AM radio reception inside passenger planes?

| |> So, in all honesty, YOU can't really say how dangerous operation of an FM |> receiver will be; but you KNOW that it's potentially harmful. | |Given that the aircraft voice comms are just above the FM BCB, and the |typical first IF is 10.7 MHz, it's not too hard to imagine the LO sitting |right on the tower comm frequency. |You may only radiate a microwatt, but you're much closer to that antenna on |the aircraft than the tower is. Inverse square law makes it very easy for |you to win that contest.

Correct. Let me offer a slightly different but illustrative example.

Since this is cross-posted to some non-ham groups, bear with me. In the 1960's I operated my amateur station on the two-meter (144 MHz) band using several hundred watts of AM and directional antennas.

I'm in Tucson where we have both a commercial airport and D-M AFB. An acquaintance of mine, also a ham, was the FAA tower chief at Tucson International.

One day he calls me on the phone and says that the tower guys at D-M, knowing he was a ham, called him first rather than the FCC, to report that I was interfering with their tower communications.

To make an involved detective story short, it turned out that another ham, who lived just outside the AFB was using a Heathkit "Twoer". The Twoer used a super-regenerative receiver and was picking up my signal and re-radiating it on the tower frequencies. I was getting blamed for the other guy's illegal transmissions.

Considering that this technology is probably used in more receivers today than any other type (garage door openers, computer wireless links, etc.) if I'm flying, I hope they are all turned off.

| |This is a pointless argument though. It's a health and safety issue, and |you either follow the airline's rules, or I hope they boot you off the plane |(optionally, landing first for your convenience) It is just that simple. |

Hey folks, let's not overdo the safety aspects here, so no one panics if aboard an airliner and sees someone using a radio. I doubt any device emitting small RF will be able to make comm reception unreadable. Even if it did, there are then fallback procedures which the pilot is required to know by heart, and the pilot is even permitted to continue flight all the way to the gate without any communication at all. Believe it or not, other aircraft may not have to be vectored out of your way, or even informed about your problem. But in reality, the pilot would simply peek at the coffee-stained nav chart and dial up another controller on another freq and ATC will say another frequency to come up on, or "stay with me."

For navigation on frequencies 108.00-117.95, besides being rather strong signals, the nature of the modulation is such that interference would have to be strong and be just so, to cause navigational error. More likely there would a panel indication of an unusable signal -- because the receiver must be designed this way, and the pilot can listen to the nav audio to hear the problem. The aircraft is also in radar contact, so that if the pilot were to wander off course -- you're allowed a fairly wide margin -- ATC tells you if outside the margin or not following a clearance if given a "direct." If you can't rectify it, you simply ask for radar vectors, or switch to GPS nav, or vice versa, or clearance to go direct to another nav beacon off the nose, or GPS direct if equipped.

Now the same considerations apply to flying the approach and landing, but the pilot would rather not have to deal with potential interference to either nav or comm, especially if the airport is 1/2 mile visibility in fog. Thus, it's not too uncommon for the pilot to grant permission to use a radio device only while in cruise.

Also, ATC will be able to tell the pilot that other aircraft are not reporting a problem, a hint of possible interference from inside the cabin. But has anybody ever heard a cabin announcement during flight to turn off any devices?

Fred F.

Everything you have written is probably correct BUT That is not the point -- The FAA and Airlines have regs and policies about portable electronic equipment aboard an airliner PERIOD

And yes a sharp flight attendent did tell me to turn off a GPS unit.

-- ID with held to protect the innocent

Fred,

Nearly all aircraft accidents are caused by a series of unlikely events all happening together, none of which by itself would be a problem.

Would you want to add one more "unlikely event" to your next flight? Do you have life insurance?

73, Dave

(to keep this on topic, I will say this: last week my garage door snagged the corona tip on my ATAS-120 and broke something inside the tuning section, and bent my trunk lid. A $300 mistake. Damn.)

Our club repeater also ended up interfering with the local tower.

It seems that the transmitter PLL was unstable, and "hopping" between that frequency, and ours. We were clearly audible in their recordings.

Lest any "experts" step in and claim that you can't receive FM on an AM receiver, I'd ask them to consider what effect the passband filter of the AM receiver's IF might have on the FM signal as it deviates from side to side....

I hit the magic codes and took the repeater down, once we determined that this was indeed the source.

A re-tweak of the transmit PLL, and a stub filter cut to pass 146.730 and reject the tower frequency, cured the problem, and insured that if it ever happens again, they probably won't hear us. The tower now has our phone numbers in their books, in case there is ever another problem. The tower complimented our rapid and assertive handling of the problem in their closing letter to the FCC.

Repeater cans don't do much for signals that are far out of band.

Ouch. That'd be categorized as a "double-plus ungood" for certain!

