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During TD system check, moving the TD switch from AUTO to LOCKED, the

fuel flow and TIT are supposed to remain unchanged. However after three

to five seconds, the TIT drops about 20°C and fuel flow 50 - 100pph.

Three TD amps, 4 TD valves, 3 relay boxes, and a J3 lead have resulted

in no discernable improvement. Coordinator has been checked, and electrical

system has been checked all the way back to the TD switch. The engine

is on the test cell.

Any thoughts on where I can look for a solution?

Thanx

PJ

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Not familiar with test cell, but; ... check the system correction at x-over during "Auto" selection, if the value is as the drop you mentioned, then it seems to me that the TD system is shifting to “nullâ€; then while in “Locked†you may perform the following two checks:

1- Temperature controlling check at 910 ̊C. (the existence or the lack of cut back).

2- Over temperature check at max TIT. (the cut back and the illumination of the correction light).

The results of the two check will limit your defective wiring target.

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Natops, the torque drops off also. When the system is operating as advertized, the

change in TIT seldom exceeds 10°C, and fuel flow 50pph.

Tenten, this is the part that kills me - this is the ONLY check that fails. Everything

else is right on the money. The checks in the cell are the same as for the aircraft.

TB400, I checked the wiring, continuity and voltage, all the way back to the engine

control panel. We have an AM37-T21D

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  • 2 weeks later...

Can’t be the anti-icing if the system having “dignity”.

If not TEST SELL issue; I advise to track and check the wires involved in locking the TD for not having any power leakage disturbing the “Brake Release Solenoid” especially through plug connections/TBs.

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