Fun fact: in smaller airplanes which have piston engines like cars do, pilots should turn on their electronic systems and instruments AFTER engine start in order to not damage the electrical equipment during the engine startup
@@LuxPlanes I fly every year a 150 with my dad, he turns on avionics before engine start, it has a garmin G3x even tho it’s not an experimental aircraft, it has never been replaced and has never reported any problems, nor with the analog avionics, I think it depends on what plane we are talking about and what the checklist says with each plane
@@sfx3256 yes of course! it depends on the aircraft and one should always consult the official manuals. but turning off the avionics before engine start isnt unheard of
For 787, APU is used to provide electricity before engine start. And some electricity is used to run a pair of Cabin Air Compressors to provide Air conditioning. (787 have 4 CAC, but usually use 2 on the ground) During engine start, most of the electricity is needed to run four Variable Frequency Starter/ Generator motor (two on each engine), so the CAC will be load shed (turn off) until the second engine started.
As a flight simmer when it comes to air conditioning usually on airbus you have to manually turn then on but on the 787 you can set the packs to auto and it will determine when to turn on and off for engine start
An Auxiliary Power Unit (APU) on an aircraft is an auxiliary engine installed in the aircraft and used to provide electrical power, air conditioning, or hydraulic power when the main engines are not running. On the ground, the APU is often used to start the main engines, to supply the aircraft with electrical power when parked away from an airport gate (i.e., when ground crew hasn't connected power), and to maintain climate control systems (air conditioning) when the main engines are not in operation. While working as cabin crew for Norwegian Airline, I encountered instances when the aircraft had difficulty starting the APU, requiring us to deal with the noise generated during ground handeling. In the air, the APU can be used to provide additional power when needed, such as during special operations or in the event of an emergency requiring independent power supply. Having 3 engines running would be very expensive for airliners.
The PACKS are also most of the time disabled during take off in case of an engine failure and to remove stress from the engines resulting in a shorter takeoff distance
Great explanation however, some aircraft don’t use the APU either it’s INOP, they don’t have one or certain airport noise abatement procedures don’t allow their usage. In these scenarios the engines are started electrically via a GPU or Ground Power Unit or pneumatically with bleed air from the auxiliary airflow air conditioning/heater system hooked to the aircraft cabin. 😅 ✈️
The APU only provides that on the ground The pressurization and air conditioning is provided by the engine in the Air(excluding the 787, which uses electricity instead)
Sorry, you’re correct, while writing the script I overlooked the fact that the APU is typically used on the ground and even though it feeds the PACKS (which include pressurization) it isn’t actually used for the pressurization. Sorry for that error
@ravejet8763 think you need to go back and read about APUs. He is right about the APU providing pressurisation of an aircraft. In some passenger aircraft it can be used during the T/O and initial climb phase to place less demand on the engines, reduce rwy used, less wear and/or increase or meet aggressive SID climb gradients. It can also be used just before landing incase of a GA. Can also be used as part as of an abnormal check list item. Most APUs have a limitation of 20,000 ft but at the end of the day it is part of the bleed air system and can be used to assist in pressurisation of an aircraft.
@@LuxPlanesno, don't apologise, some pax think they're the PIC, the APU can be used in some scenarios to assist with pressurisation up to a certain limit.
I've been on loads of flights I've travelled the world and trust me I've never had them switch off the air conditioning when starting the plane not once. I don't know why but this is so common but anyway. .
Not completely true; they turn off air conditioning so that all the air is directed to the engines but once the engines are started, the air and pressurisation etc is handled by the engines and the APU is turned off almost immediately to save fuel so it’s incorrect to say the APU handles air conditioning as its one main function that has multiple sources including the option of a ground unit to provide pressurised air in some models
They do but the APU can be used in flight in case of emergency. The only reason to shut it off is it’s not needed so running it causes undue strain and over maintenance.
APU also provides emergency bleed air pressure in case of emergency. There’s only one bleed air manifold. It’s not like the bleed air produced by it goes into a black hole, it goes to the PACKS
Why the false information? Not one single plane does the APU provide anything for pressurization and only less than 5 planes was the APU used in flight to provide anything. APU is purely for starting the main engines and some planes in Emergencies after all engines fail.
