Search Results

Laboratory and aircraft flight testing indicates that braking is the primary driver of tire wear on tactical aircraft, and that steps can be taken to significantly improve the tire wear performance. The effects of numerous other factors including aircraft characteristics, runway surface texture, tire tread compound, tire pressure, and environmental conditions were also evaluated under the Air Force’s Improved Tire Life and Extended Life Tire programs. Laboratory testing of tire wear performance using the new 168i internal roadwheel dynamometer was successfully demonstrated.

Although aircraft tires are traditionally tested on external dynamometers, the effects of the curved test surface on normal contact pressure distribution and footprint area of a tire have not been previously addressed. Using the Tire Force Machine (TFM) at the Wright Laboratory Landing Gear Development Facility (LGDF), trends for pressure distribution and footprint area were investigated for concave, convex and flat plate surfaces. This evaluation was performed using the F-16 bias, F-16 radial and B-57 bias main landing gear tires at rated load and inflation pressures. The trends for overall tire footprint behavior indicate that the more convex the surface, the smaller the contact area and the larger the normal contact pressures. Conversely, the more concave the surface, the larger the contact area and the smaller the normal contact pressures. Based on these results, the study recommends a 168″ diameter concave (internal roadwheel) dynamometer for tire wear/durability tests.

This paper presents the results of tire footprint studies which were performed to understand the effects of vertical load, camber, yaw, inflation pressure and tire construction on frictional power. Two previously worn F-16 radial and bias tire constructions were selected. All tests were conducted at low speed on a Tire Force Machine having a specialized sensor plate with embedded traction and slip sensors. The tests indicate that the total frictional power for both tire constructions are quite similar at low yaw angles, however, at 4° yaw, the bias tire generated significantly more frictional power than the radial tire.

This paper presents the results of a study in which the free rolling behavior of a F-16 tire was numerically modeled. The tire contact patch normal and shear stresses as well as the displacement distributions were obtained from a three dimensional finite element computer program used at the Wright-Patterson Air Force Base, Ohio. It is shown how the predicted deflections are in reasonable agreement with the rated load vs. deformation characteristics, while predicting the effective rolling radius using a theoretical solution. A significant development of this work is the formulation and execution of a finite difference algorithm to evaluate the contact patch slip velocity distribution by methodically manipulating the above computer program results. Slip velocities are then utilized in assessing the rate of slip energy generation at the contact patch, which directly contributes to tire wear. Finally, it is shown how even a low brake slip ratio can increase the contact patch slip energy.