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Friday, 3 January, 2003, 17:18 GMT
Concorde's chicken test
Concorde in its early days
The effects of the sonic boom were unknown

Papers newly released by the British Government reveal how scientists tested Concorde's sonic boom for damage against humans - by firing it at French chickens in a barn.
It came to be seen as one of the technological marvels of the 20th Century.

And although the prospect of supersonic travel for all eventually proved a dream too far, Concorde remains, for many, one of the finest sights in the sky.

Chicken
Tested on animals
But in the early 1970s governments knew so little about the physical effects of the sonic boom they carried out a string of tests to work out what it would do to humans and animals.

Documents released at the Public Record Office under the 30-year-rule reveal a host of international players were extremely worried they would face a flood of lawsuits from damage inflicted by the sonic boom as Concorde cruised tens of thousands of feet overhead.

Unknown effects

Concorde was designed to fly at supersonic speeds - faster than the speed of sound - and completed its first test flight in March 1969.

BA Concorde takes off
For most, Concorde flights remain beyond reach
When Concorde passes the speed of sound, atmospheric pressure waves combine to form a shockwave called a "boom carpet". It can be heard within a 60-miles radius, depending on the environment.

The shockwave sounds like a thunder crack - but in Concorde's early days nobody was quite sure what the accumulative effect of these would be on people and animals.

So in May 1972, the world's leading experts on sonic boom theory met with governments in Montreal, Canada, to discuss what mass supersonic flight might mean.

The scientists told the officials all their studies suggested the "probability of immediate direct injury to persons exposed to sonic boom is essentially zero".

How had they reached this conclusion? With the help of chickens.

Ruffled feathers

The sonic boom committee heard how experts gathered at a French chicken farm to find out exactly how much damage the phenomenon could have in a worst-case scenario.

Air France Concorde
Scientists saw supersonic flight as the way ahead
In the first test, scientists set up a mobile boom generator and fired it in the direction of chicken eggs. After subjecting the unborn chicks to the boom, the team waited for the embryos to hatch - and found no discernable injury had been caused.

"The intention was to examine the startled reaction of living beings subjected to the boom," reveal the papers.

The second test took the team and their mobile boom generator into a barn of 2,800 broiler chickens.

Presumably standing at a safe distance, the team hit the button again and boomed the unsuspecting birds. The reaction, according to the report, was startling.

There was a simultaneous cessation of all the cheeping

"It was characterised by sudden and complete immobility of all the chickens. There was a simultaneous cessation of all the cheeping for a maximum of 40 seconds - whereupon normal activity resumed.

"There was no evidence of collective hysteria crowding or crushing due to fright - even during the critical period when the feathers are grown.

"Repetition of the booms had no economic effect on the industrial raising of chickens subjected to the booms compared with those which were not."

Test flights

The experiments also included observations of human and animal behaviour during special test flights, widely publicised at the time.

Plane-spotters in France
Some still flock to watch Concorde lift off
Part of the problem for the scientists was to work out whether Concorde's sonic boom was powerful enough to destabilise buildings, disorientate people or confuse animals in fields.

According to the papers, scientists were placed at observation points to try and identify people or animals unduly affected by Concorde's boom carpet as it flew overhead.

During the British test flights along a straight route from the west coast of Scotland to Lizard Point, Cornwall, some 676 people claimed compensation for alleged damage from the sonic boom, reveal the papers.

Approximately half of the claims were apparently valid - yet forensic tests on a dozen specially-selected buildings showed no signs of damage.

Brave new world

During the early 1970s, Concorde was regarded as the future of air travel, despite unanswered questions about its environmental impact and commercial viability.

Heathrow crowded terminal
The boom today is in cheap - not fast - flights
The delegates at the sonic boom committee expected at least 36 supersonic airliners to be commercially flying by 1976. Second generation aircraft would be operating by 1981, they predicted.

The key routes for Concorde and its foreign counterparts would be the transatlantic routes between Europe and the Americas, daily flights to south-east Asia, Australia the Middle East and even the Soviet Union. By 1985 they expected there would be at least 1,000 supersonic flights a week over the Atlantic.

But thanks to the commercial problems of offering cheap enough fares, Concorde has remained the preserve of the rich, operated to this day by just British Airways and Air France.

See also:

08 Nov 01 | Business
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