@@ThereAreNoMoreNamesNot strictly true. I’ve seen flameout cause an explosion in a main engine and it didn’t cause any hydraulic issues (or any other issues except for the career of the pilot responsible). Pilots just shut off the affected engine, turned on APU for supplementary bleed air and power and landed fine.
@@AnarexicSumo he said exploded though, not failed. If it failed, then yeah they would shut it down and continue on course. But if it actually exploded, think about all the hydraulic lines in the tail that are in the explosions range.
Well if it explodes it probably won’t be able to fly because it would cause structural damage to the aircraft. But if the APU stopped working or wasn’t able to provide the air for the engine start they can actually connect an air supply to the airplane from the ground. Hope that answers your question!
@@LuxPlanesNot strictly true about the structural damage. I’ve seen flameout cause an engine explosion (wasn’t driving thankfully). Emergency Procedure is to cut fuel and shut down the engine. Landed fine.
Literally the point of the APU is to provide bleed air for startup in addition to power. The extreme majority of planes designed to fly over 10,000 feet are pneumatic start with an APU not electric.
Pilots don’t turn off the air. It is automatically done as other things when the engine start switch is pushed. 20 years ago yes they turned it off. So many aviation channels don’t even know how aircraft work.
Hey, thanks for your comment. You are correct, many modern aircraft automatically redirect the bleed air to the engine starter, that being said, it isn’t uncommon for it to still be done manually in 2023. The Boeing 737 is one of the most common airliners in the world and is an example of an aircraft where the pilots have to manually select PACKS OFF before engine start. Hope that clarifies any misunderstandings. And I apologize for it not having been clearly mentioned in the video
@@AnarexicSumoeverytime huh? 😂😂😂. Come on man. That’s only done on rare occasions for take off, when you need your best performance due to runway restrictions or climb restrictions.
There's so many things wrong that with what you just said. First of all APU does not provide air for cabin pressurization it's the GTE or to simplify the engine of the A/C. It come from the compressed air of the engine or what you called "bleed air". The APU is the one who power the A/C so basically it is the one who gives electricity. Try to see for yourself that when the A/C is on ground you still hear an engine running even though your GTE is off and that engine running is the APU, some aiport have APU on wheels don't get confused.
They’re more correct than you are. The APU typically doesn’t run in flight but it also doesn’t power anything in flight as you allege. In-flight It’s used for emergency power and emergency pressurization and there’s even a specialized computer built in its housing to open up additional compressor veins to provide additional bleed air for this exact use-case. It’s also turned on sometimes to provide additional bleed air for de-ice systems like pneumatic boots. Also there’s no APU on wheels, that’s laughable, the APU is literally a full jet turbine. There’s a thing called a diesel huffer cart that can provide bleed air and there’s a thing called a GPU that can provide power but it’s not an APU.
@@AnarexicSumo @AnarexicSumo Okay lol I didn't say it run in flight I just explain in simple so everyone can understand it and you are just stating another information about the APU. I know thats a GPU, do I really need to explain it briefly?? What is this my APU Class?? Lmao ain't no body got time for that
@@nightowl4497but you are completely wrong. 🙄. There is no electrical A/C. The APU provides bleed air. So do the engines. When the engines aren’t running, the Apu handles this.
@@AnarexicSumono, it doesn’t provide additional bleed air for boots. It’s not used for emergency pressurization. Tell me when an Apu would pressurize during an emergency? 😂 some, not all can use it to pressurize during take off, to increase take off performance, that’s about it.
Wrong. The engines supply air to pressurize the cabin, and the ac unit is a stand alone unit. The apu only supplies power to start the engines. That's its only function.
They’re more correct than you. The primary function of the APU is to provide ground power for the plane and bleed air for startup. The secondary function is to provide emergency bleed air for AC and pressurization and power to avionics and essential electronics. There’s even a specific and separate computer built into the housing for this purpose. The AC and pressurization system are the same - called PACKS - and is fed entirely by bleed air. Nothing about it is stand alone. It doesn’t function without bleed air. Some planes especially smaller ones not designed for flight over 10,000 feet can feed the AC through a RAM air scoop but by-and-large every jet flying including turboprops pressurize from bleed air including air from the APU if needed. The only thing they got wrong was whether or not the APU is on during flight. You just made everything up and are wrong about everything and should feel bad.
