Pneumatics

Question 1

Does it have air leak detection and control

Answer 1

The pneumatic system consists of a bleed air supply system and a bleed air leak detection system. The pneumatic system uses pressurized air from the engines, the auxiliary power unit (APU), or a ground air cart and sends it to the related aircraft systems.

Two bleed management controllers (BMCs) control valves and monitor sensors to regulate the pressure and temperature of the pressurized air. The bleed air leak detection system monitors the ducts of the bleed air supply, anti-icing system and trim air system for hot air leaks. This system protects the components and the structure near the ducts against an overheat condition and the risk of fire. The BMCs monitor the hot air leakage and automatically isolate the defective area to stop the leak.

Question 2

What does apu supply air for

Answer 2

Engine start, packs, that’s all

Question 3

What is BMC

Answer 3

Bleed management controller

Question 4

What is Bleed air supply

Answer 4

Apu,engines,ground source

Question 5

Is low press port 5th stage always open

Answer 5

Yes

Question 6

Does 8th stage have shutoff valve

Answer 6

Yes

Question 7

80 percent and below hp is open

Answer 7

Yes

Question 8

What happens with bleed air

Answer 8

The bleed air system uses pressurized air, supplied by the engine compressors at two stages (5th stage or higher pressure 8th stage), the auxiliary power unit (APU), or by a ground air cart. The system supplies air via insulated ducts to the air conditioning system, the engine start system, wing anti-ice system, and cowl anti-ice system. Two bleed management controllers (BMCs) monitor the various sensors and control the valves to automatically select the air source, regulate pressure and temperature to the pneumatic systems. The BMCs automatically select 5th-stage or 8th-stage air, depending on engine power settings and system requirements. An electrically controlled cross-bleed valve connects or isolates the left and the right air supply systems. Operation and air source selection may also be controlled manually from the bleed air panel, located on the cockpit overhead panel.

Question 9

What temp is bleed air reduced to

Answer 9

200 degrees through heat exchangers and fan air valve, via THC valve

Question 10

What are bleedair components

Answer 10

The bleed air supply system consists of the following components: • Bleed air panel • Bleed air ducts • Mechanical interfaces and coupling • High-pressure ground connection • Intermediate-pressure check valve • Intermediate port pressure transducer • High-pressure valve • Pressure-regulating valve • Bleed pressure transducer • Precooler exchanger •Fan ai r v alve • Temperature control thermostat • Cross-bleed valve • Bleed management controller Related system components include: • One APU load control valve (LCV). The APU FADEC directly controls this valve. Refer to APU for further information (ATA 49) • One engine starter air valve (SAV) and one turbine air starter on each engine, refer to the Power Plant Starting System for further information (ATA 71). The engine FADEC controls the SAV operation • One cowl anti-ice system on each engine. Refer to the Cowl Anti-Ice System section (ATA 30) • One wing anti-ice system. Refer to the Wing Anti-Ice System section (ATA 30)

Question 11

Air to packs is through precooler

Answer 11

Yes and direct to anti ice

Question 12

Is bleed air pipework insulated

Answer 12

Yes so skin temp does not exceed 200 degrees

Question 13

What seals are used on bleed air

Answer 13

Flexible UROSEAL joints are provided along the ducting to cope with pressure-induced loads, structural deflections and thermal expansion of the pipes. The ducts are connected to each other, using WJ13 flanges and V-band couplings. The mechanical interfaces and coupling perform as follows: • The Uroseal type sleeved flexible connectors are joints that consist of a sleeve, fitted with internal seals. The sleeve connects two ducts, each of which incorporates a stop. These flexible connectors can compensate both parallel offset and axial displacements. Such flexible connectors are used in the following locations:- Precooler hot air outlet- Precooler cold air inlet- APU supply line connection to manifold- Bleed filter inlet- Ozone converter outlet- Pack inlet • WJ13 rigid coupling is used to connect highpressure components to the bleed and trim ducts and consists of a flange and a coupling. These V-band clamps are a variable diameter type of clamp and are widely used in commercial aircraft. The WJ13 is a gaske

Question 14

What is IPPD

Answer 14

Intermediate press tranducer

Question 15

Where is bleed press transducer

Answer 15

Downstream of air bleed valve

Bleed Pressure Transducer Figure A10 The bleed pressure transducer (BPT) is installed in the aft equipment compartment. It measures, through a pneumatic sense line, the air pressure downstream of the pressure-regulating valve and supplies the information to the bleed management controller (BMC).

Question 16

What is IPPT

Answer 16

The intermediate port pressure transducer (IPPT)
is installed on the engine. It measures, through a pneumatic sense line, the pressure upstream of the intermediate-pressure check valve (low-pressure port air). It transmits an electrical signal, which indicates the measured pressure to the BMC. It is an analog gauge type sensor with temperature compensation and is supplied with 28 VDC. Pressure range is 0-178 psig with an output voltage of 0.5 to 9.5 volts. The BMC will signal the HPV to close when the low-pressure port output is sufficient (sensed by the IPPT).

