why do they forbid use of cellphone in airplanes ?

Question

if there was the slightest chance of causing a crash, they wouldn't let them onboard at all. After all, there are always several people who forget to turn their phones off.

Answer 1

Officially, AC 91.21-1B covers this subject.

Here is tha answer directly from the text of that document:

7. CELLULAR & ONBOARD TELEPHONE SYSTEMS.
a. T-PEDs have considerations in addition to those listed in paragraph 6. These include cellular telephones, citizens band radios, remote control devices, computers with wireless network capabilities, and other wireless-enabled devices such as PDAs, etc. The Federal Communications Commission (FCC) currently prohibits the use of cell phones while airborne. Its primary concern is that a cell phone, used while airborne, would have a much greater transmitting range than a land mobile unit. Their use could result in unwanted interference to transmissions at other cell locations since the system uses the same frequency several times within a market or given operating area. Since a cell phone is capable of operating on various cellular frequencies, unwanted interference may also affect cellular systems in adjacent markets or operating areas.

b. The FAA supports this airborne restriction for other reasons of potential interference to aircraft systems and equipment. Currently, the FAA does not prohibit the use of certain cell phones in aircraft while on the ground. An example might be their use at the gate or during an extended wait on the ground while awaiting a gate, when specifically authorized by the operator. A cell phone will not be authorized for use while the aircraft is being taxied for departure after leaving the gate. The unit will be turned off and properly stowed to prepare the aircraft for takeoff as per the operator’s procedures. Whatever procedures an operator elects to adopt should be clearly spelled out in oral briefings prior to departure or by written material provided to each passenger.

Answer 2

There has been speculation that any electronic device in use may interfere with the electronics in the airplane. Whether it has been demonstrated or not, the airlines or the FAA are not the rulemakers to consider. The Federal Communications Commission regulates cell phone use and they say it is illegal. The cell phone antenna will be higher than all land repeaters and tie up one channel on every tower in range.

Answer 3

I believe the fear is that if someone is actually making a call, that transmission may interfere with the plane's electronics, avionics, navigation systems, etc. Not just air-to-ground communications, but also the on-board systems. If someone's phone is left on, all that happens is that their phone rings if somebody calls them. It's when they answer, or call out, and actually start transmitting that the problems start cropping up. Or so the theory goes. There's also a theory that cell phones can cause an explosion while you're filling your car with gas. So let that be a lesson to you. Don't make a call while they're topping off the tanks on your airplane!

Answer 4

Because the cell phone signals can interfere with the plane's navigation system. This only happens if someone receives/sends a call/txt, not just by the phone being on.

Answer 5

They dont forbid them altogether if im correct, they just tell you to turn them off during takeoff and landing, from the old rumour "it interferes with the RADAR", not actually saying the RADAR is completely useless if a single person is using a phone or iPod on the plane, but something about them makes it less reliable. Presumably they dont want to take them off of everyone if they're on an 8 hour flight, especially if the in flight entertainment is down, but as you say if there was the slightest chance of a crash they wouldnt let them on.

Answer 6

It is possible for them to interfere with the controls, As a flight attendant , they also want you to use the phone onboard so they can make mega bucks!

Answer 7

There is no good reason. Cell phones do not bother cockpit avionics. The executives that I fly are constantly on their phones during takeoff and landing and I ain't about to tell them to hang up. I've probably done a thousand takeoffs and landings with cell phones going in the back with no problems whatsoever.

Answer 8

Good question, considering that the use of cell phones probably saved Congress on 9/11!

Answer 9

RGTIII has it, exactly. In plain English, the cell phone, when used on the ground, can contact a small number of towers; from the air, it can tie up literally hundreds, quickly overloading the system.

note: As for "interfering with the aircraft's navigation," that's largely a red herring, used for all kinds of lies the airlines and Homeland Security tell you (like listening on a handheld pilot's radio, which I used to do, would mess with navigation -- it's anFAA-approved, official radio, for Pete's sake; pilots use them in the cockpits!).

Answer 10

It's just a precaution that airlines take. It's just like not using your cell phone at a gas station.