What powers an aircraft prior to the APU being switched on?What is the cable connected to a plane for?In what conditions is the APU used in midair?What is “Hotel Mode” on a turboprop engine?Why do aircraft use 400 Hz AC instead of the 50 or 60 Hz of wall outlets?What is this tube connected to a 757 for?Why is the APU located in the tail for almost all commercial aircraft?What could cause the APU on a Boeing 777 to fail and also trip the GPU?In what conditions is the APU used in midair?Can airliners operate without an operating APU?What type of engine/motor is used in aircraft APU?Can the APU provide emergency thrust?Why would smoke enter the cabin if the batteries are switched off before the APU flap closes?What is the difference between an APU and an ATS?What is an “all-electric APU”?What is the fuel source for the APU on a B737?

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What powers an aircraft prior to the APU being switched on?

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What powers an aircraft prior to the APU being switched on?


What is the cable connected to a plane for?In what conditions is the APU used in midair?What is “Hotel Mode” on a turboprop engine?Why do aircraft use 400 Hz AC instead of the 50 or 60 Hz of wall outlets?What is this tube connected to a 757 for?Why is the APU located in the tail for almost all commercial aircraft?What could cause the APU on a Boeing 777 to fail and also trip the GPU?In what conditions is the APU used in midair?Can airliners operate without an operating APU?What type of engine/motor is used in aircraft APU?Can the APU provide emergency thrust?Why would smoke enter the cabin if the batteries are switched off before the APU flap closes?What is the difference between an APU and an ATS?What is an “all-electric APU”?What is the fuel source for the APU on a B737?






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margin-bottom:0;









7














$begingroup$


I know that APUs are power plants for non-propulsion related purposes and that they are turned on before takeoff.



What powers an airplane prior to the APU being turned on?










share|improve this question









New contributor



AstroSharp is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.






$endgroup$











  • 2




    $begingroup$
    Don't rush to accept, usually waiting 24 hours is recommended so all timezones can see and answer the question.
    $endgroup$
    – AEhere
    15 hours ago

















7














$begingroup$


I know that APUs are power plants for non-propulsion related purposes and that they are turned on before takeoff.



What powers an airplane prior to the APU being turned on?










share|improve this question









New contributor



AstroSharp is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.






$endgroup$











  • 2




    $begingroup$
    Don't rush to accept, usually waiting 24 hours is recommended so all timezones can see and answer the question.
    $endgroup$
    – AEhere
    15 hours ago













7












7








7


1



$begingroup$


I know that APUs are power plants for non-propulsion related purposes and that they are turned on before takeoff.



What powers an airplane prior to the APU being turned on?










share|improve this question









New contributor



AstroSharp is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.






$endgroup$




I know that APUs are power plants for non-propulsion related purposes and that they are turned on before takeoff.



What powers an airplane prior to the APU being turned on?







apu






share|improve this question









New contributor



AstroSharp is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.










share|improve this question









New contributor



AstroSharp is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.








share|improve this question




share|improve this question



share|improve this question








edited 1 hour ago









Sean

9,1695 gold badges47 silver badges119 bronze badges




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asked 16 hours ago









AstroSharpAstroSharp

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New contributor



AstroSharp is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.




New contributor




AstroSharp is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.












  • 2




    $begingroup$
    Don't rush to accept, usually waiting 24 hours is recommended so all timezones can see and answer the question.
    $endgroup$
    – AEhere
    15 hours ago












  • 2




    $begingroup$
    Don't rush to accept, usually waiting 24 hours is recommended so all timezones can see and answer the question.
    $endgroup$
    – AEhere
    15 hours ago







2




2




$begingroup$
Don't rush to accept, usually waiting 24 hours is recommended so all timezones can see and answer the question.
$endgroup$
– AEhere
15 hours ago




$begingroup$
Don't rush to accept, usually waiting 24 hours is recommended so all timezones can see and answer the question.
$endgroup$
– AEhere
15 hours ago










2 Answers
2






active

oldest

votes


















8
















$begingroup$

Onboard batteries for DC and a ground power supply for AC.



The ground supply can come either from an airport vehicle or from the stand itself.



