Questions tagged [bleed-air]

Bleed air is hot air taken from the compressor stage of turbine engines, used to power other aircraft systems.

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Why can't you operate packs on HIGH during take-off, approach and landing on a 737-800?

It's in the FCOM Limitations Chapter and I think that these phases are critical phases of flight and I don't want to reduce my engine performance by purposely creating a high demand for bleed air from ...
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Why are the affected engine's bleed and pack switched off when there is an engine bleed under MEL?

My question mainly pertains to A320neo's equipped with PW engines. The MEL procedure states that the crew has to switch off the affected side's engine bleed, and its associated pack pushbutton to off. ...
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Why can APU supply both bleed air and electrical power up to 10.000 feet but bleed air alone up to 17000?

I am reading my company's FCOM and I saw there the following information. APU Bleed + Electrical Load: Max Alt 10000 ft. APU Bleed: Max Alt 17000 ft. APU Electrical Load: Max Alt 41000 ft. If APU ...
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Why is the autopilot of the DHC-6 Twin Otter powered by bleed air?

I was just reading through the POH of a DHC-6-100 Twin Otter and was surprised to read the following: 3.8.2 LOW PRESSURE - OTHER SYSTEMS. The airframe deicing system and the autopilot are ...
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From which stages is the bleed air from a GE90?

I'm doing a university project on the GE90-115b engine and I'm having a hard time understanding this EASA type-certificate data sheet. In particular I can't figure out the air bleed extraction section ...
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What is the relation of AIR BLEED IN message with the pack system on an Airbus A320?

Before the power-up, if the pack switches are set to the ON position and the aircraft is powered up with the APU bleed off, is there a chance that the AIR BLEED IN maintenance message comes up on ...
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Why do Airbus and Boeing have different approaches to bleed air systems? [closed]

Reading Wikipedia and other questions like this, made me curious as to why Boeing uses bleedless architecture for its B787, while Airbus thinks differently for its A350 XWB (and Rolls-Royce thinks the ...
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Is the air in aircraft cabin toxic?

I just listened to the recent BBC podcast episode Aerotoxicity: the hidden dangers of flying and there were interesting claims there: Cabin air in modern passenger aircrafts comes directly from ...
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Do pilots get more fresh air than passengers? [duplicate]

There is a famous air travel myth claiming that "pilots get more fresh air than passengers".       (source: The pure cure, p.375) I would like experts to either dispel or confirm this myth, that ...
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Do pilots breathe the same air as passengers?

Do pilots breathe the same quality of air as passengers ? (i.e. identical parameters: same O2, CO2 and O3 levels, same temperature, same humidity, etc.) Do pilots breath the same air as passengers (...
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Why does the cabin air sometimes smell of kerosene? [duplicate]

Why does the cabin air sometimes smell of jet fuel, although bleed air is tapped before it comes in contact with fuel ? How is this possible? I have smelled this a couple of times in my life (twice ...
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Why and how can a fume event occur?

« A fume event occurs when bleed air used for cabin pressurization and air conditioning in a pressurized aircraft is contaminated by fluids such as engine oil, hydraulic fluid, anti-icing fluid, ...
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Is the bleed air passengers breathe tapped from the engines before or after it comes in contact with fuel? And why? Isn't this unhealthy?

Passengers are often surprised to hear that the air they breathe comes from inside the engines. This sounds unhealthy. Can you explain, why it is not ? Is bleed air tapped (for cabin pressurization) ...
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Air quality monitoring devices for a320

I looking for the air quality monitoring devices for a320. How do they look, where they located? thank you for the help
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Will the new Boeing NMA be 'more electric' than the current B787?

I understand that the B787 is the 'most electric' aircraft to date, however there have been many issues with the plane, and I'm interested in knowing if the latest Boeing New Midsize Aircraft (NMA) - ...
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When are the engine bleed air, APU and packs turned on in the B737?

When do I have to turn on the engine bleed air and APU? In videos I have seen that they are always on, and sometimes they turn them off after take-off. I also have the same question about the packs.
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What is the maximum temperature of engine bleed air for de-icing the wings?

What is the maximum temperature of the air bled from the engines of a Boeing 747-800 and an Airbus A380 to the wings for de-icing? If the air is too hot, how is it cooled?
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On the A320, why is it not recommended to use the HP ground unit when the APU Bleed is on?

Can someone explain what the HP ground unit is used for? And what damage happens to the bleed system if it is used?
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Why can't we use APU bleed air for wing anti ice on the A320?

The question says it all. While reading I came across this that we can under no circumstances use APU bleed air for supplying wing anti ice? Any reason?
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How much thrust is lost due to the bleed air system?

I've read that bleeding air for the pneumatic system from the engine core can produce important losses in thrust, and also rising the fuel consumption too. Today this problem is worse, with the more ...
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672 views

What is the function of this small hole on the B737's hydraulic reservoir line?

This is picture of a B737-800. When you open the bleed system a small amount of air is discharged from this hole (marked with an arrow, lower right). What is it for? And what happens if this hole gets ...
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How much is air mass flow rate of bleed air used for environmental control system in civil aircraft?

I'm looking for a general use-case formula or reference that I can use to calculate the total mass flow rate of bleed air use in the environmental control system of any aircraft. I'm not looking for ...
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Engine(?) & Pressurization Problem in ATR-72 [closed]

To clarify, I'm an aviation enthusiast, not a pilot. I have a question for ATR pilots (or anyone with knowledge of the ATR systems). While travelling on an ATR-72, about 15 mins after takeoff (and ...
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What kind of filters are being used to filter the bleed air?

Bleed air is using by airplanes for various purposes including deicing and also to feed air conditioning units that maintain temperature inside cabin. What kind of filters does bleed air pass through ...
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Why is bleed air taken from some stage of the compressor used for de-icing? Why not e.g. exhaust gas?

In the answers to this question, it is said that The de-icing system on most turbine aircraft (including MD-82 involved in that accident) uses bleed air from the engines, that is it extracts some ...