11.16 Pneumatic / Vacuum

Question 1

Which of the following aircraft systems commonly use pneumatic power?
A. Fuel injection, wheel steering, cargo doors
B. Pressurisation, engine starting, air conditioning
C. Radar operation, GPS alignment, autopilot

Answer 1

B. Pressurisation, engine starting, air conditioning

Question 2

What systems may use pneumatic pressure for mechanical actuation?
A. Navigation lights
B. Landing gear, flaps, brakes
C. Antennas and ELTs

Answer 2

B. Landing gear, flaps, brakes

Question 3

Which of the following is not a power source for the pneumatic system?
A. Ground air power unit
B. Hydraulic accumulator
C. Auxiliary power unit (APU)

Answer 3

B. Hydraulic accumulator

Question 4

What pressure range defines a low-pressure pneumatic system?
A. 0–5 psi
B. 1–10 psi
C. 10–50 psi

Answer 4

B. 1–10 psi

Question 5

A medium-pressure pneumatic system operates within which range?
A. 50–150 psi
B. 150–500 psi
C. 300–800 psi

Answer 5

A. 50–150 psi

Question 6

What is the typical pressure range for high-pressure pneumatic systems?
A. 500–1000 psi
B. 1000–2000 psi
C. 1000–3000 psi

Answer 6

C. 1000–3000 psi

Question 7

Pneumatic and vacuum systems fall into which four basic categories?
A. Static, dynamic, hydraulic, electric
B. Gyroscopic, static, emergency, high-speed
C. Vacuum, low-pressure, medium-pressure, high-pressure

Answer 7

C. Vacuum, low-pressure, medium-pressure, high-pressure

Question 8

How are the left and right pneumatic systems connected?
A. Via an isolation valve connected to hydraulic lines
B. Through a crossover duct or cross-bleed manifold
C. By routing through the cabin pressurisation system

Answer 8

B. Through a crossover duct or cross-bleed manifold

Question 9

What is the purpose of the cross-bleed system?
A. To increase engine power
B. To balance fuel across wings
C. To allow air to be routed to any user from either engine

Answer 9

C. To allow air to be routed to any user from either engine

Question 10

Before working on a pneumatic system, what must be done first?
A. Disconnect all electronics
B. Fully depressurise the system
C. Open the cross-bleed manifold

Answer 10

B. Fully depressurise the system

Question 11

What does the overpressure valve in a pneumatic system do?
A. Warms cold air
B. Regulates airflow to the engine
C. Protects user systems from excessive pressure

Answer 11

C. Protects user systems from excessive pressure

Question 12

What is a key advantage of compressed air over hydraulic fluid?
A. Requires no maintenance
B. Heavier and more stable
C. Fire hazard is minimal

Answer 12

C. Fire hazard is minimal

Question 13

From where is pressurised bleed air typically extracted in a turbine engine?
A. Exhaust nozzle
B. Combustion chamber
C. Engine compressor stages

Answer 13

C. Engine compressor stages

Question 14

During take-off, climb, and cruise, which bleed ports are typically used?
A. Only HP (High Pressure)
B. LP or IP (Low or Intermediate Pressure)
C. All bleed ports simultaneously

Answer 14

B. LP or IP (Low or Intermediate Pressure)

Question 15

When is high-pressure (HP) bleed air used instead of LP or IP?
A. During fuel cross-feed
B. During high-speed cruise
C. During low-speed flight or low engine power

Answer 15

C. During low-speed flight or low engine power

Question 16

What happens when bleed air is taken from the engine compressor?
A. Engine thrust increases
B. Engine power output decreases
C. Engine oil pressure increases

Answer 16

B. Engine power output decreases

Question 17

What is a potential risk of using bleed air from an engine compressor?
A. Frozen lines
B. Low humidity
C. Air contamination from fuel or lubricants