@@AnarexicSumoand you are mostly correct, but you keep telling people that every Apu can give pneumatics inflight during an emergency. This is not the case. Some can. Most can’t.
This feels like when the radio turns off in cars when the electric starter is engaged
Fun fact: in smaller airplanes which have piston engines like cars do, pilots should turn on their electronic systems and instruments AFTER engine start in order to not damage the electrical equipment during the engine startup
@@LuxPlanesdas cool
@@LuxPlanes I fly every year a 150 with my dad, he turns on avionics before engine start, it has a garmin G3x even tho it’s not an experimental aircraft, it has never been replaced and has never reported any problems, nor with the analog avionics, I think it depends on what plane we are talking about and what the checklist says with each plane
@@sfx3256 yes of course! it depends on the aircraft and one should always consult the official manuals. but turning off the avionics before engine start isnt unheard of
@@sfx3256the g3x hss its own backup battery so it lasts some 2h without external power
APU stands for Auxiliary Power Unit.
Damn I been playing flight sim for a while and I thought it meant auto pilot unit 😭 Fock me
@@ABAtradinghow..?
fucking hell lol. It even says apu next to the apu switch lmao
@@ABAtrading
So an auxiliary power unit is responsible for the death of Samurai Jack's parents
@@matttzzz2 who tf is samurai Jack..
I always wondered what that other engine was for. Thanks.
The best feeling in the world is that silence building up suspense and then the sudden intense speed up
For 787, APU is used to provide electricity before engine start. And some electricity is used to run a pair of Cabin Air Compressors to provide Air conditioning. (787 have 4 CAC, but usually use 2 on the ground)
During engine start, most of the electricity is needed to run four Variable Frequency Starter/ Generator motor (two on each engine), so the CAC will be load shed (turn off) until the second engine started.
As a flight simmer when it comes to air conditioning usually on airbus you have to manually turn then on but on the 787 you can set the packs to auto and it will determine when to turn on and off for engine start
An Auxiliary Power Unit (APU) on an aircraft is an auxiliary engine installed in the aircraft and used to provide electrical power, air conditioning, or hydraulic power when the main engines are not running.
On the ground, the APU is often used to start the main engines, to supply the aircraft with electrical power when parked away from an airport gate (i.e., when ground crew hasn't connected power), and to maintain climate control systems (air conditioning) when the main engines are not in operation. While working as cabin crew for Norwegian Airline, I encountered instances when the aircraft had difficulty starting the APU, requiring us to deal with the noise generated during ground handeling.
In the air, the APU can be used to provide additional power when needed, such as during special operations or in the event of an emergency requiring independent power supply.
Having 3 engines running would be very expensive for airliners.
The PACKS are also most of the time disabled during take off in case of an engine failure and to remove stress from the engines resulting in a shorter takeoff distance
No, that’s not the case, that’s occasionally, when the aircraft is runway limited.
Not in the 777. That things nasty loud packs are screaming the whole flight, execpt when engines are started .
Alternative Title: *Why do airplanes get super hot before takeoff*
??? AC is temporarily off for only a couple of seconds. The engines then provide AC once they are running. Maybe you’re just nervous!
@@dxmaaaNo that is a real issue. Go search "increase passenger comfort on engine start"
@@dxmaaar/whooosh
@@greatsteamrealthat was not even a joke
@@pekinoantis4405 it was
Great explanation however, some aircraft don’t use the APU either it’s INOP, they don’t have one or certain airport noise abatement procedures don’t allow their usage. In these scenarios the engines are started electrically via a GPU or Ground Power Unit or pneumatically with bleed air from the auxiliary airflow air conditioning/heater system hooked to the aircraft cabin. 😅 ✈️
The APU pressurizes the plane? I've never seen a flight with APU on
The APU only provides that on the ground The pressurization and air conditioning is provided by the engine in the Air(excluding the 787, which uses electricity instead)
Sorry, you’re correct, while writing the script I overlooked the fact that the APU is typically used on the ground and even though it feeds the PACKS (which include pressurization) it isn’t actually used for the pressurization. Sorry for that error
@@LuxPlanesI love your videos!
