Yaatri

Quite right. In analogue TV the interference is from the supply frequency, which is 60Hz. The frame rate in NTSC system, the analogue system in use in the U.S.was related to 60Hz.


iPad can only read data from onboard computers, it's not allowed to write to it. Pilots should be able to disconnect iPAd when needed, say for egress or some other reason. That iPad cannot be used as a general all pupropse communication device. It can only be used for communicating with the ground, short messages. use, such as that made by Gen Petraeus is prohibited. Details of this area is beyond my expertise. But this is what I understand. Pilots who use this can elaborate on this and correct me if I am wrong.
IPad is loaded with data, such as maps, or other flight parameters, flight manuals etc. Installation of some software/applications requires approval from one level and some from more than one level.

I don't know if the iPad is EMI hardened. As an example, computers used for sensitive/classified work at contractor's site are off the shelf items, but they have to be "prepped" and approved from classified use and those computers can only be used in a secure room. The computer will have off the shelf software, such as Windows,, Office etc. But you can't simply install it yourself, nor can you install anything else, that's not approved by appropriate authority. They may also not be connected to the local net work owned by the contractor.
So, yes, it's off the shelf, but it's not "free for all". Rules for pilots flying commercial flights vs private planes might be different, but I am sure you get the idea. What people do and how strictly they a=follow the rules, is something I don't know. I believe in following rules. Rules serve a function.

Yaatri

Don't know, but
Fact Sheet – Cell Phones, Wi-Fi and Portable Electronics on Airplanes
This was news to me too. I never bothered to find out since I don't shave.

Now you still have to obey other rules. You can't get up to go to the lav to shave.

StanSimmons

Yaatri,

I'm responding to you in this thread because the other related thread was closed while I was composing this reply. In this thread, you said:
Today's sensors may be more sensitive, but they also have much better discrimination circuits, making them MUCH better at shrugging off spurious noise.

You seem to think that modern aircraft, with systems that are designed to be redundant, and are designed to operate in an RF rich environment, can be knocked out of the sky by a phone that has a max output of 2 watts (GSM).

The time that PEDs are required to be turned off is at the same time that the aircraft is being bathed in RF from multiple airport radio sources, multiple airport radar sources and many, many radio sources from commercial activity in and around modern airports. Most of those transmitters are many times more powerful than the measly two watts max output of a GSM phone, especially since the phones are designed to reduce the RF output power to the minimum required for reliable communication - under optimum conditions, the power can be set as low as 20mW.

The CTX baggage X-Ray system in the terminal is more likely to cause RF problems on an airplane than my cell phone is.

That all said... I turn off my phone or put it in airplane mode, not because I think it is dangerous, but because that is what the FA announcements ask me to do, and it saves the battery.

Yaatri

Thank you for your response. That's quite an assumption about what I said. I have never said that a plane could be brought down by a cell phone. Please don't put words in my mouth.

Is you assume a source of radiation to be a point source, the electric field false off as inverse square law. If you take a multi pole expansion, you will have higher poles, dipole, quadrupole etc. Dipole field false off as 1 over r cubed and quadrupole false off even faster. At a distance of 5 km from the source, a 1000kW source will have an intensity of ,04 watt or 40 mW per square metre. Now 1000kW is a powerful source. Suddenly 20 mW doesn't sound so low, does it? This is just a back of the envelope calculation to give you a idea. It's not meant to be an exact calculation.
Source of radiation from all cell phones are inside the fuselage, so much of that radiation is well contained although some does escape through the windows. If you remember Huygen's principle, each point on the wavefront intercepted by the window becoems a source of radiation. Now, instead of considering cell phones at different points inside the plane, the problem is to find the combined field due to multiple sources, on at each window. The source at each window is going to be weaker than each cell phone.
What are x-ray frequencies? X-rays carry higher energy as their frequency is much higher, 300 billion MHz where as cell phones work at about 2000 MHz, and aircraft systems at tens of KHz to a few GHz. To put things in perspective, solar radiation at sea level is about 1000W per square metre. At the edge of the atmopshere, it's 1366 watts per square metre. Solar radiation that falls an aircraft is far more than this 1000 watts figure. You can arrive at that amount by multiplying solar intensity by surface area of the aircraft with appropriate factor to account for the fact that not all of the surface is perpendicular to solar radiation. It would be hundreds of thousands of watts, if not a million or two. Do you know why that's not a danger? Because almost all of that radiation is in infrared, visible and UV range, at frequencies much much higher than those used by aircraft systems, but much lower than X-rays. It's not just the power but frequency range is important too.

Good idea for reasons other than you quoted.
I also have not said that cell phone is dangerous. I am just trying to give useful information, rather than anecdotal or irrelevant information, to put things in proper perspective.
I hope it helped.

StanSimmons

I'm guessing that by "false off" you mean "falls off". Your distances in your calculations were several orders of magnitude apart. 5km vs 5m... really?

Since you bring up RF frequencies, cell phone, wifi, bluetooth, and other common PED RF sources are far above the ranges normally used in commercial aviation for comms. and far below what is used for radar.

Yaatri

Yes, Thank you. I did mean falls off. There were several other typoes there.
I think you are asking questions without thinking about what you have read. These are distances from the aircraft system. There are some components that are a few metres from passenger compartment. The 5 km is the distance of the aircraft from sources on the ground. Five km is about 16000 ft. Before an aircraft reaches 10000 ft typical distance of the aircraft from ground based sources is about 5 km. Do you understand? I told you these are back of the envelope calculations under realistic conditions. I didn't just pick 5 km and 5 m off the air. I used monopole sources, which fall off the slowest. Some sources are nit monopople, which would fall off faster.

