why do they ask us to keep our devices on airplane mode on a plane but the WiFi is allowed?
In: Technology
Airplane mode is a joke, but sometimes they can charge you extra for certain WiFi features so…
They ask you to turn your phone signals off because (very) old cell phones used analog signals that interfered with the cockpit instruments. That hasn’t been a problem in a long time but it remains as an artifact of safety. WiFi doesn’t affect the instruments either.
Airplane mode means your cell is not transmitting on the normal frequency band for cell phones. The WiFi band is different and it is being generated by the plane as its own little local VPN.
A cellphone’s cell signal maximum transmission power is 100x stronger than its wifi maximum transmission power.
When you’re up in the air and the cellphone can’t connect to a cell tower it will try transmitting at that maximum power until it finds one.
All those cellphones transmitting at maximum power will cause interference for phone users on the ground and they also take a better safe than sorry approach in terms of interfering with aircraft systems.
The onboard wifi network, requiring much less transmission power, is considered safe. Also something that has already rolled out on some airlines is installing a mini cell tower in the aircraft that phones can connect to. It will tell the phone to use low transmission power modes so there’s no need for airplane mode.
When your cell phone can’t connect to a cell tower, it will switch to increasingly longer range transmission modes until it does. When you’re in the air, this will drain your battery and result in your cell phone “yelling” at the ground below. This is a problem because, while the signal isn’t strong enough to successfully establish a connection with cell towers, it can still act as interference for other radio applications.
TLDR; it drains your battery and creates radio interference below you.
I read an aerospace engineers post once: “We simply can’t test against whatever crazy signal blasting Verizon might figure out next year, so we say no because we’re making planes that have to keep people in the air so we default to the safest option.”
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Every answer so far is not ELI5. The ELI5 answer is money. The airlines can charge you to use WiFi.
It’s largely a holdover from old theories (and maybe possibilities) that cell phones could interfere with communications and/or other instruments. Nowadays it’s also a useful way to get people to pay attention and maybe stow their devices for take off and landing.
It’s not really an FAA (Federal Aviation Administration) problem, as much as it is a FCC (Federal Communications Commission) problem:
When you’re on the ground, your phone is generally equidistant from a handful of cell towers and, at 70 mph, you are switching between them every minute or few minutes.
When you are in the air, your phone is generally equidistant from many, many more cell towers and, at 575 mph, switching between them every few seconds. At that speed, the system doesn’t wanna deal with your shenanigans!
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