9/11 & a current captain with a major international airline.Mon Apr 2, 2007 16:04
-------- Original Message --------
Subject: A captain, on Cell Phones
Date: Mon, 02 Apr 2007 13:47:59 -0700
From: Nila Sagadevan email@example.com
To: 911 Research firstname.lastname@example.org
Submitted by a friend who’s a current captain with a major international airline...
Perhaps I can shed a little light on at least one aspect of this issue
from a pilot's perspective. That being the primary reason that
cellphones are prohibited on aircraft to my understanding is that the
radio frequency effects on aircraft systems is unknown. To approve a
radio transmitter for use on an aircraft, especially an airliner,
requires that that specific device be tested for potential adverse
effects against the entire fleet of aircraft it could be used on. That
process would probably take a couple of years. Are you still using a 2
year old cell phone. Most people upgrade every couple of years. By the
time the testing is done, the phone is obsolete.
I have only heard of a few cases where cell-phones have caused problems.
1. An old DC-3 Freight plane was on approach to Spokane Washington in
bad weather. He crashed off course to one side of the runway, and if I
remember he hit a hangar on the field. Cell phone records showed that he
was on his cell phone during the approach. The question is whether the
cell phone affected his navigation system or if he was simply distracted
by trying to fly and talk on the phone. That was a very early Analog
navigation system and probably totally unshielded to EMF.
I have heard that on a couple of occasions there were problems with the
pressurization systems on earlier jetliners that the pilots were not
able to control until a flight attendant noticed a passenger on a cell
phone, and had them turn it off.
Since that time, several things have happened:
1. Cell phones have migrated to almost exclusively digital signals, and
much lower power output.
2. Aircraft electronics systems have been hardened or shielded much
better against spurious electronic signals.
3. Ground based systems used to focus the signal primarily in a
horizontal plane to minimize wasted emf energy and electricity. I have
heard that more recently they have allowed more upward signal for
aircraft systems, some of which are installed systems approved for
aircraft use. I am not certain if these use the standard cell
frequencies from the aircraft to the ground or a different band.
4. There was concern that a phone at a moderate altitude would overwhelm
the ground based system by hitting too many cell towers at once, and
also if the speed was fast, it would be switching towers so rapidly that
it would confuse the ground network. I think the ground systems have
been improved in the past 5 years or so.
Now that cell phone technology has matured a bit and the effects on
aircraft systems is better understood, there has been discussion of
allowing cell phones on aircraft, but with a repeater that is part of
the aircraft avionics equipment. The cell phone would operate in very
low power mode because the "Tower" would be right in the cabin. It would
then relay the signal to the ground, probably on a different frequency
band than normal cell phone signals, to special ground stations designed
for air to ground signals, and then it would be fed into the ground
based system. This would avoid the ground saturation and station hopping
problems, and it would be transparent to the customer other than them
probably still complaining about the surcharge on their call to cover
the special equipment and network.
I still don't think that a hand held cell phone would make a decent
connection to the ground network directly even if you had a window seat,
because the aircraft is a giant Faraday cage of aluminum skin. I have
managed to make cell calls from the aircraft at the gate with ground
antennas on the nearby buildings, but the signal is better if you go
outside. I have not tried calling from the air, and it might be dicey
job security wise, but I will ask around to see if anyone else has tried.
[Name withheld on request.]
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