When something goes wrong while flying on the Boeing 737, we use the QRH (Quick Reference Handbook). We just have to find out the correct NNC (Non Normal Checklist) and then we just read it and execute it.
For some of these checklists, we have memory items, meaning we have to know by heart some actions.
I have listed 9 memory items:
- Aborted Engine Start
- Airspeed Unreliable
- APU Fire
- Cabin Altitude Warning / Emergency Descent
- Engine Overheat
- Engine Fire, Severe Damage or Separation
- Engine Limit or Surge or Stall
- Loss of Thrust On Both Engines
- Runaway Stabilizer
APU fire switch.........Confirm..............Pull, rotate to the stop, and hold for 1 second APU switch.........................................................OFF
If there is an APU fire, we will get the following indications:
- the fire warning bell sounds
- both master FIRE WARN lights illuminate
- the APU fire switch illuminates
- the APU automatically shuts down
- the wheel well APU fire warning horn sounds, (on the ground only), and the wheel well APU fire warning light flashes.
The APU fire extinguisher system consists of one APU fire extinguisher bottle, an APU fire switch, an APU BOTTLE DISCHARGE light.
Basically, pulling the APU fire switch shutdown the APU. Rotating the APU fire switch in either direction electrically “fires” the squib discharging the extinguishing agent into the APU. The APU BOTTLE DISCHARGE light illuminates after a few seconds, indicating the bottle has discharged.
It is mandatory for one of the flight crew to remain in the cockpit whenever the APU is running in case of fire. There is also a possibility to discharge the APU BOTTLE from the wheel well.