Technology into Heaven

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

Almost three years ago SINTEF and Memscap, a company based in Horten, applied for funding to produce the next generation of precision aircraft altimeters. Together with British and Rumanian partners, the Norwegians were awarded funding for a project worth almost NOK 3 million. The project aims to raise current technology through the next generation of pressure sensors and to produce a sensor platform for the next 20 years.

Today, the partners have almost reached their goal.

“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.

Memscap

“Most people are unaware that one of the key components in international aircraft today is based on Norwegian technology,” says Ole Henrik Gusland of Memscap. The company has been producing sensors for the aircraft industry for more than 20 years, and has recently supplied cabin pressure sensors for the Airbus 380 mega-jumbo jet and Boeing's 787 Dreamliner.

The Norwegian company used to be a subsidiary of SensoNor, but was bought up by Memscap SA in 2002. Its product portfolio comprises both high-precision pressure sensors for aircraft and medical pressure sensors.

Two aircraft that have been allocated the same flight corridor need to maintain exactly the correct altitude during the whole flight if they are to avoid problems, explains Gusland. “This means that the altimeters must be correct even if the plane moves through warm and cold air strata, and such accuracy must be maintained throughout the lifetime of the aircraft. On the ground and in the air over Dubai, for example, temperatures can range from plus fifty to minus sixty degrees. Temperature differences of this magnitude are a great challenge for aircraft electronic systems. Airlines want to ground their craft as seldom as possible for calibration.”

MiNaLab

Until recently, Memscap used SensoNor to manufacture silicon chips which are then mounted and encapsulated, but since SensoNor has been bought up by a huge German concern, Memscap has been using SINTEF's Micro and Nanolaboratory for most of its R & D-oriented projects.

“SINTEF is research-oriented, and we regard SINTEF as a small-scale manufacturer and as a supplement to others, because they are close at hand and have a great deal of advanced new equipment for producing sensors,” says Gusland.

Challenges

“When a new sensor chip is being developed, it is important to understand the customer's criteria. These define our frame conditions and set out guidelines for the design. In this case, the fundamental requirement was an extremely stable signal. The sensor must not be affected by external conditions,” says Sigurd Moe of SINTEF ICT.

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.

“We believe that the new design is extremely good, and we can see that it possesses promising features capable of meeting the requirements of the aircraft of the future,” says Sigurd Moe.

Facts:
The HASTEC project (High-stability Altimeter System for Air data Computers), which is part of the EU's 6th Framework Programmes has been running for three years. The project will help to improve aviation safety, and develop next-generation pressure sensors for aircraft that will come into use in 2009. The project will be continued via HISVESTA in the EU's 7th Framework Programme , in which the sensor technology will be further developed for use in aircraft engines and for cabin-pressure measurements. These new sensor platforms will be implemented in new aircraft from 2012.
Text: Åse Dragland
Contact: Dag Ausen, tel: 0047 22 06 75 46Email: dag-ausen@sintef.no