Avoiding mid-air crossed line

Press, 27 June 1987, Page 21

Avoiding mid-air crossed line

By

VICTOR SMART,

of the London “Observer.”

Concorde came withinseconds of a mid-air collision over Berkshire in April after a simple mix-up over air traffic control messages. The pilot of the supersonic jet, “Speedbird One,” heard a message to fly to 13,000 ft. He acknowledged the instruction and began to climb, inadvertently putting Concorde on a collision course with a small turbo-prop. What had happened was that Concorde had misheard an order for another plane, a jumbo jet, “American FiveOne,” at Gatwick. When Concorde had radioed its response back to air traffic control, the jumbo jet had broadcast simultaneously, blotting out the supersonic jet’s message. Noone on the ground or in the air could be aware that the transmission was lost or that Concorde had made a mistake. For all their high-tech wizardry, modern jets rely on conventional VHF radio transmissions which can handle only one call on a wavelength. If two aircraft start to radio simul-, taneously, one of the-messages

will be blocked. . ■ ' Worse still, a vital channel can be rendered inoperative to all users for prolonged periods. This happens if a pilot inadvertently leaves on his transmitter after his message is completed giving a so-called “stuck mike.”

At the moment there is no way round the stuck mike problem, apart from switching to a less convenient channel. Pilots report hundreds of incidents of this sort every year. A British inventor, Nigel Corrigan, of Peterborough, has now JIM COLTHORPE

come up with a solution to these problems. He has developed an electronic gadget called Contran which prevents conflicting transmissions. This Is to be built in America under licence from Pipercross Communications.

Installed in airliner cockpits, it stops a pilot Starting to broadcast if the frequency is already in use. When the frequency Is busy, instead of hearing his own message over his headphones, a pilot hears the traffic already established. A pilot In the position of the Concorde captain would not have heard his acknowledgement of the order to climb, but rather the voice of the jumbo jet pilot. For emergencies there is an over-ride mechanism which cuts in immediately. Should a microphone be left on unused, the pilot is visually warned. Contran weighs only a few pounds and is easy to install. Trials are now underway on flights with an HS 748 turboprop operated by the Civil Aviation Authority from Stansted Airport in Essex.