<br>

The air-hostess voice came over the public address system in a pre-flight announcement.

>"Ladies and Gentlemen, welcome to Flight P47428 heading to Abuja Nigeria. We are the second in line to take off, and we will be airborne in ten minutes time. We ask you to fasten your seatbelts secure all baggage in the overhead compartments and under your seat. Please **turn off all personal electronic devices including cell phones and laptops**. Thank you for choosing AirPeace Airlines."
<br>

![airplane-seats-2570438_1280.jpg](https://steemitimages.com/DQmShQLSK3V9XdBZEtVjDjVdmtrqtjMctF8GTAbHFUSdpeB/airplane-seats-2570438_1280.jpg)
<sup>[Pixabay Image][Source](https://pixabay.com/en/airplane-seats-airplane-flight-2570438/)</sup>

<br>
The idea that streaming the *Black Panther* movies with the little 5.5-inch phone while onboard will bring down the Boeing 737 with its 140 plus passengers will always make one to ask more questions.

Who made these laws and for what purpose?

We will have to walk down the memory lane. In 1991 the Federal Communication Commision (FCC), the agency responsible for the regulation of communications by radio, satellite, tv, cable, etc. banned the use of cellphones and other wireless devices. This ban was because of fear of wireless interference on the aircrafts'  electronic (avionics). 

The radiowaves emissions from a cell phone may have an impact on the critical radio transmission between the ground networks ( the communication with air traffic controller and the pilot). The interface is crucial for pilot's navigation (to avoid running into thunderstorms), get landing clearing, and for taking off instructions.

Some airlines may allow you use the phone in the "airplane mode", which shuts down phone transmissions,  others may insist on turning it off.

Failure to obey this instruction may get you [arrested](https://avherald.com/h?article=44285066&opt=0) like a passenger flying in from Phoenix Arizona to El Paso in Texas, both in the USA, on September 5th, 2011.

The process is not just for the ordinary traveller as Alec Baldwin learnt. The [30 Rock](https://www.nbc.com/30-rock/) TV celebrity found out in  2011 when he got [kicked off the plane](https://nypost.com/2011/12/06/alec-baldwin-thrown-off-aa-flight-at-lax-for-playing-game-on-phone/) for refusing to turn off his iPhone as he was [playing the game *Words with Friends*](https://twitter.com/#!/AlecBaldwin/status/144174648920260608). 

The proliferation of electronics especially handheld devices (DVD players, audio players, etc.) which many passengers are wont to take on with them on a flight, is now a new concern for the aviation safety sector.

Even though these devices may not transmit data over the air, there is a possibility they emit dangerous interfering signals which may likely meddle with the aeroplane's electronics such as its GPS (positioning system electronics).







<br>

##### But do cell phones pose such danger to the flight?
<br>



<div class="pull-right"><center><img src="https://steemitimages.com/DQmWJpmV4isjvcnsvuWFdo6LuPjGQi1oEceUqfmd7m9P9j6/mobile-phone-2558523_1280.png" /><br/><em><sup><sup><a href="https://pixabay.com/en/mobile-phone-turn-off-your-cell-phone-2558523/">Pixabay Image</a></sup></sup></em></center></div>
The cell phones are capable of long-distance communication and so is its likely interference on the airplane's ground network and navigation.

But cell phone's are not the only culprit. In 1999, a DVD player caused an instrument in the cockpit to indicate the plane was facing the opposite direction as it was in reality facing. 


This claim may appear to be rare, but NASA's report gotten from different incidences of the portable electronic device causing anomalies in flight electronics show it may not be that rare. It shows out of 130 occurrences of aircraft affected system, between 1986 to 1999, 112 affected the navigation system of the aircraft.

The report could be seen on page 16, Table 10 of this 2001 report: [Personal Electronic Devices and Their
Interference With Aircraft Systems](https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20010066904.pdf).

But some school of thought have it that the modern aviation electronics are more interference-resistant compared to the old system avionics.

<br>

#### Guilt by Radiation?

<br>



<div class="pull-left"><center><img src="https://steemitimages.com/DQmUGSPr7hfDXTc4QRa7twcYBRRiAStKfeqg4XPmDJ13BTv/image.png" /><br/><em><sup><sup><a href="https://commons.wikimedia.org/wiki/File:Wifi.svg">Wikipedia CC BY-SA 3.0 authored by RRZEicons</a></sup></sup></em></center></div>

The electromagnetic interference (EMI) is the culprit here.

The PEDs were operating frequencies ranges for some kilohertz in AM radios to about 400 MHz for personal computers. If the harmonics of these frequencies are taken into account, the result is a frequency which covers the [entire range of both the aviation communication and navigation frequencies](https://www.iata.org/whatwedo/ops-infra/air-traffic-management/PublishingImages/Pages/radio-spectrum/aviation-usages-of-frequency-spectrum.pdf). The harmonics are the reoccurring multiple of an original wave pattern (fundamental frequency). 
<hr>

Frequency|Aviation use
---|:---|
10-14KHz|To determine aircraft position using ground-based transmitters
108-118 MHz| Used for navigation
328-335 MHz|Controls the glidescope system used in landings
1GHz and above|Distance Measuring Equipment (DME) checks distance between aircraft and ground-based transponders
Still in 1GHz upwards freq range|Collision avoidance, global position system, weather rather functions, etc


That implies when the radiated EMI are all taken into view, the electronic equipment aboard both commercial and military airplane is very likely at risk.



