The Story of Louis B. Gratzer

The Theory of Transonic Flow by K. G. Guderley and translated J. R. Moszynski was added into my collection as part of the International Series of Monographs in Aeronautics and Astronautics. This copy was found by me on eBay, which is a common origin for alot of my more obscure books. While the original text is in german, the Pergamon Press translated the work for wider consumption, and was printed and bound in the U.S. by Addison-Wesley Publishing Company in 1962. The Author, is a somewhat famous researcher who has a problem names after him, called the Guderley–Landau–Stanyukovich problem. The problem concerns the time evolution of converging shock waves, and more can be seen about it on the linked site. Even so, this text is now a part of my collection, but I am not the first person to own it. Before me, it appears that Boeing was in possestion of this text, more specifically the Boeing Transport Division Library.

Photo of the Theory of Transonic Flow, and the library stamp and L. B. Gratzer's signature

On this stamp you can see a cursive name, one L. B. Gratzer. Using this name, I did some research, and found that I was in possession of a piece of aerospace history, as L. B. Gratzer, AKA Louis Gratzer, was the inventor of the blended winglet.

Photo of the Gulfstream 2, first commerical airliner to incorporate Gratzer's blended winglet design.

Louis Bernard Gratzer was born in Tacoma, Washington in 1920. He attended and graduated from Bellarmire Preparatory High Schol in 1937, and went on to attend the University of Washington, where he earned a bachelor’s and master’s in aeronautical engineering. In 1953, he joined the Boeing Commerical Airplane Company, where he held positions as both an engineer and a technical manager. While at Boeing, he earned his Ph.D. in Aeronautics and Astronautics from the University of Washington in 1968. He retired from Boeing in 1986. Louis returned to the University of Washington as a affiliate associate professor in the department of Aeronautics and Astronautics. During his time as a professor, Louis worked on projects with NASA Langley Research Center.

Photo of the University of Washington

Now, before I discuss Louis’ contributions to winglet design, allow me to discuss the concept of winglets in general, and the history of them. First, what is a winglet? A winglet is a wingtip device commonly placed on the end of commerical airliner wings. The purpose of a winglet is to improve fuel efficiency, and aircraft equipped with them can save upwards of 5% less fuel. This fuel saving comes from the winglets reducing the natural vortices that form at traditional wingtips, which not only increase fuel efficiency, but also increase control authority, and therefore safety.

Photo of the blended winglet on a airbus A320neo

The functional principle that improves the performance of wings with winglets is that the high pressure and low pressure air at the top and the bottom of a wing meet at the wingtip, causing the vortices and drag. Using winglets, the air is kept from meeting, and thus performace is increased. The original idea that led to the winglet was created in 1897 by British aerodynamicist Frederick W. Lancaster. Lancaster patented wing endplates, which served to prevent the vorticies, but failed to help with lift. This weakness was somewhat addressed in the 1970’s by NASA engineer Richard Whitcomb, who took inspiration from the way birds curl their wingtips to increase lift. Whitcomb tested his more aerodynamic design in a wind tunnel and found a drag reduction of 5%.

Photo of the Richard Whitcomb in a wind tunnel

Despite the benefits, commercial airliners where not interested in incorporating Whitcomb’s design, as it still added weight and where expensive to install. However, in 1994, Louis Gratzer’s blended wingtip patent was granted, and at the time he was a senior vice president at Aviation Partners, Inc. His new design, the blended winglet, had even further gains in efficiency, and lower cost of install. This allowed Aviation Partners to sell these to airlines, today having over 10,000 aircraft fitted with the blended wingtip, and Louis’ later split scimitar wingtip design. Boeing alone estimates that they have saved a total of $50 Billion in fuel.

Photo of the later split scimitar winglet design

Louis Gratzer was a titan of aviation, and his impact will continue to pay dividends for decades to come, as our global transportation networks increase in efficient due in part to his work. Hope you learned something!

-Ethan