Civil Aviation Order 103.24 Instrument 2007 (Cth)
I, WILLIAM BRUCE BYRON, Director of Aviation Safety, on behalf of CASA, make this instrument under subregulation 21A (1) of the Civil Aviation Regulations 1988.
[Signed Bruce Byron]
Bruce Byron
Director of Aviation Safety and
Chief Executive Officer
17 December 2007
Civil Aviation Order 103.24 Instrument 2007
1 Name of instrument
This instrument is the Civil Aviation Order 103.24 Instrument 2007.
2 Commencement
This instrument commences on the day after it is registered.
3 New Civil Aviation Order 103.24
Civil Aviation Order 103.24 is repealed and a new Civil Aviation Order 103.24 substituted as set out in Schedule 1.
Schedule 1 Civil Aviation Order 103.24
Equipment standards — VHF communications transmitting equipment
This Order is to be read in conjunction with Civil Aviation Order 103.21.
1 Application
1.1 This Civil Aviation Order specifies standards for airborne communications transmitting equipment operating within the frequency range from 117.975 to 137 MHz.
1.2 These standards apply to the approval of equipment for use in Australian registered aircraft for the purpose of intercommunication with the aeronautical mobile radio service.
2 Design requirements
2.1 The equipment must be designed to produce A3 (telephony) emissions.
2.2 The frequency range and number of channels must be adequate for the intended operational purpose of the equipment.
Note Transmitters should be capable of operating on all 0.1 MHz increments from 25 to 117.975 to 137.00 MHz.
2.3 Not more than 2 controls must be used to accomplish frequency selection and tuning. These controls must switch into operation pre-set frequency determining circuits.
2.4 The transmitter must provide for transmit-receive change-over from a single press-to-transmit switch. The 1 action must accomplish all necessary switching functions, including loud speaker muting (if applicable) during transmit.
2.5 Transmitter side-tone output must be such that manipulation of a control, e.g. audio gain, by the operator is not required when changing between transmit and receive functions.
Note Sidetone level adjustment should be provided for in the transmitter.
2.6 Controls not intended for use during flight must not be readily accessible to the flight crew.
2.7 All indicators, controls and test points must be clearly marked or readily identifiable as follows:
(a) indicators and controls for in-flight operation must be marked with English symbols;
(b) indicators, controls and test points for maintenance adjustments to installed equipment must be marked with English or recognised technical symbols;
(c) controls and test points used only during maintenance at the test bench must be identifiable by means of suitable markings or other means of providing unambiguous identification, e.g. overlays, photographs.
2.8 The equipment must be designed so that any possibility of incorrect mating of connectors is minimised. Plugs and sockets without positive means to prevent incorrect mating must be suitably marked or readily identifiable with their function or circuit reference.
2.9 The equipment must be so designed that the possibility of electric shock to passengers or crew is negligible.
2.10 The equipment must be so constructed that the normal methods of mounting and the application of vibration and shock under the most severe conditions likely to be encountered by the equipment will not cause detuning or other malfunctions to occur or otherwise damage the equipment.
2.11 The equipment must be designed so that the rating of each component, with appropriate derating, is not exceeded in any localised component environment which may occur during operation of the equipment in any over-all environment implied by its classification.
2.12 The attachment of components and the restraint of plug-in components, adjustment and tuning devices, must be adequate to ensure their security and permanence of adjustment under the vibration conditions within which the equipment may be operated.
2.13 The performance characteristics of the equipment must be unaffected by operation of panel and indicator lamps incorporated in the equipment.
Note It is recommended that lamps be fitted with a dimming device or provision made for their connection into a suitable dimming circuit.
3 Conditions of test
3.1 Compliance with this Civil Aviation Order must be substantiated by tests conducted on 1 or more sets of equipment to the extent appropriate to the desired classification.
Note 1 The Director may allow some departure from certain individual requirements provided that, in his opinion, overall performance is consistent with the intended purpose of the equipment and is generally satisfactory throughout the range of environmental conditions mentioned in this Order.
Note 2 The Director must require additional tests to be conducted if particular designs or performance characteristics appear to warrant special assessment.
