Avionics General Test Equipment.pdf

Workshop Testing Equipment Calibration Standards Test equipment suitable to maintain airborne avionics equipment is essential. Prior to each use of test equipment, the technician must ensure it is serviceable and within calibration, and is the equipment called for by the manufacturer...

Workshop Testing Equipment Calibration Standards Test equipment suitable to maintain airborne avionics equipment is essential. Prior to each use of test equipment, the technician must ensure it is serviceable and within calibration, and is the equipment called for by the manufacturer or the equivalent. Before accepting it, the technician should compare the specifications of the test equipment recommended by the manufacturer and those proposed by the repair facility. The test equipment must be capable of performing all normal tests and checking all parameters of the equipment under test. The level of accuracy should be equal to or better than that recommended by the manufacturer. The calibration intervals for test equipment vary with the type of equipment, environment and use. The accepted industry practice for calibration intervals is usually 1 year, unless otherwise required. Calibration labels 2023-02-06 B-07c Maintenance Practices Page 49 of 255 CASA Part 66 - Training Materials Only  Logic Probes The two-state conditions in logic circuits are often referred to as either high or low (or on/off or 1/0). Any particular digital Integrated Circuit (IC) can be tested by simply comparing it to a known functional version of the same IC. The logic probe can be of great value in troubleshooting digital integrated logic circuits. The ideal logic probe has the following characteristics: It detects a steady logic level. It detects a train of logic levels. It detects an open circuit. It detects a high-speed transient pulse. It has over-voltage protection. It is small, light and easy to handle. The use of a suitable logic probe can greatly simplify your troubleshooting of logic levels through digital integrated logic circuitry. It can immediately show you whether a specific point in the circuit is low, high, open or pulsing. Some probes have a feature that detects and displays high-speed transient pulses as small as 10 ns wide. These probes are usually connected directly to the power supply of the device being tested, although a few have internal batteries. Most IC failures show up in a circuit as a constant high or low level. Because of this, logic probes provide a quick, inexpensive way of locating the fault. They can also display the single, short-duration pulse that is hard to detect on an oscilloscope. The illustration shows a basic logic probe. Aviation Australia A basic logic probe 2023-02-06 B-07c Maintenance Practices Page 50 of 255 CASA Part 66 - Training Materials Only  Basic Logic Probe The basic probe can be used to check the logic levels during logic gate experiments. Connect the croc clip to the 0 -V rail and use the probe to check levels at various points. Aviation Australia Basic logic probe operation Red turns on if the level is high, and green if the level is low. If both LEDs turn on, but dimly, then a high-frequency pulse train is being detected. The circuit demonstrated above can be constructed on a breadboard and tested physically. Note that pins 7, 8, 9, 12 and 13 of the CD4011 IC in the diagram are all connected to the negative supply rail. 2023-02-06 B-07c Maintenance Practices Page 51 of 255 CASA Part 66 - Training Materials Only  Oscilloscopes The oscilloscope is one of the most important measuring instruments used in analysing complex electronic circuits. It is a sophisticated voltmeter with a two-dimensional graph display that can be used to measure the voltage (amplitude) and frequency (time) of an electrical signal. It is designed to show the shape of a video pulse appearing at a selected test point. Although some oscilloscopes show video pulses more accurately than others, all scopes function in fundamentally the same way. If you learn how one oscilloscope operates, you will be able to understand others. Oscilloscope The many different types of oscilloscopes vary in complexity and include both analogue and digital versions. 