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tit indicating sys fault


MINHAS866
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Dear experts hope you all are good I have posted two pics from b-1 sec 7 I want to know Incase of tit indicating system malfunction why this says go temp cont check on ground and for in-flight go with sec 3 what's make the difference .can any body explain why it is so thanks for feedback

TMPDOODLE1471277344457.jpg

TMPDOODLE1471277361073.jpg

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Your T.I.T. indication is low and FUEL FLOW is HIGH.  So, you have two sets of 9 thermocouples (18 total); one set for the TIT indicator and one set for the Temperature Datum system.  In the flight range (above 65 degrees throttle travel) with the T.D. control switches in AUTO the T.D. system will give or take fuel to match THROTTLE position to a preset TIT temperature.  The fuel flow data is not used by the T.D. sys!  So, if there's damaged thermocouples your T.I.T. indication is wrong and you should ALWAYS assume the T.I.T. input to the T.D. sys is wrong too.  With damaged thermocouples the FUEL FLOW is more correct for measuring engine power.  

You want to play it safe especially while flying by taking the T.D. system's TEMP CONTROLLING feature out of the picture by switching to NULL because the T.D. sys only knows what the thermocouples are telling it.  In NULL the T.D. sys is no longer trying to match the T.I.T. to the throttle position (above 65 degrees).  If you have damaged thermocouples then your T.D. sys has wrong information!  You don't know the real problem until you get on the ground. You have bad thermocouple(s) AND your engine could be damaged (F.O.D., damage from overheat, incorrect fuel nozzle spray pattern or fuel control problem) and you only want to cautiously troubleshoot this problem on the GROUND.  

Your EP's state fly in NULL so that the T.D. is no longer trying to match T.I.T. data.  Pushing your T.I.T. to 910 degree for a temp controlling check is not a good idea because the T.IT. is higher (maybe much higher) than the indicator shows. Don't troubleshoot this problem in flight because you will most likely further overheat and damage the turbine!        

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Agreed. If you are ops checking the system, the chances are you have a malfunction somewhere in the indication or fuel/TD systems, or you wouldn't be ops checking it. If the malfunction is in the fuel/TD system, the situation is at least stabilized in-flight with the appropriate procedure. When you start adding variables to a stable situation, such as enabling and disabling the system with various bleed air loads and throttle positions, you can make things much worse, such as a power surge/overtemp or an engine flameout, or any sudden power change in-between. On the ground, neither are dire events when the aircraft is safely parked.

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Sir thanks a lot now got the point why temp control check on ground if controlling working good it definitely over temp so if we have to take off from diapers location put to null maintain fuel flow with other engine and operate the engine but in flight  as sir fred g said don't go to 910 for temp controlling to over temp the turbine

thanks a lot sir  for feed back 

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Sir thanks a lot now got the point why temp control check on ground if controlling working good it definitely over temp so if we have to take off from diapers location put to null maintain fuel flow with other engine and operate the engine but in flight  as sir fred g said don't go to 910 for temp controlling to over temp the turbine

thanks a lot sir  for feed back 

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