Mdthbs

Any historical references to links between JOSS and BASIC?

How to not lose focus after each disruption in flow

When can a graph be oriented to form a Hasse diagram of a finite poset?

Tool to get dual problem from any linear optimization problem (.lp)

XGBoost validation for number of trees

Are there any privately owned large commercial airports?

Does journal access significantly influence choice in which journal to publish in?

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

Can you decide not to sneak into a room after seeing your roll?

Adding elements to some sublists of unequal length

An employee has low self-confidence, and is performing poorly. How can I help?

What are the different ways one can refer to the home in everyday French

How to temporarily replace Latin characters with Greek

D&D Monsters and Copyright

How long should a test wait to assume that the result remains fixed

Consecutive numbers that are Manhattan distance 3 apart

Installing Proprietary Windows Drivers on Linux

Is self-defense mutually exclusive of murder?

Fill the Image Sequence Ep. 2

Can a successful economy exist without renting stuff?

Test if two food are the same

Modern warfare theory in a medieval setting

Can you be promoted and then fired for-cause? (Performance)

Parliament Cannot Bind Future Parliaments

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?

.everyoneloves__top-leaderboard:empty,.everyoneloves__mid-leaderboard:empty,.everyoneloves__bot-mid-leaderboard:empty{
margin-bottom:0;
}

8

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?

apu

share|improve this question

edited 2 hours ago

Sean

9,17955 gold badges4747 silver badges119119 bronze badges

asked 17 hours ago

AstroSharpAstroSharp

14344 bronze badges

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
  17 hours ago
  

  
  
  
  

add a comment
 | 

8

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?

apu

share|improve this question

edited 2 hours ago

Sean

9,17955 gold badges4747 silver badges119119 bronze badges

asked 17 hours ago

AstroSharpAstroSharp

14344 bronze badges

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
  17 hours ago
  

  
  
  
  

add a comment
 | 

$begingroup$

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?

apu

share|improve this question

edited 2 hours ago

Sean

9,17955 gold badges4747 silver badges119119 bronze badges

asked 17 hours ago

AstroSharpAstroSharp

14344 bronze badges

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.

$endgroup$

share|improve this question

edited 2 hours ago

Sean

9,17955 gold badges4747 silver badges119119 bronze badges

asked 17 hours ago

AstroSharpAstroSharp

14344 bronze badges

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

edited 2 hours ago

Sean

9,17955 gold badges4747 silver badges119119 bronze badges

asked 17 hours ago

AstroSharpAstroSharp

14344 bronze badges

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.

edited 2 hours ago

Sean

9,17955 gold badges4747 silver badges119119 bronze badges

edited 2 hours ago

Sean

9,17955 gold badges4747 silver badges119119 bronze badges

asked 17 hours ago

AstroSharpAstroSharp

14344 bronze badges

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.

asked 17 hours ago

AstroSharpAstroSharp

14344 bronze badges

2 Answers
2

active

oldest

votes

9

$begingroup$

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

answered 17 hours ago

AEhereAEhere

5,84311 gold badge2222 silver badges5757 bronze badges

$endgroup$

• 
  
  
  

  
  1
  

  
  
  
  
  
  

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

  
  
  
  

add a comment
 | 

15

$begingroup$

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):

  
  
  

  
  (source)

  
  
  

  or direct cable connections to the airport power grid:

  
  
  

  
  (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

edited 2 hours ago

answered 17 hours ago

BianfableBianfable

7,7302929 silver badges5656 bronze badges

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Then DC batteries are recharged during flight?
  $endgroup$
  – AstroSharp
  17 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
  17 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

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

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

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

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

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

  
  
  
  

add a comment
 | 

Your Answer

StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "528"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);

StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});

function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: false,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: null,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/4.0/"u003ecc by-sa 4.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
noCode: true, onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});


}
});

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

draft saved

draft discarded

Sign up or log in

StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});

Sign up using Google

Sign up using Facebook

Sign up using Email and Password

Post as a guest

Name

Email

Required, but never shown

StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2faviation.stackexchange.com%2fquestions%2f70268%2fwhat-powers-an-aircraft-prior-to-the-apu-being-switched-on%23new-answer', 'question_page');
}
);

Post as a guest

Name

Email

Required, but never shown

9

$begingroup$

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

answered 17 hours ago

AEhereAEhere

5,84311 gold badge2222 silver badges5757 bronze badges

$endgroup$

• 
  
  
  

  
  1
  

  
  
  
  
  
  

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

  
  
  
  

add a comment
 | 

9

$begingroup$

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

answered 17 hours ago

AEhereAEhere

5,84311 gold badge2222 silver badges5757 bronze badges

$endgroup$

• 
  
  
  

  
  1
  

  
  
  
  
  
  

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

  
  
  
  

add a comment
 | 

$begingroup$

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

answered 17 hours ago

AEhereAEhere

5,84311 gold badge2222 silver badges5757 bronze badges

$endgroup$

share|improve this answer

answered 17 hours ago

AEhereAEhere

5,84311 gold badge2222 silver badges5757 bronze badges

answered 17 hours ago

AEhereAEhere

5,84311 gold badge2222 silver badges5757 bronze badges

answered 17 hours ago

AEhereAEhere

5,84311 gold badge2222 silver badges5757 bronze badges

15

$begingroup$

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):

  
  
  

  
  (source)

  
  
  

  or direct cable connections to the airport power grid:

  
  
  

  
  (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

edited 2 hours ago

answered 17 hours ago

BianfableBianfable

7,7302929 silver badges5656 bronze badges

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Then DC batteries are recharged during flight?
  $endgroup$
  – AstroSharp
  17 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
  17 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

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

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

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

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

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

  
  
  
  

add a comment
 | 

15

$begingroup$

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):

  
  
  

  
  (source)

  
  
  

  or direct cable connections to the airport power grid:

  
  
  

  
  (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

edited 2 hours ago

answered 17 hours ago

BianfableBianfable

7,7302929 silver badges5656 bronze badges

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Then DC batteries are recharged during flight?
  $endgroup$
  – AstroSharp
  17 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
  17 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

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

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

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

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

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

  
  
  
  

add a comment
 | 

$begingroup$

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):

  
  
  

  
  (source)

  
  
  

  or direct cable connections to the airport power grid:

  
  
  

  
  (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

edited 2 hours ago

answered 17 hours ago

BianfableBianfable

7,7302929 silver badges5656 bronze badges

$endgroup$

share|improve this answer

edited 2 hours ago

answered 17 hours ago

BianfableBianfable

7,7302929 silver badges5656 bronze badges

answered 17 hours ago

BianfableBianfable

7,7302929 silver badges5656 bronze badges

answered 17 hours ago

BianfableBianfable

7,7302929 silver badges5656 bronze badges