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I've seen that airplanes are connected to some wire like in the picture. What is it's name and what is it for?

Danny Beckett
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ButterDog
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4 Answers4

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This is a ground power unit (GPU) which supplies the aircraft with electricity while the generators or the auxiliary power unit (APU) are not running. This is important especially during boarding, when the cabin lighting needs to remain on for passengers to embark or disembark. The GPU is also used to start the APU, which in turn provides electricity to start the engines and the generators.

A ground power unit (GPU) is a vehicle capable of supplying power to aircraft parked on the ground. Ground power units may also be built into the jetway, making it even easier to supply electrical power to aircraft. Many aircraft require 28 V of direct current and 115 V 400 Hz of alternating current. The electric energy is carried from a generator to a connection on the aircraft via 3 phase 4-wire insulated cable capable of handling 261 amps (90 kVA). These connectors are standard for all aircraft, as defined in ISO 6858.
Source: Wikipedia

Related Questions:

Can large airliners be operated without ground support?

How are turbine engines started?

Community
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SentryRaven
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    Nevertheless aircraft often have APU running during boarding, because while GPU provides electricity, it does not provide pressurized air for air-conditioning. – Jan Hudec Nov 14 '14 at 12:55
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    @JanHudec - more often than not, the AC is NOT running during boarding, and the airline apologizes that they can't turn it on until the doors are closed. At least that's been my experience in the US. – Floris Nov 14 '14 at 16:43
  • I am surprised by the use of 400 Hz for the AC. Why such high frequency? – Floris Nov 14 '14 at 16:43
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    @Floris Higher frequency generally means smaller, lighter transformers. – Geobits Nov 14 '14 at 16:47
  • @Geobits - that makes sense. Thanks! – Floris Nov 14 '14 at 16:48
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    @JanHudec It is fairly common to use a source of conditioned air from the ground as well so that the APU isn't running when not necessary. – Lnafziger Nov 15 '14 at 16:27
  • that doesn't look like a GPU, which is a generator on wheels, like so: http://www.weyer.aero/ground-power-units.html . Its just an electrical power hookup, and I don't think falls within the category of GPU – rbp Nov 16 '14 at 17:01
  • @rbp The term GPU does not only refer to generators with wheels. It is also used for mounted systems on jetways and systems let into the surface of the airport. "Some airports, like Tokyo-Haneda, have ground power feeds built right into the surface of the apron." Ref: http://www.airlinereporter.com/2014/07/ramp-operations-whats-going-on-out-there/ – SentryRaven Nov 17 '14 at 09:42
  • @Floris My experience in the U.S. is that A/C is usually running while parked at the gate, but that the A/C is sourced from an A/C unit mounted on the bottom of the jetway and connected to the aircraft with a large air hose. Some of these systems don't seem to be as powerful as the A/C provided by the aircraft A/C packs in normal operation, though. The presence and effectiveness of these systems can vary from one airport to the next, though. – reirab Dec 09 '14 at 15:00
  • @reirab thanks. I have sat in many a hot plane with the announcement that AC won't start until the engines do. In the US. On some very hot days. This is clearly not universal. Unfortunately. – Floris Dec 09 '14 at 15:03
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    @Floris Yes, as I said, it varies from airport to airport. Also, it's possible in some cases that the FAs mean that the aircraft's (significantly more powerful) onboard A/C system can't be started until the door is closed. Especially on particularly hot/sunny days, the external A/C sometimes isn't enough to keep up with the heat, especially with hot air coming in through the open boarding door. – reirab Dec 09 '14 at 15:12
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It provides power to the plane for when the engines and APU are not running while sitting at the gate to save fuel.

It allows the cabin lights to remain on so the passengers aren't tripping over each other as they board.

The power may also be used to start the APU that will in turn provide the power needed to start the main engines.

ratchet freak
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There are two kinds of GPUs:

  1. The ones that are fixed and supply power to the aircraft
  2. The ones which are mobile, which are tugged to the stationary aircraft

The cables are connected by groundcrew before the pilot shuts down all engines. It is different from pilot to pilot. The APU remains on while the aircraft is being serviced.

fooot
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RAYHAN ahmed
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  • The APU remains on. Cargo doors are opened . FMC / belt loader start unloading cargo from airplane. The gbu remains on thoughtout unloading and loading of aircraft.In certain cases the gpu might trip for certain unknown reasons – RAYHAN ahmed Jan 27 '15 at 22:05
  • GPU is the cable you are talking about in your photo. This is called GPU ground fixed unit at a operating aerodrome. – RAYHAN ahmed Jan 27 '15 at 22:07
  • Hello RAYHAN ahmed, welcome to Aviation.SE! To edit your post and add information to it you can use the edit link under your answer. – DeltaLima Jan 27 '15 at 22:10
  • Gbu means GPU my spelling mistake sorry. – RAYHAN ahmed Jan 27 '15 at 22:10
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    @RAYHANahmed Can you please update About Me section describing what you do. If you just reference about it in an answer, not everyone will understand as they may not know about your other question, where you described it. – Farhan Jan 28 '15 at 16:29
  • You will find my question to put to a GPU expert (google) my electrical engineering. – RAYHAN ahmed Jan 29 '15 at 14:49
  • Concerning a PAkistan airlines 777 that we were offloading with non operational APU and a tripping GPU. – RAYHAN ahmed Jan 29 '15 at 14:51
  • I work as a cargo aircraft loader with wide experience loading cargo pallets courier human remains. Animals etc on heavy transport aircraft since July 2002 to date. – RAYHAN ahmed Jan 29 '15 at 14:53
  • To farhan : google the following - my electrical engineering by Steve McFadyen ( what is aircraft ground power) – RAYHAN ahmed Jan 29 '15 at 15:54
  • Then look under ; my electrical. By Steve mafadyen – RAYHAN ahmed Jan 29 '15 at 16:03
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It is ground power unit. Due to the technical difficulty on ground to operate APU, which is the source of power for the aircraft. Aircraft engineers connect GPU.

Sujin
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