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Off topic - 737 runs out of battery power

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Sam

Joined: 18 May 2008
Posts: 135

Posted: Mon Oct 27, 2008 5:35 am Post subject: Off topic - 737 runs out of battery power

Speaking of standby power, here is an interesting preliminary NTSB report:

[url=http://www.ntsb.gov/ntsb/brief.asp?ev_id 081007X03940&key=1]http://www.ntsb.gov/ntsb/brief.asp?ev_id 081007X03940&key=1[/url]

 

I wonder why they didn't land when they first switched to battery power, since "The QRH procedure also referenced that, "The battery will provide bus power for approximately 30 minutes." ".

 [quote][b]

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_________________
Sam Hoskins
www.samhoskins.blogspot.com

MauleDriver(at)nc.rr.com
Guest

Posted: Mon Oct 27, 2008 10:21 am Post subject: Off topic - 737 runs out of battery power

Very interesting.  I'm not sure there is enough information here for an untrained person (me) to actually see what was done correctly or incorrectly.  But I'm thinking that the procedure that called for the standby system to be switched to BATT killed the charging of the main battery.  Conversely, it it had been left OFF, some subsystems would have been offline but the critical systems would have continued to run on battery power and the battery would have been charged....

 

 ..and while none of that quite makes sense to me, the write-up seems like a lot of bureacratic-speak that is impossible to understand outside of the 757/pro community.

 

 Good off-topic. Thanks

 do not archive

 

 Sam Hoskins wrote: [quote]Speaking of standby power, here is an interesting preliminary NTSB report:

   [url=http://www.ntsb.gov/ntsb/brief.asp?ev_id 081007X03940&key=1]http://www.ntsb.gov/ntsb/brief.asp?ev_id 081007X03940&key=1[/url]

   

 I wonder why they didn't land when they first switched to battery power, since "The QRH procedure also referenced that, "The battery will provide bus power for approximately 30 minutes." ".

   

    	  Quote: 	
		  



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gmcjetpilot

Joined: 04 Nov 2006
Posts: 170

Posted: Tue Oct 28, 2008 5:20 am Post subject: Off topic - 737 runs out of battery power

I fly the B757/B767 now, but I'm typed on the B737. I flew it for 6 years. 

I also was an instructor on the B757-400. This INFO 100% off the top 

of my head and should NOT be used for training or operation of a Boeing 

Jet. (my lawyer would be happy.)

   

  Boeing has very similar electrical architecture between models. I don't 

have time to read the report, but I can almost certainly say what can 

(and likely) happen.

   

  The battery switch got into the position that turns the battery chargers OFF.

   

  Battery power is critical even with all 2, 3 or 4 generators on line. On a 

Boeing twin engine you can have up to 4 Gens, two engine, APU and 

optional hyd motor driven gen (HMDG). The battery drives some items in 

parallel or is the only source of power to others. It can cause loss of some 

systems and have "unintended conciquences". It's indeed the  last chance 

power with out Gen power, as you say for 30 min. (Some have optional 60 

or 90 min battery power.)

  

There is a battery switch that goes in AUTO position (or BAT) at the 

start of the day. That is where it belongs and NEVER is moved in normal 

operations. The other normal position is OFF, used at the end of the day 

when parked overnight, some times not even than. If you left it off you 

would know it and not be able to start the plane. However there are other 

positions. One of these positions overrides the battery chargers (only 

used for non normal events or maintence). You can put it in that 

non normal postion after start with effort, but you would NEVER do that, 

unless directed by a check list; you should know you did it. The issue 

is accidental (brain dead) movement of the BAT switch to over ride the 

battery chargers. [1]

   

  It is VERY subtle to turn the battery  chargers off in flight and the pilots 

might not notice if they're not paying attention, could and has happened. 

The only real in indication is an EICAS message. [2]  (see B737 warning 

system below) The level of the message is just advisory on the B757/767 

and 747-400. Advisory is a white text message with an annunciation light, 

but it does not make the bells and whistles go off.

   

   

  ******

  So if you accidentally put the BAT in over ride and leave it there, you can 

drain the batteries in flight with the Gens on line!  NOTE: there is no reason 

to turn the BAT to that position after its put in AUTO. It has to be in AUTO 

or BAT to start the plane, so you would have to do a second (improper) step 

to configure the switch.

  ******

   

   

  So say the pilot accidentally turned the battery chargers OFF for some 

reason. (This  switch is not easily mistaken and requires a pull twist or 

guard moved.) So the batteries keep doing thier thing, driving what they 

need to, even while the Gens are all on line. When the battiers die all kinds 

of weird stuff happens and the plane can be in serious dodo. The engines 

will continue to run because they have continuous ignition (of jet engine 

principles) and mechanical fuel pumps. Hydraulics will work, like flight 

controls but you may have gear extension issues. [3]

   

  The bottom line is the airplane assumes that during pref light the pilots 

put all the switches in the proper position. There is no way an aircraft can 

account for all human factors. That is why the crews are well trained. I go 

through recurrance evey 6 months and have engine failures, fires, 

decompression, single engine ILS to mins and every electrical, pneumatic 

and hydraulic failure the sadistic instructor can think of. We  use check list 

and two crew cross check and standard procedures. That is why we get 

paid the big bucks, to put switches in the right position.

