why are we ask to turn off cell phones when landing or takeing in a airplane?

Question

i heard it interferes with the navigational instruments is this true and why

Answer 1

Because this a throw back to years and years ago when cell phones were much more powerful and the avionics, antennas, and wiring where not a sophisticated as they are today in the ability to filter and shield spurious signals. Also cell phone towers on the ground were not as sophisticated and worked on what is called line of sight - so on the ground you may only be withing "line of sight" to one or two towers - when airborne you could be in "line of sight" of dozens or even hundreds of cell towers and in the early days could trip all of these towers off at once. Technology has evolved though that now filters this. Modern cell phones only operate at .5 watt at in the 8-900 MHZ frequency but at one time were up to 3 watts. Aircraft communications is 118-150 mhz at about 25 watts, Aircraft navigation radios work in 108-118 mhz, and radar transponders work at over 1000mhz - so since they all work at different frequencies there is no conflicts possible. If there were conflicts between these different frequencies the pilot couldn't use the communications, navigation, and radar transponders at the same time - and they do. The FAA has taken a better safe than sorry approach by banning in flight use.

Answer 2

Supposedly the cell phone frequency is close to the transponder/DME (distance measuring equipment) on the aircraft. The transponder which returns the radar signal to Air Traffic Controll and the DME are already linked together with a supression cable because they are both on a very close frequency range and cant opperate simultaniously. Therefore, the FAA found it necessary to make the regulation banning cell phones on any flight flying under Instrument Flight Rules (in bad weather or above 18000 feet I.E. commercial airliners) because they dont want the cell phone signal to give the pilots false readings on their DME or provide a loss of transponder communication to ATC. If you are flying in a friends small aircraft for example, you can use your cell phone if you feel like it if it gets reception (I know because I am a pilot and many a time I have been at oh about 5-6000 feet and called my girlfriend). It is unlikely now a days however that any signal can interfere with any aircraft navigational system because they are so redundant such as GPS and INS. Also even if you wanted to make a call it is sure unlikely that you will get a cell phone signal at 35,000 feet!

Answer 3

Nonsense.
The possibility of interference from even a full plane of people using their cell phones at the same time is extremely low, nearly impossible. Consider this: several airlines now offer wireless internet service (802.11b/g) ON their airplanes while in flight, bathing the entire airplane in a variety of radio frequencies that are even more problematic (and closer in frequency) than that of cell phones -- and that's not a problem. If cell phone transmissions were a problem, planes would drop out of the sky every time they got within 500 feet of the ground, as they pass over dozens of high-power cell stations.

Part of the real reason is fear, and part is lobbying by both the airlines and the phone companies so you can only use the "seat phones" built into the planes, which charge exhorbitant rates and make big profits for phone and airline companies.

Answer 4

Everyone that thinks this is a myth is WRONG. I have personally experienced abnormalities due to a cell phone accidentally being left on. The abnormalities occur when the phone is sending or receiving a call. The interference affected both communication and navigation. The chances of this happening are very small, but with the number of phones, blackberries,pda's, etc. sooner or later it will affect a given flight.

Answer 5

This is one of the most widely held myths in aviation. The poster who quoted the FAA policy correctly identified the "POTENTIAL" for interference. If it can't conclusively be proven to be zero risk (generally impossible to do) the FAA leans on the term "potential" to bar lots of conduct aboard aircraft. The FAA doesn't bar it, by the way, but allows the airlines to do so based on the "potential" for interference.

In the early days of aviation, there was a risk with unauthroized transmitters interfering with aircraft communications. Later it was proven that under extremely tightly controlled circumstances that radio receiving equipment COULD interfere with aircraft navigation equipment. Basically, if you had a television set well up in the tail section, slight deviation was measureable on a very few aircraft. The ban on transmitting and receiving equipment was a knee-jerk reaction to this interference.

The truth is that cell phones operate on frequencies FAR removed from the ones used for aviation communication and navigation. Further, nearly all of these systems are essentially impervious to RF interference from consumer equipment.

The dirtly little secret with cell phones is two-fold. First of all, above about 5,000 feet AGL, they won't work anyway due to the way that the cell phone tower signals a propogated, for ground based cell phones. Also, at speed, cell phones move from tower to tower so quickly that the cell phone system can't get a lock. The second issue is competition with the hideously expensive and largely failed Airphone system. Blocking other communication methods would guarantee them a regular income stream, at least they thought. But they priced them beyond the means of the average traveler and have largely been removed from most aircraft.

Another issue is that the industry is working with cell phone providers to make it possible to use cell phones on board aircraft in flight. This would probably require either a satellite or ground based relay system to be installed on the aircraft. Once they get the technology worked out, look for it to become an option. Also look for significant extra use charges to be imposed either on a per-minute or per-flight basis. This IS coming and will likely be available within the next 3 - 5 years. All of a sudden, it will be revealed that there really is no interference -- once they have figured out a way to extract money from the consumer, of course.

By the way, look here to see the Mythbusters result. NOT what a previous poster claimed!! http://www.tv.com/mythbusters/cell-phones-on-planes/episode/661128/recap.html BUSTED!!

Answer 6

well its does interfere with there navigator while landing and taking off.
when a plane is trying to land the runway,there is a signal device at the end of ar unway which gives the plane signal (that's the navigation),that at what level the plane is n how much is the distance of the runway is. if this is disturb by the cellphones the plane may land before the runway starts and cause the damage to the wheels or in middle of the runway causing the damage to any stucture ahead after few km. or it will skit on the runway.for the safety of the passenger,staff and the planes too.so switch off the cellphone.

Answer 7

Cell Phones were not allowed to be used inside airplanes because the cell phone signals causes interference to the Radar signals.The Radar signals used for communication between the Pilot and the air traffic control room and the cell phone signals travel almost at same frequency and they cause the interference.

Answer 8

"Currently, cell phone users generally are permitted to use their phones before takeoff and after landing. FCC rules currently ban cell phone use after a plane has taken off because of potential interference to cellular phone networks on the ground. In addition, the Federal Aviation Administration (FAA) has rules prohibiting in-flight cell phone use because of potential interference to navigation and aircraft systems."

Answer 9

Not only does it interfere with the navigational systems, it also interferes with communication with the airport base. Just like when you try to use your home phone next to the cell phone, it screws up the frequencies and makes it harder to communicate.

Answer 10

There is a small possibility of it interfering with some navigational/radar equipment. With all the model cellphones out the FAA is playing it safe because they can't test each model of phone, and even if they did, I wouldn't want to be a crew that remembers which ones are OK and which aren't. Plus with testing one model would carry a R&D (Research and Development) price tag into the millions depending on the plane.
I'd rather the FAA kept it safe and continues to ban all usage.