Comparison of X-31 Flight and Ground-Based Yawing Moment Asymmetries at High Angles of Attack
Abstract
Significant yawing moment asymmetries were encountered during the high angle-of-attack envelope expansion of two X-31 aircraft. These asymmetries caused position saturations of the thrust-vectoring vanes and trailing-edge flaps during some stability-axis rolling maneuvers at high angles of attack. The two test aircraft had different asymmetry characteristics, and ship 2 has asymmetries that vary as a function of Reynolds number. Several aerodynamic modifications have been made to the X-31 forebody with the goal of minimizing the asymmetry. These modifications include adding transition strips on the forebody and noseboom, using two different length strakes, and increasing nose bluntness. Ultimately, a combination of forebody strakes, nose blunting, and noseboom transition strips reduced the yawing moment asymmetry enough to fully expand the high angle-of-attack envelope. Analysis of the X-31 flight data is reviewed and compared to wind tunnel and water tunnel measurements. Several lessons learned are outlined regarding high angle-of-attack configuration design and ground testing. (23 refs.)
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 2003
- Accession Number
- ADA419040
Entities
People
- Brent R. Cobleigh
- Mark A. Croom
Organizations
- National Aeronautics and Space Administration