@ravejet8763 think you need to go back and read about APUs. He is right about the APU providing pressurisation of an aircraft. In some passenger aircraft it can be used during the T/O and initial climb phase to place less demand on the engines, reduce rwy used, less wear and/or increase or meet aggressive SID climb gradients. It can also be used just before landing incase of a GA. Can also be used as part as of an abnormal check list item. Most APUs have a limitation of 20,000 ft but at the end of the day it is part of the bleed air system and can be used to assist in pressurisation of an aircraft.
@@LuxPlanesno, don't apologise, some pax think they're the PIC, the APU can be used in some scenarios to assist with pressurisation up to a certain limit.
Vietnam Airlines uniform 😍
Thanks for this video. I’ve always wondered what the APU was for
Good video and nice edit🎉😉
APU should not be turned on when the engines are running
Bro do not lie, I'm a pilot 😂😂
There's an external access in the engine cowling to do a manual engine start. But a ground crew or mechanic needs to do it from outside.
Ive always wondered about that! I recently flew Jet2 and just before pushback I remember the AC turning off and then came back a few minutes later.
Its funny that you used a 787 cockpit video to show this, since the 787 use electric starter for its engines :D Great video btw :)
Thank you 🙏
Apart from the twin otter and other old turboprops. It gets loud as.. it only gets quiet at cruising alt.
Same happens in my house when ever the AC turns on the lights flash off for a few milliseconds to get that little electricity to start up
I thought he was gonna say so that the passengers can hear the spool up
Have always wondered this
missed opportunity to play under pressure
That one screaming kid at the back of the plane
So basically a bigger version of the radio in your car turning off when you go to start up your car
But that one baby in the cabin NEVER gets quiet
I don't know why it gets extremely quite but I know why the air shuts off and the lights flicker.
😂😂
Something Something, packs L&R... Pressure, good engine start, Packs R Auto
i would rather the engine not even starting ty 💀🗿
Same
Then the plane is not gonna fly 😅
But when starting one of the engine successfully they are turning ac back on so don't worry.
you should learn grammar you noob🗿
The cabin is always quiet
Isn't that generally when they disconnect the ground based AC and power carts?
I love the part where he told us why the cabin gets extremely quiet before the engines start
Because the ac is off... Have you ever stepped on a plane?
I've been on loads of flights I've travelled the world and trust me I've never had them switch off the air conditioning when starting the plane not once. I don't know why but this is so common but anyway. .
Not completely true; they turn off air conditioning so that all the air is directed to the engines but once the engines are started, the air and pressurisation etc is handled by the engines and the APU is turned off almost immediately to save fuel so it’s incorrect to say the APU handles air conditioning as its one main function that has multiple sources including the option of a ground unit to provide pressurised air in some models
I always thought that they shut off the apu, I was way off, lol
They do but the APU can be used in flight in case of emergency. The only reason to shut it off is it’s not needed so running it causes undue strain and over maintenance.
APU Means
Auxiliary
Power
Unit
☝️
It's not about why passengers become extremely quiet you just change it into air conditioner
Bro, sounds like he is using the microphone from the plane 💀💀
I know this is kinda childish to say like this but of all the UA-camrs you have got to be my favorite one.
Nice vid sub
Thanks a lot! :)
i have a channel called @coolplanes333real can u pls shoutout me in ur next vid pls dude. @@LuxPlanes
However you just happen to choose that video of a 787 starting up, which does not have a pneumatic bleed air system as everyone else does 😅😅
my first flight the apu went out just before takeoff
Every flight ive been on had engines on during boarding
The engines send the air that they suck in into the plane, the APU helps start the engines
APU also provides emergency bleed air pressure in case of emergency. There’s only one bleed air manifold. It’s not like the bleed air produced by it goes into a black hole, it goes to the PACKS
@@AnarexicSumo- On SOME aircraft, not all can use APU pneumatic power inflight.
