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B737 NG Manual Gear Extension C/L

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B737 NG Manual Gear Extension C/L

Old 22nd Apr 2004, 15:24
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B737 NG Manual Gear Extension C/L

Two questions of which I have a theory on....but appreciate other thoughts.

" Wait 15 seconds after the last manual gear extension handle is pulled "
What is this 15 seconds for ?

The " landing Gear Lever .....Down " why do this ?
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Old 22nd Apr 2004, 16:29
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" Wait 15 seconds after the last manual gear extension handle is pulled "

To give the freefalling gear a chance to lock in the down position.
================================
The " landing Gear Lever .....Down " why do this ?

1 - To get rid of the Red Gear Disagree lights since the "OFF" and "UP" position acts act the same in the handle logic.

2 - If "A" Hydraulic pressure returns, it will be applied automatically.
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Old 23rd Apr 2004, 01:43
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thanks B73 variant
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Old 23rd Apr 2004, 02:39
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Hi POOKEY,

1/ I understood the 15 seconds was to ensure that the gear uplock was totally clear of the uplock hook. Otherwise, I thought, the sign would say"Hold out until the green downlock light is illuminated" or something.

2/ The gear handle has to be down to align with the gear logic that warns of "To low....Gear" and such things. Which you will get if you try to land with the gear lever not in the down position.

Cheers
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Old 23rd Apr 2004, 13:06
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Flight Detent...

You may very well be right regarding the Gear Handle position. GPWS and TCAS do depend on gear position.
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Old 24th Apr 2004, 10:50
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Hi B72567..,
I am not aware that TCAS is affected by gear position!

Pls forgive me if I am wrong!!

Cheers
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Old 24th Apr 2004, 10:59
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That sounds new to me also...
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Old 25th Apr 2004, 10:59
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To return to the question, the reason for the delay may well be along the same lines as the B747s. They have a cam actuated system to unlock the doors then the gear uplocks in the alternate mode and the cam takes about 90 sec nose, 30 sec mains (I think) to complete a cycle, hence the requirement to leave the switch in "arm" for a time. If the cycle is interrupted, there will be problems later with gear door sequencing etc.
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Old 25th Apr 2004, 22:17
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When the gear handle is placed down, the Bottom TCAS anternna becomes an Omni-Directional antenna.
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