Since the standard AC in aviation is 115V and 400Hz, the usual ground power supply needs to be converted to a higher frequency. This used to be done with a rotating converter, i.e. a motor (at 110V and 60Hz or 220V and 50Hz) driving a generator (at 115V and 400Hz), but can probably be done with solid state electronics these days. As for why the 400Hz, there is a good answer here but it boils down to: higher frequencies can work with lighter transformers, but also radiate more, so 400Hz was chosen as a compromise.






share|improve this answer










$endgroup$














  • $begingroup$
    The batteries can also provide AC, via the on-board inverters.
    $endgroup$
    – Sean
    1 hour ago


















14
















$begingroup$

Other than the APU, there are multiple ways to provide electrical power to an aircraft:




  • Battery: The battery is typically the first thing you would turn on and it usually provides DC power to emergency systems only (at least on an airliner, smaller aircraft are fully powered by the battery). Running only on battery power will however deplete the battery quickly. The battery can also be used to start the APU.


  • Ground Power: Most (maybe all) airliners can accept a connection to a Ground Power Unit (GPU), which will supply AC electrical power to run all aircraft systems on the ground. These can be either mobile units (typically powered by Diesel):



    GPU
    (source)



    or direct cable connections to the airport power grid:



    Ground Power
    (taken from this question)



  • Engine: This would be the method of last resort, but you can run an engine to provide electrical power via its generator. Note however that starting a jet engine would typically require bleed air from the APU or an Air Start Unit (ASU). Some turboprops can run an engine with a stopped propeller to provide power (Hotel mode). The engines also provide all electrical power during the flight, which is also used to re-charge the battery.


Running an APU on the apron is typically discouraged or restricted1 by the airport because of the noise and pollution. It does however provide one advantage over ground power: the APU also supplies bleed air to the air conditioning systems. Without it, air conditioning is only possible via a Pre-Conditioned Air (PCA) hose. See What is this tube connected to a 757 for? for details.



The APU is usually switched off after starting the main engines. It can however be used in the air on some aircraft. See In what conditions is the APU used in midair? for details.




1 Some airports have restrictions on when an aircraft is allowed to run the APU, e.g. Amsterdam:




The use of aircraft APU is forbidden in these stands in the period between 2 minutes after blocks for the arrivals and 5 minutes before off blocks for departure.




The APU will still be used to start the main engines during push-back.






share|improve this answer












$endgroup$














  • $begingroup$
    Then DC batteries are recharged during flight?
    $endgroup$
    – AstroSharp
    15 hours ago






  • 1




    $begingroup$
    Yes, whenever AC power is available (either from ground, APU generator or engine generators), it will be used to charge the battery.
    $endgroup$
    – Bianfable
    15 hours ago










  • $begingroup$
    What's the plug look like ?!
    $endgroup$
    – Fattie
    4 hours ago










  • $begingroup$
    @Fattie That's a nice question, you should aks it.
    $endgroup$
    – Bianfable
    4 hours ago










  • $begingroup$
    @Bianfable - thanks, I did !
    $endgroup$
    – Fattie
    3 hours ago












Your Answer








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2 Answers
2






active

oldest

votes








2 Answers
2






active

oldest

votes









active

oldest

votes






active

oldest

votes









8
















$begingroup$

Onboard batteries for DC and a ground power supply for AC.



The ground supply can come either from an airport vehicle or from the stand itself.



Since the standard AC in aviation is 115V and 400Hz, the usual ground power supply needs to be converted to a higher frequency. This used to be done with a rotating converter, i.e. a motor (at 110V and 60Hz or 220V and 50Hz) driving a generator (at 115V and 400Hz), but can probably be done with solid state electronics these days. As for why the 400Hz, there is a good answer here but it boils down to: higher frequencies can work with lighter transformers, but also radiate more, so 400Hz was chosen as a compromise.






share|improve this answer










$endgroup$














  • $begingroup$
    The batteries can also provide AC, via the on-board inverters.
    $endgroup$
    – Sean
    1 hour ago















8
















$begingroup$

Onboard batteries for DC and a ground power supply for AC.



The ground supply can come either from an airport vehicle or from the stand itself.



Since the standard AC in aviation is 115V and 400Hz, the usual ground power supply needs to be converted to a higher frequency. This used to be done with a rotating converter, i.e. a motor (at 110V and 60Hz or 220V and 50Hz) driving a generator (at 115V and 400Hz), but can probably be done with solid state electronics these days. As for why the 400Hz, there is a good answer here but it boils down to: higher frequencies can work with lighter transformers, but also radiate more, so 400Hz was chosen as a compromise.






share|improve this answer










$endgroup$














  • $begingroup$
    The batteries can also provide AC, via the on-board inverters.
    $endgroup$
    – Sean
    1 hour ago













8














8










8







$begingroup$

Onboard batteries for DC and a ground power supply for AC.



