Professor A. K. Dewdney carries out a series of experiments regarding the possibility of making cell-phone calls from planes at various altitudes. He concludes that the cell-phone calls from the "hijacked" 9-11 planes were impossible.
January 23 2003; 4:35 - 5:40 pm
Civic Airport, London, Ontario, Canada
aircraft: Diamond DA20/C1 Katana two-seater
engine: 125 hp
fiberglass/carbon fiber composite body & airframe
weight fully loaded: 1630 lbs
cellphones: one Motorola model "120 CDMA" cellphone (A)
two Motorola "i1000 plus" cellphones (B)
(both fully charged at flight time)
The flight plan consisted of four "laps," elongated circuits (shaped like a paperclip) over London, Ontario airspace. Each lap was about seven to eight miles long and two to three miles wide. Three calls were made on each of two straight legs in each lap. Calls alternated between cellphone A and cellphone B. A second i1000, intended for use at higher altitudes, slipped to the cockpit floor and could not be retrieved in those cramped quarters. A check of battery levels of the first i1000, however, showed that there had been no significant power drain on the unit.
* * * A * * * * * B * * * * A * * * * end
*
* W ----- E
*
*
* * * B * * * * * A * * * * B * * * * begin
Note: "altitude" means aboveground altitude, not height above sea level, as recorded by the altimeter.
| Lap 1 @ 1,100 feet altitude | ||
|---|---|---|
| 1st leg: | A to business number | no connection? |
| B to business number | 1 min. complete | |
| A to business number | 1 min. complete | |
| 2nd leg | B to home number | no connection? |
| A to home number | (broken) complete | |
| B to home number | complete | |
| Lap 2 @ 2,100 feet altitude | ||
| 1st leg: | A to home number | no connection? |
| B to home number | no voice, just a "beep" | |
| A to home number | no connection? | |
| 2nd leg | B to home number | 1 min. complete |
| A to home number | no voice | |
| B to home number | no voice | |
| Lap 3 @ 3,100 feet altitude | ||
| 1st leg: | A to home number | missed making the call |
| B to home number | "system busy" | |
| A to home number | incomplete | |
| 2nd leg | B to home number | "please wait: CLEARNET" |
| A to home number | incomplete | |
| B to home number | call made late, incomplete | |
| Lap 3 @ 3,500 feet altitude | ||
| A to home number | incomplete | |
| B to home number | complete, but breaking up | |
After the third call, I decided that the cockpit was too noisy to hear the message system, so I changed my plan and called home (my wife), instead.
Calls to the business number were recorded by the message system. Two calls made it through. Of the 17 calls to the home number, only about ten calls got through. In three of these, we had a conversation (of sorts) and the rest were just white noise. (no record of which)
In the preliminary test, only five of the 16 (attempted) calls resulted in any meaningful voice contact. In at least two of those calls, no connection whatever could be established with cellsites below. The composition of the Diamond Katana (manufactured right here in London, Ontario) makes it almost transparent to EM radiation at radio wavelengths and the results of this experiment are therefore optimal. Aircraft with metal skins will undoubtedly fare rather worse in the percentage of calls making it through.
| Altitude Range | Range in Feet | Call Success Rate | Percentage Success Rate |
|---|---|---|---|
| low altitude | 1100' - 2100' | 4/12 | 33% |
| mid altitude | 3100' - 3500' | 1/7 | 14% |
The purpose of this experiment was to probe the effect of altitude on cellphone service and to iron out wrinkles in experimental procedure. In the first instance, it looks as though there might well be a decline in service with increasing altitude. The phenomenon must now be mapped more carefully.
