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LASSI system being tested on an optical bench
LASSI (Laser Air Speed Sensor Instrument) is a compact remote airspeed measurement system which uses a UltraViolet (UV) laser. This system is designed to replace the Pitot tube technology currently in use.
LASSI is a collaborative project sponsored by the DTI. BAE Systems has teamed up with innovative laser manufacturer AOT Ltd. and Hull University to develop this new system. The most widespread method of airspeed measurement currently in use is the Pitot tube whereby probes measure the air pressure, from which the airspeed is deduced.
This approach means that lengthy, airframe-specific calibration is required for each installation to account for varying airflow around the aircraft. Also, system accuracy varies depending on the airspeed such that the system becomes very limited at low speeds. The probes themselves protrude from the airframe creating drag and increasing fuel consumption.
Pitot tubes also become blocked with debris from the atmosphere, so they require regular cleaning. LASSI avoids all these problems, as the system can sit behind a window conformal to the airframe and the measurement of airspeed using backscattered UV light from the atmosphere means that it can be used at all speeds and altitudes. LASSI is creating great interest and has been widely reported in the technical press.
Advantages over Pitot tube systems include:
- Fuel savings due to improved aircraft aerodynamics
- Usability at all altitudes
- Greater accuracy at all speeds
- Easier and quicker installation
- Simpler maintenance procedures
- EO countermeasures
