PIPER AIRCRAFT
PA-42-720 (Advanced Trainer)
MAINTENANCEMANUAL
A. Temperature (continued)
1. InterTurbineTemperatureSensingSystem(ITT) (continued)
(c). Calibration Checkof ITT Gauge and Wiring
CAUTION: THE THERMOCOUPLES WILL GENERATE A SMALL POTENTIALWHICH WILL PRODUCE ERRORSINTHE MEASURED VALUESIF THIS CHECK IS MADE WHILETHE ENGINE IS HOT.
NOTE: A Barfield 2312G-8TemperatureIndicatingSystem Test Set or a Barfield TT-1000Digital Turbine Temperature
TestSetmust be used for making the following calibrations.
(1.) Calibration ProcedureUsing Barfield 2312GEquipment
(a.) Removetop cowling of the affectedengineand disconnect thechromel(+, yellow) and alumel (-, red) leads from ITT probe locatedonthe engine. (b.) Recordthe outside air temp (OAT) using an accurate thermometerplaced next to the two leads removed from ITT probe. (c.) To determine millivoltvaluesto be used for testing and adjustingthe ITT gauge, proceedas follows:
1 Referring to Chart 1, determinethe millivolt values that will be observed for various ITT gauge temperatures,IF THE OAT IS 0°C (32°F). 2 If the OAT is more or less than 0°C (32°F) refer to Chart 2. Using the recorded outsideairtemperature,determinethe absolute millivolts. 3 For OAT's lessthan 0°C (32°F)ADD the absolute millivolts obtainedfrom Chart 2 to the millivolt valuesshownon Chart 1. 4 For OAT's greaterthan0°C (32°F) SUBTRACTthe absolute millivoltsobtained fromChart2 from the millivolt values shown onChart.1.
(d.) PlaceBarfieldtest set function switchto IND. Connecttheleads of the Barfield test set and precisionmultimeteras shown in Figure 501.
(e.) Press andhold test buttonon the test set, while adjustingthecalibrationknob,until millivoltvalue determined in step (c.) is shown on multimeter. Checkcalibrationof ITTgauge. Repeat the procedure for all temperaturesspecifiedon Chart 1.
(f.) If gauge is out of tolerance at any point it should bereplaced.
(2.) CalibrationProcedureUsingBarfieldTT-1000TestSet (Figure 502)
(a.) Set function switchto TEMPMEASURE.
(b.) Connectblackclipto alumel (-) thermocouple lead and red clip to chromel (+)lead.
(c.) Using ON-OFF switch,turntestset on.
(d.) Referringto Chart1, adjust TEMPADJ until temperatureto be checkedappearson
display.TheTT-1000is internally correctedfor variations of OAT; no further adjustmentsare required. (e.) ITT gaugein cockpit instrumentpanelshouldindicatethesametemperature,+ appropriatetolerances,as being displayedontest set. (f.) An opencircuitin the thermocoupleor lead wires,is indicated bythe word OPEN appearingon the test set display. (g.) If ITT gauge isout of tolerance at any pointit should be replaced.
EFFECTIVITY: 040-999
Jan 10/9077-20-00
Jan10/90 "
PIPERAIRCRAFT
PA-42-720(AdvancedTrainer)
MAINTENANCEMANUAL
A. Temperature(continued)
1. InterTurbineTemperatureSensing System (ITT) (continued)
MeterTerminal
ChromelTerminal(SmallHole)
AlumelTerminal(LargeHole)
MeterTerminal
ThermocoupleHarness Loop Resistance Check
Figure 601
Barfield Meter
ChromelTerminal(SmallHole)
AlumelTerminal(LargeHole)
BarfieldTerminalTo Ground
T5 HarnessInstallation Resistance Check
Figure 602
EFFECTIVITY:
040-999
77-20-00 PAGE3
Jan 10/90
PIPER AIRCRAFT
PA-42-720(Advanced Trainer)
MAINTENANCEMANUAL
A. Temperature(continued)
1. InterTurbineTemperatureSensing System (ITT) (continued)
NOTE: If Barfield TT1000 Tester is used connectthe black clip to the Alumel (-black) lead and the red clip to the Chromel (+red) lead.
.
L CalibrationAdjust Black(-)
Inter-Turbine Temperature Calibration Check
Figure603
CHART 1
BASIC MILLIVOLTS AND TEMPERATURE VALUES
Temperature mv (Millivolts) Tolerance 950°C (39.3 mv) + 29°C 850°C (35.3 mv) +10°C 800°C (33.28 mv) ± 5°C 750°C (31.21 mv) ± 10°C 700°C (29.13 mv) ± 20°C 600°C (24.9 mv) ± 20°C 500°C (20.6 mv) + 20°C 400"C (16.4mv) ± 20"C
3000C (12.2 mv) + 20°C
EFFECTIVITY: 4 PAGE 040-999 Jan10/9077-20-00
PIPER AIRCRAFT
PA-42-720(Advanced Trainer)
MAINTENANCE MANUAL
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