Did they make any announcements regarding this? Most people aren't going
to care about GPS, but many people are used to using their cell phones
while waiting for the door to close  and/or as soon as the wheels touch
the ground when landing. If this doesn't work in a 787 I would think
that they would make a PA announcement to that effect, rather than
having to continuously answer questions regarding the problem.

Regards,

John

On 6/2/2014 2:55 AM, Tom Van Baak wrote:

In message BB41DBA7E336413BB9D643DF4D4F613D@pc52, "Tom Van Baak" writes:

Only for short tau.  It should be pretty good at tau > 1e3 years or so ?

This is by design, so the plane can contain its own in-flight
wireless services.

WLAN in planes is no problem, there is a subset of channels which are
almost globally safe to use.

However, the next big cash-cow is supposed to be inflight mobile
phone + data, and bringing a Mobile Femtocell into any country
you might happen to fly over is a regulatory violation and paperwork
nightmare.

Originally the GSM spec had a sort of "RFC1918" facility, were one
specific frequency would be "local space", for exactly this kind of
application on marine vehicles.  Your phone would never automatically
roam to such a net, you'd have to explicitly select that a 'local space'
base-station, and you'd be stuck to it, until you manually released it.

However, given governments gold-hunt in spectrum allocations, that feature
died in the crib, and has not subsequently been revived.

Therefore airlines and cruise boats have to use regulated frequencies
if they want to offer cell-service.

Cruise-boats use a loophole in the international maritime treaties,
even when in harbour, they're under their national flag, and since
most of them are Bahamas or similar, getting a mobile license and
frequency allocation is cheap.  (Usually they crank up the power
when in harbour and milk any unsuspecting land-locked tourists with
exorbitant roaming-charges.)

Planes are not similarly "nationalized" and apart from the aeronautical
spectrum, they cannot emit any radiation for which they are not
licensed by the country they overfly.

And so they've started to build the planes as farady-cages.

It would be trivial to add a passive GPS repeater to the plane, but
the airtraffic industry has never been happy about people being
able to receive navigation signals inside planes, worrying that
somebody might try to blow up the plane at some specific place
(or non-place), so that ain't gonna happen.

--
Poul-Henning Kamp      | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG        | TCP/IP since RFC 956
FreeBSD committer      | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

On 6/2/14, 1:55 AM, Tom Van Baak wrote:

I haven't noticed it myself, but when Beechcraft was making their pusher
twin with carbon fiber, there was a whole raft of stuff they did to make
sure it could take a lightning strike, including adding a conductive
layer to the skin.  It doesn't have to be all that thick, since it's not
structural.  This is a very real concern for carbon fiber components.

And, as you note, since the windows have electric shutters, there's
probably an Indium Tin Oxide or similar coating on them, which would
make an effective shield.
(http://gizmodo.com/5829395/how-boeings-magical-787-dreamliner-windows-work)

The basic rule on shielding is that holes where the perimeter is >1/2
wavelength will pass some amount of RF, and when the perimeter is >1
wavelength (e.g. a slot half wavelength long) will pass virtually all of
it.  So your speculation about the windows in the plane being the
pathway through which cell/gps/etc signals pass is a good one.

See also
http://www.boeing.com/assets/pdf/commercial/airports/acaps/787.pdf

On 6/2/14, 2:27 AM, Poul-Henning Kamp wrote:

I don't know that it's that reasoning.  It's more about the innate
conservatism of people who make things that fly.

The reason for "radio receiver ban" originally was fear that Local
Oscillator leakage would adversely affect cockpit instrumentation:
particularly things like low frequency beacon receivers, which were none
too selective, and since navigation using the ADF and tuning to a AM
broadcast station wasn't unusual. I had to learn how to do it when
taking flying lessons: it was widely acknowledged ( in 1980) to be
nearly useless, but, hey, if all the other radios fail, any port in a
storm, etc.  About the only older radio nav technology is A-N ranges (if
you believe Wikipedia, they were gone by 1980 "mostly disappearing by
the 1970s")

Birdies in a consumer radio in your living room or car aren't a big
problem. Birdies in a navigation instrument are a potentially big problem.

