Although no date has been set for the IRFI becoming available, it has been noted that the GripTester has shown itself particularly consistent in its performance during these tests. The GripTester is a three wheeled trailer with a weight of 85 kilos. This data collection computer may be any IBM compatible PC, and the presentation of results is modern and convenient. As the runway survey takes place, the GripNumber and survey speed are shown schematically and in digital form, with colour being used to draw the operator's attention to incorrect speed or dangerously low readings. Data is automatically archived and can be easily retrieved at any time for inspection and printing.
Printing is on standard paper, in colour.
The GripTester is very easy to handle, operate, calibrate and maintain. An alternative system is the slewed or angled wheel. On most surfaces, good correlation can be achieved between braked wheel and slewed wheel devices although on transverse grooving, for example, this correlation may not hold. Fixed slip versus variable slip It is possible to design a transmission system that allows the operator to vary the slip ratio of the device. For research purposes, this is extremely interesting but it has not so far been found particularly useful for practical survey work.