2023-02-06 B-07c Maintenance Practices Page 52 of 255 CASA Part 66 - Training Materials Only  Aviation Australia Various video pulses Some oscilloscopes use a cathode ray tube (CRT) display in which controlled electron beams are used to present a visible pattern of graphical data on a fluorescent screen. They are called cathode ray oscilloscopes (CROs). Aviation Australia Basic operation of CRT To determine the size of the voltage signal appearing at the output of the signal generator’s terminals, an AC voltmeter is connected in parallel across these terminals (as shown on the left hand side in the following diagram). The AC voltmeter is designed to read the DC "effective value" of the voltage, also known as the Root Mean Square (RMS) value of the voltage. 2023-02-06 B-07c Maintenance Practices Page 53 of 255 CASA Part 66 - Training Materials Only  Aviation Australia CRO indications The peak or maximum voltage seen on the scope face is VM volts and is represented by the distance from the symmetry line CD to the maximum deflection (as shown on the right hand side in the diagram above). The relationship between the magnitude of the peak voltage displayed on the scope and the RMS voltage (VRMS) read on the AC voltmeter is Vrms = 0.707 VM (for a sine or cosine wave). 2023-02-06 B-07c Maintenance Practices Page 54 of 255 CASA Part 66 - Training Materials Only  Decade Boxes A decade box is an assembly of precision resistors, coils or capacitors whose individual values vary in sub-multiples and multiples of 10. By appropriately setting a 10-position selector switch for each section, the decade box can be set to any desired value within its range. It is normally used for load substitution. Resistance, capacitance and inductance types are available. The example shows decade boxes with five sections (five dials); boxes with six or seven sections (dials) are also available. Decade boxes 2023-02-06 B-07c Maintenance Practices Page 55 of 255 CASA Part 66 - Training Materials Only  Decade Resistance Boxes The circuit diagram of a typical 0 to 9,999,999-Ω decade resistance box is shown. Aviation Australia Circuit diagram of a decade resistance box Each switch section represents a decade, or a multiple of 10. Each resistor within a section is of the same value, 1, 10, 100, 1000 and so on, depending on the switch it happens to be in. To select a desired resistance, turn each switch to the appropriate position, placing resistors in series. 2023-02-06 B-07c Maintenance Practices Page 56 of 255 CASA Part 66 - Training Materials Only  Signal Generators Standard sources of AC energy, both audio frequency (AF) and radio frequency (RF), are often used in electronic equipment maintenance. These sources, called signal generators, are used to test and align all types of transmitters and receivers. They are also used to troubleshoot various electronic devices. The function of a signal generator is to produce AC of the desired frequencies and amplitudes with the necessary modulation for testing or measuring circuits. The amplitude of the signal generated by the signal generator must be correct. In many signal generators, output meters are included in the equipment to adjust and maintain the output at standard levels over wide ranges of frequencies. The illustration below shows an FG-30 signal generator which is mostly utilised in the avionics workshop. The FG-30 is a multi-purpose, highly reliable and low-cost 3-MHz sweep function generator. While being easy to use, it also provides many convenient features which make it an ideal instrument for electronics, education, production, and research and development laboratories. Its features include six output waveforms, a pulse generator and a sweep generator. Specifications: Frequency: 0.5 Hz–3 MHz (2.5 MHz for ramp and pulse) in six steps. Output waveform: sine, square, triangle, positive pulse and negative pulse. FG-30 signal generator 2023-02-06 B-07c Maintenance Practices Page 57 of 255 CASA Part 66 - Training Materials Only  When using the signal generator, you connect the output test signal to the circuit being tested. You can then trace the progress of the test signal through the equipment by using electronic voltmeters or oscilloscopes. In many signal generators, calibrated networks of resistors, called attenuators, are provided. Attenuators in signal generators regulate the voltage of the output signal. Only accurately calibrated attenuators can be used because the signal strength of the generators must be regulated to avoid overloading the circuit receiving the signal. The many types of signal generators are classified by use and the frequency range covered as AF generators, video signal generators, RF generators, frequency-modulated RF generators and other special types which combine frequency ranges. 