engine 5

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  • Mark created a new forum post in ATA 34 Navigation
    Inbound M.E.L. on the TCAS system. A system test from the front of the processor showed an upper antenna fault.



    The Fault Isolation Manual 34-45 Fault Tree 803 asks to verify antenna integrity with a meter, but it does not give any resistance values.

    Upper/Lower Antenna Connections on both Processor and Rack.

    Plug "A" (rack upper right) is for the top antenna elements. "B" for lower antenna.

    These numbers are for reference only:
    A1 : 5.75K Ohms B1 : 5.68K Ohms
    A2 : 15.05K Ohms B2 : 15.19K Ohms
    A3 : 31.3K Ohms B3 : 33.1K Ohms
    A4 : 85K Ohms B4 : 83.7K Ohms



    On this particular aircraft, the upper antenna was recently replaced after a brief history of failures. Two processors had been installed, but the failure repeated after only a couple of days of the processor(s) being replaced.

    I suspect (without seeing the removed antenna) that one of the four elements had shorted out in the antenna itself. This short was taking out (frying) the transceiver in each of the two previous processors. After a third processor was installed, the system has been operating normally.

    A previous discussion of a directional antenna fault on a MD-11 can be found here .

    767-300 SSM 34-45-01
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  • https://rotate.aero/forum/ata-24-electrical-general/63-rccb-power-control#63 should explain things for you.

    On the MD-10/11, these particular ones were in the forward E&E aft right wall. The majority of the power RCCB's are in the mid electrical bay, forward wall behind the three tall brown covers.
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  • My knowledge of electrical theory is weak to nonexistent. I've always thought of current flow as "power to ground", but with the 767 I've found two instances of using two phases of A/C working against each other.

    Forward window and pitot heat .

    They function....... they just don't make any sense???
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  • Mark created a new forum post in ATA 30 Ice and Rain Protection
    I recently had an aircraft with a right side window heat showing inoperative with switch selected on.



    The EICAS had a warning also.



    A test on the Window Heat Control showed only a "Control Unit" fault light. The problem did not follow a swap. The suspect unit tested fine when placed in the opposite position.




    There are basically two separate window heat systems. One controller handles the Left Front (#1), the Right Sliding (#2), and the Right Fixed (#3) windows. The other controller does R1, L2, and L3.

    Being that there are only two fault lights for each side, FWD for the #1 only and SIDE for #2 and #3, this issue could be caused by either the right side's sliding or fixed windows.

    Checking the window assemblies is quite easily accomplished from the controller rack plugs. Each window has a temperature sensitive sensor and one heater coil. Sensor resistance climbs with higher window heat. The 767's sensors came in around 300 ohms with cold windows. Both right side window sensors read good. The only other check to do is to verify the window heater coil to ground. As with most heating coils this reading should be pretty low . The right sliding window came in at 20 ohms..... the right fixed..... 1.5K ohms. Even though the controller did not pick this up, the window is bad.

    The #3 window's heater coil ground was verified along with continuity on the "controller to window" power wire. This "does" need to be done as either of them being open would render a window change as pointless.

    The controllers handle heat for the front windows slightly different than the sides. For the front window's protection from heat shock, voltage is slowly "ramped up" when power is first applied. The front window receives two phase A/C power. The controller adjusts "B" phase as the means of limiting current. The side windows receive 115 VAC in pulses.

    The controller monitors current via a set of Current Transformers on the power output wires. With this aircraft, heat was selected on, but the #3's high heater coil resistance prevented current flow. The controller sensed this, threw up a fault light, and cut the power output. I didn't verify if the sliding window was still receiving voltage or if the system renders both windows inop.


    767-200 ASM 30-41-01
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