737 800 - 737 8200 Flashcards
Electrical System
The Electrical Power System may be categorized into three main divisions: the AC power system, the DC power system, and the standby power system.
Primary electrical power is provided by two engine integrated drive generators (IDGs) which supply three-phase, 115 volt, 400 cycle alternating current. Each IDG supplies its own bus system in normal operation and can also supply essential and non-essential loads of the opposite side bus system when one IDG is inoperative. Transformer rectifier (TR) units and the main battery/battery charger supply DC power. The main and auxiliary batteries also provide backup power for the AC and DC standby system. The APU operates a generator and can supply power to both AC transfer busses on the ground or in flight.
There are two basic principles of operation for the 737 electrical system:
- There is no paralleling of the AC sources of power.
- The source of power being connected to a transfer bus automatically disconnects an existing source.
Pressurization System
Cabin pressurization is controlled by the pressure control system, which includes two identical automatic controllers available by selecting AUTO or ALTN and a manual (MAN) pilot controlled mode.
The system uses bleed air (obtained from the 5th and 9th stages of the compressor section) supplied to and distributed by the air conditioning system. The pressure controllers use the outflow valve to control the cabin altitude (up to a cabin altitude of 8,000 feet at the airplane maximum certified ceiling of 41,000 ft). One controller operates the pressurization system, and the other controller is a backup.
Two pressure relief valves provide safety pressure relief by limiting the differential pressure to a maximum of 9.1 psi. A negative relief valve prevents external atmospheric pressure from exceeding internal cabin pressure.
Modes:
AUTO – Automatic pressurization control; the normal mode of operation. Uses DC motor.
ALTN – Automatic pressurization control; the alternate mode of operation. Uses DC motor.
MAN – Manual control of the system using DC motor.
Hydraulic System
The airplane has three hydraulic systems: A, B and standby. The standby system is used if system A and/or B pressure is lost. Either A or B hydraulic system can power all flight controls with no decrease in airplane controllability.
The hydraulic systems power the following airplane systems:
Flight controls
Leading edge flaps and slats
Trailing edge flaps
Landing gear
Wheel brakes
Nose wheel steering
Thrust reversers
Autopilots
Both A and B hydraulic systems have an engine–driven pump and an AC electric motor–driven pump. The system A engine–driven pump is powered by the No. 1 engine and the system B engine–driven pump is powered by the No. 2 engine. An engine–driven hydraulic pump supplies approximately 4 times the fluid volume of the related electric motor–driven hydraulic pump.
Components powered by hydraulic systems A and B are:
System A:
Ailerons
Rudder
Elevator and elevator feel
Flight spoilers (two on each wing)
Ground spoilers
Alternate brakes
No.1 thrust reverser
Autopilot A
Normal nose wheel steering
Landing gear
Power transfer unit (PTU)
System B:
Ailerons
Rudder
Elevator and elevator feel
Flight spoilers (two on each wing)
Leading edge flaps and slats
Trailing edge flaps
Normal brakes
No.2 thrust reverser
Autopilot B
Alternate nose wheel steering
Landing gear transfer unit
Autoslats
Yaw damper
Landing gear. Landing Gear Lever position off - what does it do?
The airplane has two main landing gear and a single nose gear. Each gear has 2 wheels. The nose gear retracts forward into the wheel well.
Hydraulic power for retraction, extension, and nose wheel steering is normally supplied by hydraulic system A. A manual landing gear extension system and an alternate source of hydraulic power for nose wheel steering are also provided.
The green gear indicator lights illuminate when the related gear is down and locked.
The green lights extinguish and the red lights illuminate while the gear is in transit.
When the landing gear are up and locked, the red indicator lights extinguish.
Hydraulic pressure is removed from the landing gear system with the LANDING GEAR lever in the OFF position.
The rudder pedals turn the nose wheels a maximum of 7 degrees.
The nose steering wheel turns the nose wheels a maximum of 78 degrees.
Tell me something about the brakes on 737. How are they operated?
Each main gear wheel has a multi–disc hydraulic powered brake. The brake pedals provide independent control of the left and right brakes. The nose wheels have no brakes. The brake system includes:
- Normal brake system
- Alternate brake system
- Brake accumulator
- Antiskid protection
- Autobrake system
- Parking brake
The normal brake system is powered by hydraulic system B.
The alternate brake system is powered by hydraulic system A. If hydraulic system B is low or fails, hydraulic system A automatically supplies pressure to the alternate brake system.
The brake accumulator is pressurized by hydraulic system B. If both normal and alternate brake system pressure is lost, trapped hydraulic pressure in the brake accumulator can still provide several braking applications or parking brake application.
