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High stability Altimeter System for Transponders and Air data Computers

Final Report Summary - HASTAC (High stability Altimeter System for Transponders and Air data Computers)

The HASTAC project main target was to develop a new altimetry pressure transducer that should be better than reported state-of-the-art transducers in the marketplace. The target was to achieve a demonstrated stability better than 0.01 % (100 ppm) maximum drift error per year. Previous state-of-the-art MEMS transducers were reported to be in the 0.02 % range. Accelerated tests performed in the HASTAC project, corresponding to more than 20 years of operation in room temperature conditions, indicate that the goal has been met.

The statistical data is limited, and additional tests are still ongoing when this report is submitted. The four transducers which have been submitted to long term stability tests, including more than 1 000 thermal cycles, all indicated a 0.01 % or less drift error per year. The documented results demonstrate a stability better than 0.01 % (100 ppm)/year of full scale, which corresponds to a calibrated pressure range of -2 000 ft to 60 000 ft (1150 mbar – 50 mbarA). Additional transducers are started in tests, and the consortium will continue the data collection and further development in the Seventh Framework project HISVESTA, starting the third quarter of 2008.

The HASTAC project has developed more than 800 sensors in 40 different versions, to identify the potential causes for drift mechanisms. The knowledge established is used to make the ideal design for the new SP83 pressure sensor, which is the key element in the TP4000 transducer. The TP4000 transducer is embedded in a batch of modified air data computers by Penny & Giles, and preliminary performance testing shows very promising results. The lab test data supports the superior results reported from the transducer tests.

The project has developed a new generation of altimeter pressure sensors (SP83), fully compensated altitude pressure transducers (TP4000) and an upgraded version of air data computers (ADC), suitable for fixed wing and rotary wing applications, which have proven altitude long term stability capabilities significantly improved over the traditional types. Aircraft flight testing that was planned performed in the project was cancelled due to delay in the wafer processing task, however accuracy and long term stability tests on transducer and air data level demonstrates a significant performance improvement. The new generation of transducers with the new MEMS silicon barometric pressure sensor as the key component, will also be available for other application areas, such as transponders and cabin pressure control systems.

The results achieved in the HASTAC project does clearly indicate that TP4000 transducer is capable of performing within the target of 100 ppm (0,01 %) altitude shift per year which is a clear target for RVSM altitude sensors. The emerging HISVESTA project in the Seventh Framework Programme will benefit from all the results from HASTAC.

In addition, the HASTAC project has resulted in major know how and competence in the MEMS pressure sensor field of the industry, for example:
- increased knowledge within all the HASTAC project partners of silicon MEMS structures for avionic use,
- the basic silicon sensing structures may be used in, or modified to, other demanding aerospace applications,
- the new MEMSCAP SP83/TP4000 barometric pressure sensor will generate more business and will give aircrafts better accuracy in altitude monitoring.

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