Micro Sensors Could Deliver More Consistent Air Data

Certification Center Canada (3C) is teaming with UK start-up Surrey Sensors to develop a new type of air data instrument for aircraft that avoids the vulnerabilities of current sensors to factors such as vibration and pitot tube blockages involving ice, water, and debris. The partners have secured funding from the National Research Council of Canada and Innovate UK to produce more advanced prototypes of the technology over the next 18 months.

The system combines Surrey Sensors’ micro constant-temperature anemometer with 3C’s Airflow Performance Monitor pressure-based system, which detects contamination to wings and rotors from ice accretion. It can provide pilots with real-time warnings about the need to deploy anti-icing measures.

The partners intend the technology to serve as a backup to the main air data ports, which, if blocked, can generate incorrect values for speed, angle of attack, sideslip, and altitude. Greater certainty about the data measured should also let flight crews be less conservative about using power-hungry wing heaters that increase fuel burn.

“We are taking measurements using both pressure and heat transfer, so there is no common failure mode between these two,” David Birch, Surrey Sensors’ director of research, told AIN. “We believe this is the first [air data monitoring] system that has this level of dual redundancy.”

Tiny Sensors

The sensor itself is tiny at just one-third of a millimeter in diameter. Using heat transfer, it measures temperature variations as air passes over it, much like how humans can use a moistened finger to sense which way the wind is blowing.

Engineers from Surrey Sensors and 3C are now defining the materials that will be used for the thermally and electrically insulated housing surrounding the sensor. It can be fitted to wings or helicopter rotor blades, which have so far been difficult surfaces for installing sensors.

With some flight testing on early examples complete, the partners are still weighing factors such as how deicing fluid or bird strikes could affect the sensor. Montreal-based 3C, which provides flight test and certification services, will raise the system’s technology readiness level by conducting flight tests under known icing conditions and at variable air temperatures.

In addition to being deployed on airplanes and helicopters, the partners also see use cases for the new sensor with drones and wind turbine blades. On aircraft, it is anticipated that at least two sensors would be installed under supplemental type certificates in locations including wings, tailplanes, and along the fuselage.

“Knowing your stall margin in all phases of flight is critical,” commented 3C marketing director Alistair Chapman. “Combining these technologies will both further address this safety issue and open up new possibilities for a rotary environment.”