Bleed Air System
The purpose of the bleed air system is to collect and distribute bleed air to the systems that use bleed air. Bleed air can be supplied by the engines, APU, or an external air source. The APU or external source supplies air to the bleed air system prior to engine start. After engine start, air for the bleed air system is normally supplied by the engines.
Bleed air is used for:
1 - Air conditioning/pressurization
2 - Wing and engine thermal anti-icing
3 - Engine starting
4 - Hydraulic reservoirs pressurization
5 - Water tank pressurization
Engine bleed air is obtained from the 5th and 9th stages of the compressor section.
Fuel System
The fuel system supplies fuel to the engines and the APU. Fuel is contained in three tanks located within the wings and wing center section.
Both engines are normally pressure fed from the center tank until the center tank quantity decreases to near zero. The engines are normally then pressure fed from their respective main tanks. Check valves are located throughout the fuel system to ensure the proper direction of fuel flow and to prevent transfer of fuel between tanks.
Each fuel tank uses two AC powered fuel pumps which are cooled and lubricated by fuel passing through the pump. Center tank pumps produce higher pressure than main tank pumps. This ensures that center tank fuel is used before main tank fuel, even though all fuel pumps are operating. Individual pressure sensors monitor the output pressure of each pump.
APU
The auxiliary power unit (APU) is a self contained gas turbine engine installed in the tail of the airplane.
The APU supplies bleed air for engine starting or air conditioning. An AC electrical generator on the APU provides an auxiliary AC power source.
The APU starts and operates up to the airplane maximum certified altitude. The APU supplies bleed air for both air conditioning packs on the ground or one pack in flight. Both transfer busses can be powered on the ground or in flight.
Fuel to start and operate the APU comes from the left side of the fuel manifold when the AC fuel pumps are operating. If the AC fuel pumps are not operating, fuel is suction fed from the No. 1 tank. During APU operation, fuel is automatically heated to prevent icing.
Electrical power to start the APU comes from No. 1 transfer bus or the airplane main battery. With AC power available, the starter generator uses AC power to start the APU. With no AC power, the starter generator uses battery power to start the APU.
Moving the battery switch to OFF on the ground or in the air automatically shuts down the APU because of power loss to the electronic control unit.
The automatic start sequence begins by moving the APU switch momentarily to START. This initiates opening of the air inlet door. When the APU inlet door reaches the full open position the start sequence begins. After the APU reaches the proper speed, ignition and fuel are provided. When the APU is ready to accept a bleed air or electrical load the APU GEN OFF BUS light illuminates.
Tell me about the wings of the 737-800
The 737 has swept back wings with an angle of 25º.
For each wing, leading edge devices consist of:
- Two Krueger flaps inboard of each engine, because they are less efficient than slats and promote a root stall (swept-back wings have a tendency to stall at the tip first). This helps maintain aileron effectiveness and prevent the loss of control that can occur during a stall.
- And four slats outboard of each engine. The difference between krueger flaps and slats is that deploying a slat will form a slot (re energise (increase the kinetic energy of) the boundary layer), deploying a Krueger flap does not.
The TE devices consist of double slotted flaps inboard and outboard of each engine.
Each wing has 4 flight spoilers and 2 ground spoilers. In flight, spoilers are used as speed brakes, to slow the airplane or increase the rate of descent, or automatically to help the ailerons in roll control On the ground, ground spoilers destroy lift and increase braking efficiency, they operate together with the flight spoilers.
Winglets are vertical aerofoils which partly block the air flowing from the bottom to the top surface of the wing, reducing the strength of the tip vortex, thus reducing induced drag and fuel burn.
Winglets on the 737-800 have demonstrated drag reduction in the 5-7% range, which increases range and fuel efficiency.
The wing anti–ice system provides protection for the three inboard leading edge slats by using bleed air.
Each wing has a tank with a capacity of 3915 kg.
Tell me the differences between the 737-800 and the 8200 (Max)
- New CFM-LEAP-1B Engines which are bigger than the CFM56-7B engines (diameter is bigger by 8 inches), this gives a 9:1 bypass ratio versus 5:1, the maximum thrust is 29,300lbs versus the older engine’s 27,300lbs.
- This version is quieter thanks to its new engines, it is also 12% more fuel efficient and has 7% reduction in operating costs.
- The MAX is approximately 3,000kg heavier than its equivalent NG. This is because each new engine is 385kg heavier than the CFM56-7. This extra weight requires stronger (and therefore heavier) engine struts, wings, fuselage and landing gear. The upside of this strengthening is that operating weights (MTOW, MZFW etc) have been increased by 3,175kg to compensate.
