Alva LeRoy Addy, affectionately known as Tad, died on November 16, 2018 at the age of 82. At his request no funeral will take place. Burial will take place at Dallas Hillview Cemetery, Dallas, South Dakota where his parents, Alva Isaac Addy and Nellie (Brumbaugh) Addy are buried.

Alva Leroy Addy was born on March 29,1936 at Dallas, South Dakota. He attended school in Dallas and graduated from Gregory High School. He graduated with a degree in mechanical engineering from South Dakota School of Mines & Technology in 1958. Tad married Sandra Ruth Turney on June 8, 1958.

While working for General Electric he earned a Master of Science degree from the University of Cincinnati in 1960. In 1963 Tad received a Doctor of Philosophy degree from the University of Illinois at Urbana-Champaign, where he then joined the faculty of the Department of Mechanical and Industrial Engineering.

From the earliest landmark publications of his research findings he held an international reputation in the fluid dynamics research community. The US Army Research Office funded the research of Professor Addy and his colleagues at the University of Illinois at Urbana-Champaign continuously for more than three decades. His research was applied to many aircraft, missiles and rockets including the Space Shuttle and the Concorde.

In addition to being a successful researcher, he was an award-winning teacher at Illinois. Professor Addy's enthusiasm for teaching and support of multidisciplinary student projects made him popular among undergraduates. In 1993, the University of Illinois College of Engineering students selected him as an Honorary Knight of St. Patrick. A Fellow of the American Society for Engineering Education, in 1990 he was honored with the society's Ralph Coates Roe Award for outstanding teaching and notable contributions to the engineering profession.

Professor Addy also served as department head for the Department of Mechanical and Industrial Engineering from 1987-1998, and during this time he had a profound impact on the department's direction. Guiding the quality of education provided, research conducted, and public service completed, he influenced the careers of thousands of engineers. During his tenure, the department was consistently ranked among the best in the nation.   Further, he contributed to the field of engineering through work with professional societies. A Life Fellow of the American Society of Mechanical Engineers, in 2006 he was named an Honorary Member, which is that society's highest honor.

After Tad and Sandra retired in 1998 they enjoyed the design and construction of a home on a mountaintop in the Black Hills near Spearfish, South Dakota. Tad loved to drive and they traveled the highways and byways of our nation by car. Many happy hours were spent at home in his beautiful woodworking shop. In retirement he served for a number of years as a Trustee of the South Dakota School of Mines & Technology Foundation.

Tad is survived by his wife, Sandra; by his sister Betty Ruth Travnicek; and by his nephew Gary (Janice) Travnicek. Also surviving are sisters-in-law Colleen Hanna and Nancy Hanson; brother-in-law Mike Turney; and several nieces and nephews from those families.