3.2 During and subsequent to the application of the specified tests, the equipment must not exhibit evidence of any condition which would be detrimental to its continued satisfactory performance.
3.3 Unless otherwise mentioned or required, tests must be conducted under room ambient conditions.
Note Room ambient conditions should be:
atmospheric pressure — 810 to 1050 mb or 24 to 31 inches Hg;
air temperature — +10 to 40°C;
relative humidity — less than 85%.
3.4 Unless otherwise mentioned or required, the equipment must be operated at normal rated power supply voltage and frequency. Variations up to ± 2% of voltage and ± 2% of frequency will be accepted.
Note 1 Normal rated voltages and frequencies are those specified by the manufacturer for continuous or stated duty cycle operations for the equipment. Usual rating will be 13.75 or 27.5 volts for DC and 115 volts at 400 Hz for AC operated equipment.
Note 2 For equipment designed to operate on a variable frequency AC supply the terms “selected test frequency” and “critical test frequency” should be used and noted in the test reports.
3.5 Where a voltage level at radio frequency is specified, it must be interpreted as the voltage actually occurring between the points stated, or the point and equipment frame, as appropriate.
3.6 Unless otherwise agreed by the Director, the duty cycle for VHF communications transmitters must be:
(a) in stand-by mode — continuous;
(b) in transit mode — not less than 1 minute ON and not more than 4 minutes OFF in sequence with the transmitter modulated at least 80% by a 1 000 Hz sine wave signal or by speech to a level exceeding 85% on peaks.
3.7 Accepted test procedures must be used for the conduct of the performance tests required by these Equipment Standards. Unless otherwise agreed by the Director, the same procedures must be used for the conduct of similar tests under environmental, low voltage and normal test conditions.
Note Suggested test procedures are contained in Appendix I.
3.8 Evidence that test equipment is properly calibrated and checked must be made available at the Director’s request.
3.9 Minor modifications to correct deficiencies noted as a result of the tests may be made at any stage of the tests provided that such tests as the Director considers necessary are repeated.
Note Results of repeated tests should be identifiable with the specific modification.
4 Minimum performance requirements under normal test conditions
4.1 Frequency tolerance
The carrier frequency must be controlled to within 0.005% of the assigned carrier frequency over the operating temperature range for which the equipment is rated.
4.2 Carrier power output
The unmodulated RF power output supplied to a resistive load equal to the nominal impedance of the antenna transmission line for which the transmitter is designed must be not less than:
15 5 1 watts for ratings I5 I4 I3 I2 I1 L2 L1 V2 V1
Note Transmitters intended for use in aircraft operating above 35 000 feet on routes where reliable communications may be required over ranges exceeding 200 nautical miles should have a power output capability of at least 25 watts.
4.3 Residual radiation
When all sources of primary power are connected to the equipment and all controls set for normal operation, except that the press-to-transmit switch is “OPEN”, the RF power output at the carrier frequency must not exceed 0.02 microwatts.
4.4 Carrier noise level
The ratio of the demodulated output obtained when the carrier is modulated 85% at 1 000 Hz to the demodulated noise must be not less than:
35 26 dB for ratings I L V
4.5 Modulation capability
The transmitter must be capable of producing 85% modulation of its output carrier from a sinusoidal input signal of 1 000 Hz and an amplitude consistent with the output of aircraft microphones specified by the manufacturer for use with the equipment.
4.6 Modulation limiting
The application of abnormally high levels of audio input signal must not result in over modulation of the output carrier.
4.7 Audio frequency response
The overall audio frequency response must be such as to provide clearly intelligible transmission of any normal human speaking voice and attenuation of those frequencies which may detract from, or do not significantly contribute to, intelligibility.
Note Qualitative assessment of audio frequency response may be used until suitable standards are determined for all components of communications systems. The audio frequency response (modulation fidelity) of airborne transmitters will be generally acceptable if the depth of modulation varies by not more than 2:1 when the frequency of a constant level audio signal is varied over the range from 350 to 2 500 Hz. Improved intelligibility has been obtained with a modulation characteristic rising from approximately 400 to 2 500 Hz and attenuating frequencies below 350 Hz and above 3 000 Hz at 18 dB, or more, per octave.
