Next-generation Sensors May Help Avert Airline Disasters

The following year, two planes collided in mid-air over Überlingen in the south of Germany on the edge of Lake Constance. One was a Russian passenger flight from Moscow to Barcelona, while the other was a cargo plane heading for Belgium from the Persian Gulf. Seventy-one persons died.

Safety need to be improved

As air transport grows, take-offs become more tightly spaced and more and more planes are circling airports as they wait for permission to land, the potential for disasters increases.

Last year alone, international air traffic grew by 5.9 percent. Parallel to this increase, the minimum distance between aircraft in the air in European airspace has decreased. The minimum vertical distance between aircraft has been halved from 600 metres to 300 for planes flying above 29000 feet. The idea has been to increase airspace capacity by 20 percent. Routes are shortened, and airlines expect to save the huge sum of NOK 30 billion a year in fuel costs alone.

But what above safety up there? In the wake of a number of disasters in the air in 2001 and 2002, the EU took up the problem and resolved that certain aspects of the industry should be studied in detail and evaluated in terms of safety. Several projects were launched under its 6th Framework Programme. One of these was the HASTEC project, which was to develop the next generation of pressure sensors for better aircraft altitude measurement.

Next-generation sensors

“There is a need for aircraft sensors that are more accurate than current models, which are large and reliable, but expensive systems,” says Sigurd Moe of SINTEF ICT. “Among other things, they need to be more stable throughout their life-cycle. The problem with current sensors is that they need to be checked and calibrated regularly, and this is an expensive process since the aircraft needs to be grounded.

Challenges

The problem is that mechanical tensions may develop in the connection with the sensor package itself. The scientists therefore had to produce a silicon based sensor structure in which such tensions would not transmit/propogate into the chip itself. The solution was a spiral silicon element in which the pressure-sensitive part was not affected even if the mounting stretches and drags the element.

SINTEF produces silicon wafers with hundreds of chips on each wafer, several of which are laid on top of each other and glued together before being sawn into chips. Individual chips are then selected and integrated into a sensor package that has been developed by Memscap. The company produces, assembles and tests the sensor package itself.

The first prototype has now been delivered to Memscap by the scientists for further testing and mounting. During the first six months of 2008 these new-technology sensors will be flight tested.