TP 13579 PROCEEDINGS of the 2nd International Meeting ... - UQAC

IMAPCR ’99
144. To perform a linear regression, a virtual reference device made up of combinations of
devices was constructed (IRFI Reference Selection 1998).
145. Mr. Wambold concluded that:
• a reference device for the IRFI is needed;
• STBA device is offered as an interim reference device;
• devices must be calibrated periodically against the reference;
• calibration against the reference device should be carried out annually.
146. When asked whether each device will have its own “a” and “b” in the statistical model IRFI
= a + b DEV (even if the devices are of the same make), Mr. Wambold confirmed that each
device will have its own unique set of parameters, a and b.
147. Comments were offered from the floor that tires, tire pressures, and load make the
difference and not the measuring devices, and that the test surface conditions should be
invariable. Mr. Wambold added that all tests were done with standard tire pressure of
100 psi.
Physical Methodology for IRFI
148. Arild Andresen, Mobility Friction Technology, Norway, and Chairman of the ASTM
Subcommittee, proposed a standardized test methodology for calculating the IRFI for
operational use.
149. The physical methodology for the IRFI comprises a number of fixed surface classes, master
models for each friction measuring device, pavement friction differentiated by segment, and
computer programs.
150. The advantage of the proposed methodology is that it is based on a universal concept and
has potential for higher precision and reproducibility.
151. Identification of friction characteristics by surface classes offers more flexibility and
comprehensiveness in making rules, and the methodology can be adapted to differences in
wheel-braking performances of different types of aircraft.
152. A comment was offered from the floor that the methodology was interesting, but that slush
and dust on ice are missing.
153. Another comment was that drag and friction are different entities; consequently, a dual
wheel system may be used for measuring friction and drag separately. Mr. Andresen replied
that no such device exists.
154. When asked whether the IRFI will be qualified by surface conditions (e.g., wet pavement),
Mr. Andresen replied that calculations will be made, but that only one number will be
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