Question 17

WHAT IS HIGH PRESS VALVE

Answer 17

High-Pressure Valve Figure A8

The high-pressure valve is found in the nacelle and installed on the high-pressure port of the engine compressor. This valve is electrically operated and pneumatically actuated. It supplies bleed air from the high-pressure port (8th stage) of the engine compressor when the pressure from the lowpressure port is not sufficient. It moves the air supply back to the low-pressure port when the air pressure comes back to a sufficient level. The valve body has a butterfly plate connected to the pneumatic actuator through a shaft. The butterfly plate opens when there is upstream pressure (>12.3 psig) and when the solenoid is energized. It closes when there is no upstream pressure or the solenoid is deenergized. The solenoid controls the opening and the closing of the valve. Differential pressure between the top and the bottom part of the actuator chamber moves the piston up or down to keep the airflow pressure to a constant level. The pressure regulator supplies constant airstream pressure in the actuator chamber. A microswitch installed on the valve body indicates to the DAU and associated BMC if the valve is open or fully closed.

Question 18

What is fan air valve controlled by

Answer 18

Fan Air Valve Figure
A12 The fan air valve is installed in the pylon. It supplies cold air from the engine fan stage to the precooler exchanger. The air pressure from the temperature control thermostat (THC) pneumatically operates the fan air valve. The valve is equipped with two end-of-travel microswitches to indicate the fully closed and fully open positions. Fan air valve position information is provided to the associated air conditioning system controller (ACSC). The fan air valve has a locking device to lock the valve in the open position for dispatch purposes.

Question 19

What is THC

Answer 19

Temperature Control Thermostat Figure A12 The temperature control thermostat (THC) is installed on the bleed duct in the aft equipment compartment. It controls the fan air valve to make sure that the temperature downstream the precooler exchanger does not exceed approximately 200°C (392°F). Differential expansion of the materials of the stem is caused by increased temperature in the ducting. This restricts a controlled leak, which allows more pressure to pass to the fan air valve. The fan air valve, in turn, will open and allow greater cooling air through the precooler exchanger. The THC is equipped with a solenoid valve, controlled by the associated air conditioning system controller (ACSC). When 28 VDC is applied to the solenoid, high air pressure is supplied which causes the fan air valve to open fully. The ACSC will energize the THC solenoid when auxiliary pressurization has been selected or if a seized air cycle machine is sensed. (Refer to ATA 21 for more details).

Question 20

What is crossbleed valve

Answer 20

Cross-Bleed Valve Figure A13
The cross-bleed valve is installed between the left and right bleed ducts in the aft equipment compartment. It is an electrically operated isolation valve. It can give connection between the right and left bleed systems for the auxiliary power unit (APU) bleed and for the engine start. It is equipped with two end-of-travel microswitches to indicate the full open and full closed positions. Position information is provided to both BMCs and the DAUs. The electrical actuator of the valve is insulated against heat radiated from the valve body by means of a heat shield.

Question 21

What does channel B do

Answer 21

More a monitoring system

Question 22

What does BMC do

Answer 22

Bleed Management Controller Figures A14 and A17
The bleed management controller (BMC) is installed in the main avionics compartment. It monitors and controls the functions of the bleed air system and of the wing anti-ice system and monitors the cowl anti-ice system. There is one BMC for each side of the bleed air system. BMC 1 is dedicated to the left side of the aircraft and BMC 2 is dedicated to the right side of the aircraft. Each BMC consists of two separate channels, the control channel (CH A) and the monitor channel (CH B).

Question 23

How many channels do BMC,s have

Answer 23

Each BMC consists of two separate channels, the control channel (CH A) and the monitor channel (CH B).

Question 24

What monitoring does BMC use

Answer 24

Each BMC has an internal control/monitoring channel dialogue via an internal RS-422 link. Both BMCs crosstalk to each other via an ARINC 429 bus. Each BMC communicates to the corresponding air conditioning system controller (ACSC) via an ARINC 429 bus. The BMCs communicate with the DAUs via ARINC 429 buses.

Question 25

How does bleed air work

Answer 25

OPERATION Figures A18, A19 and A20 The bleed air system is normally supplied from the engine low-pressure ports. The pressure downstream of the pressure-regulating valve (PRV) is sensed by the bleed pressure transducer (BPT) and is monitored by the bleed management controller (BMC). The pressure at the low-pressure port (5th engine stage) is continually sensed by the intermediate port pressure transducer (IPPT) and is also monitored by the BMC. The BMC signals the high-pressure valve (HPV) to open when the bleed air pressure is too low for proper operation of the downstream systems (sensed by the BPT). The BMC signals the HPV to close when LP pressure is sufficient (sensed by the IPPT). The HPV is automatically signaled to close by the BMC whenever the PRV is signaled to close. On an ISA standard day at sea level, the bleed air would be approximately:
1. APU 248°C (478°F) @ 55 psi (no pneumatic load)
2. Engine high-pressure port 133°C (271°F) @ 30 psi (idle) 407°C (764°F) @ 210 psi (T/O)
3. Engine low-pressure port 77°C (170°F) @ 19 psi (idle) 277°C (530°F) @ 100 psi (T/O)

