Lecture. Aircraft and Spacecraft Instrumentation

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Jana Kopecká
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1 Lecture Pressure and temperature measurements on aircraft propulsions, torque, fuel flow, fuel used & vibration measurements, anti-ice systems, fire annunciators

2 Měření okamžité a celkové spotřeby paliva (FF, FU) pístové motory od 200 do 1200 kg/h proudové motory od 300 do 8000 kg/h. Uspořádání turbinkového snímače průtoku paliva

3 Uspořádání turbinkového snímače průtoku paliva s hustotní korekcí

4 Vyhodnocení okamžité a celkové spotřeby paliva Vyhodnocení okamžité spotřeby paliva Mikroprocesorem řízený systém pro vyhodnocení okamžité a celkové spotřeby paliva

5 Měření krouticího momentu Měření s převodem na tlak oleje v planetovém soukolí 1.Vnitřní ozubené kolo 2. Převodová kola 3. Klec převodových kol 4. Vnější ozubené kolo 5. Válce s tlakem oleje L410

6 Měření krouticího momentu Vyhodnocení krouticího momentu pomocí tlaku oleje

7 Měření krouticího momentu pomocí torze hnací hřídele

8 Pressure measurements Manifold pressure - piston engines

9 Oil pressure sensor with moving magnetic core 1. sensing coil Excitation coil 28V 400Hz 2. sensing coil 1. pressure chamber p 1 Active variable air gap p 2 2. pressure chamber Moving ferromagnetic core Two same diaphragmas mag 1. pressure chamber p 1 Power supply 28 V, 400 Hz The differential pressure range 0 to 160 PSI ± 2% The accuracy ±0.75 PSI Temperature range -50 C to 150 C.

10 Oil pressure sensor with silicon diaphragm Stainless- Inductive steel body ratio device with rotary inductors Measured pressure Stainless steel diaphragm Silicon oil 36 V/400 Hz Silicon diaphragm with diffused strain gauges Silicon diaphragm with strain gauges Standard pressure container R 0 - R R 0 + R Suplly current Output signal Electrical connection R 0 + R R 0 - R Oil Tlak & fuel paliva pressure a oleje - L L39 aircraft Strain-gauge Tenzometrický bridge with snímač silicon s křemíkovou diaphragm membránou Oil pressure indicator in range (0 80) PSI (1PSI = 6,8948 kpa ) Fuel pressure indicator in range (0 120) PSI Old engines oil pressure (0 4) kg/cm2, fuel pressure (0 60) kg/cm2

11 Oil pressure sensor with silicon diaphragm Stainlesssteel body Measured pressure Stainless steel diaphragm Silicon oil Silicon diaphragm with diffused strain gauges Silicon diaphragm with strain gauges Standard pressure container R 0 - R R 0 + R Suplly current Output signal Electrical connection R 0 + R R 0 - R Power supply V DC Range for gear box oil pressure 0 to 200 PSI Range for brake hydraulic system up to PSI Temperature range 50 C to 170 C Output voltage mv (non-amplified), 0-10V DC (amplified) Accuracy ± 1% FS

12 Engine pressure ratio

13 Engine pressure ratio (EPR) EPR in range (0 2) Evaluation of EPR Output to the gauge Differential transducer U D Z U V U REF Core Excitation Excitation Connection box Inlet pressure sensor PT 2 Output pressure sensor PT 4.95

14 Temperature measurements Bi-metallic temperature system up to 60 C (140 F) Mechanical bulbs temperature system small airplanes - engine oil temperature jet airplanes compressor inlet temp.

