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x-over TiT


sharif101
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#2 -7b eng x-over tit before light off 840 c after light off 790c & did not hold td amps test,coordinator check,td sys all wiring ck,t-block ck,new thermocouples,y lead ck,engine relay changed ,problem remain.finaly all td sys components & wiring swap with #3 eng one by one but problems doesn't exist.

Please give any idea

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Well, if it's not the J3 lead, the cables between the coordinator and the Amp, or the Relay Box, then I'm thinking it is an issue with the power being supplied to the Amp. There is also a Temp Control Relay you might swap with #3 to see if that's causing it. It is located inside the cargo compartment. Just follow the wiring schematic to figure out where it is if you can't find it. Also, if the fuel control is failing, it may just be becoming too rich for the TD valve to take enough fuel. If this were the case, the fuel control would be more than 100 rich.

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It seems the only thing you have not yet swapped to another engine is the Speed Sensitive Control. Let me see if I read your problem correctly.

You advance the throttle up to flight idle, and I am guessing #2 engine is higher in TIT than the other 3. Then, you advance the throttle up to crossover, and TIT becomes 840. You move the throttle up above crossover, and the TIT becomes 790, but then TIT goes back up by itself. Do I have this correct? Does the light pop back on when temperature shoots back up, or does the light stay off all the time above crossover? Is there any other malfunction, such as the TD Valve Brake Check, Temp Control Check, Temp limiting? Does this still happen with the A/C Instrument and Engine Fuel Control Invertor in the opposite position (D/C instead of A/C, or A/C instead of D/C)?

What is your Auto Start temp? What is your Null Start Temp? When TIT moves up, does torque and fuel flow also increase?

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Yes speed sensitive control also swaped with #3 eng.i think you understand the problem. Starting tit both null & auto is 800 deg.

Before x-over #2 eng tit is more than #3 but after x-over #2 tit less than #3.#2 takeoff tit 965deg & #3 977deg. Fuel flow 200pph less.when throttle advance approx 80deg position tit remain 840 and then fuel flow ,tit,torque increase .but at null tit,fuel flow increase with normal way.td controlling ck tit increase 40 deg but cut back 20 deg not previous rating.limiting ck With td locked fuel correction light came on at 961 deg.but during td test limiting tit set 977 deg..when x-over TIT cut back to 790 and again goes up at that time correction light remain off.

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Forgive me, but it is very difficult to troubleshoot a problem this complex without being there in-person, so please feel free to disagree with me on anything.

It sounds like you have so far swapped the TD Amp, TD Valve, Coordinator, Speed Sensitive Control, Relay Box, TD Null Relay, Thermocouples, Y-Lead, T-Block, thermocouple harnesses, and J3 lead from Amp to TD Valve. The only things left are the Left-Hand Wiring Harness (Spider Box), or wiring between the TD Amp, J-Box, and Firewall.

The last thing I would recommend is swap engines between #2 and #3 and see if the problem stays or moves. It's a big job for just diagnosing, but it would tell you if aircraft wiring is the cause, or if the engine is defective. If the problem stays with the engine, you may have a new part that is bad. It may seem like a big job to do on just the suggestion from someone on the internet, but you've already done everything else that causes this. Do you have any engineering support from Lockheed to help you?

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