Fusible Plug

Mark, do you have any ideas on what is temperature rated fusible plug which is used in evacuation system.?

Is this about what a fusible plug is or what temp they let go at?

What is it? and How does it work?......would you mind explaining thoroughly....

Fusible plugs melt or rupture when a certain temperature is met or exceeded. They are a safety device.

On aircraft wheels, they (what we call) "thermal" or melt open to relieve an overly hot tire so that the whole thing doesn't blow up.

I'm not sure on a evacuation slide, but I'm guessing a small nitrogen bottle (that inflates the slide) must have a thermal release or fusible plug on it for the same reason..... not have the bottle explode.
  
     
     
 

Please have a look at the FAA AD I have just emailed

Within 42 months after the effective date of this AD, do an inspection to determine if any fusible plug has part number (P/N) B13984-3, stamped with Lot PA-21 or PA-22. A review of the airplane maintenance records is acceptable to make this determination if it can be conclusively determined from that review that a part not having P/N B13984-3, stamped with Lot PA-21 or PA-22, has been installed.

The carrier I work with does not use escape slides. From previous employment, I believe the slides have a serviceable tag installed. I doubt that tag showed the bottle part number or mod status. I’m not sure that the bottle is visible in a packed slide. Much less the plug part number and mod status.

This AD was from 2018. Slides are timed items. I’m pretty sure all slides certified after that year are in compliance. If you can’t verify the bottle information from the 8130 repair documentation, I see no other choice than to replace it with a certified and “in-date” slide.

1-Does the plug work as a thermal release of escape slide bottle as you explained?
2-Does the plug releases compressed gas in responce to direct heat flux (e.g. direct heat flux of conflagration in aircraft)?
3-Is there an automatic deployment controler that senses emergency condition and triggers a switch to deliver high current to the fusible plug that makes it melted?

Again..... I do not know to much about aircraft slides or inflatable rafts. I have to guess that the standard inert gas used is nitrogen for the bottle.

From AeroSavvy .....

• Dry nitrogen contains no water vapor. The lack of moisture reduces tire pressure variations at temperature extremes (water density varies significantly at different temperatures). With the effects of moisture eliminated, change in tire pressure due to temperature is linear and predictable.

There is no electrical circuit to a plug. The plug reacts to heat. If a bottle (or tire) has to much internal/external heat, the plug will melt and the gas pressure inside will be released to atmosphere.

I worked in Houston for several decades. It was not uncommon in the summertime to have an aircraft pull into the gate with hot brakes. Some of that heat is transferred to the wheel. If a tire "thermaled" you could hear a hissing as you did your walk-around. That was the internal tire pressure being released. It did require a tire change, but that is a minimal task compared to a tire blowing up. Large aircraft use "split rims". If the bolts holding the halves together fail, you now have two flying projectiles that don't care what or who they hit. I "never" spent time standing next to the broadside of a hot tire. You always look at it from the ends.

This is the result of thermaled tires.