine the internal lightning transient environment.
5. Establish the Transient Control Levels (TCL) and the
Equipment Transient Design Levels (ETDL).
6. Compliance verification.
7. Determination and implementation of the corrective
measures.
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Markus Farner, 14. 10.2011
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Functional Hazard Assessment FHA
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Failure Effects, Classification and
Severity
Classification of Failure Conditions
Allowable Qualitative Probability
No Safety Effect
<----Minor----->
<----Major---->
<--Hazardous--->
< Catastrophic>
No Probability
Requirement
<---Probable---->
<----Remote---->
Extremely Improbable
Effect on Airplane
Effect on Occupants
No effect on Operational capabilities or
safety
Inconvenience
Slight reduction in
functional capabilities
or safety margins
Physical discomfort
Significant reduction
in functional capabilities or safety margins
Physical distress,
possibly including
injuries
Effect on Flight
Crew
No effect on flight
crew
Slight increase in
workload
Physical discomfort or
a significant increase
in workload
Extremely
<------------------>
Remote
Large reduction in
functional capabilities
or safety margins
Serious or fatal injury
to a small number of
passengers or cabin
crew
Physical distress or
excessive workload
impairs ability to perform tasks
Allowable Quantitative
Probability:
Average Probability
er
Flight Hour on the
Order of:
No Probability
Requirement
<------------------>
<10-3
<------------------>
<10-5
Lightning Protection in Aviation
Markus Farner, 14. 10.2011
<------------------>
<10-7
Normally with hull loss
Multiple fatalities
Fatalities or incapacitation
<10-9
36
System Lightning Certification Level
Level A:
Electrical and electronic systems whose failure would
contribute to a failure of function resulting in a
catastrophic failure condition for the aircraft.
Level B:
Electrical and electronic systems whose failure would
contribute to a failure of function resulting in a hazardous
failure condition for the aircraft.
Level C:
Electrical and electronic systems whose failure would
contribute to a failure of function resulting in a major failure
condition for the aircraft.
No certification for Level D (minor) and Level E (no effect)
Lightning Protection in Aviation
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Lightning Strike Zones for Aircraft
A
a
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Lightning Transient Level
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Identntify
Level A
System
Determine
Aircraft
Lightning Zones
Determine Lightning
Current Path &
Waveforms
Define Aircraft TCL
& Lighting
Protection Features
Define System
ETDLs & Lighting
Protection Features
TCL
Verification
Method?
ETDL
Verification
Method?
Level A Display only
ATL
verified by
Test
ATL
verified by
Analysis
ATL
verified by
Similarity
Use RTCA
DO160
Section 22
ETDL verified
by Qualification
Tests
ETDL
verified by
Similarity
Compare
ATLs & ETDLs
Modify
Aircraft
Protection
No
Margin
Acceptable?
No
Modify
System
Protection
Yes
Lightning Protection in Aviation
Markus Farner, 14. 10.2011
Lightning Compliance
Demonstration
40
Questions?
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