- The 737 8200 cockpit is more refined and uncluttered, it has four large 15-inch LCD screens.
- The 737 8200 has a reshaped tail cone which reduces drag, giving 1% less in fuel burn.
- Fly-by-wire spoiler system – improves stopping distances and reduces weights.
- Nose gear strut is 8 in. longer. The 737 8200 landing gear handle is a two-position handle (UP/DOWN). The center “OFF” position that removed hydraulic pressure from the actuators has been removed as the depressurization function is automated through a proximity switch system.
- Also, the 737 MAX has 197 seats compared to the 737-800 which only has 189, a new emergency exit was added, toilets moved back, galley spaces lowered and the seats are slimmer.
- New electronic bleed air system – increased optimisation of the cabin pressure and ice protection systems, giving better fuel burn. (the electric controller allows the aircraft to tune in the amount of air that is needed rather than the all or nothing system.
- The thrust line has changed because the engines had to be moved forward and up to accommodate the larger fan diameter. Any handling differences as a result of this have been tuned out by Boeing in the flight control system to make the types feel the same to flight crew. (necessary to keep certification under the same type certificate)
- The standard wingtips of the MAX are boomerang winglets (currently optional on the 737- 800), the lower split-scimitar winglet aerofoil generates a vertical lift component that is vectored away from the fuselage and also slightly forward increasing the efficiency of the wing. (reducing fuel costs)
MCAS
MCAS - Maneuvering Characteristics Augmentation System
The new 737 8200 engines are larger and had to be mounted slightly higher and further forward from the previous NG CFM56-7 engines to give the necessary ground clearance.
But moving the engine up and forward had a side effect, when the airplane was in full thrust, the nose tended to point too far upward, which could lead to a stall. This was a problem, because the 737 8200 was supposed to behave exactly like the NG. So Boeing came up with a workaround. They installed software that automatically pushed the nose downward if the pilot flew the plane at too high AOA. They called it Maneuvering Characteristics Augmentation System. But because Boeing was selling the 737 8200 as pretty much the same plane as the 737 NG, they didn’t highlight the new system. MCAS relied on information from a single Angle of Attack (AOA) sensor to monitor the angle of the airplane. In the two accidents, a single AOA sensor gave incorrect information to MCAS, which caused it to activate. In both cases, MCAS engaged repeatedly when the sensor continued to incorrectly report a high AOA.
When does MCAS activate?
MCAS was designed to activate only when all three of the following conditions occur at the same time:
The pilot is flying the airplane manually.
The airplane nose approaches a higher-than-usual angle.
The pilot has the wing flaps up.
Pitot tubes on the 737 and what they indicate
There are 2 main pitot probes, one on the LHS and the other on the RHS, and a auxiliary pitot probe on the RHS.
2 primary static ports per side.
The pitot static system supplies data for the ADIRUs and standby flight instruments.
Pitot tubes measure total pressure (ram air), which consists of dynamic pressure plus static pressure. Static pressure is also measured by the static ports.
In the 737, two pitot probes and four static ports interface with the air data modules, which convert air pressure to electrical signals and send these data to the ADIRUs. Each pitot air data module is connected to its on–side pitot probe; there is no cross connection. The air data module connected to the Captain’s pitot probe sends information to the left ADIRU, while the air data module connected to the First Officer’s pitot probe sends information to the right ADIRU.
How many seats are on a 737-800?
The Boeing 737-800 has 189 seats in a single class configuration.
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What type of engines are on a 737-800?
The 737-800 has a high-bypass turbofan engine called the CFM56-7B (27,300 pounds of thrust), with a bypass ratio of 5.4:1
How many flight attendants are there on a 737-800?
There are 4 flight attendants, 1 for every 50 seats.
Pressurisation of the cabin in cruise on a 737-800?
Normally around 6000 - 8000ft, (between 11 - 12 psi).
What are winglets and what advantages do they give on a 737-800?
Winglets are vertical aerofoils which form part of the wing tip. Winglets partly block the air flowing from the bottom to the top surface of the wing, reducing the strength of the tip vortex, thus reducing induced drag and fuel burn
Winglets on the 737-800 have demonstrated drag reduction in the 5-7% range, which increases range and fuel efficiency
What is the fuel capacity of a 737-800?
Redondeando: 26.000 liters or 20.900 kg
Exacto: 26.025 liters or 20.896 kg
Fuel density = 0.8029 kilograms per liter
What is the range of a 737-800?
3115 NM