4.8 Audio frequency distortion
The combined distortion and noise in the demodulated transmitter output must not exceed 25% of the total demodulated output at modulation frequencies of 350, 1 000 and 2 500 Hz when the level of the audio input to the transmitter is held constant at a value which produces at least 85% modulation at the frequency giving maximum response.
4.9 Sidetone characteristics
Audio frequency response and distortion of the sidetone output must be substantially similar to the audio frequency response and distortion of the carrier modulation.
4.10 Spurious emissions
Note 1 Equipment which complies with the requirements of either Category 1 or 8 equipment specified in Appendix A to RTCA Paper 120-61/DO-108 will be deemed to comply with this paragraph.
Note 2 The emission of spurious radio frequency energy of a transient nature resulting from the manual operation of switches, but not including emissions from circuits operating as a result of the operation, may exceed the limits mentioned in this paragraph if its duration does not exceed 1 second.
4.10.1 Emissions from antenna
(a) The power in any spurious emission present at the antenna terminal on any discrete frequency from 190 kHz to 1 200 MHz when the transmitter is modulated 30% at 1 000 Hz must be 40 dB or more below the power emitted at the selected frequency but must not, in any case, exceed 25 microwatts and need not be less than 10 microwatts.
(b) The power in any spurious emission present at the antenna terminal on any discrete frequency from 190 kHz to 1 200 MHz, excepting the selected frequency, when the transmitter is in the “stand-by” condition, must not exceed 1 nanowatt (for ratings I and L) or 20 nanowatts (for rating V) into a resistive load equivalent to the nominal antenna impedance of the transmitter.
4.10.2 Emissions from interwiring
This requirement is applicable only to equipment for which an I rating is desired.
Unwanted radio frequency energy on any cable must be of such level, or must be contained in such manner, that the level of signals on discrete frequencies from 190 kHz to 1 200 MHz induced in another cable run with it does not exceed 1 000 microvolts. (Refer to Appendix I for suggested test procedure.)
Note Although this requirement does not apply to transmitters with L or V ratings, a similar standard is desirable. Particular attention should be given to minimising spurious emissions within the frequency ranges from 190 kHz to 20 MHz and 108 to 136 MHz in order to provide reasonable assurance that mutual interference limits mentioned in other Civil Aviation Orders can be met. Transistorised inverters in power supply circuits are frequently responsible for unacceptable emissions.
4.11 Channel selection time
The maximum time for the equipment to change from 1 channel to any other must not exceed 10 seconds.
4.12 Operation of mechanical devices
Mechanical devices must perform their intended function. Marginal operation must be avoided.
4.13 Variation of primary power frequency
The equipment must comply with this Equipment Standard when the primary power frequency is varied throughout the range for which the equipment has been designed. For equipment designed to operate from a nominally constant frequency supply, it must be assumed that the frequency will vary by at least ± 5%.
4.14 Application of conducted voltage transients
This requirement is applicable only to equipment for which an I rating is desired.
Note 1 Although specified for I rating equipment only, it is desired that this requirement be applied, where practicable, to all equipment, especially that which incorporates solid state devices susceptible to damage by voltage transients.
Note 2 This requirement is expressed in this interim form pending further investigation of the magnitude and effects of aircraft electrical system voltage transients.
4.14.1 Intermittent transients
After application of intermittent transients as specified in paragraph 10.1 of RTCA Paper 120-61/DO-108, the equipment must not exhibit evidence of damage and must continue to function without degradation.
4.14.2 Repetitive transients
When the equipment is subjected to the repetitive transients test specified in RTCA Paper 120-61/DO-108, paragraph 10.2, the carrier noise level must not be degraded more than 6 dB below the performance mentioned in paragraph 4.4 of this Order.
4.15 Conducted and radiated interference susceptibility
These requirements are applicable only to equipment for which an I rating is desired.
Note Although these requirements do not apply to equipment with L or V ratings, a similar standard is desirable, especially for the former, in order to provide reasonable assurance that mutual interference limits, mentioned in other Civil Aviation Orders, can be met.
4.15.1 Conducted audio frequencies
The ratio of the demodulated output obtained when the carrier is modulated 85% at 1 000 Hz to the demodulated noise must be not less than 35 dB when the equipment is subjected to the test specified in RTCA Paper 120-61/DO-108, paragraph 11.