   

  Long story short this has happend before (one time on a B747-400 with 

Asian airline). 

   

   

  [1] The batteries are not directly connected to the aircraft electrical system, 

in that they are powered/chargers through battery chargers. As you may 

know the primary gens are all AC. DC is from inverters. 

   

  [2] EICAS (engine indicating alert/annunciation system).  The levels are 

WARNING, CAUTION, ALERT and ADVISORY. They should notice it but 

some times its missed. The Boeing 737 goes back to the 60's and had 

it's first major upgrade in mid 80's and than later the "new gen" which 

was a new wing. The cockpit got incremental upgrades in glass and EFIS, 

however the EICAS system is rudimentary. In  fact it is non existent. They 

have the classic annunciation lights all over the panels and one "6-Pak" 

master caution annunciation on the glare shield. You have to physically 

look at of for the light in the panel. The later EICAS has a tube with actual 

text message that often jives with the title of the check list you need to 

address. SO ITS EASIER TO MISS IT ON THE B737, BUT YOU HAVE 

TO REALLY NOT BE PAYING ATTENTION. 

   

  

[3]  Please arm chair expert save us your sanctimonious outrage how 

stupid the engineers are and how you know better. You can't make a 

system fool proof or take all control out of the hands of the crew. You 

have to put a switch in the right position at the start of the flight and off 

at the end of the day. Not every contingency or multiple failures can be 

garded against. A well trained competent crew is required to fly a jet. For 

example the fuel control switches even if  garded can be turned off 

(meaning inadvertent engine shut down). It happened once. You have to 

pay attention when flying any plane but even more in a large jet. Things 

happen fast. That is why I like my Cubs and RV. They have less 

complication. I suggest every one strive for simplicity in their kit plane 

system designs. (internally regulated alternators ROCK!(at); externally 

regulated alternators SUCK! LOL)



             [quote][b]

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BobsV35B(at)aol.com
Guest

Posted: Tue Oct 28, 2008 5:46 am Post subject: Off topic - 737 runs out of battery power

Good Morning Mr Jet Pilot,

  

 For What It Is Worth, the aircraft in question was a Boeing 757, not a 737.  Just a little bit of research could have revealed that fact

  

 Happy  Skies



Old Bob

 Also rated on the 737 and 757/767 as well as many other aircraft.

  

  In a message dated 10/28/2008 8:23:30 A.M. Central Daylight Time,  gmcjetpilot(at)yahoo.com writes:

  	  Quote: 	
		     I fly the B757/B767 now, but I'm typed on the B737. I flew it for 6    years. 

I also was an instructor on the B757-400. This INFO 100% off the    top 

of my head and should NOT be used for training or operation of a    Boeing 

Jet. (my lawyer would be  happy.)

	






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  [quote][b]

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phudes(at)ix.netcom.com
Guest

Posted: Tue Oct 28, 2008 7:13 am Post subject: Off topic - 737 runs out of battery power

On Oct 28, 2008, at 6:16 AM, <gmcjetpilot(at)yahoo.com>  

<gmcjetpilot(at)yahoo.com> wrote:



 	  Quote: 	
		   I fly the B757/B767 now, but I'm typed on the B737. I flew it for 6  

 years.

 I also was an instructor on the B757-400.


	


Is this a new variant? I didn't know Boeing made a 757-400.



Pete Hudes

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gmcjetpilot

Joined: 04 Nov 2006
Posts: 170

Posted: Wed Oct 29, 2008 1:42 am Post subject: Off topic - 737 runs out of battery power

 	  Quote: 	
		  From: BobsV35B(at)aol.com

Good Morning Mr Jet Pilot,

For What It Is Worth, the aircraft in question was a Boeing 757, not a 737.

  
	


Thanks, as I said you can turn the battery chargers off on all Boeing jets. I don't know the specifics of the case because I did not look it up, sorry, but from the description this is one of those gotchas.

   

   

  >From: Peter Hudes <phudes(at)ix.netcom.com>

 	  Quote: 	
		  Is this a new variant? I didn't know Boeing made a 757-400.

Pete Hudes

   
	


  They don't. It was a typo, 747-400. Sorry my bad; I taught it from 1989-1993. Haven't been in one since. This model did have an inadvertent battery charger  shut down as I mentioned. It's just not something that's suppose to happen, if the crew is paying attention, but stuff does happen.



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