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Power down 737 buzzer/sound

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Power down 737 buzzer/sound

Old 9th Dec 2015, 12:33
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Power down 737 buzzer/sound

Hi there,

when you power down the 737, just before you turn off the battery, the 737 gives a distinct sound.

Is it harmfull to turn off the battery while this sound is still on or has Boeing a special purpose with this sound?

I have been told that if you turn off the battery while the sound is still on , the next crew might have a failure/alert upon powering up, because some sort of internal check has not been completed.

Anybody any comment on this.

Thanks
Boss du Manche is offline  
Old 9th Dec 2015, 14:51
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That sound is usually the gyro in the standby instruments spooling down, so its ok to turn it all off.

If the aircraft is on Battery power alone the sound could be the IRS horn in the Nose wheel bay, stating the IRS are powered by DC power only.

For the latter, the IRS would have to be on still. My guess is the first suggestion and its the gyros spoiling down.
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Old 9th Dec 2015, 15:34
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That buzzer is a warning that the right IRS will loose power in 5 mins.
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Old 9th Dec 2015, 20:04
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Which variant are we talking about?
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Old 9th Dec 2015, 20:42
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If no external AC source the buzzer is the BAT discharge warning. It is associated with the R IRS on DC, but it is BAT discharge. On the ground, the R IRS on DC is not too important. The BAT discharge is significant, as when you come out in the morning and try to crank the APU. Whoops!
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Old 10th Dec 2015, 08:49
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I don't think it's the IRS horn the question is about since if it's a power down we are talking about, you probably turned off the IRS anyway. The sound is when you for example turn off the ground power, a second later it comes a sound that last for a second and then you turn off the battery.
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Old 10th Dec 2015, 13:34
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There is no noise on our NGs during the Electrical Power Down regardless if the battery is discharging. Try setting the STANDBY POWER switch to OFF on the ground prior to the secure procedure, this isolates the standby system and causes a battery discharge with no alarm. The noise on our NGs is only present if the IRS is on.
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Old 11th Dec 2015, 06:41
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You might be hearing the altitude alerting chime when you flick off the battery, thats the MCP losing power...
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Old 11th Dec 2015, 11:04
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There is actually another aural warning that hasn't been mentioned. It starts after a specific time on battery power and it's NOT the IRS warning. I recently learnt about it in our annual tech. exam but I cannot for the life of me remember anything more specific.

I'll see if I can dig it up.
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Old 12th Dec 2015, 08:37
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It's the baggage handlers moaning that another plonker pilot has powered down and left them in the dark
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Old 12th Dec 2015, 08:50
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That's what the Ground service switch is for mate. Power down is a two man job....

Mind you if the baggage handlers were a bit quicker.....
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Old 12th Dec 2015, 09:50
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Originally Posted by RVF750 View Post
That's what the Ground service switch is for mate. Power down is a two man job....
My company treats it like a missile launch where you have to move two keys in unison. "On mark in 3..2..1..LAUNCH!"

Why? Why can't you just hit the ground service switch on the way out the door?
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Old 16th Dec 2015, 12:24
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That is correct, that's the sound I am refering to.
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Old 16th Dec 2015, 12:26
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Okay, thanks. I will try to search the internet for this. Maybe you are correct. But does it matter if you turn the battery off, during this sound? Does it affect any systems?
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Old 16th Dec 2015, 13:07
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Otto Throttle,
I'm replying as a "plonker pilot". The company I work for has S.O.P's. You may be aware of these.
I have a great admiration and respect for our engineers, a fanatastic bunch of men and women, who, also understand S.O.P's.
When our procedures call for the de-powering of the aeroplane, we do so. The before said engineers, who understand our procedures, when required, ask if we could not do so on this occasion so as to facilitate certain other requirements...
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