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Chock

Powering up a Norwegian 800NG at night

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Posted (edited)

Here's a snap of a Norwegian Boeing 737-800 on stand 9 at EGCC early this morning, about 2am if I recall correctly. Without an air bridge on that stand, we've used mobile stairs front and rear to board people, the GPU is still connected at this point, as passengers board but it went on the APU right after this pic so we disconnected the power moments after this pic was taken, but not before we'd had to offload a bag from the rear hold, which is annoying, but happens, then we pushed it out.

For those of you who use GSX etc and who are curious about the GPU and how all that stuff works. The big yellow box you can see has two lights on it which are illuminated, there are two buttons alongside the lights, there are two more buttons and lights (not illuminated) duplicated to the right on that panel. Large aircraft such as A330s, 777s etc, use both power sources, so you have to plug two connectors in and use all the buttons on that panel, but smaller aircraft such as this 737 only have one socket and only use one connector which is why only the left ones are lit up. To connect the power, there is another panel at the other end of that pantograph, not visible in this shot, that has a swipe card reader on it which you swipe with a security card, this enables the power and will allow you to alter the voltages the GPU delivers. Power being available is shown on the panel on the GPU by the upper left light illuminating to indicate it is available. You can't make it out in this shot, but that light is amber.

Most jets use 115v, but some little regional props use 28v, so you can select a suitable voltage depending on the plane. When you've swiped the main panel and unlocked it to get power running, you plug the cable into the aeroplane (the plug has numerous female sockets on it, some of which are different sizes, so it  can only go in the correct way, it is very heavy and so you also clip a strap to a ring inside the aeroplane's access panel recess, to support the weight of the plug and cable). When it's all connected up, then you press the lower of those two buttons you can see on that panel to start the power, that light is green, the upper button cuts the power, so the two lights you can see are indicating power is available and is being supplied.

After it's all connected, you give the crew a hand signal to confirm they have ground power although they usually know because there is a light on their overhead which illuminates, however, it's only when we've confirmed all is good that they will rely on it because the plugs can be a bit of a faff to connect and because they are heavy, they can sometimes fall out if not secured properly, so we'd only give them the okay signal when we knew it wasn't gonna do that, otherwise they might shut off the APU and then not have any power at all.

At that time in the morning, there are few departures, mostly it is stuff coming in and being unloaded only, then left on the stands for a few hours ready for morning flights at which point they are loaded, so I heard this 737 on the radio in the pushback truck as we drove to another stand to sort out another aircraft making it to the runway and getting clearance to go very quickly owing to the lack of movements to the runway at that time.

The yellow extendable pantograph for the GPU which you can see in that pic is a right pain in the @ss incidentally, the wheels are supposed to castor freely, and they do on most of them, but not on that one at stand 9, it takes a real effort to move it lol. The other wires you can see coming out of the access panel below the cockpit, where the GPU is plugged in, are the headsets, which were on a spitter allowing two pairs of headphones to be connected because someone was training on doing the headsets for pushback. The forward starboard door had not long since been closed, it having had an elevator up to it for a few passengers who were unable to use the stairs.

The nice thing about a 737 is that it is small and low to the ground, unlike its rival the A320, so all of that plugging stuff in and opening panels etc can be done without stretching to reach things. Like many NGs, this particular 737 has a powered 'magic carpet' moving floor in the rear hold to help with loading bags, meaning you can stack a row of bags up against the bulkhead as they come up the elevator, then move that bulkhead back, with the floor and the bags, stack again, repeat etc. without that equipment, you'd need two people in the rear hold, one at the cargo door chucking bags to someone further in the hold, who then stacks them.

dVfBsiG.jpg

 

Edited by Chock
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Alan, what is that GPU attached to? The ones we used on the remote stands were pulled around by a tug. That one almost looks like it is attached to a jetway.

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Posted (edited)

We do have mobile GPU trucks, but rarely use them unless there is a problem. Most stands have GPUs which are plumbed into the airport's power and look like that one in the pic.

The little steel framed cage you see in the pic which has the electrical panel and which the power cable is coming from is mounted on four castoring wheels so you can move it near the aeroplane as we have done. It  is attached to an extendable pantograph which you see coming toward you in the pic, the pantograph sections have castoring wheels, so you can extend it a long way out onto the ramp without a big cable dragging along the ground because the cable which the unit takes power through runs back along inside the pantograph's box sections (you can see part of that cable covered in red insulation material at the lower right of the pic where one of the pantograph's hinged sections is). That power cable goes to a junction box where the power can be turned on and off and different voltages selected etc, and that goes into the airport's main power supply.

 

Edited by Chock
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Thanks for the explanation. It makes sense now.

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