Cell phones in the air

So the illegal activity is not just *making calls* while in the air, but
having the phone *turned on*. People with other GSM and CDMA devices that
don't look like phones, such as Blackberries and other PDAs would have to
disable the wireless function before takeoff. Yet another item for the
takeoff checklist.

In article ,
says...
In article ,
Eric Greenwell wrote:

Apparently, the RAS community doesn't include any cellular system
engineers, or perhaps they have to take an oath of secrecy. This
question comes up amongst airplane people, too, and I've never seen a
reply anywhere from someone that actually is trained and knowledgeable
about the systems.

I wouldn't call myself a "cellular system engineer" but I've written
code that runs in the controlling computers for cell phone systems (both
GSM and CDMA), and I've spent time driving around measuring signal
strengths and data rates and diagnosing localized problems with those
things and with handoffs from one cell site to another.

In the CDMA system as used in the USA and by Telecom here in NZ), the
phone maintains up to three site in the "active set", plus half a dozen
more in the "candidate set". One of the sites in the active set is the
current pilot, which is the one that data is actually being sent
through. The phone has dedicated hardware (called a "finger") to
monitor and talk to each of the three active set members, and a single
extra set of hardware to scan the candidate set in turn, and decide
whethe to move one of them into the active set (replacing another one).
The phone will handoff to one of the other sites in the active set if
that signal gets enough better than the current pilot for long enough.

Each cell site has a set of up to twenty "neighbours" programmed into it
by the phone company. A new site can not get into the candidate set
unless it is a neighbour of one of the sites in the active set. Thus
sites too far away can not tie up resources in the phone or the network
(although if they have a strong signal they can appear as "noise" and
make it harder to talk to nearby but weak sites).

There are several other mechanisms to prevent far-off sites from talking
to a phone. One is the "search window". Typically cell sites in a city
are set up to reject communication attempts from phones that are more
than, say, 20 "chips" (about 5 km) away. Also the antennas themselves
will often have downtilt (either mechanical or electronic or both)
applied so that the main beam can't be picked up from too far away.

All the above applies to the newer digital systems (CDMA, though GSM is
similar) which should not be troubled at all by a few people in
slow-moving gliders. The older analogue systems were far less
sophisticated and could be much more easily swamped. Phones travelling
at 1000 km/h would do interesting things as there is usually, for
example, around a three second delay before handing off to a cell site
with a better signal.

Thanks for the interesting cellphone guff Bruce. A couple years back I
was VFR enroute Omarama = Christchurch, and noted that I could not send
text messages, yet could place calls. What's the go there? (Vodafone).
I was certainly in range of sites - 'bout 5K' for much of the flight,
and even couldn't send texts while in visible range of Christchurch.

--
Duncan

Roger Worden wrote:
So the illegal activity is not just *making calls* while in the air, but
having the phone *turned on*. People with other GSM and CDMA devices that
don't look like phones, such as Blackberries and other PDAs would have to
disable the wireless function before takeoff. Yet another item for the
takeoff checklist.

I hope pilots will keep their takeoff checklists brief and pertinent to
safe flight. Don't clutter it with things that aren't causing problems.
If you are concerened about it, put it on the checklist you use after
your preflight list, but before you crawl into the cockpit.

--
Change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

Slick wrote:
Also, don't forget about, "fly the airplane."

AKA "Bernoulli before Marconi"

In article ,
Duncan McC wrote:

Thanks for the interesting cellphone guff Bruce. A couple years back I
was VFR enroute Omarama = Christchurch, and noted that I could not send
text messages, yet could place calls. What's the go there? (Vodafone).
I was certainly in range of sites - 'bout 5K' for much of the flight,
and even couldn't send texts while in visible range of Christchurch.

Cell phone sites generally use directional antennas, with typically
three "sectors" at each cell site, pointing in different directions.
The antennas are designed so that most of the power goes in those
directions, and not far above or below the horizon, but antennas aren't
"perfect", so not all of the power is in the main beam. There are also
weaker "side-lobes" and (especially when electronic downtilt is applied)
quite a bit of "top-lobe" -- that is power going upwards or nearly so.

The phone company doesn't do anything to try to make sure that the
top-lobes provide good coverage for the entire sky. Quite the opposite
in fact -- they try to minimize them (when they think about them at all,
which isn't often).

Hell, that might be one reason they say not to use them in planes -- if
they said it was ok to do that then people might form some expectation
of it working all the time, which it doesn't.

I don't know why GSM voice calls would work when SMS didn't, as they
both use the same antennas and signals. I can only assume that it was
purely a matter of bad luck due to the timing of where you tried what on
your flightpath.