2023-02-06 B-07c Maintenance Practices Page 58 of 255 CASA Part 66 - Training Materials Only  Radio Frequency Testing RF Signal Generator A typical RF signal generator contains, in addition to the necessary power supply, three main sections: an oscillator circuit, a modulator and an output control circuit. The internal modulator modulates the RF signal of the oscillator. In addition, most RF generators are provided with connections through which an external source of modulation of any desired waveform may be applied to the generated signal. Metal shielding surrounds the unit to block signals from the oscillator entering the circuit under test by means other than through the output circuit of the generator. A block diagram of a representative RF signal generator is shown below. Aviation Australia Block diagram of a representative RF signal generator The function of the oscillator stage is to produce a signal which can be accurately set in frequency at any point in the range of the generator. The type of oscillator circuit used depends on the range of the frequencies for which the generator is designed. In low-frequency signal generators, the resonating circuit consists of a group of coils combined with a variable capacitor. One of the coils has a selector switch attached to the capacitor to provide an LC circuit that has the correct range of resonant frequencies. The function of the modulating circuit is the production of audio (or video) voltage which can be superimposed on the RF signal produced by the oscillator. The modulating signal may be provided by an audio oscillator within the generator, or it may be derived from an external source. In some signal generators, either of these methods of modulation may be used. In addition, the pure unmodulated signal from the oscillator can be used, when desired, to disable the modulator section. The type of modulation used depends on the application of the particular signal generator. The modulating voltage may be a sine wave, a square wave or a pulse of varying duration. In some specialised generators, provision is made for pulse modulation in which the RF signal can be pulsed over a wide range of repetition rates and at various pulse widths. 2023-02-06 B-07c Maintenance Practices Page 59 of 255 CASA Part 66 - Training Materials Only  Usually the output of the generator contains a calibrated attenuator and often an output-level meter. The output-level meter indicates and controls the output voltage of the generator by indicating arbitrary values of output readings in tenths through the value of 1.0. The attenuator selects the amount of this output. The attenuator, a group of resistors forming a voltage-dropping circuit, is controlled by a knob which is calibrated in microvolts. When the control element is adjusted so the output meter reads unity (1.0), the reading on the attenuator knob gives the exact value of the output in microvolts. If output voltage is desired at a lower value, the control is varied until the meter indicates some decimal value less than 1.0, and this decimal is multiplied by the attenuator reading to give the output in microvolts. RF Directional Wattmeter A directional wattmeter is designed to measure forward or reflected power in coaxial transmission lines under any load condition. It is inserted between the transmitter and load. Plug-in elements determine the power rating and radio frequency (RF) range. Rotate elements to read forward or reflected power. RF directional wattmeter If an antenna system matches the characteristic impedance of the transmitter, all the power is radiated. The power travelling along the transmission line to the antenna is called the forward power. If an antenna system does not match the characteristic impedance of the transmitter, some of the power is reflected back to the transmitter. The power travelling along the transmission line back to the transmitter is called the reflected power. At any transmission line, the forward power and reflected power add or subtract. 2023-02-06 B-07c Maintenance Practices Page 60 of 255 CASA Part 66 - Training Materials Only  The forward power in the transmission line is Pf = Vf²/Z = If²Z, and the reflected power is Pr = Vr²/Z = Ir²Z, where Z is the line impedance. So the actual power, P, delivered to the load is the forward power less the reflected power. For example, if a directional RF wattmeter reads 90 W forward power and 10 W reflected power, the actual transmitter output power is 80 W. 2 V f 2 Pf = = I × Z f Z 2 Vr 2 Pr = = Ir × Z Z Most RF wattmeters operate with a line impedance of 50 Ω. The standing wave ratio (SWR) can then be calculated from forward (Pf) and reflected power (Pr) measurements, reading from the directional wattmeter. SWR is calculated