Aircraft Systems: APU and Electrical Power

Aircraft Type Specific Information

• 05.01 Specifications: Includes Auxiliary Power Unit (APU), Electrical Power, Air Conditioning and Pressurization, and In-Flight Entertainment (IFE).

• 05.01.01 Auxiliary Power Unit (APU): The APU is a gas turbine engine that can operate both in the air and on the ground. It provides electrical power and bleed air for airplane systems, acting as a backup for external ground services when necessary.

• 05.01.02 Electrical Power: The electrical system supplies 115-volt AC and 28-volt DC power. Ground power can also be provided by the APU or external power carts. Electrical power in galleys shuts off automatically if other generators fail.

• 05.01.03 Air Conditioning and Pressurization: Bleed air for air conditioning and pressurization is usually supplied by the turbofan engines (under wings). The flight deck controls cabin temperature, which is separately controlled for the flight deck and passenger cabin.

• 05.01.04 IFE (In-Flight Entertainment): Some aircraft models have IFE systems (inboard or outboard) for passenger use. However, IFE systems are to be used only when instructed by the SCCM. Usage is restricted during taxi, takeoff, and landing unless it's a mandatory safety briefing.

05.02 Configuration

• 05.02.01 Passenger Seating: The B737 800 has 189 economy class seats, arranged 6 abreast. Seats located at over-wing emergency exits do not recline. All seats have seatbelts and a restraint bar for bag storage.

• 05.02.02 Overhead Stowage Bins: Above the passenger seats are overhead bins for storing baggage, often including blankets, pillows, and equipment. Bins have weight capacity limits to avoid dangerous overloads.

• 05.02.03 Passenger Service Units and Oxygen System: Located underneath overhead bins, passenger service units include air vents, reading lights, a call button, and indicators showing "Fasten Seatbelt" and "No Smoking" warnings. Each unit also has oxygen masks. Cabin crew stations have additional oxygen masks.

05.03 Cabin Doors

• 05.03.01 Opening Doors - Normal Operation: Doors open by rotating the handle. A red safety strap is usually located above each door.

• 05.03.02 Closing Doors: Use the handle to start closing, follow the hinge release to continue. The door must be locked by the mechanism that it locks into.

• 05.03.03 Exterior Operation of Doors: Exterior door operation is available for opening and closing.

05.04 Arming and Disarming Escape Slides

• All doors have escape slides located below
• The slide must be placed in "armed" mode before each flight by removing the girt bar from the hooks and placing it in the floor brackets
• To disarm, remove and place into hooks beneath the slide
• There is a safety slide strap located above each door

05.05 Emergency Operation of Doors

• 05.05.01 Escape Slide Specifications: Each door has a single lane escape slide, typically 508 cm long and 153 cm wide. The system is pressured with Nitrogen or CO2/nitrogen mix for quick inflation, and re-entry straps on the sides.

• 05.05.02 Deployment of Slides: Deploy the slide as indicated, with the aircraft being used and door opened to allow safe ejection

• 05.05.03 Using Slides for Ditching: If a ditching is necessary, do not use the aft doors, use the forward ones

05.06 Emergency Evacuation Routes

• Emergency evacuation can be performed through four service doors and four over-wing emergency exits.
• Flight deck crew members can use sliding windows.

05.06.01 Slide Length, Width and Doorsill Height

• Details of slide dimensions and doorsill height.

• 05.06.02 Usable Exits: The appropriate exits to use for various scenarios are outlined.

05.07 Over Wing Emergency Exits

• Four over-wing exits are present in the B737-800. The doors are opened using mechanical locks and a spring-loaded handle.
• A 28-volt DC flight lock system manages the opening and closing of over-wing doors in situations including takeoff, landing, flight and ground operations.

05.08 Cabin Crew Stations

• Stations are located in specific areas for cabin crew.
• Seats have seatbelts/shoulder harnesses.
• Equipment like interphone/PA system is found at the stations

05.09 Cabin Lighting System

• Lighting can be independently controlled and adjusted.
• There are different light types and settings for various areas.

05.10 Cabin Communication System

• Handset is used to make calls across all areas (flight deck-cabin, cabin-cabin, etc.).
• The handset has specific features for different calls or announcements
• There is a reset button before placing handset back in its cradle.

05.11 Galleys

• 05.11.01-05.11.09: Details of various galley components (power, circuit breakers, water, waste, sinks, trolleys, ovens, etc.) and their required operation and maintenance requirements.

05.12 Lavatories

• 05.12.01-05.12.04: Information about lavatory features (toilets, wash basins, mirrors, vanity items, etc.), the waste system and their maintenance. Specific details for various aspects of lavatory operation are provided.

05.13 Flight Deck

• 05.13.01 Flight Deck Video Surveillance System: Real-time video surveillance of the area near the flight deck entrance.
• 05.13.02 Flight Deck Door: The flight deck doors have a three-position switch (Unlocked, Auto, Deny)
• 05.13.03 Flight Deck Windows: Two flight deck windows provide secondary emergency exits.
• 05.13.04 Flight Deck Seats: Adjustable pilot and co-pilot seats.

05.14 Internal Doors and Curtains

• Information about internal doors and their operation