Even in the 1980s, there were a lot of planes flying with fairly archaic
radios, although I suspect no commercial jet was using a VFO tuned
radio:  they'd be using "banks of crystals" or PLL tuning. In general
aviation, the first non VFO radios were from King in the 60s, and I
think synthesizers came in around 1970 (King KX 170 and 175).  I was
astounded at the number of crystals in one of my Narco radios when I
took it out of the plane to fix it (a 1973-74 vintage radio).  Half that
box was basically a big rotary switch and dozens of crystals.

Typical spurious responses in a COM or NAV receiver would be something
like -60dB down, but a few milliwatts leaking from some guy's FM radio
on board would easily be bigger than than that, since the receiver
threshold is about 1 microvolt into 50 ohms (-110 dBm).

Once the rule is in place, it's very, very hard to get it removed,
because of the "if we allow X, and a plane has a problem, everyone is
going to say "it was because of X" even if it wasn't, so let's just keep
things the same."

On Mon, Jun 2, 2014 at 8:57 AM, Jim Lux jimlux@earthlink.net wrote:

Well, it is quite unusual for IFR (instrument flight rules) operation. But
VFR pilots would sometimes use an AM broadcast station for navigation
assistance.

Not entirely. I still make sure my planes are equipped with ADF (LF/MF
direction finding) due to my experience with GPS outages over the Caribbean
and Atlantic. I have experienced outages of over an hour where both my
panel-mount and hand-held GPS receivers stopped working. ADF was all I had.
I suspect that since I was flying a plane popular with drug-smugglers (a
Piper Aztec), I was being tracked, followed, and GPS jammed. (I lived in
the Virgin Islands, traveling to Florida on a regular basis. I would stop
in the Turks and Caicos or Bahamas to refuel.)

They could be and they are. Interestingly enough, the only radios that ever
interfered with my VHF nav receivers were my own VHF comm and nav
receivers. LO leakage from one radio would show up on one of the others. I
have never experienced that problem with any consumer device.

Even in the 1980s, there were a lot of planes flying with fairly archaic

A "crystalplexer" radio that was dual-conversion with both LOs using
switched crystals. CB radios used the same thing back in the late 1960s and
early 1970s. PLL LOs came later.

Typical spurious responses in a COM or NAV receiver would be something like

That may be true but I have never experienced it, even when I tried. The
only time I have ever experienced interference with my comm or nav radios
it was from another comm or nav radio in the plane. Most use a 10.7MHz IF
which means, for the spectrum from 108MHz-138MHz, you are very likely to
have a lot of overlap between LO and desired receive frequency.

Once the rule is in place, it's very, very hard to get it removed, because

Amen.

--
Brian Lloyd
Lloyd Aviation
706 Flightline Drive
Spring Branch, TX 78070
brian@lloyd.com
+1.916.877.5067

On Mon, Jun 2, 2014 at 1:55 AM, Tom Van Baak tvb@leapsecond.com wrote:

I bet this is nothing to do with carbon fiber vs. aluminum skin.  Both
would have to be conductive.  I bet it's the metal film on the windows.
The metal skin of the older planes would have been a perfect shield but
the windows let the signals in.  But on the new plane the windows have a
conductive metal film.  So I bet the difference is entirely because of the
change in window design.

Even in buildings some "energy saving" windows have coatings that are
conductive and don't allow GPS to pass.

Chris Albertson
Redondo Beach, California

In message 538C82B8.5020504@earthlink.net, Jim Lux writes:

Actually, there was a very specific incident where somebody brought
a television on a plane in order to see something important.  We're
talking 1950-1960 timeframe and and a tube-television.

Apparently this disturbed something in the cockpit, but there is
no evidence to indicate that it was actually a problem in the
cockpit, only that they spotted some kind of noise.

And that's when and why the FAA introduced the ban.

--
Poul-Henning Kamp      | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG        | TCP/IP since RFC 956
FreeBSD committer      | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

Wonderful. It also means cell phones will crank up their power searching for a signal, and the passengers are sitting inside a microwave oven since the RF energy can't escape.

Thankfully there are alternative ways to fly.

Bye,
Said

Sent From iPhone

On Jun 2, 2014, at 8:45, Chris Albertson albertson.chris@gmail.com wrote:

On 2 Jun 2014 10:03, "Tom Van Baak" tvb@leapsecond.com wrote:

or even while seated inside a plane. I figured the aluminum frame of the
plane was thin enough that photons at cell, GPS, and gamma frequencies
easily pass through the outer shell or the windows.