Are blutooth wifi and GSM frequencies as far away from aircraft frequencies than X-ray frequencies are?
X-rays carry higher energy as their frequency is much higher, 300 billion MHz where as cell phones work at about 2000 MHz, and aircraft systems at tens of KHz to a few GHz.
Wifi,Bluetooth, GSM 400MHz ~ a few GHz
Air craft systems~ tens of kHz to a few GHz
X-rays 300 billion MHz
Do you get the idea?
The EMI concern is before it reaches the circuitry you talk off. Instrument circuitry will simply amplify it. Antenna cannot discriminate between a stray source and a an intended source.
I welcome your questions. Answers to all your objections were already there. You just have to stop and think about what I had said if you don;t have the background.

planemechanic

Stop and think about this.


There have been ZERO cases of proven interference by consumer electronics on commercial aircraft in all of history.

Yaatri

It's not relevant to what we are discussing here.

StanSimmons

Oh, I understand what you are attempting to say... I just don't believe that aircraft systems, with their multiple backup systems, all of which are designed to filter spurious signals, are being adversely effected by puny 20mw to 2watt transmitters that are on frequencies that are not harmonics of the aircraft safety systems. If an aircraft is susceptible to interference from PEDs, then that aircraft is too poorly designed (or maintained) and shouldn't be in service.

I have seen two anecdotal stories of aircraft nav systems having odd things happen that the pilots attributed to passenger equipment, however, the NTSB has no confirmed incidents, in commercial aircraft, related to passenger PEDs causing interference that I can find. If you have any NTSB or FAA reports that specifically fault passenger PED incidents I would love to see them.

Your argument seems to be that there is a possible danger, my argument is that if there is a danger, that it is so small as to be negligible and likely not even measurable. I'm more worried about the idiot texting while driving than the one texting while flying.

Yaatri

You seem to be getting the idea. I am trying to look at the issue like an educated person will look at it. You seem to be doing the same. You still don't seem get the point that the field of ground sources is not that much stronger than that of a 100 cell phones. So it's not ll that puny. The saving grace is that the cellphones are inside the fuselage. It's not just shielding, that must be good, it's also terminations of shields, grounds. If a ground is disrupted, shielding is imperfect. Stray capacitances and inductances all are sources of potential coupling, which can affect systems with degraded terminations, grounds or shields. A cellphone operating at 900MHz has wavelength of 33 cm, similar in cize to window openings. When the wavelength is close to the obstacles and openings, diffraction effects also come into play.
which itself acts as shield, imperfect though. Even with all the schemes, such as orthogonalisation, cell phone calls get dropped.

No, I don't. See, the problem is that what the pilots report is just an report. Electromagnetic data in the cabin space at that point is not recorded. So all we have is pilot's story, which cannot be evaluated in absence of any data. Pilot's main responsibility is to get the aircraft off the ground, fly it safely and get it back on the ground. We can't expect the pilot or the crew to conduct experiments and/or collect data, that would be needed to analyse the incident in detail. Things don;t ust happen. If anomalies are observed during a flight, and explanation has to be found. Was the pilot drunk, hallucinating, or there was an intermittent connection to ground or to a terminal? Or was the pilot trying to cover some mistake---a serious allegation. My purpose of doing such back of the envelope calculations is to try to understand the issue in terms of well established principles of physics and electrical engineering. They are not meant to prove that there is imminent danger, but just to see if there are pathways through which anomalies "could" be
explained. This is not proof of anything, just a technical direction.

My argument is that there is potential for trouble, maybe even serious,depending on which system is affected and for how long. Without extensive data an calculations I cannot quantify it.
Thanks for the discussion. It's an interesting problem. For me, x million flights without a death or injury is not a scientific argument. That argument is irrelevant to the discussion we, you and I, are having here. It's simply disruptive.

Yaatri

There is no hypocrisy. If one doesn't understand what's being discussed, I can see why one would be bored. That's Ok.

None of this is relevant to the discussion. What you do on the ground is your business. It's in no way relevant to this discussion.

I find it utterly silly to have an opinion without understanding it. I am not an enforcer. I can only explain.

Once again, all of the above is completely irrelevant to what we are discussing here. None of the activities you describe affect anyone else but those doing it, nor are they in any way participate in electromagnetic phenomena.

It's hard not to laugh at all of what I read above. But, laughing does nothing. I can laugh at you and you can laugh at me. Does it make a difference? I explain. If you understand, great. If you don't I can't make you. If you understand and don't agree, that's fine too. The only way to discuss this is in terms of things that matter. Flipflops, bicycle rides, fire clothes you wear, cotton, synthetic or wool, don;t matter.
Can you please let those who want to discuss this carry on? Thank you.

planemechanic

True, you have proven that facts have no place in your discussions.

Yaatri

Listen. We know what your opinion is. You are welcome to contribute to it with something other than personal attacks.

StanSimmons

Ah, so your argument is entirely theoretical, with no empirical evidence of any real world problems in commercial aircraft? I understand your concerns, but I disagree with your conclusions. Absent real evidence of problems, it seems to be a bit of a "snipe hunt".

If the FAA wants passengers to pay attention during announcements, takeoff and landings, then they need to say exactly that... not give reasons that sound like BS, and have no history or empirical data behind them. We get enough of that from the TSA.

planemechanic

LOL

And we all know what your opinion is, and it gets repeated ad nauseum. I never attacked you, just pointed out that you were explicitly ignoring a fact that hasn't changed during all of these discussions. If you don't want me to respond to you then you can simply stop responding/rejecting my posts. You are not the one who decides who can or cannot post in this or any other thread.