Aiaa 2001-4374 a Lumped Parameter Model of Turboprop Aircraft Operating on Gravel Runways

The purpose of an aircraft Takeoff Performance Monitoring System (TOPMS) is to provide to the pilot information pertaining to the level of safety with which a takeoff is proceeding. The authors have developed a theoretical dynamic model to investigate the feasibility of using an observer system during the roll and takeoff phases of aircraft operation to provide to the pilot the information that is needed to manoeuver safely. This model was validated using a prototype device installed in a 19-passenger commercial turboprop aircraft. Unlike previous work in this field, this investigation focussed on various factors that are unique to the far-northern environment. Further, the Global Positioning System(GPS) was proposed as the sole source of kinematic information. This provided the possibility that a TOPMS could be devised that would require no additional ground-based installation. The results of a practical investigation that was conducted to validate the theoretical model and signal processing technique appears in AIAA 2001-4170. The investigation showed that it was possible to predict the displacement of an aircraft to within 15 [m], the length of the test aircraft, in sufficient time to aid the pilot in decision-making. TAKEOFF PERFORMANCE MONITORING The "critical engine failure recognition speed" (V1) is defined as the speed above which takeoff could safely continue if the most critical engine failed. In the event that the aircraft has reached a point such that the remaining runway is equal to the required safe stopping distance and has not yet reached a speed of V1, the takeoff must be aborted. It is standard practice for pilots to reduce takeoff thrust to a level that would allow acceleration to V1 followed by deceleration to rest such that the entire length of the runway would be used. This practice prolongs the service life of the aircraft engines. One of the most common aviation accident events continues to be runway overrun during takeoff or landing. In the case of takeoff runway overrun, the problem is often associated with engine power loss. This problem is further aggravated in inclement weather where runway surfaces are contaminated by water or ice. Pilots of multi-engine aircraft must evaluate a complex set of variables in situations involving varying winds, limited control of ground traction, and necessary application of reverse thrust. Some parameters of importance in a TOPMS include wheel bearing viscous friction, aircraft drag, runway slope, engine thrust, aircraft velocity, position relative to the end of the runway, and frictional coefficient between the aircraft tires and the runway. Previous work in the design of takeoff performance monitors accounted for such variables individually, which led to a large uncertainty in the predicted displacement. The most significant uncertainty pertained to the measurement of runway friction coefficient. In far-northern regions, however, the majority of airports consist of gravel runways. On gravel runways, the principal means of reducing speed is through the * Doctoral Student, Department of Mechanical Engineering † Associate Professor, Department of Agricultural and Bioresource Engineering ‡ Dean Emeritus, College of Engineering Copyright © 2001 by Shane D. Pinder. Published by the American Institute of Aeronautics and Astronautics, Inc. with permission.