@@AnarexicSumonot all aircraft can do this.
For the need of what APU means it mean Auxiliary power unit.
I love airplanes and I love your video I love you so much and I like watching them❤❤❤
@@gertrudekatimba wha-
New to aviation nice vid but what about turboprops
Turboprops also use an APU typically or a purely electric start if they don’t have high crank horsepower requirements.
Because they turn off the pacs due to the bleed air from the apu needed for the engine start.
My flight had an apu issue so engines weren’t Starting and it was so hot for hours
The APU?
Thank you, come again!
I'm not an aviation fan, so I'm asking if the APU is an additional engine?
no, its used to provide electrical power on the ground
.etc
@@BarometricQuad thanks
@@cr34t_electric system, not hydraulics.
PACKS need too be turned up when starting the engines
Pack is Turned off before engine start because The air pressure would not be enough to start the air starter turbines
From the APU
PACKS go off to spin the turbines for engine start
It's the PACKS!!! Not the APU!
Screw you I clicked on the video with my headphones in on full volume 😂
Good video though 👏🏼👏🏼
The first clip is a vietnam airline cabin
Isn't the cabin pressurized by bleed air from engines?
Well actually if a GPU is connected to the aircraft, that could also start the engines.
No it can’t. A GPU provides electric power. Only small business jets use electric starters, all the bigger airplanes use pneumatic starters.
Wait, so if the apu doesn't work how does the engine start
@@cr34t_it’s called a huffer cart.
hmm im quite sure the normal engines pressurize the cabin
Pilots dont turn ac off its automatic.
Depends on the airplane type.
Boeing 737 and MD11 is loud lol
Why the false information?
Not one single plane does the APU provide anything for pressurization and only less than 5 planes was the APU used in flight to provide anything.
APU is purely for starting the main engines and some planes in Emergencies after all engines fail.
And after the engines start, the engines provide the compressed air needed for the air conditioning and pressurization.
It feels like I just un subbed from the LuxPlanes channel but I didn’t I swear
Okay but that doesn’t explain why they get quiet 🤷🏽♂️
The airflow is pretty strong and loud in the cabin. So when they turn that off, the airflow stops and the cabin gets significantly quieter.
Before I get the answer: they turn off the packs to redirect bleed air to the engines
Got it!
If the APU exploded?
Then the hydraulic pumps in the tail will be destroyed, which will basically cause another JAL123 or UAL232
@@ThereAreNoMoreNamesNot strictly true. I’ve seen flameout cause an explosion in a main engine and it didn’t cause any hydraulic issues (or any other issues except for the career of the pilot responsible). Pilots just shut off the affected engine, turned on APU for supplementary bleed air and power and landed fine.
@@AnarexicSumo he said exploded though, not failed. If it failed, then yeah they would shut it down and continue on course. But if it actually exploded, think about all the hydraulic lines in the tail that are in the explosions range.
@@AnarexicSumothe more responses I see you make, the more I realize you don’t know as much as you think. 😅
Interesting
Чел, говори по медленнее, прошу, очень уж трудно тебя понять с первого раза! Но я стараюсь 😂🙏🏻
Favorite plane?
“Simple”
Bro ask then answer quickly
PRESSURISATION
There’s no pressure on the ground
Yeah, people die temporarily-
It's sarcasm..
exellent
The packs
W vid
Thanks man! :)
u didn't know
Face reveal plssss
Face reveal can be found over on instagram when subscribing to the LuxPlanes account :)
I.E bleed air
Huh?
What if the APU explodes?
Well if it explodes it probably won’t be able to fly because it would cause structural damage to the aircraft. But if the APU stopped working or wasn’t able to provide the air for the engine start they can actually connect an air supply to the airplane from the ground. Hope that answers your question!
@@LuxPlanesOhhh ok
@@LuxPlanesNot strictly true about the structural damage. I’ve seen flameout cause an engine explosion (wasn’t driving thankfully). Emergency Procedure is to cut fuel and shut down the engine. Landed fine.
@@AnarexicSumoengine isn’t in the same location as an Apu.