The ground supply can come either from an airport vehicle or from the stand itself.



Since the standard AC in aviation is 115V and 400Hz, the usual ground power supply needs to be converted to a higher frequency. This used to be done with a rotating converter, i.e. a motor (at 110V and 60Hz or 220V and 50Hz) driving a generator (at 115V and 400Hz), but can probably be done with solid state electronics these days. As for why the 400Hz, there is a good answer here but it boils down to: higher frequencies can work with lighter transformers, but also radiate more, so 400Hz was chosen as a compromise.






share|improve this answer










$endgroup$



Onboard batteries for DC and a ground power supply for AC.



The ground supply can come either from an airport vehicle or from the stand itself.



Since the standard AC in aviation is 115V and 400Hz, the usual ground power supply needs to be converted to a higher frequency. This used to be done with a rotating converter, i.e. a motor (at 110V and 60Hz or 220V and 50Hz) driving a generator (at 115V and 400Hz), but can probably be done with solid state electronics these days. As for why the 400Hz, there is a good answer here but it boils down to: higher frequencies can work with lighter transformers, but also radiate more, so 400Hz was chosen as a compromise.







share|improve this answer













share|improve this answer




share|improve this answer



share|improve this answer










answered 15 hours ago









AEhereAEhere

5,8231 gold badge22 silver badges57 bronze badges




5,8231 gold badge22 silver badges57 bronze badges














  • $begingroup$
    The batteries can also provide AC, via the on-board inverters.
    $endgroup$
    – Sean
    1 hour ago
















  • $begingroup$
    The batteries can also provide AC, via the on-board inverters.
    $endgroup$
    – Sean
    1 hour ago















$begingroup$
The batteries can also provide AC, via the on-board inverters.
$endgroup$
– Sean
1 hour ago




$begingroup$
The batteries can also provide AC, via the on-board inverters.
$endgroup$
– Sean
1 hour ago













14
















$begingroup$

Other than the APU, there are multiple ways to provide electrical power to an aircraft:




  • Battery: The battery is typically the first thing you would turn on and it usually provides DC power to emergency systems only (at least on an airliner, smaller aircraft are fully powered by the battery). Running only on battery power will however deplete the battery quickly. The battery can also be used to start the APU.


  • Ground Power: Most (maybe all) airliners can accept a connection to a Ground Power Unit (GPU), which will supply AC electrical power to run all aircraft systems on the ground. These can be either mobile units (typically powered by Diesel):



    GPU
    (source)



    or direct cable connections to the airport power grid:



    Ground Power
    (taken from this question)



  • Engine: This would be the method of last resort, but you can run an engine to provide electrical power via its generator. Note however that starting a jet engine would typically require bleed air from the APU or an Air Start Unit (ASU). Some turboprops can run an engine with a stopped propeller to provide power (Hotel mode). The engines also provide all electrical power during the flight, which is also used to re-charge the battery.


Running an APU on the apron is typically discouraged or restricted1 by the airport because of the noise and pollution. It does however provide one advantage over ground power: the APU also supplies bleed air to the air conditioning systems. Without it, air conditioning is only possible via a Pre-Conditioned Air (PCA) hose. See What is this tube connected to a 757 for? for details.



The APU is usually switched off after starting the main engines. It can however be used in the air on some aircraft. See In what conditions is the APU used in midair? for details.




1 Some airports have restrictions on when an aircraft is allowed to run the APU, e.g. Amsterdam:




The use of aircraft APU is forbidden in these stands in the period between 2 minutes after blocks for the arrivals and 5 minutes before off blocks for departure.




The APU will still be used to start the main engines during push-back.






share|improve this answer












$endgroup$














  • $begingroup$
    Then DC batteries are recharged during flight?
    $endgroup$
    – AstroSharp
    15 hours ago






  • 1




    $begingroup$
    Yes, whenever AC power is available (either from ground, APU generator or engine generators), it will be used to charge the battery.
    $endgroup$
    – Bianfable
    15 hours ago










  • $begingroup$
    What's the plug look like ?!
    $endgroup$
    – Fattie
    4 hours ago










  • $begingroup$
    @Fattie That's a nice question, you should aks it.
    $endgroup$
    – Bianfable
    4 hours ago










  • $begingroup$
    @Bianfable - thanks, I did !
    $endgroup$
    – Fattie
    3 hours ago















14
















$begingroup$

Other than the APU, there are multiple ways to provide electrical power to an aircraft:




  • Battery: The battery is typically the first thing you would turn on and it usually provides DC power to emergency systems only (at least on an airliner, smaller aircraft are fully powered by the battery). Running only on battery power will however deplete the battery quickly. The battery can also be used to start the APU.


