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737 Strange DEU/FD problem

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737 Strange DEU/FD problem

Old 11th Nov 2014, 09:55
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737 Strange DEU/FD problem

The other day, we had a strange problem. On arriving on stand, the ground power died just as we put it on, leaving the usual requirement to reset the Yaw Damper &c. All other flight deck indications were normal.

FDs were switched on, but LNAV would not arm prior to departure. Upon rotation, the flight directors disappeared completely. This was solved by cycling the FD switches and re-selecting the desired modes.

The suggestions was that occasionally intermittent power failures cause CDS failures/faults that do not annunciate and only present themselves in this fashion. Despite many GPU failures, this is the first time I've experienced this before and would welcome any suggestions as to the root cause.
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Old 11th Nov 2014, 19:07
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The root cause?
An interrupted power supply.
It's not always only upsetting the "usual items", but sometimes more.
If in doubt, power down and up again.
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Old 11th Nov 2014, 19:21
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I was had a situation where the left IRS aligned perfectly on ground power, but the right IRS wouldn't. Switched the power source to the APU and viola.
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Old 13th Nov 2014, 13:45
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Reset the FCC and/or DEU CB's or depower the aircraft completely. Will clear most of your problems.
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Old 13th Nov 2014, 15:40
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Run the APU...avoid most of these problems. My APU comes on the moment I enter the aircraft...good elec power and decent air conditioning! I've lost count the amount of times ground power has left me stranded. Not to mention the nice warm air they try to pump in during a lovely 90 degree day in Miami or Dallas!
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Old 13th Nov 2014, 15:57
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Run the APU...avoid most of these problems.
- all well and good and a 'jolly good idea' if you have one and are 'allowed' to use it without the CEO running up the airstairs and screaming blue murder - or has policy changed at a certain LOCO?
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Old 13th Nov 2014, 16:33
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Simple...you tell your CEO that safety and customer service come before fuel savings and furthermore, is your office any warmer than a nice cushy 72 degrees (22 C) and does the power keep getting interrupted? thanks and good day Sir
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Old 13th Nov 2014, 17:00
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Ah, but big brother is alive & well in EU. Some environmental guru has decreed that in an airport with 10's of movements per hour, fuel truck, catering trucks, countless run about vehicle on the move, etc. etc, running the APU longer than 10 mins after ATA & 10 mins prior ATD will upset the local population of whatever animal you care to think of: by noise & air pollution. Thus it is banned. The same said guru no doubt has a finger in the pie of people who make GPU's (which are possibly more polluting on both counts) and stand in-built airco units. Common sense went down the swannie years ago: witness the often slow speed restrictions on highways passing airports. You are passing through urbanisation so slower speed equals better air quality. Yep, until the next 737/340/380 launches.
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Old 13th Nov 2014, 17:07
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you tell your CEO that safety and customer service come before fuel savings and furthermore
- whereupon your CEO reminds you that the Employment Office in town is warm............'thanks and good day Sir' as you said................happy dreams, aa.
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Old 13th Nov 2014, 18:15
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Amusing stood on the ramp in a certain place the other day that is known for power cuts around mid-day. About 15 NG's parked up and the chorus of nee-nah horns is a tell tale the power is out.....


Usually takes a minute before the first sound of an APU winding up closely followed by the rest. just in time for the power to come back on. However the cost of starting is drummed into us so now the airfield is full of APU's running for 30-40 minutes.


The joys of.....
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Old 13th Nov 2014, 20:50
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- whereupon your CEO reminds you that the Employment Office in town is warm............'thanks and good day Sir' as you said................happy dreams, aa.
Doesn't work that way here, maybe over there it does. I have no problem reminding management of their priorities...safety and customer service are top priorities in the flight manual. Sorry Mr CEO, I don't run your airline, you don't fly my planes...respectfully

Edit: forgot about Europe's ridiculous environmental rules and restricted APU use at airports. So have everyone on board sweat and create health hazards on board the aircraft...genius!
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Old 15th Nov 2014, 17:30
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Have you heard of air conditionning units?
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Old 16th Nov 2014, 03:48
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Sure I've heard of them... They just don't put out cold enough air!
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