Im the 69th commenter😊
The APU isn’t an engine it’s exactly what it’s called Auxiliary Power Unit
It’s literally a full jet turbine engine. The only difference is it’s smaller, has a different GMAD, and has a different control computer.
Tou don’t take air from APU you take electricity which powers the compressors and gives air to the engines
Might depend on the aircraft. Systems I'm familiar with direct bleed air from the apu for starting, packs, and adp operation.
Literally the point of the APU is to provide bleed air for startup in addition to power. The extreme majority of planes designed to fly over 10,000 feet are pneumatic start with an APU not electric.
Pilots don’t turn off the air. It is automatically done as other things when the engine start switch is pushed. 20 years ago yes they turned it off. So many aviation channels don’t even know how aircraft work.
Hey, thanks for your comment. You are correct, many modern aircraft automatically redirect the bleed air to the engine starter, that being said, it isn’t uncommon for it to still be done manually in 2023. The Boeing 737 is one of the most common airliners in the world and is an example of an aircraft where the pilots have to manually select PACKS OFF before engine start. Hope that clarifies any misunderstandings. And I apologize for it not having been clearly mentioned in the video
I turn it off every time I take off. You don’t know how planes work.
@@AnarexicSumoeverytime huh? 😂😂😂. Come on man. That’s only done on rare occasions for take off, when you need your best performance due to runway restrictions or climb restrictions.
@@LuxPlanesyou are correct. I’m still flabbergasted how the 73 still hasn’t fixed that.
There's so many things wrong that with what you just said.
First of all APU does not provide air for cabin pressurization it's the GTE or to simplify the engine of the A/C. It come from the compressed air of the engine or what you called "bleed air". The APU is the one who power the A/C so basically it is the one who gives electricity. Try to see for yourself that when the A/C is on ground you still hear an engine running even though your GTE is off and that engine running is the APU, some aiport have APU on wheels don't get confused.
They’re more correct than you are. The APU typically doesn’t run in flight but it also doesn’t power anything in flight as you allege. In-flight It’s used for emergency power and emergency pressurization and there’s even a specialized computer built in its housing to open up additional compressor veins to provide additional bleed air for this exact use-case. It’s also turned on sometimes to provide additional bleed air for de-ice systems like pneumatic boots. Also there’s no APU on wheels, that’s laughable, the APU is literally a full jet turbine. There’s a thing called a diesel huffer cart that can provide bleed air and there’s a thing called a GPU that can provide power but it’s not an APU.
@@AnarexicSumo @AnarexicSumo Okay lol I didn't say it run in flight I just explain in simple so everyone can understand it and you are just stating another information about the APU. I know thats a GPU, do I really need to explain it briefly?? What is this my APU Class?? Lmao ain't no body got time for that
@@nightowl4497but you are completely wrong. 🙄. There is no electrical A/C. The APU provides bleed air. So do the engines. When the engines aren’t running, the Apu handles this.
@@AnarexicSumono, it doesn’t provide additional bleed air for boots. It’s not used for emergency pressurization. Tell me when an Apu would pressurize during an emergency? 😂 some, not all can use it to pressurize during take off, to increase take off performance, that’s about it.
Wrong. The engines supply air to pressurize the cabin, and the ac unit is a stand alone unit. The apu only supplies power to start the engines. That's its only function.
They’re more correct than you. The primary function of the APU is to provide ground power for the plane and bleed air for startup. The secondary function is to provide emergency bleed air for AC and pressurization and power to avionics and essential electronics. There’s even a specific and separate computer built into the housing for this purpose. The AC and pressurization system are the same - called PACKS - and is fed entirely by bleed air. Nothing about it is stand alone. It doesn’t function without bleed air. Some planes especially smaller ones not designed for flight over 10,000 feet can feed the AC through a RAM air scoop but by-and-large every jet flying including turboprops pressurize from bleed air including air from the APU if needed.
The only thing they got wrong was whether or not the APU is on during flight. You just made everything up and are wrong about everything and should feel bad.
@@AnarexicSumoand you are mostly correct, but you keep telling people that every Apu can give pneumatics inflight during an emergency. This is not the case. Some can. Most can’t.
Apu provides electricity
Same@randomplanenoob