said by patcat88:Come on, any aircraft engineer who didn't RF shield the plane's circuit boards would be doing prison time right now.
Wow, there are a lot of people who think they are RF engineers today.
The problem is not shielding of circuit boards. It's whether an errant transmission blocks reception by a navigation radio.
All digital electronic devices emit RF. A digital device has an internal clock, that may be anything from 1 MHz to 1 GHz or higher. That generates RF, albeit at a much lower level than devices designed to transmit. To quote Montgomery Scott: you can't change the laws of physics.
In addition, even if you aren't transmitting, a RECEIVER can transmit RF. Look up "superheterodyne receiver" on Wikipedia, and read the section on local oscillator radiation.
You can design the device to shield RF emissions. But, it is difficult to completely seal it unless it is a metal box with no buttons, plugs, etc. The best you can do is reduce it as low as possible. That what FCC class B certification is about: it has to be below a certain level, but that level is not zero.
Oh, and it gets worse: two transmitters in close proximity on different frequencies can generate a transmission on a THIRD frequency. This is known as inter-modulation. Since modern electronic devices change their clock frequencies regularly (mostly to conserve power when they are idle), you can see how it's really hard to predict what will happen when a bunch of them are in close proximity to each other.
However, that's only the transmission side of the issue. The next inevitable question is: why don't the aircraft receivers reject these unwanted signals? Aircraft navigation and communications use several different frequency bands. On any given flight, the pilots will be switching frequencies many times. And depending on the phase of the flight, the signals being received may be relatively weak, and more susceptible to interference.
All it takes is for an electronic device to inadvertently transmit on the same frequency an aircraft receiver is receiving, and you'll have interference. Some of the navigation radios work by measuring the phase of a received signal, so it doesn't take much to mess them up. Once again, it is the laws of physics. A very low power transmitter on the plane can block receipt of a signal from a much more powerful transmitter far away.
Fortunately, the instruments usually indicate when there is interference, and pilots are trained to switch to alternate means of navigation. So, one outage is not going to cause an accident. But, accidents are rarely caused by a single event -- it's a chain of events. A communication or radio outage caused by interference can be a distraction, and become the first or subsequent event in a chain that leads to an accident.
However, after writing all that, I agree with a previous poster: modern electronic devices are mostly well-shielded, and unlikely to emit enough RF to block aircraft radio reception unless they are damaged. But, it hasn't always been like that, even as recently as the past decade.