I do have quite a bit of data on that, having measured the attenuation both
in flight tests and on the ground. (I don't trust the latter anyway.) I
can't share it unfortunately.

But you should be aware of of how the systems in aircraft that allow one to
use a phone work. The cellular operators were keen that one could not cause
interference on the ground by a phone connecting to many base stations. For
this reason the planes incorporate a noise generator that raises the
background noise so that the phone cant hear any cell sites on the ground.
I would not expect that to be enabled below about 3000 m, but it is quite
possible that the noise generator was on.

I would not expect it to jam GPS frequencies,  but certainly those used by
mobile phones.

Dave

I've flown on 787s three times before, and am about to do so again later today.  The prior times I used my cell phone as normal and didn't give it any thought.  This time I'll pay particular attention and report back.  Twice for me have been Ethiopian Air, once London-Addis, once Dulles-Addis. The third time was ANA Osaka-San Francisco.  Today will be London-Addis again, but a different actual plane, since the previous one is one of the ones that burned.

            -Bill

I'm posting this from inside an Ethiopian 787, on the ground, with the doors closed.  I just completed a fifteen-minute voice call initiated from inside the plane, with reasonable reception and no drops, while the doors were open.  And I was able to get a new GPS location in less than two seconds (though that wasn't from cold boot, so I don't know whether it was able to accelerate the process using cached data previously received). The phone (an iPhone 5S) is showing three bars inside the plane, and was varying between three and four bars outside. Note that the non-linear mapping of signal strength to "bars" is a matter of intense negotiation between carriers and vendors, and shouldn't be taken as a literal indicator of anything at all.  Likewise, Ethiopian may have ordered planes with significantly different options than ANA (no center overhead storage in business, for example) and used different paint formulation.

Nevertheless, in this specific case, I'm not seeing anything that seems out-of-the-ordinary relative to other aircraft.

            -Bill

On 6/2/14, 7:16 AM, Brian Lloyd wrote:

Back in 1980, the examiner asked me how to do it, but didn't make me do it.

I was referring to the "AM station as beacon", and to be fair, they were
all talking about compared to conventional VOR/DME, and maybe if you had
one of them new fangled RNAV units that mathematically transformed
VOR/DME into lat/lon, etc.

On Mon, Jun 2, 2014 at 10:36 PM, Jim Lux jimlux@earthlink.net wrote:

He wasn't allowed to. It is not part of the practical test standard for the
private pilot certificate. Still, it is useful.

I have been flying long enough to experience nearly every form of
electronic navigation available in aircraft. I have actually flown an
Adcock "A/N" range. I have landed an aircraft in instrument conditions
using precision approach radar (PAR or GCA). I have used ADF, VOR, DME,
RNAV, LORAN-C, INS, and now GPS. Airplanes haven't changed much but boy the
radios sure have!

ADF is less accurate than VOR/DME. It is much less accurate than DME/DME.
It is archaic. But it works. If the beacon is at the airport itself ADF is
amazingly accurate for making an approach. It has a unique characteristic
that it is difficult to jam. (LORAN-C was better and I REALLY miss
LORAN-C as a backup to GPS.)

There are large stretches of the Atlantic and Caribbean where the only two
navaids that are available are GPS and LF/MF NDBs. Sure I can use
pilotage/ded-reconing and hop from island to island. But I have now
experienced multiple total GPS outages. It makes me nervous the dependence
we are developing on a system that is surprisingly vulnerable to a
denial-of-service attack.

I do hope that LORAN-C comes back. The original idea of the European
Galileo system to use LORAN-C to distribute DGPS data was brilliant. The
DGPS datalink was itself a source of high-quality time and position
information that is nearly impossible to jam. What a concept!

Has anyone considered how a large-area GPS outage would effect us? I
really don't like having all my eggs in one basket.

--
Brian Lloyd
Lloyd Aviation
706 Flightline Drive
Spring Branch, TX 78070
brian@lloyd.com
+1.916.877.5067

On Mon, 2 Jun 2014 20:18:00 +0100
"Bill Woodcock" woody@pch.net wrote:

You probably know this, but just in case, cell phone GPS is assisted,
i.e. AGPS. It uses tower information to assist in lock. [Also data, as
many a roamer has found out when billed. On an iphone, the saving
grace is it has real problems with APN settings, so often it won't use
the assist when roaming.]

