Mr. Robert Wozniak, the chief test engineer for Boeing’s V/STOL (Vertical Short Take-off and Landing) Wind Tunnel located in Ridley Park, PA, has asked our group to develop a measurement system to accurately determine the yaw of aircraft models being tested in the wind tunnel. The current method to determine yaw is very labor intensive and not as accurate as desired by Boeing’s customers. It is therefore our task to develop a new method or improve the existing one.
The group has undergone an intense investigation of many technologies to determine the most plausible system. Ring laser gyroscopes, photogrammetry, and local GPS were the technologies that were the most thoroughly investigated. Magnetic fields were also considered, but are too variable due to wind tunnel properties and interference. The use of a laser measurement system was also considered which is similar to local GPS, but does not take the dynamics of the model into consideration.
Ring laser gyroscopes were a potential solution when coupled with accelerometers. They are extremely accurate and would be durable enough for the test models. Ring laser gyroscopes may not however provide the necessary degree of accuracy.
Photogrammetry is another accurate and high technology solution for resolving the position of the model in the wind tunnel. This system works by taking pictures of the object in space from various angles. It is able to resolve the exact position of the model using triangulation techniques.
After considerable research, local GPS was determined to be the best solution to the problem. This was determined using a screening and scoring matrix. This technology works by emitting infrared laser signals that are detected by sensors on the model. Using multiple sensors and transmitters the system is able to determine the absolute position of the test model within the wind tunnel. The accuracy is extremely high using this technology. The system can resolve the yaw angle within the specified 0.05 degree accuracy design criteria. Our contact at Arc Second is extremely helpful and has provided us with a technology demonstrator unit.
Wind tunnels are a major aerodynamic research tool, which play an instrumental role in the testing and delivering of accurate data. For decades, research using wind tunnels has been on-going to advance aeronautic performance, to reduce environmental effects, and to explore new system concepts. In order to produce such sophisticated products, several tests and experiments must be performed.
The Boeing Company is the leading manufacturer of aerospace products and research. Boeing’s V/STOL subsonic wind tunnel test facility located in Ridley Park, PA is the largest commercially operated wind tunnel in the United States. Boeing also operates two other wind tunnels in the United States: a transonic facility in Seattle and a supersonic facility in St. Louis.
Boeing uses the three facilities to test various aircraft designs. The Ridley Park, PA facility, which has logged more than 65,000 test hours since opening in 1968, is the nation's only facility that can test powered helicopter rotor models.
When testing aircraft models in the wind tunnel, it is necessary to accurately determine the pitch, roll, and yaw attitudes. The pitch and roll angles can easily be determined since they can be referenced to the local gravity vector. Measuring the yaw angle is problematic however since there is no absolute reference.
The current method used to measure the yaw angle of test models in the wind tunnel is very time consuming. Also, extreme care and operator skill is required as well as recalibration when any changes are made to the system. Using the side forces applied to the model, the deflection of the sting must be calculated and taken into consideration along with the readings obtained from the encoder at the yaw axis.
It is therefore our task to develop a yaw measurement system that is more accurate, easier to use, and less time-consuming for the operator.
The following are the objectives of our project:
· Develop a working subscale prototype yaw measurement system
· Research the available technologies to determine the best potential solution to the problem of yaw measurement
· Prepare at least two back-up designs in case the original doesn’t perform as expected
· Investigated technologies should be weighted for accuracy potential (yaw angle measurement within .05 degrees of actual), stability of measurement, ease of use, robustness, productivity, and initial capital investment
· Recommendations for future improvements to enhance performance and potential issues involving scaling up from model scale to full scale