15 Wheatstone bridge system Thermocouple temperature system

16 Thermometer with ratio rotary inductors α Pt = ( ).10-3 C -1 α Ni = ( ).10-3 C -1 Inductive ratio device with rotary inductors Screw-coupling with connection Resistive temperature sensor Mica wafer Resistive wire

17 Measurement of engine or gearbox oil temperature Output connector Mica wafer Temperature range from -40 C to 200 C. Accuracy better than 0.5 C Typical measuring current 1mA. Self heating error of 100 Ω RTD less than 1 C (current < 12mA) Typical sensor resistance 50, 100, 500, Response time of RTD 3 to 5 seconds Sensing element with resistive wire

18 Combined engine indicator oil and fuel pressure, oil temperature

19 Měření vibrací motoru Blokové schéma obvodů měřiče vibrací s elektromagnetickým snímačem

20 Měření vibrací motoru Elektrické náhradní obvody akcelerometru Zdroj náboje Zdroj proudu Zdroj napětí

21 Povrchový mikrofon

22 Ice detection in flight 1. Ice detection exist: a) temperature/moisture probe 2. Icing has formed: a) visual ice detection light hot rod detector b) pressure Smiths ice detector c) torque serrated rotor d) vibration frequency vibrating rod ice detector

23 Temperature/moisture probe Ice cannot form unless there is moisture and freezing temperature. therefore The moisture has to be measured first, then it has to be evaluated if the freezing temperature occurs

24 Ice detection light - aircraft equipped with the light that illuminates parts of the wing that are deemed critical for ice accumulation. Hot rod ice detector (Teddington ice detector)

25 Smiths ice detector Serrated rotor ice detector

Vibrating rod ice detector Detected ice Flowing outer air with water droplets Ferromagnetic magnetostrictive resonator tube Vibrations Electronic feedback circuit Flowing outer air with water

26 Vibrating rod ice detector Detected ice Flowing outer air with water droplets Ferromagnetic magnetostrictive resonator tube Vibrations Electronic feedback circuit Flowing outer air with water droplets Detected ice Excitation coil Sensing coil Ferromagnetic magnetostrictive resonator tube Resonator has a shape of small tube Vibrations with diameter of app. 7 mm and the length of 25 mm. It is manufactured from Excitation special coil ferromagnetic alloy called NISPAN. Electronic feedback circuit Sensing coil

27 Optic fiber ice detector Light transmitter Forming ice Glass window Forming ice Glass window IR Laser Optic fibers IR light detectors Minimal detectable ice layer thickness Light used for reflection detection Sensor weight 0.1 mm IR less than 1 pound

28 Fire annunciators Fire-overheating conductive detector Fan compartment detector - upper right (mounted on engine pylon) Fan compartment detector - upper left ` The wire consists of a central nickel conductor encapsulated in a porous material (aluminum oxide). The porous material is saturated by special salt and covered by inconel or stainless-steel tube. Engine core compartment detector Fan compartment Typical length range 40 cm up to 5 m detector - lower Critical temperature range from 124 C up to 600 C Wire diameter 2.3 mm Specific resistance 50 MΩ/cm (below the critical temperature) Total capacitance 10pF (below the critical temperature) Sensor supply voltage 115V/400Hz

29 Fire-overheating pneumatic detector Normal pressure inside the sensor 20 psi Typical critical temperature of fire loop 315 ± 30 C Typical critical temperature of overheat loop 205 ± 30 C Relay and light supply voltage 28V DC OFF Fire-alarm loop Tc=315 C Alarm pressure switch Overheat loop Metal hydridecoated rod Overheating Loop Tc=205 C Alarm pressure switch OFF ON Test pressure switch Tube with inert gas Fire loop Test pressure switch ON Test 28V DC 28V DC Test Fire Alarm 28V DC 28V DC Overheating warning

30 Bimetallic thermal switch Typical switch temperature 300 C Typical shunt current 10 A Typical switch voltage 28 V Rated performance (in cycles) Time constant more then 7s

31 Ionization smoke detector Alarm light Electronics output Reference chamber Smoke filter Ionization source Test chamber Smoke particles The supply voltage 115V AC and 28V DC Solid particles - products of combustion with size of 0.2 to 60 microns

32 Photoelectric smoke detector Air from monitored compartment 28V DC Pilot Light Light reflected by smoke particles Light detector Signal processing To other smoke detectors Warning relay Smoke particles ventilator 115V AC Test Light 28V DC Light trap Size of detected particles units of µm Reaction time 60 seconds after fire rise Power supply for the sensor 28V DC Power supply for the fan 115V AC

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