by using the following formula: (1 + √ P r /P f ) SW R = (1 − √ P r /P f ) For example, during the test of an aircraft antenna system, the readings from an RF directional wattmeter for forward and reflected power are 100 W and 25 W respectively, and from the above formula, the SWR on the antenna feed line is 3:1. The SWR is usually defined as a voltage ratio called the VSWR, for voltage standing wave ratio. For example, a VSWR of 1:1 indicates the impedances of the antenna and its transmission line are matched. A VSWR value of 3:1 denotes a maximum standing wave amplitude that is 3 times greater than the minimum standing wave value. High VSWR degrades transmitter performance and can permanently damage the transmitter. It is also possible to define the SWR in terms of current, resulting in the current standing wave ratio (ISWR), which has the same numerical value. The power standing wave ratio (PSWR) is defined as the square of the VSWR. 2023-02-06 B-07c Maintenance Practices Page 61 of 255 CASA Part 66 - Training Materials Only  Aviation Australia Standing wave ratio A diagram of a Bird Model 43 Wattmeter is shown as an example. This is an insertion-type RF wattmeter designed to measure RF power and load match in 50-Ω coaxial transmission lines. It is intended for use with CW, AM, FM and TV modulation, but not pulse modulation. The meter provides direct readings in watts with an expanded scale for easy reading. The scale is graduated for 25, 50 and 100 W (full scale). Elements are available in a variety of power and frequency ranges. To make measurements, a Bird Plug-In Element is inserted into the line section socket and rotated against one of the stops. To measure incident (forward) power with the wattmeter, rotate the element so the arrow points towards the load. To measure reflected power, position the arrow towards the RF power source. A small catch in the corner of the socket face presses on the shoulder of the element to keep it in proper alignment. Two N-type connectors (one male and one female) are located on either side of the wattmeter case to connect the instrument between the power source and the load. The meter’s zero setting should be checked when no RF power is present. When no power is applied, the pointer should rest exactly on 0. 2023-02-06 B-07c Maintenance Practices Page 62 of 255 CASA Part 66 - Training Materials Only  Aviation Australia Diagram of a Bird Model 43 RF Wattmeter Current is produced in the coupling circuit by the travelling waves in the line section. Both inductive and capacitive coupling contribute to this. The inductive current flows in the direction of the travelling wave, while the capacitive current is independent of the direction of the travelling wave. Therefore, the inductive current produced by one of the travelling waves adds in phase with the corresponding capacitive current, while that produced by the wave travelling in the opposite direction subtracts. The additive, or ‘arrow’, direction is assigned to the forward wave. The electrical characteristics of the element are carefully adjusted so that, for the reverse travelling wave, the inductive current completely cancels the capacitive current. The result is directivity greater than 25 dB. Thus, the element is sensitive at either of its settings, but to only one of the two travelling waves. The wattmeter measurements are also independent of position along the transmission line. Like similar diode devices, the Bird 43 indicates the carrier component of amplitude modulation, with very little response to side band components added by modulation. Note the storage position on the side of the directional wattmeter for an element not currently used. Typically, two extra elements can be stored in the housing, one on each side. Remember to use an element correctly rated for both power output and frequency. As a rule, use an element that will result in a two-thirds scale reading on the meter at the transmitter's rated power level. Dummy loads can be used for fault finding. Ensure they are correctly rated for both power output and frequency. 