As far as operating procedures is concerned, it is probably best to make calls to a number you know well, to be familiar with the various status messages on each cellphone display screen, and to have someone at the other end who can log the time of the call, as well as to summarize the content. (The cockpit in most light aircraft is so noisy that one cannot always hear a voice at the other end, although I did hear my wife talking somewhat clearly on two occasions.) Also, it is important to be very organized, having a special carrier case for cellphones, writing/recording materials, etc. The airspeed of the Katana was just a little fast for me to comfortably make the calls and stay organized at the same time. Two of the calls were made rather late in the current lap, even as we began to climb out to the next one. It would be better to have a separate person operating the cellphones. We also need a meaningful call classification system to fill the gaps between complete failure and an audible conversation.
All calls were handled by the Bell Mobility Network, which has some 25 cellsites operating in the London area. I have now located all the cellsites in London, Ontario, thanks to a very helpful set of maps provided by a local cell phone aficionado: <www.arcx.com/sites/>
Plans are now under way for Part Two. This will involve a Cessna four-seater (with an aluminum skin), five or six cellphones of various types, an expert to operate them on my queue, and a flight plan that will explore the effect up to 10,000 feet beyond which, according to one airline pilot, there is absolutely no hope of getting through.
A. K. Dewdney
(with thanks to Corey Barrington, pilot with empire Aviation)
Weather: unlimited ceiling, light scattered cloud at 3,000 and 25,000 feet, visibility 15 miles, wind 5 knots from NW, air temperature -12 C.
For this experiment, we flew a circular route, instead of the elongated oval. The circle centred on the downtown core and took us over most of the city suburbs. All locations below are referred to the city centre and are always about three miles distant from it.
At times specified by the director, the operator made a call to a specified number, stating the code number of the cellphone (1 to 4) and the altitude. The receiver recorded whatever was heard and the time the call was received. At the first three altitudes of 2000, 4000, and 6000 feet abga each cellphone was used once. At 8000 feet abga, only C2 and C3 were tried, C1 and C4 now being hors de combat.
| Time (pm) | Call No. | C# | Loc. | Operator Recorder |
|---|---|---|---|---|
| 5:05 | started taxi to runway | |||
| 5:12 | takeoff | |||
| 5:14 | at 2000 feet (above-ground altitude) | |||
| 5:15 | Call #1 | C1 | N | success not very clear |
| 5:17 | Call #2 | C2 | W | success not very clear |
| 5:19 | Call #3 | C3 | SW | failure |
| 5:21 | Call #4 | C4 | S | success not clear/ breaking up |
| 5:24 | climbed to 4000 feet abga | |||
| 5:25 | Call #5 | C1 | NE | failure |
| 5:26 | Call #6 | C2 | N | success clear |
| 5:27 | Call #7 | C3 | NW | failure |
| 5:29 | Call #8 | C4 | W | failure |
| 5:33 | climbed to 6000 feet abga | |||
| 5:34 | Call #9 | C1 | SE | failure |
| 5:36 | Call #10 | C2 | E | failure |
| 5:37 | Call #11 | C3 | NE | failure |
| 5:38 | Call #12 | C4 | N | failure |
| 5:39 | Call #13 | C1 | NW | failure |
| 5:40 | Call #14 | C2 | SW | success clear |
| 5:42 | Call #15 | C3 | S | failure |
| 5:43 | Call #16 | C4 | SE | failure |
| 5:44 | Call #17 | C1 | E | failure |
| 5:45 | Call #18 | C2 | NE | failure |
| 5:45 | Call #19 | C3 | NE | success breaking up |
| 5:46 | Call #20 | C4 | N | failure |
| 5:49 | begin climb to 8000 feet abga (cellphones 2 and 3 only) | |||
| 5:50 | Call #21 | C2 | W | failure |
| 5:50 | Call #22 | C3 | SW | failure |
| 5:51 | Call #23 | C2 | S | success buzzy |
| 5:53 | completed climb to 8000 feet abga | |||
| 5:58 | Call #24 | C3 | SE | failure |
| 5:58 | Call #25 | C2 | E | failure |
| 5:58 | Call #26 | C3 | E | failure |
| 5:59 | Call #27 | C2 | NE | failure |
| 6:00 | Call #28 | C3 | N | failure |
| 6:01 | Call #29 | C1 | N | failure |
| 6:01 | Call #30 | C2 | NW | failure |
| 6:02 | Call #31 | C3 | NW | failure |
| 6:02 | Call #32 | C4 | NW | |
| 6:15 | landed at airport |
To the extent that the cellphones used in this experiment represent types in general use, it may be concluded that from this particular type of aircraft, cellphones become useless very quickly with increasing altitude. In particular, two of the cellphone types, the Mike and the Nokia, became useless above 2000 feet. Of the remaining two, the Audiovox worked intermittently up to 6000 feet but failed thereafter, while the BM analog cellphone worked once just over 7000 feet but failed consistently thereafter. We therefore conclude that ordinary cellphones, digital or analog, will fail to get through at or above 8000 feet abga.