Answer 17

C. Air contamination from fuel or lubricants

Question 18

Which of the following is not one of the three main types of cabin air compressors?
A. Centrifugal compressors
B. Magnetic compressors
C. Positive displacement compressors

Answer 18

B. Magnetic compressors

Question 19

What is the basic function of a positive displacement compressor?
A. Compresses air using rotating blades at high speed
B. Moves a fixed volume of air and compresses it mechanically
C. Uses heat to expand and compress air

Answer 19

B. Moves a fixed volume of air and compresses it mechanically

Question 20

What type of compressor uses high-speed rotation to increase pressure?
A. Roots-type blower
B. Multi-stage reciprocating compressor
C. Centrifugal compressor

Answer 20

C. Centrifugal compressor

Question 21

What is a main advantage of a Roots-type blower?
A. It is temperature-regulated
B. It can deliver more air than the system uses
C. It uses fuel to generate air

Answer 21

B. It can deliver more air than the system uses

Question 22

How are engine-driven centrifugal compressors typically powered?
A. Through external battery packs
B. Via engine accessory drive shafts
C. By ground air units only

Answer 22

B. Via engine accessory drive shafts

Question 23

What three essential details must be marked on a high-pressure air reservoir?
A. Manufacturer, model number, and location of use
B. Date of manufacture, safe working pressure, last hydrostatic test date
C. Operating temperature range, capacity, installation date

Answer 23

B. Date of manufacture, safe working pressure, last hydrostatic test date

Question 24

What is the function of the control valve on a high-pressure air reservoir?
A. It increases bottle pressure
B. It acts as a charging valve
C. It keeps air sealed inside the bottle until system use

Answer 24

C. It keeps air sealed inside the bottle until system use

Question 25

How can high-pressure pneumatic bottles be charged? A. Only through a ground crew connection B. Only by an APU C. Either onboard compressor or ground source

Answer 25

C. Either onboard compressor or ground source

Question 26

Why are wire-wound steel constructions used for pneumatic reservoirs? A. To reduce corrosion B. For strength under high pressure C. To improve oxygen storage

Answer 26

B. For strength under high pressure

Question 27

What are the five commonly used types of air compressors? A. Reciprocating, rotary, hydraulic, axial, and centrifugal B. Reciprocating, rotary, centrifugal, axial, and Roots-type blower C. Rotary, hydraulic, electric, centrifugal, and static

Answer 27

B. Reciprocating, rotary, centrifugal, axial, and Roots-type blower

Question 28

What does a reciprocating air compressor use to compress air? A. Rotors and gears B. Multi-stage pistons C. Vanes and diaphragms

Answer 28

B. Multi-stage pistons

Question 29

How does a rotary screw air compressor compress air? A. Uses spinning vanes in a drum B. Compresses air by heating and cooling cycles C. Traps air between two meshed rotors, reducing its volume

Answer 29

C. Traps air between two meshed rotors, reducing its volume

Question 30

Which type of compressor uses centrifugal force and a diffuser to increase air pressure? A. Axial B. Roots blower C. Centrifugal

Answer 30

C. Centrifugal

Question 31

In an axial compressor, how is air compressed? A. Through staged pistons B. By passing through alternating rotors and stators C. By heating the air and releasing it into a tank

Answer 31

B. By passing through alternating rotors and stators

Question 32

What is the main function of a Roots-type blower? A. Increase temperature of air before compression B. Pump air through magnetic levitation C. Move a fixed volume of air into the system using lobed rotors

Answer 32

C. Move a fixed volume of air into the system using lobed rotors

Question 33

How is an aircraft vacuum pump usually driven? A. Electrically powered via batteries B. From the engine accessory drive C. By a hydraulic actuator

Answer 33

B. From the engine accessory drive

Question 34

What are the two main types of positive displacement vacuum pumps? A. Oil-free and oil-fed B. Wet type and dry type C. Piston and gear driven

