Standby Power Question

[larshgf 2]

Qustions concerning Standby Power has been asked in this forum before. After searching relevant threads about this issue I still have a few questions.As far as I understand the standby power system is armed when the Standby Power Switch is in the guarded AUTO position. The function of the Standby Power according to descriptions of the electrical system in 737NG (fx smartcockpit.com) is to "provide 115V AC and 28V DC to essential systems in the event of loss of all engine or APU-driven AC power" Starting with a cold and dark cockpit I have tried to switch ON the battery but omit to set the Standby Power switch in the guarded AUTO-position. Following the usual startup procedure I was then able to start both engines but most of the small blue and amber lightsignals on the overhead panel did not work and neither did the displays on the main panel (PFD, ND etc). Even after having both engines run no displays or small overhead panel light did work. Is this not a fault in the PMDG simulation or is it the same way in a real 737NG cockpit?If the simulation is correct one must conclude that the Standby Power MUST be in the guarded AUTO-position in order to make the small signal lights and displays "come to live" ?Looking forward to answersBest RegardsLars PS: I'm trying to make an "annotated edition" of the standard startup procedure with comments and explanations. Many people have problems with this issue "starting up the C&D cockpit", and my ambition is to upload a file to the AVSIM library, a file which might answer some of the typical questions.

[Jet Tech 31]

Lars,Items powered by the Stby Bus will not work unless the stby power switch is in Auto or On. In a cold and dark aircraft, you would normally select the Battery on, and the STBY power switch would already be in auto. turning on the battery would power the stby bus. Once the engine or Apu generators are online, they take control of the bus from the battery (in auto) if you select the ON position, the Batter should power the stby bus regardless of power sources available. RegardsPaul Gollnick :-cool Technical Operations/Customer Operational SupportPrecision Manuals Development Groupwww.precisionmanuals.comhttp://www.precisionmanuals.com/images/forum/devteam.jpg

[larshgf 2]

Paul,I just thought that the Standby Power was some kind of potential power which was activated when a failure developed in the electrical system of the aircraft. But that's not so...?And the Standby Bus: which items does it power ? I guess one is the small signallights in blue and amber on the overhead panel? And another item is the PFD, ND and the EFIS?RegardsLars

[Qavion 19]

I just thought that the Standby Power was some kind of potential power which was activated when a failure developed in the electrical system of the aircraft. But that's not so...?Lars...The Standby Bus is in use at all times. Only the device powering the Standby Bus changes (Eng Gen, APU Gen, Battery, External Power).And the Standby Bus: which items does it power ? I don't have a simple list, but it includes lots of important stuff in the cockpit, including the #1 navigation systems (VOR #1, DME #1, ATC #1, ADF #1, etc).The Standby Bus is limited in power, however. You won't get this running heavy duty hydraulic pumps, flap electric motors, Weather Radar Transceivers, HF Transmitters, etc. The Standby Bus is, essentially, something which will give you some idea of where you are and how to get home flying manually.Hope this helps.Cheers.Ian.

[larshgf 2]

Ian,I guess that your answer is for the real 737NG and that the PMDG version is simulation this situation rather accurately.Thank's for your answerLars