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Faro
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Prevalence of Ground Electric Power Supply

Thu Jun 06, 2019 9:16 am

In major airports with jetway parking stands, is ground electric power supply usually provided and used by airliners during power-on and start-up? Or is the APU the usual resource used to provide start-up power after being powered on by battery power?

What about secondary airports and the like? Is the availability of ground electric power mainly a function of airport size/importance or not?


Faro
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Starlionblue
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Re: Prevalence of Ground Electric Power Supply

Thu Jun 06, 2019 9:46 am

At major airports, external power is typically provided at the stand. However in some cases due to the cost it may be more economical to use the APU.

At many major airports, APU usage is limited by regulation, so of course they have to provide external power.

Even with external power, you need the APU for engine start because you need bleed air to power the starter. So the APU is still used, both on engine start and on arrival.
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Okie
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Re: Prevalence of Ground Electric Power Supply

Thu Jun 06, 2019 12:30 pm

Starlionblue wrote:
Even with external power, you need the APU for engine start because you need bleed air to power the starter. So the APU is still used, both on engine start and on arrival.


The 787 uses electric starter/alternator which is capable of engine start without APU.
However it has to have at least 2 of the 3 external ground power connections made to provide enough current.
I am not sure if that option is used in normal practice.

Okie
 
shamrock137
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Re: Prevalence of Ground Electric Power Supply

Thu Jun 06, 2019 12:51 pm

Faro wrote:

What about secondary airports and the like? Is the availability of ground electric power mainly a function of airport size/importance or not?


Faro


Any airport served by an airline would need to have ground power available. The APU can be used, but aircraft are able to be dispatched with the APU inoperative. Additionally, smaller turboprops may not have an APU such as the Dash 8, Saab 340, etc. The other component is ground air. With the APU off, their is no way to provide hot or cold air in the cabin, unless its a 787 with the electric packs. If an aircraft is left on ground power with no ground air connected in the summer, the cabin temp can get above 90F/32C quickly, even if the outside temp is only 75F/23C.
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e38
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Re: Prevalence of Ground Electric Power Supply

Fri Jun 07, 2019 2:30 am

faro, at the company at which I work, it is operational policy to use external power (ground electrical power) as much as possible to reduce fuel consumed by running the APU.

External power (ground electrical power) is available at just about every airport we serve, normally through an electrical power supply and control box attached to the jetway. At airports we serve where we park at a remote hard stand, our ground operations personnel will normally position a ground power unit (GPU) next to the aircraft.

As such, upon landing, the APU is started as part of the "After Landing Checklist," but we try to time the starting of the APU so it becomes fully operational just prior to arrival at the gate. Once parked at the gate with the APU running, we can shut down the engines right away; however, when ground personnel connect external power to the aircraft (usually within one or two minutes after block in) we transfer the electrial system to external power and shut down the APU.

As Starlionblue mentioned in Reply # 2, "Even with external power, you need the APU for engine start because you need bleed air to power the starter." This is true, but again, at the company at which I work, in order to minimize APU usage, our operations policy is to delay starting the APU until approximately 5 - 10 minutes prior to departure time.

So, to answer your question, at the company at which I work, we always try to maximize the use of external power, and it is available at most airports we serve.

With regard to your other question, "What about secondary airports and the like? Is the availability of ground electric power mainly a function of airport size/importance or not?"

faro, I don't know what criteria determines whether or not an airport has external power available; however, at the airports we serve that do not have external power, yes, those tend to be smaller stations with only a few flights per day.

Just an aside, we do not leave the aircraft with the APU running without either turning over responsibility of the aircraft to the oncoming crew, or to a mechanic. If we overnight at one of the smaller airports without external power available, a mechanic will meet the aircraft (either a company mechanic or a contracted mechanic) to discuss any maintenance discrepancies that need to be corrected overnight and once we turn over responsibility of the aircraft to the mechanic, we depart to our layover hotel and the mechanic will shut down the APU once all the post flight inspections and checklists have been accomplished.

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Dalmd88
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Re: Prevalence of Ground Electric Power Supply

Fri Jun 07, 2019 7:58 pm

If the airport can handle transport category aircraft there is almost always ground electrical power available. If there are no jet ways then there is an FBO that has a ground power electric cart that does 440v. Those carts are everywhere. Now an air start cart could be a little hard to find at a remote field, but is common at any station that has regular air carrier ops.
 
stratclub
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Re: Prevalence of Ground Electric Power Supply

Fri Jun 07, 2019 11:45 pm

Okie wrote:
Starlionblue wrote:
Even with external power, you need the APU for engine start because you need bleed air to power the starter. So the APU is still used, both on engine start and on arrival.


The 787 uses electric starter/alternator which is capable of engine start without APU.
However it has to have at least 2 of the 3 external ground power connections made to provide enough current.
I am not sure if that option is used in normal practice.

Okie

On the 787 3 stingers is preferred, however it will it will start on 2 stinger, however, most electrical aircraft loads will be shed. and only one of the 2 starters will operate. The generators/starters are called VFSG (Variable Frequency Starter Generator)
 
Okie
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Re: Prevalence of Ground Electric Power Supply

Sat Jun 08, 2019 7:22 pm

stratclub wrote:
On the 787 3 stingers is preferred, however it will it will start on 2 stinger, however, most electrical aircraft loads will be shed. and only one of the 2 starters will operate. The generators/starters are called VFSG (Variable Frequency Starter Generator)


Question: how do you know if you are dispatching with or without a MEL'd APU since you would not start it before flight when using Ground Power for engine start?

Okie
 
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AirKevin
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Re: Prevalence of Ground Electric Power Supply

Sat Jun 08, 2019 8:42 pm

Okie wrote:
stratclub wrote:
On the 787 3 stingers is preferred, however it will it will start on 2 stinger, however, most electrical aircraft loads will be shed. and only one of the 2 starters will operate. The generators/starters are called VFSG (Variable Frequency Starter Generator)

Question: how do you know if you are dispatching with or without a MEL'd APU since you would not start it before flight when using Ground Power for engine start?

You'd check the maintenance log as you were getting the flight ready.
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fr8mech
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Re: Prevalence of Ground Electric Power Supply

Sat Jun 08, 2019 8:56 pm

Dalmd88 wrote:
If the airport can handle transport category aircraft there is almost always ground electrical power available. If there are no jet ways then there is an FBO that has a ground power electric cart that does 440v. Those carts are everywhere. Now an air start cart could be a little hard to find at a remote field, but is common at any station that has regular air carrier ops.



440V?

Or, 3 phase, 400hz 110V?

Okie wrote:

Question: how do you know if you are dispatching with or without a MEL'd APU since you would not start it before flight when using Ground Power for engine start?

Okie


An inoperative APU, APU generator to APU air would be listed on the flight dispatch paperwork. If you missed that, then the INOP sticker next to the switch should tip the flight crew off.

Of course, the system can fail at start or during use. In which case, the MEL would be applied and ground elec/air would be used.
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exFWAOONW
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Re: Prevalence of Ground Electric Power Supply

Sun Jun 16, 2019 11:29 pm

I always looked at the flight release for the outbound flight prior to the inbound arrival to see if tha APU was inop. It was a real pita to find out the a/c had no APU at the gate, as the ground power cart was stored way over in the cargo building. We didn’t have an air start cart, but we could borrow an air bottle from another airline. It was good for two JT9 / CFM56 starts. If it didn’t light up in two tries, it was an automatic 30 minute delay to re-charge the bottle and try again.

While I worked there, the jetways did not have ground power. It was all APU. Today, I believe all the jetways have ground power and conditioned air.
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