Answer 34

B. Wet type and dry type

Question 35

What defines a wet-type vacuum pump? A. Lubricated using fuel from the main tank B. Uses engine oil for lubrication and recirculates it through a separator C. Uses water to cool down the pump

Answer 35

B. Uses engine oil for lubrication and recirculates it through a separator

Question 36

What is a key feature of a dry-type vacuum pump? A. Water-cooled vanes B. Steel vanes requiring daily lubrication C. Carbon vanes that are self-lubricating

Answer 36

C. Carbon vanes that are self-lubricating

Question 37

What is a venturi vacuum system? A. A mechanical compressor used in jet engines B. A vacuum source using the pressure drop created by air acceleration C. A type of electric vacuum generator

Answer 37

B. A vacuum source using the pressure drop created by air acceleration

Question 38

What is the main disadvantage of a venturi vacuum system? A. It is expensive to operate B. It causes overheating in avionics C. It is inefficient and has limited output

Answer 38

C. It is inefficient and has limited output

Question 39

What is a venturi tube commonly used for on small or home-built aircraft? A. Powering electronic avionics B. Providing suction for gyroscopic instruments C. Cooling cabin air

Answer 39

B. Providing suction for gyroscopic instruments

Question 40

What are common issues with venturi systems? A. Excessive oil pressure B. Ice formation, foreign object blockage, filter or plumbing faults C. Electrical short-circuits and overheatin

Answer 40

B. Ice formation, foreign object blockage, filter or plumbing faults

Question 41

What is the primary purpose of a pneumatic pressure control regulator? A. Increase system pressure for high-altitude operations B. Reduce high-pressure air to a lower, usable pressure C. Cool down compressed air before delivery

Answer 41

B. Reduce high-pressure air to a lower, usable pressure

Question 42

Which of the following are commonly used pressure control valves in aircraft pneumatic systems? A. Shut-off valves, heat exchangers, bleed valves B. Pressure relief valves, control valves, check valves, restrictor valves C. Expansion valves, torque converters, piston actuators

Answer 42

B. Pressure relief valves, control valves, check valves, restrictor valves

Question 43

What is the function of a pressure relief valve (PRV)? A. Allow air into the system at start-up B. Prevent excess pressure from damaging components C. Filter dust and moisture from intake air

Answer 43

B. Prevent excess pressure from damaging components

Question 44

What is the purpose of a control valve in a pneumatic system? A. Store compressed air B. Automatically lubricate pneumatic seals C. Direct compressed air to perform a specific function (e.g. braking)

Answer 44

C. Direct compressed air to perform a specific function (e.g. braking)

Question 45

What is the function of a check valve in a pneumatic system? A. To regulate moisture levels in the air B. To allow airflow in only one direction C. To control the air temperature

Answer 45

B. To allow airflow in only one direction

Question 46

What is the function of a restrictor valve? A. Limit the volume and speed of airflow to the user system B. Reduce air pressure to zero C. Increase airflow when needed

Answer 46

A. Limit the volume and speed of airflow to the user system

Question 47

What does a variable restrictor valve use to control airflow? A. A set of rotating vanes B. A temperature sensor C. An adjustable needle valve

Answer 47

C. An adjustable needle valve

Question 48

What happens if an air filter becomes clogged with dirt? A. The system shuts down automatically B. The air is re-circulated through the compressor C. A relief valve opens, allowing unfiltered air to continue

Answer 48

C. A relief valve opens, allowing unfiltered air to continue

Question 49

What is the purpose of a moisture separator in a pneumatic system? A. Add lubrication to dry air B. Remove moisture created by the compressor C. Prevent dust from entering the intak

Answer 49

B. Remove moisture created by the compressor

Question 50

Where is the moisture separator located in a pneumatic system? A. Upstream of the air intake B. Inside the cabin airflow control system C. Downstream of the compressor

Answer 50

C. Downstream of the compressor

Question 51

What is the purpose of a moisture separator in a pneumatic system? A. Add lubrication to dry air B. Remove moisture created by the compressor C. Prevent dust from entering the intake

