Pneumatics Flashcards

1
Q

What do large gas turbine a/c use for their pneumatic system

A

Engine bleed air

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2
Q

Small a/c have a pneumatic system driven by

A

A vacuum pump driven by the engine via a quill shaft

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3
Q

What is quill drive designed to do if the torque load becomes excessive

A

Designed to shear if the torque load becomes excessive

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4
Q

Some older turboprop and piston engined a/c use pneumatics for

A

L/d gear

Brakes

Flaps

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5
Q

Moisture separator

A

Prevents ice buildup which could come from moist air - takes the moisture out

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6
Q

Desiccator

A

Picks up any excess moisture after the moisture separator

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7
Q

When is the emerg system used - pneumatics blower system

A

When the isolation valve is closed

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8
Q

Adv and disadv of an air pressure system

A

Won’t run out

More dangerous - high pressure system - you can’t see if there is a leak

Cheaper, simpler and lighter

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9
Q

Blower

A

Sucks air in - compressor

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10
Q

Mass flow control valve - blower system

A

Controls the mass flow to maintain the correct amount in the cabin - will send a signal to the spill valve to open/close to maintain the correct mass of air

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11
Q

Choke valve purpose and how it works

A

Located in the cabin blower system - purpose - raise the temp of the air if required

How - applying a back pressure to the blower

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12
Q

Pack valve

A

Controls the air conditioning - either on/off

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13
Q

How does the a/c regulate the mass flow for an a/c using bleed air for pneumatics

A

Mass flow controller sends a signal to the variable metering orifice which opens and closes to maintain the correct mass flow

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14
Q

Bleed air is fed from

A

From the LP stages of the Hp compressor

From the engine compressor

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15
Q

Bleed air is cooled by

A

An air conditioning pack

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16
Q

Isolation valve

A

Allows each pneumatic system to work in isolation - once opened one engine can supply both engines

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17
Q

HPSOV

A

Designed to open slowly on eng start to prevent a surge of air pressure - also req to close quickly to stop smoke and fumes reaching the cabin

18
Q

Materials for pneumatics

A

Plastic and fibre glass for low pressure systems

Stainless steel for high pressure systems

19
Q

Normal cause of overpressure - pneumatics

A

Usually caused by the failure of the high pressure shut off valve - sensor drives the valve shut

20
Q

Safety device to prevent overheat

A

Electrical temp switch downstream of the bleed air control valve will close the valve

21
Q

Overheat action by the pilot - pneumatics

A

Close the bleed switch and then open the isolation valve to make up for the lost system - allows 1 engine to supply both a/c packs

22
Q

Light a/c obtain hot air from and the possible risk

A

A heat exchanger wrapped around the exhaust this is then mixed with cold air - risk of carbon monoxide

Can also receive to air from a combustion heater

23
Q

Combustion heater

A

Burns fuel to generate heat and warm the air

Separated heating to keep you warm

Takes heat from the fuel the tanks and burns it

24
Q

Safety devices required with a combustion heater

A

Automatic fuel shutoff

Adequate fire protection

25
Purpose of air conditioning
To supply a constant delivery of clean air, to the cockpit and cabin, within a set temp range
26
What is conditioned air
Air which is treated for pressure and temp
27
Do we control humidity
No We take all the water out and put a little back in
28
Fresh air requirements
1 pound of fresh air per seat per min under normal circumstances 0.5 pound of fresh air per seat per min following a failure of any part of the system - lowest is can be Between 18 - 24*C
29
At 40,000ft the humidity is about
1-2% Ideally it should be about 30%
30
Carbon monoxide contamination not to exceed
1 part in 20,000 - legal limit
31
Bootstrap (air cycle) system consists of
``` In the specific order of Primary heat exchanger (precooler) Compressor Secondary heat exchanger (intercooler) Turbine ``` It is the combined effect of the secondary heat exchanger and the turbine = cooling
32
Bootstrap system is most efficient at
High mass flow values
33
Cold air unit/air cycle machine in a bootstrap system is made up of
Compressor, shaft, turbine
34
When stationary/slow in the air - how does the a/c provide ram air
Uses a fan powered by an electric motor - electrically driven of by a third wheel on the cold air unit
35
2 types of water separators and where it is located
Impingement or centrifugal Located downstream of the turbine/ air cooler
36
Centrifugal water separator
Air-driven fan throws water outwards - water is drained and collected
37
Impingement water separator
Moisture sticks to the cold collector tubes and collects at the bottom
38
How does the humidifier work
Same as a carburettor- air tube - sucks water out and into the airflow
39
What is the recirculating fans
Draws air from underfloor area through filters and is reintroduced into the conditioned distribution system - prevents stagnation
40
What is gasper air
Cold conditioned air supplied to the pax through punkah louvres
41
Trim air
Low pressure, high temp air Allows us to control different temps in each cabin