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Working Theory In Jet Crash: IPhone In Cockpit Is To Blame (appleinsider.com)
Apple Insider reports:
Apple on Friday said that it's open to cooperation with French authorities, who are exploring the possibility that two of the company's devices were linked to the crash of EgyptAir Flight 804 in 2016. The flight's first officer may have plugged an iPhone 6s and an iPad mini 4 into the wrong socket in the jet's cockpit, French officials told Le Parisien. That may have triggered runaway heat, in turn sparking a fire.
At the moment, the investigation is being helped by an engineer from the French National Center for Scientific Research, as well as two people fron the French defense ministry, including a physics professor and an engineer specializing in batteries. Results from the investigation should be submitted by Sept. 30. Apple told the Parisien that it wasn't aware of evidence linking its devices to the EgyptAir disaster.
At the moment, the investigation is being helped by an engineer from the French National Center for Scientific Research, as well as two people fron the French defense ministry, including a physics professor and an engineer specializing in batteries. Results from the investigation should be submitted by Sept. 30. Apple told the Parisien that it wasn't aware of evidence linking its devices to the EgyptAir disaster.
I don't know if this is the case in the Airbus A320, but in smaller aircraft (including GA airplanes) there often is a power port that looks like the cigarette lighter port in many cars. They easily fit USB car chargers such as this one. (For years I used an earlier generation of this very adapter in a Cessna 172 to power my iPad.)
The problem is, unlike in a car where the power port is always around 12-14 volts, the voltage in aircraft has (to the best of my knowledge) never been standardized. I've heard of airplanes which pump out up to 28 volts (instead of 12-14 volts), which is why if you are not certain of the airplane you're flying in, you need a specialized adapter such as this one.
Since so many aircraft have power ports at 12 volts, many pilots I know simply buy a car power adapter. But if you plug it into a 24 volt power port (and the ports are often unmarked: the only way to tell is to crack open the airplane's POH), you're going to have a bad time.
There have been standards in place for quite some time now governing the power capacity of USB ports. (https://en.wikipedia.org/wiki/USB#Power)
Sorry this is a bit of a long-winded explanation but it's all stuff you have to know to understand the issue.
The iPhone is somewhat "notorious" for refusing to charge off a port that doesn't communicate the amount of current it is allowed to draw. ("you cannot charge form this device" popup of some sort, I don't recall the exact message you get) This caused frustration from some who bought cheap car and wall adapters and found their iPhone wouldn't charge from them, despite other phones charging fine. To Apple's credit, this was the correct and (fire) safe behavior. Devices that just continue blindly and overheat themselves or other accessories are just plain poor design, but should still not be capable of posing a hazard in the charger.
Voltage (5v in this case) is supplied "on supply", in other words the power source dictates the voltage and the accessory needs to be capable of handling it. Accessories that can't tolerate how high the voltage is will probably be damaged by it, and could pose an overheat/fire hazard. Since all USB are supposed to run at 5v, voltage is not an issue because USB supplies and accessories all expect 5v.
Current on the other hand, is supplied on demand, meaning the accessory decides how much power to draw from the supply. If it draws too much again there is an overheat/fire risk, but this time from the supply not the accessory. Power (in the form of current, where power = voltage x current) overdraw has become an important consideration with USB now that it's become something of the de-facto battery charging standard. Larger devices (like bigger cell phones and especially tablets like iPads) can "quick charge" their large batteries by drawing more current at 5v. But the supply needs to be capable of safely delivering the higher power. The USB spec says to use DC drop resistors on the D+ and D- data lines to communicate fixed values that the accessory can look up in a table to determine how much power the supply claims it can safely deliver. These resistors aren't necessary to USB data function and can be omitted but then the accessory has no way of knowing how much power it can safely draw. It should then default to the "bare minimum" of 25mA of current, which would charge most modern devices very slowly. (or like the iPhone, just flat out refuse to charge at all) This is enough power though to operate unpowered accessories like mice and keyboards. Some larger accessories (like tablets and battery banks) can adjust the amount of power they draw to suit the maximum specified by the supply. An iphone can charge at either 500mA or 1000mA, for example, depending on the charger it's attached to. Again it's very important to understand the amount of power being drawn by the accessory is entirely determined BY the accessory. The phone is charging at 500mA NOT because that's how much the charger physical can provide, but because it has TOLD the phone how much it can safely provide and the PHONE is only demanding 500mA form it at as result.