Answer 51

B. Remove moisture created by the compressor

Question 52

What is the role of a chemical drier in a pneumatic system? A. Reduce temperature of pressurized air B. Absorb moisture from system lines and components C. Neutralise corrosive air contaminants

Answer 52

B. Absorb moisture from system lines and components

Question 53

What is pneumatic power used for on an aircraft? A. Only for pressurisation and air conditioning B. Engine start, anti-ice, and cabin lighting C. Engine start, air conditioning, pressurisation, anti-ice, and various pressurisation systems

Answer 53

C. Engine start, air conditioning, pressurisation, anti-ice, and various pressurisation systems

Question 54

Which of the following is NOT powered by pneumatic pressure? A. Wing thermal anti-ice B. Air conditioning system C. Fuel injection system

Answer 54

C. Fuel injection system

Question 55

What precaution must be taken when supplying an aircraft with external pneumatic air on the ground? A. Connect it only while the APU is running B. Ensure no one is inside the aircraft C. At least one window or door must be open to prevent cabin pressurisation

Answer 55

C. At least one window or door must be open to prevent cabin pressurisation

Question 56

What is the purpose of the pneumatic manifold or ducting system? A. Mix bleed air with cabin air B. Transfer electrical signals for engine control C. Distribute compressed air from sources to user systems

Answer 56

C. Distribute compressed air from sources to user systems

Question 57

What materials are pneumatic ducts typically made from, and why? A. Steel, for high strength and cost B. Lightweight, corrosion-resistant tubing, sometimes gold-coated for hydrocarbon protection C. Rubber and plastic for flexibility

Answer 57

B. Lightweight, corrosion-resistant tubing, sometimes gold-coated for hydrocarbon protection

Question 58

What is the purpose of the pre-cooler in a pneumatic system? A. Heat incoming air for de-icing B. Maintain cabin temperature C. Reduce the temperature of engine bleed air before distribution

Answer 58

C. Reduce the temperature of engine bleed air before distribution

Question 59

What component is used to vary the amount of cooling air passing through the pre-cooler? A. Engine throttle lever B. Temperature control sensor C. Fan Air Valve (FAV)

Answer 59

C. Fan Air Valve (FAV)

Question 60

What happens if a leak occurs in a pneumatic duct? A. Air stops flowing and the system shuts down B. The aircraft automatically switches to hydraulic power C. It causes overheating, detected by overheat sensors

Answer 60

C. It causes overheating, detected by overheat sensors

Question 61

How can the pneumatic system on modern aircraft be controlled? A. Only automatically by the pneumatic controller B. Only manually using circuit breakers C. Either manually via the pneumatic control panel or automatically by the pneumatic controller

Answer 61

C. Either manually via the pneumatic control panel or automatically by the pneumatic controller

Question 62

What system on a Boeing aircraft displays pneumatic system alerts and indications? A. ECAM B. EICAS C. MCDU

Answer 62

B. EICAS (Engine Indicating and Crew Alerting System)

Question 63

What is the Airbus equivalent of Boeing’s EICAS for displaying pneumatic system warnings and indications? A. TCAS B. PFD C. ECAM

Answer 63

C. ECAM (Electronic Centralised Alerting Monitor)

Question 64

On the pneumatic synoptic display, what do green flow bars indicate? A. Low pressure in the system B. Which duct or component is damaged C. The direction of airflow and which sources and users are operating

Answer 64

C. The direction of airflow and which sources and users are operating

Question 65

Where are the isolation valve control switches located for the flight crew? A. On the side console B. On the main instrument panel C. On the overhead panel

Answer 65

C. On the overhead panel

Question 66

Which display shows a detailed overview of the pneumatic system, including valve positions and duct pressures? A. The CDU B. The Multi-Functional Display (MFD) C. The PFD

Answer 66

B. The Multi-Functional Display (MFD)