Fire Bottle Squib Test

[NSEU]

Quick question, gentlemen....

Is it correct to assume that when a fire bottle is discharged, that the squib pushbutton test will then fail? Does the test not only check the wiring to the squib, but that the squib itself hasn't fired?

Or should only the low bottle pressure indications be used to check for discharge.

Sometimes we assume certain things to happen

Thanks.
Rgds
NSEU

[gorter]

Aircraft type?

And yes it does make a difference.

[NSEU]

Boeing.

e.g. 747-400, 767-300

[Wmn]

The squib test checks continuity THROUGH the squibs and gives you a quick clue about the status of the squib circuit. If there is no or too low test current, too high resistance in the firing element etc the test will fail.

The low pressure light indicates low pressure in the fire ext agent bottle, but to be sure, look at the gauge on the bottle.

I guess a detonated squib will break the firing element and cause an open circuit, but I'm not sure.

Refering to you question about bottle discharge;
The low pressure light is the only way for the pilots to know whether the fire agent has been released or not. Then hopefully the fire warning will go out.

[mono]

On the 767 the test does actually put current thru the squib

IIRC there is a warning in the AMM to ensure the correct light filament is used in the test lights as the incorrect filament COULD result in enough current to fire the squib. Not 100% about this as I don't have access to the manuals.

[NSEU]

I guess a detonated squib will break the firing element and cause an open circuit, but I'm not sure.

That's the problem. I'm not sure either

Yes, using a lamp with too low a resistance will allow too much current to go to the squib during test and will fire the squib.

Cheers
NSEU