2023-02-06 B-07c Maintenance Practices Page 63 of 255 CASA Part 66 - Training Materials Only  Wattmeter and dummy load Relevant Youtube link: Directional Wattmeter (Video) 2023-02-06 B-07c Maintenance Practices Page 64 of 255 CASA Part 66 - Training Materials Only  Attenuator An attenuator is an electronic device that reduces the amplitude or power of a signal without appreciably distorting its waveform. It is effectively the opposite of an amplifier, though the two work by different methods. While an amplifier provides gain, an attenuator provides loss, or gain of less than 1. Attenuators are usually passive devices made from simple voltage divider networks. Its input and output impedances are usually matched to the impedances of the signal source and load respectively. An RF attenuator is an RF component used to make RF signals smaller by a predetermined amount, which is measured in decibels. There are two general categories of attenuators: Fixed Variable. A fixed attenuator, often called a pad, is used in a wide variety of applications and can satisfy almost any requirement where a reduction in power is needed. An attenuator extends the dynamic range of devices such as power meters and amplifiers, reduces signal levels to detectors and matches circuits. They are used daily in lab applications to aid in product design. Attenuators are also used to balance out transmission lines that otherwise would have unequal signal levels. Various fixed and adjustable RF attenuators are shown. Various RF attenuators 2023-02-06 B-07c Maintenance Practices Page 65 of 255 CASA Part 66 - Training Materials Only  Attenuator Probe An attenuator probe has an internal high-value resistor in series with the probe tip. This gives the probe a higher input impedance than that of the oscilloscope. Aviation Australia Schematic representation of a basic attenuation probe Because of the higher input impedance, the probe can measure high-amplitude signals that would overdrive the vertical amplifier if connected directly to the oscilloscope. The diagram shows a schematic representation of a basic attenuation probe. The 9-MΩ resistor in the probe and the 1-MΩ input resistor of the oscilloscope form a 10:1 voltage divider. Since the probe resistor is in series, the oscilloscope input resistance is 10 MΩ when the probe is used. Thus, using the attenuator probe with the oscilloscope causes less circuit loading than using a 1:1 probe. Before using an attenuator probe to measure high-frequency signals or for fast-rising waveforms, you must adjust the probe compensating capacitor (C1) according to instructions in the applicable technical manual. Some probes have an impedance equaliser in the end of the cable that attaches to the oscilloscope. The impedance equaliser, when adjusted according to the manufacturer's instructions, ensures proper impedance matching between the probe and oscilloscope. An improperly adjusted impedance equaliser results in erroneous measurements, especially when you are measuring high frequencies or fast-rising signals. 2023-02-06 B-07c Maintenance Practices Page 66 of 255 CASA Part 66 - Training Materials Only  Avionics Aircraft System Testing Time-Domain Reflectometer A time-domain reflectometer (TDR) is used for cable length measurement and fault locating on virtually all types of cable, including twisted pair, coaxial and parallel conductors. Access to two conductors from one end is required. A metal time-domain reflectometer The TDR transmits pulses of a known shape and amplitude into one end of a cable that travel along the cable at a speed determined by its velocity of propagation. As the pulses reach impedance changes in the insulation of the cable, indicative of a fault or cable end, reflections are caused that travel back along the cable and are identified by the TDR. The size, shape and general nature of the reflected pulses indicate the type of fault encountered, and the time taken for the pulse to be reflected enables an accurate measurement of distance to the fault to be determined. Vp is a ratio of the speed of light. This is a measure of how fast a signal travels along a line. A radio signal travels in free space at the speed of light, approximately 300,000,000 m/sec. A signal travels in a transmission line much slower than this. In twisted pair cable, the velocity of propagation may be between 40% and 75% of the velocity in free space. There is a direct relationship between velocity of propagation Vp and wavelength λ: Vp = λf. Vp is often stated either as a percentage of the speed of light or as time-to-distance. When the time- to-distance figure is used, it may be known as propagation delay and is expressed as ns/100 m or m/km. 2023-02-06 B-07c Maintenance Practices Page 67 of 255 CASA Part 66 - Training Materials Only  Aviation Australia The principle of time-domain reflectometer Also, since distance is related to time and the amplitude of the reflected step is directly related to impedance, the comparison indicates the distance to the fault as well as the nature of the fault. Various fault indications by TDR In the illustration, views (A), (B), (C) and (D) illustrate typical transmission line problems that can easily be identified by using a TDR. In addition to showing both the distance to and the nature (resistive, inductive or capacitive) of each line discontinuity, time-domain reflectometry also reveals the characteristic impedance of the line and indicates whether losses are shunt or series. They are also used to locate and analyse connectors and splices. 