Demonstration of a Method for Determining Critical Store Configurations for Wing-Store Flutter
Abstract
A gradient-directed numerical search technique is presented for determining those configurations of multiple external stores that are most flutter-critical for a given aircraft. The search is performed in a design space defined by the store properties at each specified store location. Constraints on the space are imposed by the extent of the aircraft store inventory. From expressions for the derivatives of flutter speed with respect to the store properties, gradient directions in the space are computed to guide the search. The search technique used is called Rank One Correct and belongs to the class of quadratically convergent search algorithms. To demonstrate the technique on a realistic problem, the A-6E aircraft and its extensive store inventory were analyzed. Searches of the inventory singled out two potentially critical configurations that gave flutter speeds well within the flight envelope for low assumed values of structural damping. Comparisons with the results of previous A-6 studies (which did not identify these configurations as critical) were made and possible explanations for the apparent anomaly were explored. It was concluded that, if these configurations had been uncovered during aircraft design, they would have been flagged for flight flutter test. Their omission is evidence of the extreme difficulty and poor reliability of current practice. The new method offers an efficient alternative to current practices for determining potentially flutter-critical store combinations from the many thousands (or even millions) of store loadings that can occur on modern attack aircraft.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 1980
- Accession Number
- ADA092257
Entities
People
- Edward J. Laurie
- Richard R. Chipman
Organizations
- Grumman