The Surface Friction Tester is a vehicle that is used at airports mainly for friction measuring on runways. It is an indispensable equipment at airports that often have adverse weather conditions : heavy rain, ice or snow.
In Spain are mainly used adapted vehicles by Swedish SARSYS (www.sarsys.se) , although there are also trailers with tester to join to any vehicle. On the website of SARSYS show all models they have. Spain uses the SAAB adapted in most airports. In this link SARSYS shows how their Testers work.
The SAAB vehicle is adapted to hold the measuring equipment eliminating the rear seats and the back trunk practically useless for any transport. The rear seat space is occupied by a large water tank which is used when there is no rain, in the dry runway.
In the trunk is the wheel that measures the friction and the system of raising and lowering of the wheel to be controlled from driver's position.
Taking measurements is simple initially be programmed in the onboard computer the runway to be tested, indicate whether to use water (with dry runway) and take the starting position.
The vehicle must achieve and maintain a constant speed of 96 km/h (with cruise mode) before starting the measurement. There are exceptions for measurements at lower speeds. The measurement is performed on the 2 sides of the runway, and the computer displays the measurement on each side and the average of both.
After the complete measurement of the runway, the computer gives a graph and values to be able to interpret if the friction is not good enough for the movement of aircraft, both takeoff and landing, although it is primarily in the landings where more this test is requested. In addition, the friction sample sections with which to guide the aircraft the best position to start the braking action.
In addition to measurements on runways, the computer is programmed to perform measurements on taxiways or other surface, such as in a parking.
This is a video of SAAB in an airport in Spain: