Topic Author
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Seatbelt Sign -- 'auto' Vs. 'on'

Tue Jul 06, 2004 1:19 pm

A related post this evening caused me to think of this question.

In many cockpits, the seatbelt and no-smoking signs have three settings: 'off,' 'auto,' and 'on.' What's the difference between 'auto' and 'on?'
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RE: Seatbelt Sign -- 'auto' Vs. 'on'

Tue Jul 06, 2004 3:54 pm

I asked a pilot about that once when visiting the cockpit, if I remember correctly, he told me that in the "auto" position, the signs would automatically go on during descent when they deployed the flaps. Can any pilots confirm?


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RE: Seatbelt Sign -- 'auto' Vs. 'on'

Tue Jul 06, 2004 3:58 pm

That's correct!

In Auto once you deploy the flaps you hear the chime!
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RE: Seatbelt Sign -- 'auto' Vs. 'on'

Tue Jul 06, 2004 4:04 pm

It's if you drop alt. have turns over a certain amount of *'s and if there is turbulence. I find this to be a very useful system but how do the pilots know if it's on or off. I know that when it goes on or off about 1-3min after the pilot comes on "Ladies and Gents, the seatbelt sign has been turned on, it seems as though we are going into some choppy stuff so we're going to ask you all to return to your seats, thanks again" or "Ladies and Gents, at this time we have reached our cruising altitude and have turned off the seatbelt sign, even though this sign is off we ask you for both your own safety and for the safety of the crew that when you are in your seats that you keep your belt fastened. Thanks again and I'll be back on when we start our decent into XXX, thanks again and welcome aboard" If they know when to say this is there something that is on the LCD's that will say if it's on or not?

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RE: Seatbelt Sign -- 'auto' Vs. 'on'

Wed Jul 07, 2004 1:41 am

Most airliners are designed to have the "Auto" mode automatically illuminate the seatbelt signs when either the landing gear or the flaps are extended.
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RE: Seatbelt Sign -- 'auto' Vs. 'on'

Wed Jul 07, 2004 1:55 am

Gnomon to quote one airline's B-737 manual:

AUTO - The NO SMOKING sign illuminates when the gear is down and extinguishes when the gear is up.

AUTO - The SEAT BELT sign illuminates while the flaps or gear are extended (1 to 40) and extinguishes when the flaps and gear are UP.

OFF or ON manually operates either sign.

You can see that this does not meet the FAA's criteria for when these sign need to be on. Hence, most US airlines never use the AUTO positions.

That is a correct answer for the 737, the specifics might be slightly different for different types. Be cautious of bad guesses on the Tech/Ops forum.

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RE: Seatbelt Sign -- 'auto' Vs. 'on'

Wed Jul 07, 2004 1:59 am

The no smoking sign tends to be left in the auto position - the chime at gear up is a useful way to releasing the cabin crew. The lights remain on all the time though.
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