  • Ground Power: Most (maybe all) airliners can accept a connection to a Ground Power Unit (GPU), which will supply AC electrical power to run all aircraft systems on the ground. These can be either mobile units (typically powered by Diesel):



    GPU
    (source)



    or direct cable connections to the airport power grid:



    Ground Power
    (taken from this question)



  • Engine: This would be the method of last resort, but you can run an engine to provide electrical power via its generator. Note however that starting a jet engine would typically require bleed air from the APU or an Air Start Unit (ASU). Some turboprops can run an engine with a stopped propeller to provide power (Hotel mode). The engines also provide all electrical power during the flight, which is also used to re-charge the battery.


Running an APU on the apron is typically discouraged or restricted1 by the airport because of the noise and pollution. It does however provide one advantage over ground power: the APU also supplies bleed air to the air conditioning systems. Without it, air conditioning is only possible via a Pre-Conditioned Air (PCA) hose. See What is this tube connected to a 757 for? for details.



The APU is usually switched off after starting the main engines. It can however be used in the air on some aircraft. See In what conditions is the APU used in midair? for details.




1 Some airports have restrictions on when an aircraft is allowed to run the APU, e.g. Amsterdam:




The use of aircraft APU is forbidden in these stands in the period between 2 minutes after blocks for the arrivals and 5 minutes before off blocks for departure.




The APU will still be used to start the main engines during push-back.






share|improve this answer












$endgroup$














  • $begingroup$
    Then DC batteries are recharged during flight?
    $endgroup$
    – AstroSharp
    15 hours ago






  • 1




    $begingroup$
    Yes, whenever AC power is available (either from ground, APU generator or engine generators), it will be used to charge the battery.
    $endgroup$
    – Bianfable
    15 hours ago










  • $begingroup$
    What's the plug look like ?!
    $endgroup$
    – Fattie
    4 hours ago










  • $begingroup$
    @Fattie That's a nice question, you should aks it.
    $endgroup$
    – Bianfable
    4 hours ago










  • $begingroup$
    @Bianfable - thanks, I did !
    $endgroup$
    – Fattie
    3 hours ago













14














14










14







$begingroup$

Other than the APU, there are multiple ways to provide electrical power to an aircraft:




  • Battery: The battery is typically the first thing you would turn on and it usually provides DC power to emergency systems only (at least on an airliner, smaller aircraft are fully powered by the battery). Running only on battery power will however deplete the battery quickly. The battery can also be used to start the APU.


  • Ground Power: Most (maybe all) airliners can accept a connection to a Ground Power Unit (GPU), which will supply AC electrical power to run all aircraft systems on the ground. These can be either mobile units (typically powered by Diesel):



    GPU
    (source)



    or direct cable connections to the airport power grid:



    Ground Power
    (taken from this question)



  • Engine: This would be the method of last resort, but you can run an engine to provide electrical power via its generator. Note however that starting a jet engine would typically require bleed air from the APU or an Air Start Unit (ASU). Some turboprops can run an engine with a stopped propeller to provide power (Hotel mode). The engines also provide all electrical power during the flight, which is also used to re-charge the battery.


Running an APU on the apron is typically discouraged or restricted1 by the airport because of the noise and pollution. It does however provide one advantage over ground power: the APU also supplies bleed air to the air conditioning systems. Without it, air conditioning is only possible via a Pre-Conditioned Air (PCA) hose. See What is this tube connected to a 757 for? for details.



The APU is usually switched off after starting the main engines. It can however be used in the air on some aircraft. See In what conditions is the APU used in midair? for details.




1 Some airports have restrictions on when an aircraft is allowed to run the APU, e.g. Amsterdam:




The use of aircraft APU is forbidden in these stands in the period between 2 minutes after blocks for the arrivals and 5 minutes before off blocks for departure.




The APU will still be used to start the main engines during push-back.






share|improve this answer












$endgroup$



Other than the APU, there are multiple ways to provide electrical power to an aircraft:




  • Battery: The battery is typically the first thing you would turn on and it usually provides DC power to emergency systems only (at least on an airliner, smaller aircraft are fully powered by the battery). Running only on battery power will however deplete the battery quickly. The battery can also be used to start the APU.