2023-02-06 B-07c Maintenance Practices Page 68 of 255 CASA Part 66 - Training Materials Only  IFR NAV-402AP Nav/Comm Test Set The IFR NAV-402AP is a completely self-contained unit designed to meet the functional testing and calibration of MKR (Marker Beacon), VOR (VHF Omnidirectional Radio Range), ILS (Instrument Landing System) and COM (Communications) avionics. The test set is designed to be used both as a bench and ramp tester. It includes: A signal generator for MKR, VOR, LOC, G/S and COM systems with both XTAL and VAR frequency modes. A VOR bearing selectable in 0.1° steps. A built-in 90° bearing monitor of VOR output. Simultaneous LOC-G/S output. Sweep LOC DDM to test autopilot capture mode. An RF power meter for COM XMTR power, 0–10 W and 0–100W. A built-in counter to display generator frequency, COM XMTR frequency, or 0 dBm external frequencies from 1 MHz to at least 300 MHz. A built-in battery and charger supply. MKR / NAV / COMM test set 2023-02-06 B-07c Maintenance Practices Page 69 of 255 CASA Part 66 - Training Materials Only  MICHEL 2210 Nav/Comm Ramp Tester Provides test signals for localiser, glideslope, VOR, MKR and COMM. The signals may be radiated or connected directly to the unit under test. A demodulated signal is available for direct connection to some converters. The unit improves on the NC 2200, which it replaces. Improvements include the following: Higher RF power Precise localiser and glideslope deflection Calibrated VOR bearings in 10° increments Crystal-controlled modulation frequencies Longer battery life Internal antenna with adjustable length Smaller size. MICHEL 2210 NAV-COMM ramp tester 2023-02-06 B-07c Maintenance Practices Page 70 of 255 CASA Part 66 - Training Materials Only  IFR 4000 Nav/Comm Test Set The IFR 4000 is a compact, lightweight and weatherproof unit. This unit is designed for testing ILS, VOR and MKR receivers and VHF AM/FM and UHF AM transceivers. IFR 4000 NAV / COMM test set Its useful features include: Accurate measurement of VHF/UHF transmitter, frequency, output power, modulation (AM and FM and receiver sensitivity) Generation of ARINC 596 Selective Calling Tones Accurate measurement of VHF/UHF antenna and or feeder SWR Simulation of localiser and glideslope (CAT I, II and III) signals with variable DDM settings Swept localiser DDM for coupled auto-pilot testing (simultaneous localiser, glideslope and MKR signals) Simulation of VOR beacon with variable bearing Simulation of MKR, Selectable Airways (Z), Outer and Middle Marker Tones Guided Test capability cuts down total test time 5.7-in. LCD display with user-adjustable backlight and contrast Internal battery allows 8 hr operation before recharge. 2023-02-06 B-07c Maintenance Practices Page 71 of 255 CASA Part 66 - Training Materials Only  ATC/DME Tester MICHEL 3300 Transponder Test Set The 3300 (P/N: NC-3300) is designed to test Air Traffic Control (ATC) transponders on the bench as well as when they are installed in aircraft. As such, the 3300 contains an interrogation transmitter. The intended range of the interrogation is less than 100 ft. When used for ramp testing, the interrogation signal is comprised of pulse groups (PGs) transmitted at a PRF of 235 PG/s. A pulse group consists of three or four pulses with a nominal width of 0.80 µs. Michel 3300 2023-02-06 B-07c Maintenance Practices Page 72 of 255 CASA Part 66 - Training Materials Only  Distance Measuring Equipment Distance measuring equipment (DME) consists of portable units which can typically be operated on an internal battery. The test set comes with an antenna that is usually mounted on a tripod and located within a specified distance from the aircraft. The equipment produces simulated, highly accurate DME range and velocity signals on all channels. DME test sets can normally also be used to check ATC transponder systems. The DME range output is usually available from 0 to 399 NM in 1-NM steps and within 0.07-NM accuracy. Variable velocity outputs, which can simulate inbound or outbound tracks to accuracies of 0.02%, can also be simulated. The DME system has two physically separated sub-systems: an airborne interrogator