4.15.2 Audio frequency magnetic fields
The ratio of the demodulated output obtained when the carrier is modulated 85% at 1 000 Hz to the demodulated noise must be not less than 35 dB when the equipment is subjected to the test specified in RTCA Paper 120-61/DO-108, paragraph 12.
4.15.3 Radio frequencies (radiated and conducted)
The ratio of the demodulated output obtained when the carrier is modulated 85% at 1 000 Hz to the demodulated noise must be not less than 30 dB when the equipment is subjected to the tests specified in RTCA Paper 120-61/DO-108, paragraph 13.
5 Minimum performance requirements at low primary voltage
5.1 When all primary power input voltages are simultaneously reduced to 80% of normal rated for dc, and 90% of normal rated for AC supplies:
(a) the carrier power output must be not less than 1 half of that mentioned in paragraph 4.2; and
(b) the modulation capability, under the conditions mentioned in paragraph 4.5, must be not less than 50%; and
(c) the maximum time for the equipment to change from 1 channel to any other must not exceed 10 seconds; and
(d) mechanical devices must perform their intended functions.
6 Minimum performance requirements under environmental test conditions
Note Environmental test procedures are mentioned in Civil Aviation Order 103.21.
6.1 Altitude test
When the equipment is subjected to this test:
(a) there must be no evidence of arcing, burning or other deleterious effect; and
(b) the requirements of paragraphs 4.2 (Carrier power output) and 4.5 (Modulation capability) must be met.
6.2 Depressurisation test
When the equipment is subjected to this test, it must continue to function as intended. Some degradation of performance may be permitted.
There must be no evidence of any condition occurring as a result of this test which may cause complete failure of the equipment.
6.3 Short time operating high temperature test
When the equipment is subjected to this test:
(a) there must be no evidence of overheating of any component or exudation of grease or other compounds; and
(b) the equipment must continue to function as intended. Some degradation of performance, within the following limits, is permitted:
(i) carrier power output must not decrease more than 6 dB below that mentioned in paragraph 4.2 and must, in any case, be at least 0.5 watt;
(ii) carrier noise level must not increase more than 6 dB above that mentioned in paragraph 4.4;
(iii) modulation capability must be at least 50%;
(iv) audio frequency response must be such that the requirement mentioned in paragraph 4.7 can be met.
6.4 High temperature test
When the equipment is subjected to this test:
(a) there must be no evidence of overheating of any component or exudation of grease or other compounds; and
(b) the requirements of paragraphs 4.1 (Frequency tolerance), 4.2 (Carrier power output), 4.5 (Modulation capability), 4.7 (Audio frequency response), 4.8 (Audio frequency distortion) and 4.12 (Operation of mechanical devices) must be met.
6.5 Temperature variation test
When the equipment is subjected to this test the requirements of paragraphs 4.1 (Frequency tolerance), 4.2 (Carrier power output), 4.5 (Modulation capability) and 4.7 (Audio frequency response) must be met.
6.6 Low temperature test
When the equipment is subjected to this test:
(a) carrier power output must be not less than:
10 3 watts for ratings I5 14 I3 I2 I1 L2
(b) modulation capability must be at least 50%; and
(c) the requirements of paragraphs 4.4 (Carrier noise level), 4.7 (Audio frequency response), 4.8 (Audio frequency distortion), 4.11 (Channel selection time) and 4.12 (Operation of mechanical devices) must be met.
6.7 Humidity test
6.7.1 After the equipment has been subjected to this test, and immediately following the 15 minute warm-up period, the carrier power output must be within 3 dB of that mentioned in paragraph 4.2, modulation capability must be at least 50% and the requirements of paragraphs 4.7 (Audio frequency response) and 4.12 (Operation of mechanical devices) must be met.
6.7.2 Within 4 hours from the time primary power is applied, the requirements of paragraphs 4.2 (Carrier power output), 4.5 (Modulation capability), 4.11 (Channel selection time) and 4.12 (Operation of mechanical devices) must be met.
6.8 Resonance search
When the equipment is subjected to the resonance search, there must be no evidence of excessive flexure of the chassis or mounting and components must not develop independent movement which would be likely to result in failure of the component or its attachment to the equipment.