>PED interference can be established via the antennas which are mounted on the fuselage and support different types of communication. Electromagnetic fields radiated by PEDs can be transmitted to the exterior of an aircraft through the fuselage apertures (windows). Furthermore, these RF fields can be received by communication or navigation-related antennas mounted on the skin of the fuselage. [Source](https://www.researchgate.net/publication/3056579_HIRF_penetration_and_PED_coupling_analysis_for_scaled_fuselage_models_using_a_hybrid_subgrid_FDTD22FDTD24_method).


<br>

#### The shielding problem

<br>

<div class="pull-left"><center><img src="https://steemitimages.com/DQmenRKbZeWfog2ZCDvhx2fMf2kdo9MRdnotEY2eRfdwY4K/image.png" /><br/><em><sup><sup><a href="https://commons.wikimedia.org/wiki/File:Wifi.svg">Free image from the U.S. Air Force photo by Christopher Okula: Aircraft avionics being tested at an controlled electromagnetic environment shielded against radio frequency interference </a></sup></sup></em></center></div>

Sometimes the wires from the antennas to the receivers pass through the aircraft's fuselage section following the inside of the aircraft skin (which is often less than a meter from a PED-wielding passenger).

The thin sheet fibreglass or other non-conducting material that is the shielding material offers little or no shielding between a PED EMI and the wiring.

Though the wires critical to the navigation are well shielded, most interference from portable emitting devices is often due to radiation that is picked up by the antennas.

Shielding also degrades over time; aluminium oxidises rapidly in air, this reduces its effectiveness as a proper shielding is dependent on a good grounding. That is, once the ground is not sufficient, the electrical resistance connection to ground increases.

A shield in mint condition is also susceptible to interference which can affect the aircraft's navigation or communication's systems.

The aluminium skin of the aircraft offers an outstanding amount of shielding, the holes on it in the form of windows provides a great escape route for radiation.

<br>

#### A More Modern Approach

<br>

Modern aeroplanes are said to be more hardened or immune to electromagnetic interference. This improvement prompted for a relaxed rule on the use of PEDs in some flights in the USA following the [2013 FAA upgraded rules](https://edition.cnn.com/2013/10/31/travel/faa-portable-electronic-devices/index.html).


The new rules made it possible for the use of particular PED (non-transmitting device) at below 10,000 feet. Before, you are only allowed to watch already downloaded games, movies, etc. without connecting to the internet at *above* 10,000 feet.

So you can only use the allowed devices at **airplane mode** at below 10,000 feet.



While many argued that the use of cell phone is much safer now with modern aircraft and its resistance to interference and wants to be allowed to make voice calls, Federal Communications Commission (FCC) Chairman [Ajit Pai](https://en.wikipedia.org/wiki/Ajit_Pai) issued this statement dashing all hopes of that ever happening in April 2017.

>“I stand with airline pilots, flight attendants, and America’s flying public against the FCC’s ill-conceived 2013 plan to allow people to make cellphone calls on planes. I do not believe that moving forward with this plan is in the public interest. Taking it off the table permanently will be a victory for Americans across the country who, like me, value a moment of quiet at 30,000 feet.” <sup>[FCC](https://apps.fcc.gov/edocs_public/attachmatch/DOC-344324A1.pdf)</sup>

So, assuming it is all *safe* to make a phone call, I bet some passengers will like to have a quiet sleep without someone making an annoying call all through the 2 hours or more flight that you are forced to sit beside them :)


<sup>**References**</sup>

* <sup>[NASA:Personal Electronic Devices and Their
Interference With Aircraft Systems](https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20010066904.pdf)</sup>
* <sup>[FAA Regulation on PED Ban](https://www.faa.gov/news/fact_sheets/news_story.cfm?newsId=14774)</sup>
* <sup>[Aviation Frequency Spectrum and its Uses](https://www.iata.org/whatwedo/ops-infra/air-traffic-management/PublishingImages/Pages/radio-spectrum/aviation-usages-of-frequency-spectrum.pdf)</sup>
* <sup>[Boeing on Interference from Electronic Device](http://www.boeing.com/commercial/aeromagazine/aero_10/interfere_textonly.html)</sup>
* <sup>[IEEE Spectrum article "Do Portable Electronics Endanger Flight?" by Tekla S. Perry and Linda Geppert](http://ieeexplore.ieee.org/document/535255/)</sup>
* <sup>[FAA Allow Some PED Use at Below 10,000 Feet](https://edition.cnn.com/2013/10/31/travel/faa-portable-electronic-devices/index.html)</sup>

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