and a ground transponder. The system provides the aircraft with distance information from a ground station. The distance between the aircraft and the station is the slant range distance (i.e. line of sight) and not the horizontal distance. Paired pulses, at a specific spacing, are sent out from the aircraft (interrogator) and received at the ground station. The ground station (transponder) then transmits paired pulses back to the aircraft at the same pulse spacing, but on a different frequency. The time required for this round-trip signal exchange is measured in the airborne DME unit and translated into distance (nautical miles) from the aircraft to the ground station. A correction factor is applied during the translation to cater for the ground station processing delay. DME 2023-02-06 B-07c Maintenance Practices Page 73 of 255 CASA Part 66 - Training Materials Only  Pitot-Static Test Sets Pitot/static test sets are basically used to test aircraft pitot and static systems. They can be used to test: Altitude indications Airspeed indications Vertical speed indications (rate of climb/descent) Air Data Computer operation Transponder operation at simulated altitude Cabin pressurisation warnings The possible presence of leaks in pitot and static systems. Pitot-static test sets 2023-02-06 B-07c Maintenance Practices Page 74 of 255 CASA Part 66 - Training Materials Only  Pitot/Static Tester ADTS 500 The ADTS 500 is a self-contained, portable pitot-static tester for the flight line and provides two LCD display panels, function keys, a hand pump and pressure outlet ports. This microprocessor-controlled tester uses solenoid valves for automatic over-pressure and rate-of-change protection and can be programmed to set pitot/static limits. The case lid has stowage space for the power supply cable and pitot and static hoses; the lid can be removed during operation. The tester is powered by internal rechargeable batteries or external power supplies. The ADTS 500 tester can be used to perform sense and leak tests on pitot and static systems. It accurately measures altitude and airspeed pressures and, with the integral hand pump, provides accurate air data. Pitot/Static Testing Procedure The procedure used for testing aircraft pitot/static systems is quite straightforward. For each aircraft type, however, there are minor differences in procedure due to the variations in pressure detection equipment and other pitot-static devices utilised on different aircraft. We will examine the general procedure used in pitot/static leak testing. To find specific information for an aircraft you are working on, refer to the Aircraft Maintenance Manual (AMM). Before commencing a pitot/static leak test, make sure you do the following: Check the aircraft’s maintenance documentation (maintenance release, worksheets or logbook as appropriate to the work required) to make sure that the mandatory entry requiring a pitot/static leak check has in fact been entered. Obtain the applicable AMM and read the section containing the pitot/static leak test procedure. This is where you will find any relevant information regarding special precautions and unusual procedures unique to that particular aircraft type. The testing method consists basically of applying pressure and suction to the pressure heads and static vents respectively, using a leak tester and coupling adaptors. Pitot/static leak testing machines provide positive and negative pressures for leak checks. Because the type of machine used varies between maintenance sections, you must know how to operate the particular machine used by your maintenance section before connecting it to the aircraft pitot/static system. Do not increase or decrease pressure at a rate exceeding that specified in the AMM. The rate is normally given in feet per minute. CAUTION: The use of the mouth and lungs to apply pressure and suction to a pitot/static system is considered a bad practice. It is not a well-controlled pressure and could seriously damage the instruments in complex systems. 