If the phone wants 1000mA and the charger is telling it that it can only safely supply 500mA, but the phone just ignores that and tries to draw 1000mA, the charger's acceptable responses are both limited and well-defined. Quality chargers will simply detect the overdraw and stop providing power, and your phone will probably go into charge for a fraction of a second and then immediately stop charging. You might ask yourself "why doesn't the charger just refuse to provide more power than it can safely manager?" Power = Voltage x Current. To keep Power constant (at 500mA) when the device has rigged current it is drawing so that it will get 1000mA, it COULD cut the voltage in half since it has control over that. BUT that violates USB standards. They specifically say you can't do that, your only response is to TURN OFF the supply of power entirely. The accessor
I work for the Department of Redundancy Department.
Indeed, laptops and iDevices charge just fine from the 110 V 400 Hz outlet on the circuit breaker panel behind the first officer's seat. I don't know why anyone thought it was a good idea to shape it like a standard American power outlet given the totally different frequency, but I've seen quite a few colleagues use it and have also used it myself on the ground on occasion. It's unlikely to have anything to do with the fire. The only reason they're investigating it is because they've seen camera footage of the plane parked at the gate with the first officer's iPhone and iPad lying on the glareshield (not even charging). They just have to rule out any cause, no matter how unlikely.
Just responding to several replies to my previous post all at once here.
Unless the USB ports were following the very first standard (back when peripherals were only allowed to draw a piddly 100mA) they still should be watching the current and kill power if there's an overdraw. Age is not an excuse for unsafe behavior since it's always been specified how you should handle overdraw. by the accessory.
Part of the story here is those drop-resistors. People ask "why can't the charger and the device communicate two-way?" The answer is those resistors. It costs money to build in communications, not a lot but china's cheap. If you want a cheap charger, 5 cents in resistors beats a buck in an IC and 6 other support components. And back when USB came out, prices were a lot higher. So the chargers just set the voltage and are supposed to shut down if the accessory ignores them and overdraws. But again, that's added cost and China won't support that. They'd much rather overspec on the package and overheat in your cigarette lighter jack. You're more than likely to just fry it after a few weeks of overdrawing abuse, in which case you'll just go buy another one, and that's precisely what they want anyway, so don't expect that to change anytime soon. Ignoring the standard is in their best interest.
Yeah.... "firebugs". Do not use them. Ignoring the maximum power rating on your charger is like sticking your fingers in your ears and humming when someone warns you not to do something dangerous. So unless you're trying for a Darwin Award, don't use those. If you insist, then for the love of god don't leave it charging unattended! There's a real risk you'll set your car on fire while you're getting groceries or something.
Your electronics background should help here. If a device is setting its load to draw a certain power, and your supply can't manage that much current, dropping the voltage is the opposite of what you ought to be doing to maintain power. It's a bit of a paradox problem. "The only winning move is not to play". Shut off. Dropping the voltage will cause most good phones to stop charging. Then the charger rebounds voltage since the load disappears. Then a few seconds later the phone starts charging again. Rinse and repeat. I think most of us have seen a phone do that, chirp chirp chirp chirp, as it continuously bounces between "charging" and "not charging". In case you haven't ran into that, the phone doesn't actually get charged, it's just super annoying for anyone nearby that has to listen to it. So please don't design a power supply that does this, it only helps if you're a cheap power bank that doesn't care but yet somehow has a buck-down regulator that can still operate at voltages approaching the load voltage (typically 3.7v)
3.7 volts is incredibly common right now in devices. Here's a nice primer for the new arrivals: http://www.instructables.com/i...
Pretty much every cell phone on the planet uses a flat lipo pack since they're currently the best price point for storage-density. Modern semiconductors tend to be made for lower voltages, so this is fine. A li
I work for the Department of Redundancy Department.