D. H. Klyde, R. E. Magdaleno, and J. G. Reinsberg, The Effect of Tire Pressure on Aircraft Ground Handling, Journal of Guidance, Control, and Dynamics, Vol. 25, No. 4, pp. 558-564, 2003. (AIAA 2002-4798, STI-P-586)Handling of ground vehicles is dominated by the ability of the tires to generate cornering and braking forces. Tire forces are primarily a function of the contact patch slip angle, the longitudinal slip ratio, normal load, and inflation pressure. As part of a program to assess the ground handling of a Navy trainer, comprehensive tire tests were conducted on a set of nose and main gear tires. The results of this testing indicated that improvements in ground handling may be seen by setting the nose tire pressure to the higher carrier service pressure, while the main gear tires remained at the lower field service pressure. Specifically, the nose gear tire data revealed a significant reduction in nose tire cornering stiffness at the higher pressure. To test for such an improvement, a flight test program was undertaken in which the proposed tire configuration was evaluated against the baseline aircraft configuration. Rudder pedal frequency sweeps were used to determine heading attitude bandwidth parameters at several speeds and a Runway Offset Capture and Hold maneuver was used to generate pilot handling qualities assessments. The frequency sweep data indicated a significant improvement in heading attitude bandwidth as a function of airspeed for the high pressure nose tire configuration. For one evaluation pilot, the Runway Offset Capture and Hold ratings indicated a one to two handling qualities rating point improvement and a one PIO tendency rating point improvement with the high pressure nose tire configuration. The ratings of the second evaluation pilot did not vary significantly between configurations, however his comments indicated a clear preference for the new configuration. It was demonstrated through time history comparisons that the differences between the two evaluation pilots resulted primarily from pilot technique.

D. H. Klyde, T. T. Myers, R. E. Magdaleno, and J. G. Reinsberg, Identification of the Dominant Ground Handling Characteristics of a Navy Jet Trainer, Journal of Guidance, Control, and Dynamics, Vol. 25, No. 3, pp. 546-552, 2002. (AIAA 2000-3903, STI-P-568)An assessment is described of the ground handling problems associated with a Navy jet trainer including the lower order equivalent systems modeling approach that was used to determine the dominant ground handling characteristics (i.e., oversteer/understeer). It was found that just after touchdown the aircraft may be slightly understeer, but understeer gradient decreases with speed becoming oversteer at roughly 80 kts. From roughly 80 to 40 kts, this variation is such that it remains close to the stability boundary. Aerodynamic forces appear to provide a significant stabilizing effect at higher speeds. Thus, in the 80 to 40 kn region where the aircraft operates near the stability boundary, controllability as measured by yaw rate command bandwidth is the primary manual control problem, not instability per se.

D. H. Klyde, J. G. Reinsberg, E. Sanders, and A. Kokolios, Flight Test Evaluation of Stability Augmentation Steering System for Aircraft Ground Handling, Journal of Guidance, Control, and Dynamics, Vol. 27, No. 1, pp. 41-51, 2004. (AIAA 2003-5318, STI-P-610)A flight test program was conducted to evaluate a newly developed Stability Augmentation Steering System, or SASS. Designed to improve the ground handling characteristics of a Navy jet trainer, the SASS features a yaw rate feedback that is used to set the heading attitude bandwidth as desired, while providing an essentially constant rudder pedal sensitivity variation with speed. Flight test efforts were conducted to assess performance of two SASS configurations against the baseline aircraft configuration. Three pilots evaluated the ability of the aircraft to perform a runway offset capture and hold maneuver, essentially a lane change task, with and without braking. The task with braking was found to be the better separator in terms of pilot ratings for the two SASS configurations when compared to the baseline aircraft. The flight test program found that the SASS significantly improved the ground handling of the aircraft.