-- Bruce

--
Bruce | 41.1670S | \ spoken | -+-
Hoult | 174.8263E | /\ here. | ----------O----------

The people you see erratically on the road talking on cell-phones
aren't the only people on the road talking. Think about it a bit.
You/we only notice the 'cell-phone drivers' who are incapable of
multi-tasking because ther ARE erratic. Try looking at each driver as
you pass them or are being passed. You will be surprised to find the
majority of cell-phone talker's driving is normal. I know this based
upon over 15 years of driving L.A. and other SoCal freeways 35,000+
miles per year (I am thankful I don't have to do THAT anymore!).

It is fashionable for us to deride all cell-phone users as unsafe based
upon our observations of a very visible minority but that is not an
accurate representation of the reality.

But about flying cell-phone use:
I could address the subject of whether it takes more attention time to
press a PDU button and read the resulting display vs. opening and
reading a map in your lap. But that is another subject isn't it?

What is the difference if I am sitting on top of San Jacinto mountain
using my cell-phone or if I am flying near SanJac doing the same? Or if
I am using my cell when on the 'Rim of the World' highway vs. flying
above it? I think we (gliders) have been swept into the total general
aviation category again.

It seems to me that other that banning it totally, cell-phone use in
gliders and balloons should be legal for emergency, flight planning,
and essential communications. Totally unenforcable of course, but the
current law isn't being enforced is it? Would they cite me and fine me
for 'emergency' use of a cell-phone in flight?

I have used my cell-phone in flight only a very few times. On one very
important occasion, when radio communications with my crew had failed,
I was able to avoid an airstrip with temporarily dangerous ground
conditions by using my cell to communicate with my crew. (No this
wasn't during a contest!)

Would this stop some idiot from flying around the local airport
chatting with his wife and flying unsafely? No, you can't keep idiots
like that out of the air anymore than we can keep them off the road.

Go wrote:


I have used my cell-phone in flight only a very few times. On one very
important occasion, when radio communications with my crew had failed,
I was able to avoid an airstrip with temporarily dangerous ground
conditions by using my cell to communicate with my crew. (No this
wasn't during a contest!)

Safety communication is allowed during a contest - no problem with that
part of using a cell phone.

--
Change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

There is another point on the cell phone issue. There was recently a airplane
crash that destroyed the ELT, but the pilot had a cell phone he had left on.
It was a fatal, but the family was able to call the phone and get a signal.
Using the cell phone technology to triangulate, they found the plane within
hours in a remote area. Think of it as a back up ELT when you aren't able to
be found with the ELT. It certainly sounds like the technology is now able
to handle cell phones in the air, but the law hasn't caught up with the
technology. Digital vs. analog tech.

Hi,

The people you see erratically on the road talking on cell-phones
aren't the only people on the road talking. Think about it a bit.
You/we only notice the 'cell-phone drivers' who are incapable of
multi-tasking because ther ARE erratic. Try looking at each driver as
you pass them or are being passed. You will be surprised to find the
majority of cell-phone talker's driving is normal.

It may be as normal as most (moderatly) drunk driving. You can and usually
make do make it home even if you are a bit woozy.

We have had quite a bit of public discussion here in Germany and a lot
of research. The result of that research after being filtered through
the legislative jungle is that using a mobile phone without hands-free
equipment while driving is now forbidden. It is also widely accepted
that using a telephone _at_ _all_ while driving is a hazard, so if there
is an accident and it is discovered that one of the drivers was one the
phone he is very likely to be assigned at least part of the blame for it
by a judge even if he was using it hands-free.

It is also interesting to note that talking to a person that is physically
present seems to be not at all that demanding. So there is no pressure to
regulate normal conversation in cars :-).

I do not believe however that this research can easily be extended to
aircraft. Mainly because the allowed time to react is generally much
shorter on the road than in the air.

Ciao, MM
--
Marian Aldenhövel, Rosenhain 23, 53123 Bonn. +49 228 624013.
http://www.marian-aldenhoevel.de
"Ich hoffe Sie können mir helfen. Ein Freund hat mir einen tollen
Bildschirmschoner aufgespielt, aber jedesmal wenn ich die Maus bewege
ist er weg."

Marian Aldenhövel writes:

It is also interesting to note that talking to a person that is
physically present seems to be not at all that demanding. So there
is no pressure to regulate normal conversation in cars :-).

I do not believe however that this research can easily be extended
to aircraft. Mainly because the allowed time to react is generally
much shorter on the road than in the air.

The big difference it seems is that you are listening and concentrating
on ONE EAR. This distorts the visual field, and biases attention cues
toward the phone side. The visual distortion is AWAY from the phone,
so there is a large mismatch.

Using a speaker is far safer than a single ear phone.

--
Paul Repacholi 1 Crescent Rd.,
+61 (08) 9257-1001 Kalamunda.
West Australia 6076
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