Cell phone techology is fundamentally flawed when used in flight/altitudes
(even tall buildings).
Problem: there is a limited number of frequencies (or bands) allocated by
the authorities, and must be "resusable" on a grid of "cells" with minimal
overlap from cell to cell.
Cellphone users in flight (or any high altitude) occupy a given "channel"
over potentially hundreds of "cells". Each tower, hearing a strong signal
on that user's channel, no longer considers that channel to be available to
other users: when all the channels are busy, calls can't be made by cell
phone clients, and they can't take calls either, the system is overloaded.
If you juggle the numbers in your head, considering the number of aircraft
in flight -- around any given aircport, times the number of people that
have cell phones (on average) per aircraft, then you see the problem. Out
of six on my row in a recent domestic flight, three of us had cell phones
(that I could see). I leave the math to the reader.
Eric Lifsey
Compliance Manager
National Instruments
"Brent
DeWitt" To: <[email protected]>,
<[email protected] <[email protected]>
etcom.com> cc:
Sent by: Subject: RE: consumer electronics
used on board
owner-emc-pst aircraft
[email protected]
01/25/2001
12:09 PM
Please
respond to
"Brent
DeWitt"
It's conceivable, but the folks at Qualcomm I did base station testing for
seemed to think the problem was real, and they don't make aircraft systems.
-----Original Message-----
From: [email protected] [mailto:[email protected]]On Behalf
Of [email protected]
Sent: Thursday, January 25, 2001 10:26 AM
To: [email protected]
Subject: RE: consumer electronics used on board aircraft
I may regret saying this, but isn't it conceivable that the FCC Rules that
make it illegal to use a cell phone in the air has more to do with the
right
of the airline to sell expensive phone time, than the technical issues? :(
-----Original Message-----
From: Brent DeWitt [mailto:[email protected]]
Sent: Thursday, January 25, 2001 10:08 AM
To: Mike Hopkins; 'Colgan, Chris'; 'Emc-Pstc' (E-mail)
Subject: RE: consumer electronics used on board aircraft
My background is the pretty much the same as Mike's, which is probably why
I
agree with his response. I just wanted to add that the prohibition on cell
phone usage (in the US at least) is not FAA or airline driven, but mandated
by the FCC. The architecture of the cellular system is rather carefully
planned. The placement of antenna sites, coverage and hand-off algorithms
are based on the propagation from land based phones, which is quite
different from a phone in an airliner 25000' feet up. The FCC has
therefore
made it illegal to operate a cell phone after the wheels of the plane leave
the ground.
Regards,
Brent DeWitt
"Takeoffs are optional. Landings are mandatory"
-----Original Message-----
From: [email protected] [mailto:[email protected]]On Behalf
Of Mike Hopkins
Sent: Wednesday, January 24, 2001 11:38 AM
To: 'Colgan, Chris'; 'Emc-Pstc' (E-mail)
Subject: RE: consumer electronics used on board aircraft
As a frequent flyer and private pilot with some knowledge of EMC, I'll
throw
in a few comments:
It is clear to me that consumer electronics can interfere with aircraft
electronics, and I've probably heard all the same horror stories -- DC10
finds itself off course on landing, false engine warnings, interrupted
communications, etc... It isn't clear to me how prevalent this problem is
or
if it happens often enough to be considered a problem. One instance of
electronic interference is enough to have everyone up in arms against the
use of ANY electronics in ANY airplane.
On a 747 flight to the Pacific, I'd bet there are as many as 30 to 40 lap
top computers operating together at some point during the flight.
Additionally, there are probably another 40 to 50 walkman tape players or
CD
players in operation, plus the on-board entertainment systems and a few
in-flight telephones being used. On shorter flights, there may still be a
large number of laptops being used by business people plus tape/CD players
and air phones and the like in use during the flight. I don't think this is
a general problems for aircraft electronics.
HOWEVER; if radio or television receivers or cell phones were allowed, I
believe the level of interference could easily reach the level of being at
least disruptive to aircraft systems if not downright dangerous. I have
personally seen commercial scanners and FM broadcast receivers that will
interfere with voice comms -- 118MHz to 136MHz -- which means they could
certainly interfere with nav equipment operating between 108MHz and 118MHz
(VOR's and ILS's, specifically). I also have a Garmin hand held GPS system
that I cannot find anything that it will interfere with nor have I found
anything that interferes with it (except things getting in the way of the
antenna - Maybe I'm just lucky?).
My sense is the following: Interference with nav stuff is the most likely
--
a VOR indicator off, or something like that. With GPS back-up (or getting
to
be primary) in most aircraft, a faulty Nav indication would likely be
caught
before it was a problem (NOT so if you're on an ILS approach in IMC
(Instrument meteorological conditions) where a faulty indication can run
you
into terrain -- this is why no electronics should be operated on the
aircraft below 10,000 feet on take-off or approach).
I doubt a cell phone caused the Saab to crash -- most airplanes will still
fly even with all electronics blocked out (don't know if the Saab is fly by
wire or not, but I don't think so). Horizontal situation indicators and
gyro's are driven by vacuum and in larger airplanes, there's back-up
vacuum,
red flashlights in the cockpit, etc... Upsetting autopilot controls might
cause the airplane to do something erratic, but that sort of thing should
be
recoverable as long as someone in the cockpit is paying attention.
Enough of that -- need to get back to my real job....
Mike Hopkins
KeyTek
-----Original Message-----
From: Colgan, Chris [mailto:[email protected]]
Sent: Wednesday, January 24, 2001 6:15 AM
To: 'Emc-Pstc' (E-mail)
Subject: consumer electronics used on board aircraft
There is growing concern amongst professional aircrew about the use of
consumer electronics (CD players, mobile phones, hand held GPS etc) on
board
aircraft. Some claim that passenger electronics has definitely interfered
with navigation systems, primary flight displays or engine warning systems.
There are rumours that a mobile phone contributed to the demise of a
Crossair Saab 340 on 10 Jan 2000 killing all passengers and crew. Some
pilots reckon that it is absolute nonsense.
Knowing what you do, about how EM disturbance can affect electronics
equipment, that it is almost impossible to make electronics equipment
completely immune to EM effects, that FCC class B or CE marked equipment
has
not been tested (presumably) with avionics in mind etc, etc, how do you
feel
when the guy next to you on your flight gets his Minidisc player or laptop
out? Remember, when you are descending through a cloud layer, the pilot is
relying solely on electronics receiving equipment to get the aircraft on
the
runway.
Do you think all consumer electronics should be banned from aircraft, that
FCC or CE equipment is okay or that the whole issue is scaremongering
piffle.
Any comments gratefully received, I will post a summary on a professional
pilots forum and let you know that results.
Regards
Chris Colgan
Compliance Engineer
TAG McLaren Audio Ltd
The Summit, Latham Road
Huntingdon, Cambs, PE29 6ZU
*Tel: +44 (0)1480 415 627
*Fax: +44 (0)1480 52159
* Mailto:[email protected]
* http://www.tagmclarenaudio.com
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