6.9 Anti-vibration mounting attenuation test
When the equipment is subjected to this test:
(a) the mountings must not attain their limit of displacement in any direction; and
(b) magnification of vibration amplitude must be confined to frequencies below 20 Hz.
6.10 Vibration test
When the equipment is subjected to this test:
(a) there must be no evidence of detuning, upset of adjustment or other malfunctions; and
(b) the requirements of paragraphs 4.2 (Carrier power output), 4.4 (Carrier noise level), 4.7 (Audio frequency response) and 4.12 (Operation of mechanical devices) must be met.
6.11 Acceleration test
After the equipment has been subjected to this test, there must be no evidence of it breaking free from its mountings.
Appendix I
Test procedures
1 It is recognised that compliance with some of the minimum performance requirements mentioned in this Civil Aviation Order may be determined using alternative test procedures. However, paragraph 3.7 states that “accepted” test procedures are to be used and the Director may require a full description of the procedures actually used should there be any doubt as to the validity of the results of any test.
2 Procedures suitable for the conduct of most of the tests mentioned in this Civil Aviation Order are contained in RTCA DO-186. In some instances, suitable test procedures may be determined from the wording of the requirement.
3 For the convenience of manufacturers who do not have ready access to RTCA DO-186, or certain of the test equipment mentioned in it, the following information on acceptable test procedures may be useful.
3.1 Residual radiation (paragraph 4.3 refers)
(a) For this test, all sources of primary power must be applied to the equipment, all controls set for normal operation, but the press-to-transmit switch NOT operated. Connect a suitable tunable receiver — such as a field intensity receiver — to the antenna terminal of the transmitter under test. Ensure that correct impedance matching is achieved.
(b) The transmitter under test may be set to approximately 120 MHz.
(c) Tune the tunable receiver to the frequency to which the transmitter is set and note the presence and level of any signal indication.
(d) A signal generator in place of the transmitter under test may be used to determine the level of any observed signal and this converted to power by calculation.
3.2 Spurious emissions (paragraph 4.10 refers)
3.2.1 Emissions from antenna
(a) Connect the antenna terminal of the transmitter under test to suitable load or artificial antenna via a “T” attenuator. The load should provide means for indicating that the transmitter is delivering rated power. (An RF wattmeter would be suitable.)
(b) Connect a suitable tunable receiver — such as a Field intensity receiver — to the attenuated output terminal of the “T” attenuator. Ensure that correct impedance matching is achieved in all RF line connections.
(c) Modulate the transmitter output to 30% with a 1 000 Hz signal. The transmitter may be set to approximately 120 MHz.
(d) Tune the tunable receiver across the specified frequency range and note the presence and level of signal indications.
(e) A signal generator in place of the transmitter under test may be used to determine the levels of noted signals and these converted to power by calculation.
3.2.2 Emissions from interwiring
(a) The test conditions should simulate a typical installation in an aircraft.
(b) Mount the equipment by its normal means, approximately centrally, on a copper, brass or aluminium groundplane measuring at least 0.76 metre or 30 inches wide and having an area of at least 1.1 square metre or 12 square feet.
(c) This test should preferably be conducted in a screened room with the groundplane connected to the room shielding by low reactance paths from at least both ends of the groundplane.
(d) Where the length of interconnecting cables is not specified by the manufacturer, these should be at least 1.52 metre or 5 feet long and arranged as in a typical installation. Cables should be raised about 50 mm or 2 inches above the groundplane to reduce shunt capacitance effects. Only those cables so specified by the manufacturer in wiring diagrams applicable to the equipment may be screened.
(e) Bonding straps across vibration isolators, etc, should be fitted where these would be used in a normal installation. Bonding must not be used in any place where it would not normally be used in an installation.
(f) Tie in with each bundle of cables in the simulated installation an 18 or 20 gauge insulated cable, unterminated at both ends. Connect a suitable tunable receiver — such as a field intensity receiver — to this “pick-up” cable.
(g) Tune the tunable receiver across the specified frequency range and note the presence and level of signal indications. A signal generator may then be used to determine the levels of noted signals.
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