It should be noted that several of the calls rated here as "successes" were difficult for the Recorder to hear, witness description such as "breaking up" or "buzzy."
| Altitude (in feet) | Calls Tried | Calls Successful | Percent Success |
|---|---|---|---|
| 2000 | 4 | 3 | 75% |
| 4000 | 4 | 1 | 25% |
| 6000 | 12 | 2 | 17% |
| 8000 | 12* | 1 | 8% |
* includes three calls made while climbing; last successful call was made from just over 7000 feet.
The four cellphones operated via four different cellular networks (cellsites). Because calls were made from a variety of positions for each network, it cannot be said that failures were the fault of cellsite placement. the London, Ontario, region is richly supplied with cellsites belonging to five separate networks.
It may be noted in passing that this experiment was also conducted in a radio-transparent aircraft with carbon-fibre composite construction. Failure to make a call from such an aircraft with any particular brand of cellphone spells automatic failure for the same cellphone from a metal-clad aircraft flying at the same altitude. A metal skin attenuates all cellphone signals to a significant degree. It may safely be concluded that the operational ceiling for cellphones in aluminum skin aircraft (most passenger liners, for example) would be significantly lower than the ones reported here.
It may therefore safely be concluded that cellphone calls from passenger aircraft are physically impossible above 8000 feet abga and statistically unlikely below it.
A. K. Dewdney
February 25/03
C1 Motorola i95cl - Telus Mike Network - 800 Mhz IDEN
C2 Motorola StarTac - Bell Mobility - 800 Mhz Analog
C3 Audiovox 8300 - Telus PCS Network - 1.9 Ghz CDMA / 800 MHz
C4 Nokia 6310i - Rogers AT&T - 1.9 Ghz GHz GSM. (Tri-Band - Has an
1.8 GHz and 900 Mhz GSM these are European frequencies)
IDEN - Integrated Digital Enhanced Network
CDMA - Code Division Multiple Access
GSM - Global Systems for Mobile Communications
Power output of these handsets. The Nokia 6310i and Audiovox 8300 when in digital mode will output 0.2 Watts.
When the Analog Motorola StarTac is operating it is at 0.6 Watts optimal.
When and IF the Audiovox 8300 is in analog mode it will operate at 0.6 Watts (However, this is not normally the case - you will see wattage levels around 0.52 - 0.45 approximately)
Both the Telus Mike (C1) and Motorola StarTac (C2) operate in the 800 MHz range. This will allow the signal to travel at a great distance. However, the IDEN (Mike) network has fewer site locations and is a newer Digital network. Most digital technologies operate on a "all or none" basis. When it has signal it will work well. As the signal fades, one hears no static, but some digital distortion just before the call drops.
Mike Network: Newer, all-digital network with modern antenna design, and fewer cellsites
Bell Mobility Analog: Older, analog network with less focused antenna design but many cellsites
Telus PCS: Newer, digital network with multiple frequencies, modern antenna design, and many cellsites
Rogers GSM: Our newest digital network with modern antenna design and many
cellsites
A. K. Dewdney,
February 25th 2003