B737-345 PMC Questions
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B737-345 PMC Questions
Being one of the millions of pilots who isout of work, and currently reviewing the flight manuals with no access to aB737 I have become uncertain as to theillumination of the PMC warning lights and have the following questions..
I would appreciate if someone who iscurrently flying the 737 300-400-500 could clarify the illumination of the PMClights as follows.
On the ground engines NOT running /preflight complete.
PMC switches “on” are the ON lights illuminated ?
PMC switches “off” are the INOP lightsilluminated ?
I ask this question because the PMC ispowered by the N2 control alternator, only when engines running and at over 46%N2. therefore with engines not running the PMC’s are un-powered and I am unsureof the status of the warning lights.
If the lights illuminate as above then theswitching is purely a preflight action to switch the PMC on, (28v DC bus 1& 2) which will actually not activate until 46% N2 is reached, the N2control alternator being its power source.
Next question is if a fault can be detectedprior to engine start or not.
If the PMC is switched “ON” (pre flight- engines not running) and has afault, will the INOP lights illuminate at this stage, or will it only manifestitself after 46% N2 when powered, since the switching is purely an activation /deactivation switch.
Now the operations manual states that “ThePMC INOP light is suppressed below starter cut out engine speed. I interpretthat as the inop light will not indicate a fault but only a swith “off”
Whilst the Maintenance manual is morespecific and states that “The starter cut out relay when energized alsoinhibits the PMC INOP indication”
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Inflight or engines running no questions,its quite strait forward, however I have found some points of interest foranyone interested.
According to maintenance manual if afailure of the J2 connector has occurred the PMC INOP light in the controlcabin will not come on ( J2 connector is the power source from the N2 ControlAlternator)