  • Ground Power: Most (maybe all) airliners can accept a connection to a Ground Power Unit (GPU), which will supply AC electrical power to run all aircraft systems on the ground. These can be either mobile units (typically powered by Diesel):



    GPU
    (source)



    or direct cable connections to the airport power grid:



    Ground Power
    (taken from this question)



  • Engine: This would be the method of last resort, but you can run an engine to provide electrical power via its generator. Note however that starting a jet engine would typically require bleed air from the APU or an Air Start Unit (ASU). Some turboprops can run an engine with a stopped propeller to provide power (Hotel mode). The engines also provide all electrical power during the flight, which is also used to re-charge the battery.


Running an APU on the apron is typically discouraged or restricted1 by the airport because of the noise and pollution. It does however provide one advantage over ground power: the APU also supplies bleed air to the air conditioning systems. Without it, air conditioning is only possible via a Pre-Conditioned Air (PCA) hose. See What is this tube connected to a 757 for? for details.



The APU is usually switched off after starting the main engines. It can however be used in the air on some aircraft. See In what conditions is the APU used in midair? for details.




1 Some airports have restrictions on when an aircraft is allowed to run the APU, e.g. Amsterdam:




The use of aircraft APU is forbidden in these stands in the period between 2 minutes after blocks for the arrivals and 5 minutes before off blocks for departure.




The APU will still be used to start the main engines during push-back.







share|improve this answer















share|improve this answer




share|improve this answer



share|improve this answer








edited 1 hour ago

























answered 15 hours ago









BianfableBianfable

7,72029 silver badges56 bronze badges




7,72029 silver badges56 bronze badges














  • $begingroup$
    Then DC batteries are recharged during flight?
    $endgroup$
    – AstroSharp
    15 hours ago






  • 1




    $begingroup$
    Yes, whenever AC power is available (either from ground, APU generator or engine generators), it will be used to charge the battery.
    $endgroup$
    – Bianfable
    15 hours ago










  • $begingroup$
    What's the plug look like ?!
    $endgroup$
    – Fattie
    4 hours ago










  • $begingroup$
    @Fattie That's a nice question, you should aks it.
    $endgroup$
    – Bianfable
    4 hours ago










  • $begingroup$
    @Bianfable - thanks, I did !
    $endgroup$
    – Fattie
    3 hours ago
















  • $begingroup$
    Then DC batteries are recharged during flight?
    $endgroup$
    – AstroSharp
    15 hours ago






  • 1




    $begingroup$
    Yes, whenever AC power is available (either from ground, APU generator or engine generators), it will be used to charge the battery.
    $endgroup$
    – Bianfable
    15 hours ago










  • $begingroup$
    What's the plug look like ?!
    $endgroup$
    – Fattie
    4 hours ago










  • $begingroup$
    @Fattie That's a nice question, you should aks it.
    $endgroup$
    – Bianfable
    4 hours ago










  • $begingroup$
    @Bianfable - thanks, I did !
    $endgroup$
    – Fattie
    3 hours ago















$begingroup$
Then DC batteries are recharged during flight?
$endgroup$
– AstroSharp
15 hours ago




$begingroup$
Then DC batteries are recharged during flight?
$endgroup$
– AstroSharp
15 hours ago




1




1




$begingroup$
Yes, whenever AC power is available (either from ground, APU generator or engine generators), it will be used to charge the battery.
$endgroup$
– Bianfable
15 hours ago




$begingroup$
Yes, whenever AC power is available (either from ground, APU generator or engine generators), it will be used to charge the battery.
$endgroup$
– Bianfable
15 hours ago












$begingroup$
What's the plug look like ?!
$endgroup$
– Fattie
4 hours ago




$begingroup$
What's the plug look like ?!
$endgroup$
– Fattie
4 hours ago












$begingroup$
@Fattie That's a nice question, you should aks it.
$endgroup$
– Bianfable
4 hours ago




$begingroup$
@Fattie That's a nice question, you should aks it.
$endgroup$
– Bianfable
4 hours ago












$begingroup$
@Bianfable - thanks, I did !
$endgroup$
– Fattie
3 hours ago




$begingroup$
@Bianfable - thanks, I did !
$endgroup$
– Fattie
3 hours ago











AstroSharp is a new contributor. Be nice, and check out our Code of Conduct.









draft saved

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