Comparison of X-31 Flight and Ground-Based Yawing Moment Asymmetries at High Angles of Attack
Cobleigh, Brent R. and Croom, Mark A. (2001) Comparison of X-31 Flight and Ground-Based Yawing Moment Asymmetries at High Angles of Attack. Technical Report NASA/TM-2001-210393, Research Engineering, NASA Dryden Flight Research Center.
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Abstract
Significant yawing moment asymmetries were encountered during the high-angle-of-attack envelope expansion of the 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.
| EPrint Type: | NASA Technical Memorandum |
|---|---|
| Keywords: | Asymmetry, Water tunnel test, Wind tunnel test, X-31 aircraft, Yawing moment |
| Subjects: | (01 - 09) Aeronautics: (05) Aircraft Design, Testing And Performance Aircraft/Project: X-31 |
| ID Code: | 57 |
| Deposited On: | 01 June 2004 |
| Additional Information: | 18 pages. Paper MP-69-P-42, presented at the Symposium on Advanced Flow Management, May 7–11, 2001, Loen, Norway. Mark Croom, NASA LaRC, Hampton, VA. |
