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RECENT DEVELOPMENTS IN LIGHTENING TEST
STANDARDS FOR AIRCRAFT AND AVIONICS
NICHOLAS WRIGHT1, SWITZERLAND, EOIN SUGRUE2, IRELAND, MAXIM ERMAKOV3, RUSSIA
1
EMC Partner AG, 2 Amideon Systems Ltd, 3 ZAO “Energopromimport”
Abstract. There is a general movement towards synchronisation of the many diverse standards applicable to
avionics and aircraft testing in both the civilian and military fields. Foremost of these and widely accepted as
an ‘international’ standard is the new edition of RTCA/DO160D. The latest additions are embodied in
change No. 3 from December 2002. This paper provides an overview of the new standard focusing on the
Lightening Test part and differentiates between special requirements, outlining the impact on test equipment
and test load and the authors experience in carrying out these tests.
1. Introduction
The lightening induced transient susceptibility of aircraft
and avionics is a major element of RTCA/DO160D. This
standard includes statements which are not self
explanatory and require experience with these test types
to interpret the correct meaning.
2. Background
The external lightning environment can be simplified
into four waveform components A, B, C & D as shown
in Figure 1. These interact with an aircraft’s structure to
induce voltage and current transients on the internal
cabling and equipment.
through several coupling path. For practical purposes,
these can be narrowed down to two basic mechanisms:
aperture coupling and resistive coupling.
2.1 Resistive coupling
This mechanism produces voltages in loops existing
between cables and an aircraft structure. If the structure
is highly conductive, the voltages may have the
waveshape associated with the external environment.
Because of this, the most common transient voltage is
that associated with component A. This translates to the
waveform 4 definition 6.4/70µs. This waveform can also
be present in cable shields derived from the shield
current and transfer impedance.
Low resistance cables, connected at both ends to the
airframe structure will be subject to a current transient,
derived from the external lightning event, galvanically
coupled between the low inductance airframe and the
relatively high inductance cables. An aluminium
airframe presents a low impedance path so the transients
will be long but relatively low in amplitude. Structures
comprising insulation material such as carbon fibre give
rise to long transients with higher amplitudes than
aluminium structures.
Figure 1 Lightening Waveform Components
These different transfer characteristics have resulted in
two waveforms being employed.
 Waveform 5A (40/120µs) models resistive
coupling through an aluminium structure.
 Waveform 5B (50/500µs) models resistive
coupling through a carbon fibre structure.
Component (A) represents the initial stroke of a
lightning event with amplitudes up to several hundred
kiloamps this component carries the highest energy
level. Component (B) is an intermediate current of some
tens of kiloamps reducing to component (C) which
represents current flowing in the lightning channel. This
can last for some milliseconds with currents in the
hundreds of amperes range.
Component (D) corresponds to restrikes on the airframe
with peak amplitudes in the tens of kiloamp range.
There are several mechanisms over which the external
lightning event is coupled into an aircraft’s systems. In
reality, most transients are induced as complex waves
2.2 Aperture coupling
Where the aircraft structure is not homogeonous, EM
waves can penetrate and transients will be induced in the
internal electronic systems. The single largest event is
the initial stroke (component A), this can be coupled as a
magnetic field, penetrating the structure and inducing
currents with the waveform 1 (6.4/70µs) shape. Electric
and / or magnetic fields penetrating the structure will
excite resonances in cables having the damped
sinusoidal form and ranging in frequency from 1MHz to
10MHz. These are modelled by the waveform 3 1MHz
& 10MHz transients.
Voltages between cables and the structure exhibiting the
component A waveform (6.4/70µs) will drive a
waveform defined as waveform 2 (0.1/6.4µs).
3. Applicability
Test transients have been derived from measurements
performed on aircraft systems under lightning strike
condition as outlined in the Table 1.
(current). PIN injection test requirements are shown in
the following Table 3.
Level
Waveforms
3
1 MHz
4
6.4/70 µs
5A
40/120 µs
Voc/Isc
Voc/Isc
Voc/Isc
1
100/4
50/10
50/50
2
250/10
125/25
125/125
3
600/60
300/60
300/300
4
1500/60
750/150
750/750
5
3200/128
1600/320
1600/1600
5B
50/500 µs
1
2
3
6.4/70µs
0.1/6.4µs
1MHz/10MHz
Current
Voltage
Voltage/Current
4
5A
5B
6.4/70µs
40/120µs
50/500µs
Table 3 PIN Injection Test Requirements
Voltage
Voltage/Current
Voltage/Current
4.1.2. Cable Bundle Single Stroke
Cable bundle tests are performed using an injection
probe to couple transients. Tests are performed on fully
configured functioning equipment to determine
equipment survivability. Voltage and current levels have
to be monitored during the test process to ensure the test
limit is not exceeded and/or the test level is reached.
Table 1 Test Transients 1 to 5
Two transient types are specified under waveform 5. The
waveform 5A is intended to be used for aircraft with
primarily metallic structures and 5B to be used for
aircraft with more composite material in the structure.