2023-02-06 B-07c Maintenance Practices Page 75 of 255 CASA Part 66 - Training Materials Only  WARNING: Failure to observe these precautions will damage the sensing elements in the pitot/static instruments. Do not place sideways load on pitot heads – you may compromise their critical alignment. Ensure heat is turned off and isolated electrically. Do not apply suction to pressure ports. Do not apply pressure to static ports. The pitot pressure entry hole, drain holes and static holes or ports should be inspected to ensure that they are not blocked. The sizes of the drain holes and static holes are aerodynamically critical; therefore, they should never be cleared of obstruction with tools that are likely to cause enlargement or burring. Use only approved static port blocking devices when performing tests. Do not use tape to block static ports unless permitted to do so. If tape is used, enter that information in the aircraft documentation and remove the tape after testing. General Electric Modern GE ADTS 500 Series Pitot Static Test Kit 2023-02-06 B-07c Maintenance Practices Page 76 of 255 CASA Part 66 - Training Materials Only  Turbine Temperature Tester The TT1000A is a completely self-contained, battery powered aircraft turbine temperature system tester capable of measuring system lead resistance and insulation and performing indicator run-outs with a range of up to 1000 °C. The unit was specifically designed to meet all requirements for testing aircraft Chromel-Alumel (CH- AL) turbine temperature measuring systems and accurately displays thermocouple outputs in degrees Celsius. The TT1000A is engineered for maximum ease of operation and includes an automatic digital display which practically eliminates human error and reduces testing time to a minimum. The test leads incorporate automatic temperature compensation to remove induced voltage caused by a ‘Cold Junction’ created when the test leads are attached to the aircraft. All of the features designed into the TT1000A have been added to reduce maintenance time and cost as well as to provide a maintenance-friendly tester for measuring and displaying resistance of thermocouples, thermocouple rings and system lead circuits. The TT1000A simulates a CH-AL thermocouple with or without simulated system lead resistance. It simulates thermocouple outputs and system lead resistances from 0 to 25 Ω. It also measures and displays the insulation resistance of system wiring and other components. TT1000A digital turbine temperature tester 2023-02-06 B-07c Maintenance Practices Page 77 of 255 CASA Part 66 - Training Materials Only  Fuel Quantity Indication (FQI) Test Set The Model PSD 60-1AF AC Field Calibration Unit is a state-of-the-art test set designed to test capacitance-type liquid gauging systems and their line-replaceable unit components. This test set can be used whenever a capacitance measurement, capacitance substitution or insulation measurement is required. When it is used with a capacitance-type fuel gauging system, this test set performs four basic functions: Measures capacitance values of individual or sets of tank units (a trade term for sensor/transmitters) and/or fuel gauging circuits Inserts appropriate capacitance values of a fuel gauge circuit to allow a functional calibration check Introduces adequate capacitance to simulate the function of the compensator Measures insulation resistance of tank units and cabling. FQI test set There are many types of Fuel Quantity Indicator (FQI) test sets. These may be powered either from AC or DC (typically 115 V AC at 400 Hz, 28 V DC). 2023-02-06 B-07c Maintenance Practices Page 78 of 255 CASA Part 66 - Training Materials Only  Remember to take the following precautions when using FQI test sets: Use an FQI test set only in accordance with its operating instructions. Test only in accordance with the applicable AMM. Ensure correct earthing of the test box – fuel and sparks do not mix. Loop Resistance Testers Loop resistance testing analyses the circuits of cables by measuring and recording the resistance at two locations of interest within a loop. If the resistance values exceed the allowable or expected value, additional resistance is occurring along the path in the form of corrosion. Corrosion degrades electrical ground paths through a chemical interaction between metal and another element, usually air (oxygen), water, salt or a chemical such as Skydrol. The presence of oxygen or water causes an oxide to form between the contacting surfaces. The oxide is an insulator, which limits the flow of electrical current. Gradually the resistance across the junction increases and, over time, the electrical junction can be completely broken. Loop resistance tester When the resistance reaches a predetermined level, maintenance personnel must take corrective action, usually by cleaning the affected junctions, securing loose connections or replacing the cable. Loop resistance testing offers the advantages of: Simplicity in isolating cable loops The ability to measure currents and voltages across junctions. 2023-02-06 B-07c Maintenance Practices Page 79 of 255 CASA Part 66 - Training Materials Only