Question 26

What altitude is apu bleed air inhibited

Answer 26

Above 30000ft,

Question 27

What is engine bleed transfer

Answer 27

Engine Bleed and Transfer
When 28 VDC is applied to the solenoid of the HPV, provided there is sufficient pressure upstream of the valve (>12 psig), the valve will open. The solenoid is energized by the SPDA, according to a command from the corresponding bleed management controller (BMC). Automatic Transfer When the ENG BLEED rotary switch is set to the AUTO or ON position, the BMC controls the HPV. There are three threshold points for the LP to HP transfer, depending on demand (monitored by BPT):
• 23 psig for same side pack operation only (see Note below) • 30 psig for pack and corresponding wing antiice operation • 36 psig for pack and anti-ice operation of both wings NOTE The system does not allow both air conditioning packs to be supplied from one engine, due to the inability of the precooler to cool the volume of air needed. When the HP port supplies the bleed air system, the pressure sensed by the IPPT is read by the BMC, which signals the HPV to close, when this pressure is sufficient. There are three threshold points for HP to LP transfer, depending on demand (monitored by IPPT): • 27 psig for pack operation only • 34 psig for pack and corresponding wing antiice operation • 40 psig for pack and anti-ice operation of both wings

Question 28

What happens when fire handle pulled

Answer 28

Fire Handle
The HPV closes whenever the associated fire handle is pulled. The HPV can only open once the fire handle has been reset.

Question 29

What is overheat protection

Answer 29

Overheat Protection
The wing anti-ice system is protected against incorrect use of HP bleed due to a drift in IPPT reading, which could cause an overheat of the ducts and components. This is performed by the BMC monitoring P30 burner pressure (an engine parameter which is read on the ARINC 429 bus) and is always active. The HPV closes when P30 exceeds 190 psia, and opens when P30 is below 173 psia.

Question 30

What is bleed air leak detection system

Answer 30

The bleed air leak detection system protects the aircraft against hot air leaks from the air ducts of the bleed air system, the anti-icing system and the air conditioning trim air system. The bleed air leak detection system consists of dual bleed leak detection sensing elements (loops) and two bleed management controllers (BMC). The bleed air system has sense elements (loops) installed along the insulated ducts of the pneumatic system to sense any overheat caused by leaks. The wing anti-ice system has loops installed along the wing supply ducts and piccolo tubes. The air conditioning system has loops installed along trim air duct. The duct insulation has holes to direct any leaks over the sense elements. The bleed management controllers (BMCs) continuously monitor the loops to determine if a leak has occurred. If a leak is detected, the bleed management controllers (BMCs) or the air conditioning system controllers (ACSCs) will automatically set the valves to isolate the defective area and stop the leak.

Question 31

What is acsc

Answer 31

Air con system controller

Question 32

What are bleed air detection loops

Answer 32

Bleed Leak Detection Loops
Figures B1, B2 and B3 The bleed leak detection loops consist of two concentric tubes, the space between them being filled with an insulated eutectic salt. In case of a local temperature increase, the salt becomes conductive and the measured resistance between the tubes drops suddenly. The bleed air leak detection system has the detection loops that follow: • Left bleed leak detection loop • Right bleed leak detection loop • Trim air bleed leak detection loop • Wing supply leak detection loop • Fixed leading edge wing leak detection loop •
Slat 1 wing leak detection loop •
Slat 2 wing leak detection loop •
Slat 3 wing leak detection loop •
Slat 4 wing leak detection loop
All bleed air ducts are monitored through an arrangement of dual loops. The wings, however, are monitored by a single loop for each of the outboard and inboard sections, and by another single loop that covers both sections of the wing.

Question 33

How does bleed air detection work

Answer 33

The monitoring channel (channel B) of the bleed management controller (BMC) continuously monitors (CBIT) the resistance of the bleed air leak detection elements. When both loops in the same circuit indicate a bleed air leak has occurred, the controller will isolate the affected manifold by closing the appropriate valves. When a leak is detected (by air leaking from holes in insulation shell onto the leak detection loops), the appropriate BLEED LEAK, WING A/I LEAK, or TRIM LEAK caution message is displayed on EICAS and the BMC and/or the ACSC automatically close the relevant valves (see table B1).

Question 34

What message is for leak

Answer 34

Caution message on EICAS, followed by a bleed supply valve

Question 35

What temp will leak tell EICAS

Answer 35

Left Bleed Leak Detection Loop The left bleed leak detection loop is attached to the frame adjacent to the left supply duct assembly. It is installed in the aft equipment compartment and the left pylon area. At 123°C (255°F) and above, the loop senses a leak. When a leak is sensed, the EICAS primary page shows a L BLEED LEAK indication. Right Bleed Leak Detection Loop The right bleed leak detection loop is attached to the frame adjacent to the right supply duct assembly. It is installed in the aft equipment compartment and the right pylon area. At 123°C (255°F) and above, the loop senses a leak. When a leak is sensed, the EICAS primary page shows a R BLEED LEAK message.