I believe the magic words are "slope detection". The resulting audio on the AM receiver isn't great (it's often distorted) but it's certainly there.

Well done!

--
Dave Platt                                    AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
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[Dramatic generalization mode on] [Dramatic generalization mode off]

Nice sweeping piece of dis-information there buddy.

How about this: Nearly all aircraft accidents are caused by a single failure in a single component or a single failure to do something. Pitot tubes that are taped over. Fuel tanks that explode. Structural failure that causes entire pieces of fuselage to peel off while in flight. Fuel leaks that turn large jets into gliders. Cabin fires caused by the overload of a single wire powering the entertainment system. Air pressure equalization valves that bleed cabin air rendering the occupants unconscious and results in a ghost plane flying thousands of miles before crashing. Failure to de-ice. Overloading resulting in stalling upon take-off. Failure to secure cargo upon takeoff. Being struck in the fuel tank by a piece of debris on the runway kicked up by the tires. An engine ingesting a flock of birds. A shipment of improperly-disarmed oxygen generators placed in the cargo hold. Lack of proper lubrication of tail jack-screws. Tail fins that are not as strongly connected to the fuselage as they should be. Need I continue?

A series of events will surely happen AFTER any of those incidents, none of which are either unlikely or unexpected, and by and large would have no effect on the outcome.

Will the in-flight use of an FM radio EVER cause a plane to run out of fuel? Or cause a sudden ice build-up on the wings? Or blow out a tire upon landing? Or an overload of the electrical system leading to a fire? Will the feeble RF emitted by the LO even be detectable OUTSIDE the plane, where the plane's antennas are located?

If you read the various documents on the web relating to issues of in-flight use of PED's (personal electronic devices) it's clear that

1) The FAA and NTSB are either negligent or a bunch of cowards for not forcing the AIRCRAFT MANUFACTURERS to determine the level of susceptibility of their planes to PED's. Instead the issue is pawned off to the aircraft operators when logically it should be the airplane makers!

2) The use of cell phones (analog and perhaps more frequently GSM) seems to have the most influence of any PED. The next most frequent culprit seems to be laptop computers.

3) No incidence of communication failure or disruption seems to have ever been documented by a passenger's FM radio receiver.

4) MANY MANY incidences of navigation equipment errors caused by improper installation / connection of the equipment, or interference caused by one of the plane's other systems where these were first attributed to a PED.

5) Planes have to fly near high-power commercial radio and TV transmission towers. They fly through the beams of powerful radar signals. They get struck by lightning. There are those that say that for a (commercial jet) to be certified there is no way that a certified plane could be susceptible to the stray RF given off by PED's (at least PED's that are non-intentional radiators). 6) The authorities would probably not admit it, but the ban or restrictions on PED use in planes probably has more to do with insurance/liability reasons, or passenger distraction reasons, than it does for technical (interference) reasons.

PED's are here to stay. There will be more of them, and people will use them wherever they are. It makes just as much sense to ban them or perform half-ass on-board supervision on a plane for these devices as it is to ban them from cars. PED's used cars cause injury and death each year (due to driver in-attention). Instead of banning radios, phones, and entertainment systems in cars, they instead come from the factory with them installed! Where's your crusade against that situation? Where are your dire warnings here?

Nothing caused by or brought on board by a passenger (short of alcohol, a gun, a bomb, or otherwise a strong intent to do harm) will or has ever caused anything bad to happen on a plane or to a plane. No gun ever brought on board (and there have been MANY!) has ever discharged. No can of hairspray has ever exploded in the cargo hold.

There is relatively little variety in the types, makes or models of commercial airplanes flying today. There is a high degree of uniformity in construction of these vehicles. There have been millions of flights over the past, say 20 years. There have been many hundred million passengers carried by these planes. There surely has been ample opportunity for all sorts of PED's to be used on these planes (surreptitiously or with consent). If any particular plane model (or even specific plane) had a systemic or inherent susceptibility to a PED, it would have been recognized by now.

What is a Pitot tube anyway? I have seen a switch for most aircraft in Flight Simulator marked "Pitot Heat", what is that?

Lots of data, not much information. No cites given.

Angry crap.

Some Guy wrote:

Pitot tube at URL;

Re Pitot Heat -- see URL:

Sez The system shown employs a heated pitot tube to prevent ice formation, a necessary feature for flight in instrument conditions.

--
ID with held to protect the innocent


>
>   What is a Pitot tube anyway? I have seen a switch for most aircraft
> in Flight Simulator marked "Pitot Heat", what is that?
>
>

events

I'll bet there's no record of a U.S. airline accident caused by faulty navigation equipment for any reason, or at least excluding maybe the early years. General aviation, yes.

