BThumme

It really bothers me that something UA advertises has to be requested. This is channel 9 all over again. I just don't want this to ultimately end up being a FA decision on whether or not there is power available.

FTstudent

The thing that puzzles me the most is changing the order of plugging in the individual pieces of my Nexus 7 makes a difference. Everything connected and working on ground power. Then power comes back on at 10,000 and tablet is not charging. Unplug. Light goes green. Plug back in, green light goes off and no charging. So then unplug the cable from tablet. Plug in the adapter to the outlet. Next connect power cable to device, and now it's working. sUA plugs seem more finicky and location is terrible for the plug/unplug game.

WineCountryUA

Part of this is likely the turn-on charging surge of the power adapter. Power adapters when power is first applied look essentially like a short circuit for a short time. Once the AD to DC convertor is "charged up" then the current draw is normal. In a system with a low current level circuit "breaker" (like they are on plane) and fast response, the protection circuit may kick in. Unplug / reconnect will reset the protection circuit and because the power module will stay partially charged, the retry turn-on surge then will be much lower. Might take a couple of tries if not done quickly. The dynamics of this is very depending on the circuit protection and the power module and the device connected.

raehl311

The short answer is that the in-seat power systems are not intended to be used.

Or at least, that's the way they were designed.

The outlets have very low current limits. Go over the limit, they shut off. Things that go over the limit include... pretty much everything.


Your best chance of success is don't try and charge a battery and use a laptop at the same time, and plug in your adapter first and then wait a bit for the capacitors in the adapter to charge up before plugging your adapter into your device.


I also carry a separate power adapter for my laptop that I know maxes out at 65W just for use on airplanes. Usually works, but if my laptop is on, only charges the batter a couple of percent per hour.

WineCountryUA

Never heard of a phone, pad, tablet, e-reader, ..... that would not work. Most laptops also work fine -- but not the high-end large screen performance laptops -- which is not a huge percentage of the market,

For those with 17" workstation level laptops that is a good solution, at least the battery level is maintained and will charge better when idle/closed.

misdirected baggage

I use a 17" high power Laptop for scientific work and only have about 25% success on UA, regardless of aircraft type or cabin. I often find that repeated attempts to plug it in will eventually allow it to "grab" power. Once connected, I'm usually able to stay powered up, although not always. So, my suggestion is to keep trying and you may get powered up. Using a slower charger can help, but not easily compatible with my computer. I rarely have problems with tablet chargers on UA, so it is a pretty low amount of power they dribble out to PAX. Really annoying when I'm trying to work, but better than nothing, I suppose.

phkc070408

When flying EWR-ORD in F on the 737-900 and ORD-PEK on the upper deck of the 747, I was having problems charging my devices. It seams that sometimes, not always, when I plugged my charger into the AC power, the green light would go off, and it would come back on when I pulled it out. It happened more on the second half of both flights. I was only trying to charge my iPad with a 2.1 Amp charger. Thankfully in J they had the USB plug as well. While that did not provide enough power to charge my iPad, it definitely kept it from draining as fast.

Flying home, we will be on the sCO 777-200ER NRT-EWR in Y. We are taking codeshare NQ or NH from CAN to NRT and we only have about two hours on the ground, so I may not get everything fully recharged. We are returning in Y so we won’t have the USB plug.

Are there any tricks or idiosyncrasies with the power that would prevent it from failing halfway through the flight? Is there anything I can do to prevent the green light from turning off when I plug something in? Is there anything the FA’s can do if I have that problem?

Thanks in advanced.

sbm12

Odds are your device is drawing too much power and tripping the internal circuit breaker on the outlet. That's also why the USB plug only gave it enough juice to keep running rather than to also charge.

As for the mid-flight thing, I believe there are groups of outlets on the same circuit in addition to individual overload protection so the issue may have been related to you and your fellow passengers together all drawing too much power.

Richard Chen

Using the USB charging limits the amps (.5A or 1A) to 1/4 or 1/2 of what the wall charger uses thus not tripping the breaker for the circuit.

Kacee

Curious. My Apple MagSafe 2 charger pulls 3.05 amps and I've never experienced this particular problem. The more common issue is the charger won't stay in the socket.

I think it would be more accurate to say that, in the aggregate, the users on the circuit were pulling too much power. A 2 amp pull is not in itself a problem. Also, I recall reading an explanation of how the system works, and my recollection is that calling this a circuit breaker trip is not really an accurate description. It's more like a phased blackout based on aggregate draw.

WineCountryUA

Beside the steady state current value, the other key parameter is the turn-on surge -- the current that is drawn at initial turn-on / plugging in. It is determined by the design and is typically not an issue with normal 15A service but can be in a reduce capacity system like this situation.

phkc070408

So why would UA design a system that is unable to handle the load that one can reasonably expect it to be used at?

Then again, why would they buy a wifi system that can't handle capacity either. I guess I just answered my own question.

$$$$$$$$$$$

physioprof

Is it a trivial engineering issue to provide unlimited power on an airplane? And regardless, UA didn't design the power systems on airplanes. Finally, the reasonable expectations for in-seat power usage on airplanes have changed dramatically since the time most airplane power systems were designed and now.

wto605

The physical plug itself is also "checked" to avoid anything besides an accepted plug type. This system can be particularly finicky with two-pronged adapters and one power is cut it will remain cut until the device is completely removed an reinserted. That may have been your issue, my suggestion would be to grab a something with a ground plug (a good example would be or a short extension cord, although your local hardware store should have it at a much better price).

Actually every power system has almost the exact same design due to the safety regulations (which are a very good idea). Electricity is both the life-blood of complex avionics (and in the case of the 787 used extensively in the flight controls) and of extreme potential danger to the aircraft. Both of those needs come before the outlet under your seat and require complex systems (with very conservative limits) to service.

phkc070408

So you're saying that a system that can provide enough power to power a laptop for 180 (or however many) passengers on a 777 has the ability to bring down an aircraft, and thus the power is rationed to prevent this. I can totally accept this answer.

Now, in the case of the narrow-body aircraft (less 737-900s), that only have power in F and Y+, would there be maybe a little more power available for each user, since fewer people are plugging into the system?

So for a high powered device such as a MacBook Pro, might it be first come first serve? In other words, plug it in as soon as you reach 10,000 feet and keep it plugged in?