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Squib circuit on overhead emergency exit of B757-200/300

Posted: Fri Jan 31, 2020 10:43 am
by HAWK21M
Anyone aware of the Squib circuitry related to the overhead emergency exit of the B757-200/300
The reason this was in place.

Re: Squib circuit on overhead emergency exit of B757-200/300

Posted: Fri Jan 31, 2020 8:50 pm
by BravoOne
Overhead Emergency Exit?

Re: Squib circuit on overhead emergency exit of B757-200/300

Posted: Sat Feb 01, 2020 11:31 am
by HAWK21M
BravoOne wrote:
Overhead Emergency Exit?

Affirm
Some models have a squib circuit connected thru the Overhead Emergency exits...is this for the power door assist as there is no question of Fire extinguishers located out there.

Re: Squib circuit on overhead emergency exit of B757-200/300

Posted: Sat Feb 01, 2020 12:31 pm
by unimproved
Isn't it for the slide since it isn't physically connected to the door?

Re: Squib circuit on overhead emergency exit of B757-200/300

Posted: Sat Feb 01, 2020 2:05 pm
by Dalmd88
unimproved wrote:
Isn't it for the slide since it isn't physically connected to the door?

First are we talking about the OverWING Emergency Exits?

I don't recall a squib for those exits. You pop the latch and manhandle the exit. The slide is activated just like the door slides. A cable pulls the pin on the inflation bottle in the slide pack. No squib.

Same is true for the regular door assist bottles. The cable actuates a valve. The only squibs are for the fire bottles. Two cargo pit, APU, and engine.

Re: Squib circuit on overhead emergency exit of B757-200/300

Posted: Sat Feb 01, 2020 2:31 pm
by BravoOne
HAWK21M wrote:
BravoOne wrote:
Overhead Emergency Exit?

Affirm
Some models have a squib circuit connected thru the Overhead Emergency exits...is this for the power door assist as there is no question of Fire extinguishers located out there.



You need to define what "overheard" as there are no overhead exits that I'm aware of on the 757?

Re: Squib circuit on overhead emergency exit of B757-200/300

Posted: Sat Feb 01, 2020 3:58 pm
by 7673mech
Dalmd88 wrote:
unimproved wrote:
Isn't it for the slide since it isn't physically connected to the door?

First are we talking about the OverWING Emergency Exits?

I don't recall a squib for those exits. You pop the latch and manhandle the exit. The slide is activated just like the door slides. A cable pulls the pin on the inflation bottle in the slide pack. No squib.

Same is true for the regular door assist bottles. The cable actuates a valve. The only squibs are for the fire bottles. Two cargo pit, APU, and engine.



Negative - at least on the 767 the squibs circuitry is there to activate the squibs that open the door the overwing exit slide sits on.
There is one at the front of the door and one at the aft.
Above the overwing exit is a handle that you can put into a maintenance position prior to manually opening the door.

The 757's I worked on had 4 doors so I am not sure if this is the same.

Re: Squib circuit on overhead emergency exit of B757-200/300

Posted: Sun Feb 02, 2020 7:14 pm
by Lpbri
For a 757 with offwing escape slides, the autofire switches are above the sill of each over wing hatch. When the hatch is opened, the switch sends a signal to fire the bottle squibs. Bottle pressure opens the slide door, rotates the carrier, and inflates the slide. The squibs are tested on the maintenance panel in the flight deck.

Re: Squib circuit on overhead emergency exit of B757-200/300

Posted: Mon Feb 03, 2020 1:15 pm
by HAWK21M
BravoOne wrote:
HAWK21M wrote:
BravoOne wrote:
Overhead Emergency Exit?

Affirm
Some models have a squib circuit connected thru the Overhead Emergency exits...is this for the power door assist as there is no question of Fire extinguishers located out there.



You need to define what "overheard" as there are no overhead exits that I'm aware of on the 757?


Overhead exits as in Exit doors over the Wing root access areas.
There were B757s with Large passenger door without overwing exits and some B757s with two doors over the wing root area on each side.
Since I work of STC modified B757s the overwing exits are not present hence the question.

Re: Squib circuit on overhead emergency exit of B757-200/300

Posted: Mon Feb 03, 2020 1:16 pm
by HAWK21M
Lpbri wrote:
For a 757 with offwing escape slides, the autofire switches are above the sill of each over wing hatch. When the hatch is opened, the switch sends a signal to fire the bottle squibs. Bottle pressure opens the slide door, rotates the carrier, and inflates the slide. The squibs are tested on the maintenance panel in the flight deck.

Thanks