(h)
Exceedance Data Display - The BITE test button enables display of the maximum exceedance and the accumulated time of all exceedances, since the last power down, for N1, N2 and EGT parameters.
C. Primary Display Parameters Indication
(1)
N1 Parameter
(a)
N1 consists of two input signals, the actual N1 signal and the limit N1 signal. The actual N1 input signal is an alternating electrical signal from the engine fan-mounted sensor. The limit N1 input signal is a dc ratio from the FMC via the digital analog adapter.
(b)
The actual N1 parameter value is displayed by the LED counter and pointer. The limit N1 parameter value is displayed by means of an LED circular bug display and in manual set mode by a 7 segment LED numeric counter display in addition to LED bug display.
(c)
The manual set knob selects the source of the limit N1. With the knob pulled out the limit N1 bug and the manual limit N1 (MAN SET) values are set by turning the knob. With the knob pushed in the limit N1 bug is driven by the FMC.
(d)
The manual limit N1 (MAN SET) readout is blank if the FMC limit N1 source is used.
(e)
If the FMC input fails, the N1 bug freezes and dashes show in the MAN SET N1 limit display. If N1 transmitter fails, the N1 pointer and counter displays slew to zero, after 2 seconds, the N1 pointer will blank and dashes will show across the N1 counter.
(2)
EGT Parameter
(a) The EGT input signal is a dc voltage from engine-mounted chromel/alumel thermocouples. The EGT parameter value is displayed by a LED counter and pointer.
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(b) The EGT display provides a visual indication of a condition that may lead to an abnormal engine start. The EGT digital counter will flash to alert the flight crew of the impending engine abnormal start.
(3)
N2 Parameter
(a)
The N2 input signal is an alternating electrical signal from the engine high pressure compressor speed sensor.
(b)
The N2 parameter value is displayed by an LED pointer and a digital counter.
(4)
FF/FU Parameter
(a)
The fuel flow (FF) input signal is from the engine-mounted sensor. The FF parameter is displayed on an LED counter and pointer.
(b)
The fuel used (FU) indication is obtained on the FF LED counter by depressing the bezel-mounted FUEL USED pushbutton and remains displayed for 10 seconds.
(5)
TMA
(a)
The thrust mode annunciation (TMA) input signal is from the flight management computer (FMC) on ARINC 429 digital data bus. As commanded by digital input the TMA is displayed by means of a 5-character sixteen-segment alphanumeric LED display. The TMA will display one of the following messages:
CLB (Climb)
CON (Continuous)
CRZ (Cruise)
G/A (Go Around)
R-CLB (Reduced Climb)
R-TO (Reduced Takeoff)
TO (Takeoff)
(b)
The TMA shows the active FMC limits. The TMA display is blank if FMC fails. Dashes show across the TMA if the FMC sends a no computed data (NCD) signal.
D. Manual Set Knob
(1) There are two Manual Set Knobs, one located in the lower left-hand front bezel and the other located in the lower right-hand front bezel. The Manual Set Knob allows the pilot to disconnect the input signal from FMC and set the N1 limit value manually.
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(2)
Manual setting of N1 limit value can be accomplished by pulling out and rotating the knob. Pulling the knob out disables the FMC generated input signal, removes the N1 bug drive failure indication (if present), causes the MAN SET numeric counter to illuminate, and allows the limit N1 to be set manually by rotation of the knob.
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