1366. Rapidloads – A Preliminary Design Loads Prediction Technique for Aircraft

Paper

Abstract

The timely prediction of aircraft flight loads for use during the early stages of preliminary design continues to be a concern for those charged with this responsibility. There is seldom enough known about the configuration at this point to make use of the latest tools. A majority of the data that is available concerns the complete vehicle only. Information such as weight distributions and air load distributions for the primary components (body, wing, tails) quite often are minimal or non-existent. The procedures and tools available for predicting these distributions are generally complex and require the expenditure of a significant amount of time to obtain the required data. These factors tend to eliminate their use in the early stages of preliminary design when response time is at a premium.
A flight loads prediction technique called RAPIDLOADS is being developed to overcome these deficiencies. This effort is sponsored by the
Naval Air Development Center (NADC), Warminster, Pennsylvania. The Vought
Corporation, under NADC Contract N662269-79-C-0710, is developing RAPIDLOADS and will complete the program during the last quarter of 1980.
RAPIDLOADS is an outgrowth of the Fighter Aircraft Structural Loads (FASTLODS) program, reference 1. It consists of a set of computer programs controlled by an executive routine. Two modes of operation are available:
– Batch
– Interactive through a Tektronix 4081 graphics terminal
Symmetric and antisymmetric flight maneuvers of the following types may be used in the analyses.
– Symmetrical pull-up and push-over
– Abrupt pitch
– Rudder kick and reversed rudder
– Roll initiation, reversed roll, and roll termination
The maneuvers may be performed at subsonic and supersonic speeds. Through the use of user selected maneuvers at appropriate ‘points-in-the-sky’, a set of design loads may be produced within a very short time – usually hours rather than days or weeks. Loads data for the body and each lifting surface (wing, tail, etc.) are in the form of shear, bending moment, and torsion distributions. All loads calculations are based on the assumption that the structure is rigid. These data may be stored on magnetic files for use with other analysis methods.