I have no problem with any airline with a flat "no" policy on this, because things do happen even if rarely. NASA gathers the PED incident data, and over a 14-year period, there have been less than

100 events, mostly in cruise, most not classed as potentially serious. The reason they were reported is because the equipment told the pilot about it, and often ATC did so too. Also, NASA has to take the pilot's word for it that the anomaly was caused by a PED.

Fred F.

Dave, try these:

Boeing has investigated alleged interference from portable electronic devices (PEDs) and concluded:

"As a result of these and other investigations, Boeing has not been able to find a definite correlation between PEDs and the associated reported airplane anomalies."

You can look this up at:

Aero 10 - Interference from Electronic Devices

Here's another one:

Electromagnetic interference with aircraft systems

Dave Bush> Lots of data, not much information. No cites given.

Well, I'll be flying to philly again tuesday. My dualband HT goes in my breifcase, but with the battery detached during flight.

YES.

I was on a flight from Toronto to Tampa a few years ago and somewhere over the Carolinas the pilot came on the PA and calmly informed us they have spent the last 45 mins trying to find the source of a buzzing noise on their radios. (He also reinforced the fact that they were all still working, but there was a buzzing noise on the audio.) He politely told everyone to turn off any electronic devices they may be using. The flight attendants quickly verified passenger compliance a few minutes later. About 10 mins after that, he came on the PA to say it was gone and instructed everyone to leave them off for the duration of the flight, not that there was any danger, but it was distracting to have a constant buzzing coming over the radio.

I did notice a couple of laptops had been fired up, but sitting in your seat is not exactly an ideal vantage point to see what everyone else was doing.

Do I think someone's radio is going to make the plane fall from the sky? Of course not. Is there a remote possibility it could cause birdies or other RF anomalies that 'could' affect things? Sure.

On one flight, a few years earlier still, WITH the ok from the flight deck (you know, in those friendlier years when you could say 'hi' through the open cockpit door when you were coming out of the bathroom) I used my FT-470 handie for a few mins. The pilot knew what ham radio was, knew I was going to be on UHF (because I told him that's where I would try for a quick QSO) and he very politely said "Sure, but only for

5 minutes, then turn it off. What seat are you in?" I thanked him kindly, returned to my window seat, and did manage to get into some repeater in Maine for about a minute or two. The funny thing was he was in the galley as we were getting off the plane, I thanked him again, and he asked if I had any luck, I said 'yep' and asked him if I came over anything up front. He smiled and said "Nope, and we were up there looking to see if you would."

The purpose of my sharing this snippet from many years ago is not to illustrate there's no danger in using a receiver (or in this case, a low power transmitter) while on a plane, but using one does not automatically imply you're going to write off the comm/nav systems.

My $.02

It's so damn complicated that nobody can answer the question. Airliners are going in the direction of all-electronic flight control and management systems. Somebody's LO won't affect fuel consumption, uhh, unless it affects the microprocessor or sensors controlling the engine. It's unlikely, a lot of work goes toward making it extremely unlikely. But remember, I said unlikely, not impossible.

Ice on the wings? What controls the de-icing boot?

Blow a tire? Is the braking circuit all-mechanical, or do you have something akin to power boost and anti-lock sensing?

Is the LO detectable outside the fuselage, near the antennas? YES, damn it, YES. I have measured it, with calibrated field strength meters. Don't give me your damn dumb opinions when I have seen the results myself. And is the LO emission strong enough to degrade or deny a navcom signal. YES or MAYBE or COULD BE. It depends on the passenger's radio, how he holds it, is he next to a window, is the fuselage unusually leaky to RF, what seat is the passenger in, what station is the radio tuned to, are the batteries new or weak, how weak is the navcom signal, what is the attitude of the aircraft, is the navcom receiver getting old, even are there multiple passenger receivers acting on the navcom (if they are all like you, how many of 300 passengers will have personal electronics running?).

The POSSIBILITY of interference is undeniable. The PROBABILITY is very difficult to predict. The safe course is to deny you your entertainment for several hours to ensure maximum safety. Is that too much to ask of you?

Ed wb6wsn

Not to cast aspersions on Boeing research, as they are quite reputable, but if they had found correlatable evidence of PED's interfering with avionics, who gets sued? The passenger, a Hong Kong radio manufacturer, or the aircraft builder?

In any case, the reports of interference keep coming in, despite the difficulty of replicating the problem. Obviously, the problem is rare and elusive, but, as in most Electromagnetic Compatibility issues, the easiest, surest, and cheapest cure is to control the source of the problem.

Just turn off ALL passenger electronics for the duration of the flight. Read a book for 2 hours, and let your kid kick the seat in front of him.

Ed wb6wsn

Ed wb6wsn

The first note of personal responsibility and common sense yet seen in this thread. Congratulations!

Ed wb6wsn

My world is as an instrument rated pilot and one who services aircraft avionics. And you must have missed my other post where I said PEDs should be off at all times.

Fred F.