Impulses are applied to the test object by either:
- Direct injection on the cable or pins (PIN Injection)
- Indirect injection on cables with an injection clamp
- Ground injection where the impulse is connected onto
the equipment or cable ground.
Test levels specify the internal aircraft environment.
- Level one, is applied to equipment and wiring in a well
protected environment
- Level two, is applied to equipment and wiring in a
partially protected environment
- Level three, is intended for equipment and wiring in a
moderately exposed environment
- Levels four and five are intended for equipment and
wiring in a severe electromagnetic environment.
Level
Waveforms
1
6.4/70
µs I
2
0.1/6.
4 µs
3
1
MH
z
3
10
MHz
4
5A
6.4/70 µs 40/
V
120
µs
5B
50/500
µs
Vlimit/Itest
Vtest/Ilimit
Vtest/Ilimit
Vlimit/Itest
1
50/100
100/20
50/100
50/150
2
125/250
250/50
125/250
125/400
3
300/600
600/120
300/600
300/1000
4
750/1500
1500/300
750/1500
750/2000
5
1600/3200
3200/640
1600/3200
1600/5000
Table 4 Cable Bundle Test Requirements
Single stroke events are used for damage assessment on
avionic sub-systems and equipment. They can be divided
into two categories:
Note: Inductance of the EUT cable primarily limits
waveform 3 current. For example, a cable length of 50
cm has an inductance of approximately 0.5 µH and as a
consequences the impedance at 10MHz Z = 2f x L =
31 Ohm. To attain current limits for the Single Stroke, a
driving voltage from the generator would need to be:
- at level 4
300A x 31 Ohm = 9.3 kV
- at level 5
640 A x 31 Ohm = 19.8 kV
These voltage levels are unrealistic and can never be
reached. Using this example it can be demonstrated that
the limits of waveform 3 are maybe applicable at 1 MHz
but never at 10 MHz. To be more precise, the waveform
3 column should be divided into two with current limits
at 10 MHz 10 times lower than for 1MHz.
4.1.1 PIN injection
The transient is applied directly to the system interface
circuits and is used to assess the dielectric withstand
voltage of the interface components. PIN injection
waveforms are defined in terms of the test signal
measured in an open circuit (voltage) and a short circuit
4.2. Multiple Stroke
Multiple Stroke waveforms are applied to determine the
Electro-Magnetic Compatibility (EMC) of systems, subsystems and equipment. The multiple stroke waveform
set (Figure 2) comprises a series of 14 transients the first
of which represents the initial stroke (component A),
4. Transient Requirements
Three transient events are specified in Table 2:
SS
MS
MB
Test Designations
Single Stroke
Multiple Stroke
Multiple Burst
Table 2 Transient Requirements
4.1 Single Stroke
followed by 14 transients at 50% of the first which
correspond to restrikes (component D) on the airframe.
Multiple Stroke transients are applied to cable bundles
only using an injection probe.
The pulses are most intense at the time of initial
lightning attachment to the aircraft structure. The
predominant waveform responses are the damped
sinusoidal waveforms in a frequency range from 1MHz
to 10MHz.
Figure 2 Multiple Stroke Waveform
Level
1
2
3
4
5
1
6.4/µs I
2
0.1/6.4 µs
3
1/10MHz
Vlimits/Itest
Vtest/Ilimits
Vtest/Ilimits
First
50/506)
50/50
100/20
Subseq.
25/25
25/25
50/10
First
125/125
125/125
250/50
Subseq.
62.5/62.5
62.5/62.5
125/25
First
300/300
300/300
600/120
Subseq
150/150
150/150
300/60
First
750/750
750/750
1500/300
Subseq.
375/375
375/375
750/300
First
1600/1600
1600/1600
3200/640
Subseq.
800/800
800/800
1600/320
4
6.4/70 µs V
5A
40/120 µs
5B
50/500 µs
Vtest/Ilimits
Vlimits/ITest
First
25/506)
20/606)
Subseq.
12.5/25
10/30
First
62.5/125
50/160
Subseq.
31.25/62.5
25/80
First
150/300
120/400
Table 6 Damped Sinusoidal Test Levels
Subseq
75/150
60/200
First
375/750
530/800
Subseq.
187.5/375
150/400
First
800/1600
640/2000
In relation to the comments made earlier about
waveform 3 (Figure 4) current limits, it is clearly evident
that the limits of the Multiple Burst requirement are
significantly (approximately ten times) lower.
Subseq.
400/800
320/1000
Level
1
2
3
4
5
Table 5 Multiple Stroke Test Requirements
4.3 Multiple Burst
Multiple Burst waveforms are also used to determine the
Electro-Magnetic Compatibility (EMC) of systems, subsystems and equipment. The multiple burst waveform set
is characterised by randomly spaced groups of 20 low
amplitude current transients. Each impulse contains
rapidly changing currents. Multiple burst transients are
derived from lightning leader progression or branching.
