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Aircraft phone calls "big business" say optimists

The world's aircraft operators think they may have broken out of the trap of having to ban mobile phones in flight - by providing inflight phone services for mobile phones.

The trick, announced by The WirelessCabin consortium, which is headed by the German Aerospace Centre, is an EC-funded initiative to put pico-cells into the aircraft themselves.

Technically, this ends both objections to having live onboard cellphones.

The normal explanation for the aircraft ban on using phones is that they may interfere with flight instrumentation. In fact, the more pressing reason is that they interfere with ground-based phone switching equipment.

By putting a phone cell on the aircraft, the WirelessCabin consortium plans to force the phones on the plane to reduce the power of their transmissions, so that they no longer reach the ground, and cause indetectable interference to any equipment on the plane itself.

But whether the deal can be made to pay for itself, is a moot point. Traditionally, aircraft passengers have proved very resistant to the idea of paying for phone calls.

According to an eWeek report, "the cell includes a power-limiting mechanism that forces the handsets to transmit at one-thousandth of their usual output."

This would mean that the signals would be trapped inside the metal hull of the aircraft. In normal use, a cellphone has to transmit near maximum power to get a signal through the small holes in the fuselage. If the phone can be persuaded to "throttle back" then the major problem will be solved.

The main problem is that at 35,000 feet, a phone can transmit simultaneously to all the local phone masts for more than 20 miles in each direction. In heavily populated areas, that's several hundred cells. Each cell will try to "register" the phone with the central switch equipment, causing an impossible problem for the phone networks.

This isn't likely to be a special feature of the cell. Hand-held phones use transmit power control by default, cutting the amount of electricity they draw from their batteries to the minimum by only radiating with enough energy to reach the nearest cell. If the cell "mast" is actually inside the fuselage, then they would be able to reach, and register themselves with the transmitter at the lowest possible power level.

According to the consortium, the founders believe that airline passengers will form a "big market" - a claim which barely stands examination.

Working on a rule of thumb basis that at any moment, there are 3,500 aircraft in the air in the world as a whole, with an average of around 200 passengers, the total number of possible phone users involved would be somewhere between 5,000,000 and a million people.

Serving a mere million people with phone cells installed in each of the world's 50,000 operating aircraft would require passengers either to make calls pretty much continuously all the time they are in the air, or would require them to pay a hefty premium on normal cellphone charges. In the past, airline passengers have proved very reluctant to spend money on phone calls, and special-purpose aircraft phones have recently been taken out of service in most airlines which tried them.

The safety argument would be more convincing if airline staff took any active steps to disable or even detect "live" cellphones in flight. In reality, the flight staff can't even tell if a phone on board is switched on or not - and as often as not, people leave their phones in luggage and hand baggage powered up. It is a pretty rare flight these days in which passengers won't hear at least one phone ring in the air, either in someone's pocket, or in an overhead locker.

In an environment where security staff will confiscate wooden tooth picks because they are "sharp" the fact that they will let you carry an operating phone onto the plane indicates where they rate the risk level.

However, even if the payback in phone fees is small, the phone companies may go for the WirelessCabin option, because of the reduction in complications caused to their network switching equipment.