I recall my GSM phone making some RF burps once when I was using it
in the desert where there was no cellular service. But the poster that
said the phone would listen before transmitting has a good point, so I
need to repeat this experiment sometime. I was using a spectrum
analyzer and picked up my phones chirping.

Regarding radiation, I've used my Geiger counter at mile high altitudes
in Nevada and never got a count per second, even with the gamma shield
not used. You can look at the DOE CEMP stations:
http://www.cemp.dri.edu/
Some of the radiation monitors are not working, but this one is and it
has typical readings of 15uR/hr.

As a crude estimate, 1000CPM = 1mR/hr, or 1CPM = 1uR/hr. So I suspect
the 60CPM received in Colorado is use to local radiation rather than
cosmic rays.

My Ludlum isn't calibrated, but I've compared it to one from the DOE
using their source and it matched close enough for government work.

nuts wrote:
....

1 Mile high is still on the ground compared to an airplane's 8 miles high.
Those 7 additional miles of altitude result in an atmosphere that is very
sparse with the air molecules necessary to block cosmic radiation.

TVB's readings correlate well with graphs I have seen on other websites.

-Chuck Harris

On 6/3/14, 5:51 AM, Chuck Harris wrote:

A handy number to remember is 18,000 ft or 6,000 meters: that's the
"halving height" where the air pressure is 50% of sea level, so at
36,000 ft, the air pressure is 25%, etc.

http://www.acd.ucar.edu/Events/Meetings/HEPPA/pdf_files/Aviation_Hazards/Shea.pdf

makes an interesting point that a number calculated back in the 60s
(orders of magnitude too high) has achieved urban legend status.

page 17 has some plots.. for 9449 m (31000 ft), 2 uSv/hr, for 11,887
m(FL390) >5 uSv/hr  (pretty big change for only 2000 meter change in
elevation)  (1 uSv = 0.1 mrem)

another source (DoE http://lowdose.energy.gov) gives 25 mrem/yr at 427
ft, 40 mrem/yr in Denver(5,280ft), 130 mrem/yr in Leadville (10,157 ft)

Yet another source shows (for Galactic Cosmic Rays)
0 ft 31 mrem/yr (310 uSv/yr = 1 uSv/day)
5000 ft 55 mrem/yr
10k ft 137 mrem/yr
30k ft 1.9 rem/yr  (2.1 uSv/hr)
50k ft 8.75 rem/yr (87500 uSv/yr = 10 uSv/hr)
80k ft 12.2 rem/yr

I note that this doesn't follow a nice exponential curve (e.g. it's a
big jump from 0.14 to 1.9 with a change of from 10k to 30k ft). The Shea
presentation from UCAR makes the point that there's a fairly complex
radiation transport process with scattering and secondary emissions.

Jim Lux wrote:
...

The correlations I was mentioning were for amateur measured fluxes while
flying at about 40,000 ft.

One thing worth mentioning is that all methods of measuring radioactive
fluxes are not equal.  The ubiquitous G-M tube is made in a myriad of different
configurations whose abilities range from measuring only very hard gamma
rays to softish Xrays in the 10KeV range.  And some G-M tubes have capability
of making very misleading measurements of alpha and beta particles in addition
to gamma.

And then there is the scintillation type of meter, which uses a material that
fluoresces on exposure to whatever particle, or energy level, that is interesting
to its maker.

I have measured numerous sources using a variety of different G-M tubes and
scintillation counters, and the "differences of opinion" the different counters
have is rather wide.

My Victoreen 425-110, made for 10KeV gamma and above, but not beta or alpha
is a real ninny, and thinks everything is drastically hot... But then it was
made for use by the medical community in their nuclear medicine and x-ray
exposure tests...  My various PDR-27's, on the other hand, aren't too impressed
with much of anything.  Kind of what you might expect from counters that were
meant for use by military folk that had to go into suspicious areas regardless
of the risk.

I'm not sure what sort of G-M counters were being used for TVB's test, and
for the others that have shown up on the web... It is probable that the
users of these counters were not all that sure themselves.

I am pretty sure, however, that this branch of TVB's thread has left the cover
of the time-nuts charter...

-Chuck Harris