Figure 3 Multiple Burts Waveform
Figure 4 Damped Sinusoidal V/I Waveform
Levels
Waveform
3H 1 MHz
3H 10 MHz
VTest/ILimit
1
60/1
2
150/2.5
3
360/6
4
900/15
5
1920/32
5. Important Points to note when using DO 160D
DO160D includes statements which are not self
explanatory and require experience with these test types
to interpret the correct meaning.
a) The waveforms can only be guaranteed in the
calibration set-ups because cable bundle
impedances are unknown and will affect voltage
and current transients.
b) Within the calibration set-up, the waveform should
be verified in Voc (open circuit) or Isc (short
circuit) conditions only.
c)
d)
e)
f)
A test system should be able to reach the levels
(current or voltage amplitudes VTest, ITest or VLimit,
ILimit) defined for induced cable bundle test or
ground injection.
NB: the waveform in the real test conditions may
differ from the waveform in the calibration set- up.
For cable bundle tests only VTest or ITest waveforms
are defined, for VLimit or Ilimit the waveform is not
clearly defined. Therefore only the absolute value
should be noted.
Waveform 2 carries a notice that: ‘Ideally, the
waveform 2 generator will produce waveform 1 in
the short circuit calibration loop of Fig 22-16’. Our
experience is the opposite; the waveform 1
generator produces an approximate waveform 2 at
open loop conditions. It is a fact that neither a
waveform 1 generator can be designed to generate
waveform 2 in an open loop, nor can a waveform 2
generator be designed to generate waveform 1 into
a short circuit. DO160D, despite this misleading
notice, does actually define two distinct waveforms
(1) and (2) both must be applied separately.
For PIN injection the generator impedance is
defined as Voc/Isc, see table 22-2 of DO160D.
These values define the generator virtual
impedance. For all other tables 22-3, 22-4, 22-5 and
waveforms the ITest or VTest values represent the test
level (voltage or current) and the Vlimit or Ilimit
values represent the limits intended to prevent overstressing the EUT.
These are often misinterpreted as the generator
source impedance. This is incorrect. In order to
reach test levels or test limits, it may be necessary
to vary the coupling technique changing the
effective test impedance (generator plus coupler).
6. Test Equipment Requirements
Avionics testing to DO 160D requires distinct impulse
test types, with very diverse waveform characteristics
and energy content. Waveforms 2 and 3 can be
incorporated into a single test instrument as can
waveforms 1, 4 and 5.
equipment. As there was no single source for all the
equipment required, the emphasis was placed on the skill
and technical competence of the test engineer, needless
to say, equipment assembly and set-up times were
extremely long and test repeatability was a constant
challenge. Today the multiple stroke and multiple burst
are mandatory, meaning the previous approach is no
longer an option. Specialist test equipment with a high
level of computing power, designed as a single system
including generators, injection probes and calibration
jigs, is the only way to ensure compliance with the
DO160D requirements.
7. DO 160D compatibility with other avionics
Standards
The waveforms from DO160D are used as the basis for
many other standards both in the civilian and military
environments. Some examples of current standards are
the NH 90 GRS helicopter standard, Airbus A380,
Boeing D6-16050-4C, EUROCAE ED-84 (SAE
ARP5412), FAA AC 20-136 and ISO 7137.
All waveforms used in these standards are the same, the
differences lie mainly in the Multiple Stroke (MS) and
Multiple Burst (MB) definitions.
8. Conclusion
Experience dealing with users of avionic test systems has
shown that only 10% of applications require a level 5
ability. As previously discussed, the need for level 5
testing is only for equipment that will be fitted in a
severe electromagnetic environment. Test equipment to
meet this much higher test level is priced significantly
higher than equipment for level 3 or 4.
Having said that, should the need for level 5 testing
become real, then clearly a level 4 test system that can be
extended to cover this is a distinct advantage against the
purchase of new equipment.
The latest information from research and test experience,
shows that frequencies other than the 1MHz and 10MHz
can be present in civilian aircraft. In reality, platform
resonances at many frequencies up to 17MHz have been
encountered. This and other information is currently
being compiled into a revision for the DO-160 standard.
9. References
RTCA/DO-160D Environmental conditions and test
procedures for airborne equipment.
Section 22: Lightning Induced Transient Susceptibility.
December 5 2002 (change No. 3)
EMC requirements for avionics: RTCAI DO-160D
change 1 and 3 ITEM 2002, Erik Borgstrom,
In the past, it was typical that only single stroke testing
would be carried out. This was because the multiple
stroke and multiple burst tests were not mandatory and
single stroke testing could be performed using a variety
of readily available (but largely ill suited) test
10 Information about the Authors
Nicholas Wright, Currently International Sales
Manager for EMC Partner based in Switzerland
Eoin Sugrue, Managing Director of Amideon Systems
Ltd, based in Ireland and Moscow have worked in the EMC
market for over fifteen years, [email protected]
Maxim Ermakov, Currently Commercial Manager of
ZAO “Energopromimport”, Moscow, [email protected]