Research Programs

V-22/ Ship/ Helicopter Aerodynamic Interaction Phenomena (VSHAIP)

Scale model tiltrotors on deck

During shipboard compatibility trials conducted aboard an LHA amphibious assault ship in January of 1999, the V-22 aircraft experienced an uncommanded roll while on deck with rotors turning. The incident was attributed to an interaction with the wake of a CH-46 being recovered to a spot 255 feet upwind of the V-22. At the time the relative wind-over-deck (WOD) was recorded as 357 deg at 38 knots. Because of its potentially negative impact on shipboard operations and safety, the V-22 uncommanded roll in response to the approach of an upwind aircraft was classified as a deficiency requiring correction prior to operational deployment.

To successfully resolve what became known as the V-22 “Roll On-Deck” (ROD) problem, the V-22 Integrated Test Team launched a comprehensive multi-phase program composed of math model development and validation in parallel with full-scale ground-based and shipboard downwash surveys and interaction testing. These efforts were designed to gather the engineering data in build-up fashion that ultimately led to the design, implementation, and demonstration of a fix [1]. Early on in the program, it was decided that a wind tunnel test could provide valuable insight into the aerodynamic interaction mechanisms involved and help identify the worst-case ROD scenarios before the V-22 returned to sea trials. The objectives of the V-22/ Ship/ Helicopter Aerodynamic Interaction Phenomena (VSHAIP) wind tunnel investigation were stated as follows:

• Identify critical combinations of upwind aircraft downwash, proximity, and WOD conditions based on measured thrust asymmetry/rolling moment response of an on-deck V-22.

• Quantify the flow field disturbance generated by the upwind rotorcraft and ship combined wake for conditions of various rotorcraft operating upstream of a V-22 on-deck of the LHA.

The resulting joint Army/NASA/NAVAIR 1/48th-scale wind tunnel test was conducted in two separate entries in the Army 7-by 10-Foot Wind Tunnel Facility at Ames Research Center, funded in part by the V-22 Joint Program Office. The first entry, VSHAIP I [2-5], conducted between October 2001 and April 2002, focused on quantifying the contributions of the ship airwake and investigating the interaction between an upwind CH-46 and an on-deck V-22. The second entry, VSHAIP II [6], examined the interactions between the on-deck V-22 and two higher disk-loading rotorcraft: an upwind CH-53E and an upwind V-22.

References

Silva, M. J., Yamauchi, G. K., Wadcock, A. J. and Long, K. R., “Wind Tunnel Investigation of the Aerodynamic Interactions Between Helicopters and Tilt-rotors in a Shipboard Environment,” American Helicopter Society 4th Decennial Specialist's Conference on Aeromechanics, San Francisco, CA, January 2004. Download

Wadcock, A. J., Yamauchi, G. K., Heineck, J. T., Silva, M. J., and Long, K. R., “PIV Measurements of the Wake of a Tandem-Rotor Helicopter in Proximity to a Ship,” American Helicopter Society 4th Decennial Specialist's Conference on Aeromechanics, San Francisco, CA, January 2004. Download

Yamauchi, G. K., Wadcock, A. J., and Derby, M. D., “Measured Aerodynamic Interaction Between Two Tiltrotors,” American Helicopter Society 59th Annual Forum, Phoenix, AZ, May 2003. Download

Derby, M. R. and Yamauchi, G. K., “Design of 1/48th- Scale Models for Ship-Rotorcraft Interaction Studies,” 21st AIAA Applied Aerodynamics Conference, AIAA-2005-1347, Orlando, FL, June 2003. Download

Silva, M. J., Wadcock, A. J, Yamauchi, G. K., Van Aken, J. M., and Shinoda, P. M., “ Wind Tunnel Investigation of the Shipboard Aerodynamic Interactions Inducing the V-22 Tiltrotor Uncommanded Roll on-Deck Response,” American Helicopter Society 61st Annual Forum, Grapevine, TX, June 2005. Download

Johnson, W., Derby, M. D., Wadcock, A. J., and Yamauchi, G. K., “Wind Tunnel Measurements and Calculations of Aerodynamic Interactions Between Tiltrotor Aircraft,” American Institute of Aeronautics and Astronautics, 41st Aerospace Sciences Meeting and Exhibit, Reno, NV, January 2003. Download

Rajagopalan, R. G., Niazi, S., Wadcock, A. J., Yamauchi, G. K., and Silva, M. J., “Experimental and Computational Study of the Interaction Between a Tandem-Rotor Helicopter and a Ship,” American Helicopter Society 61st Annual Forum, Grapevine, TX, June 2005. Download

Point of Contact:

Gloria Yamauchi
NASA Ames Research Center
Moffett Field CA 94035-1000