Aircraft Wheel thermal fuse plugs.
Thermal Sensitive Inflation Pressure Release Devices for tubeless aircraft wheels or easier thermal fuse plugs prevent violent explosion of tires when maximum temperatures are exceeded.
Note; when a wheel explodes (Main tire pressure can be as high as 205 PSI), it will happen sideways so NEVER approach a suspected overheated wheel from the side.
Four thermal fuse plugs mounted in each inner wheel half prevent tire explosion caused by hot brakes. The plugs are designed to completely release the contained inflation pressure from a tubeless tire when brake generated heat causes the tire or wheel to exceed a safe temperature limit and melt to release tire pressure at approximately 177°C or 192 °C depending on model.
FCOM 1 SP 16 (adverse weather) talks about brake heat radiation and it’s negative effect on temperature levels that may melt the (thermal) fuse plug, deflating the respective tire.
FCOM 1 PD section provides in Quick Turn Around Limit Weight tables that indicate maximum Aircraft weight against OAT and PA, which also needs to be corrected for slope and wind. When this limit weight is exceeded you should honor the respective cool down period on the ground depending on the category brakes mounted on the aircraft, where after a check has to be performed to determine if the fuse(s) have not melted (deflated tire) before commencing takeoff.
When a Brake Temperature Monitoring System (BTMS) is installed note the Brake Temp light, when illuminated honor the respective timeframe as above and check the fuse (tire) before takeoff.
The FCOM 1 PI section contains a Recommended Brake Cooling Schedule to determine the Adjusted Brake Energy (or indicated by the BTMS) indicating what action is required covering a No Action, a Caution and Fuse Melt Zone area.
The Caution and Melt zones indicate dangerously heated brakes and require safety precautions such as:
- Caution on ground, delay takeoff
- Caution in flight, delay raising the gear
- Melt zone on ground, vacate runway, do not set parking brakes and wheel/brake replacement could be necessary.
- Melt zone in flight, delay raising the gear.
Read your current FCOM for procedures and values.