The 737CL/NG use sensor elements for fire warning
Each element has three pressure switches and two resistors as a network, with resistance varying as function of temperature. One pressure switch
senses overheat, another senses fire and the third senses a loss of gas pressure (Fault).
There are always 2 elements to chech a area. Loop A and loop B.
The conditions of both loops are combinated in the detection unit as follows:
Copy/Paste out of 737CL AMM (737NG alike)
A fire is indicated as follows:
(1) The appropriate (engine 1 or engine 2) fire switch handle on the P8 control stand illuminates and unlocks.
(2) The master FIRE WARN lights on lightshield panel P7 illuminate.
(3) The fire bell sounds.
An overheat is indicated as follows:
(1) The appropriate engine overheat light - ENG 1 or ENG 2 OVERHEAT - on the P8 control stand illuminates.
(2) The master CAUTION and OVHT/DET lights on lightshield panel P7 illuminate.
A fault is indicated as follows:
(1) The FAULT light on the P8 control stand illuminates.
The bell may be silenced and FIRE WARN lights may be extinguished by pressing either FIRE WARN light or the BELL CUTOUT switch.
The master CAUTION and OVHT/DET lights may be extinguished by pressing either CAUTION light.
Fire switch, overheat, and fault lights remain illuminated until the fire, overheat, or fault is removed from the system.
So I think that the instructor is wrong.
If you have a Fire warning LT, you have a FIRE.
(BTW: You know that Bell is not U/S
)
But this is only the opinion of an Greesemonkey
