A Review of Computer Simulations for Aircraft-Surface Dynamics

Introduction D the design of an aircraft heavy emphasis is placed on flight-induced motions and loads. However, groundbased operations produce an environment that can generate significant aircraft dynamics uncomfortable to passengers or damaging to the cargo. In addition, high vertical accelerations in the cockpit represent a potential disorientation problem for the pilot, which may cause landing or takeoff accidents. Perhaps more important, the aircraft structure can be subjected to large local deformations leading to stress failure, or the gears could experience loads beyond their design limits. For normal commercial aircraft and airports, ground loads (except for landing impact) should be of secondary concern. But aircrafts such as crop dusters and small private planes, which often operate from unimproved fields, experience a harsh environment during ground operations. Of greatest importance is the growing need of military aircraft to be operational from austere airfields. Most current U.S. Air Force (USAF) aircraft operate on rigid, smooth, paved Main Operating Base (MOB) surfaces. In all of the recent wars that the United States has been involved in, it has enjoyed air superiority, and its airbases were generally well protected and operational under normal procedures. Future conflicts may, however, be fought from MOBs vulnerable to enemy attack, and MOB surface damage or MOB denial is anticipated. Therefore, the USAF is placing greater emphasis on aircraft-surface operations, particularly on bomb damaged repaired (BDR) surfaces, soil, and other emergency surfaces. One effort to meet this challenge, which is presently under way in the United States, is to define the rough surface capabilities of mainline fighters and cargo planes. The USAF is establishing these capabilities through a program called HAVE BOUNCE under which: 1) Simulations are prepared for each aircraft on BDR runways. 2) Aircraft component weaknesses are identified through simulation. 3) Simulations are validated with test data. 4) Operational limitations are developed. In the past 5-10 years a substantial number of computer simulations have been developed to predict aircraft-surface interaction. Many of these programs have been written by USAF personnel or have been contracted to various organizations by the USAF. Others have been developed by aircraft companies to meet their own needs, or by individuals at universities, or in foreign countries (most notably in NATO countries). The objectives of this study were to review the literature concerning aircraft-surface dynamic simulation techniques: 1) to establish a historical view of the improvement in the state of the art, 2) to recognize the individuals and organizations that have played a prominent roll in advancing the state of the art, 3) to develop a knowledge base of physical phenomena that have been simulated, 4) to identify mathematical techniques that have been used, 5) to classify the simulations according to their general purpose, complexity, and accuracy, and 6) to suggest areas in which simulation techniques could be improved, and test could be run to validate the simulations. This report contains a brief summary of the computer programs written to predict the dynamic displacements and forces resulting from nonflight aircraft operations. The capabilities of each program along with their limitations and numerical techniques are cited.