Frank L. Stulen

Frank Lem Stulen (January 22, 1921 – June 25, 2010) graduated from Carnegie Mellon University (then Carnegie Tech) in 1942 with a degree in aeronautical engineering. After graduation, Stulen served in the U.S. Army Corps of Engineers and in the U.S. Air Force from 1942 to 1946, where he was head of the Propeller Lab, Rotary Wing Branch based out of Wright-Patterson Air Force Base. After a meeting with John T. Parsons, he was hired as Chief Engineer and Vice President of Engineering at Parsons Corporation in Traverse City, Michigan.

While working at Parsons Corporation, he invented numerical control of machine tools in collaboration with Parsons. Though Parsons developed many of the core ideas, it was Stulen, as chief engineer, who turned these ideas into working machines and processes. In 1985, Stulen and Parsons were jointly awarded the National Medal of Technology by President Ronald Reagan for "Revolutioniz[ing] Production of Cars And Airplanes With Numerical Controls For Machines".

Stulen was also Mayor of Traverse City, Michigan, in 1961 and 1962. he died in Traverse City Michigan on June 25, 2010 of heart failure at 89

Life Stulen was born on January 22, 1921, in Pittsburgh, Pennsylvania. He went to Carnegie Mellon University (then called Carnegie Tech), and moved to Traverse City, Michigan, to begin his work with Parsons.

Development of numerical control In 1942, Parsons was told that helicopters were going to be the "next big thing" by the former head of Ford Trimotor production, Bill Stout. He called Sikorsky Aircraft to inquire about possible work, and soon got a contract to build the wooden stringers in the rotor blades. At the time, rotor blades were built in the same fashion that fixed wings were, consisting of a long tubular steel spar with stringers (or more accurately ribs) set on them to provide the aerodynamic shape that was then covered with a stressed skin. The stringers for the rotors were built from a design provided by Sikorsky, which was sent to Parsons as a series of 17 points defining the outline. Parsons then had to "fill in" the dots with a French curve to generate an outline. A wooden jig was built up to form the outside of the outline, and the pieces of wood forming the stringer were placed under pressure against the inside of the jig so they formed the proper curve. A series of trusswork members were then assembled inside this outline to provide strength.

Parsons set up production at a disused furniture factory and ramped up production, but one of the blades failed and it was traced to a problem in the spar. At least some of the problem appeared to stem from spot welding a metal collar on the stringer to the metal spar. The collar was built into the stringer during construction, then slid onto the spar and welded in the proper position. Parsons suggested a new method of attaching the stringers directly to the spar using adhesives, never before tried on an aircraft design. It was a labor-intensive prototype of today's 2.5 axis machining (two-and-a-half-axis machining).

Legacy The Parsons-Stulen building, home of the Northwestern Michigan College Aviation Campus at Cherry Capital Airport, is named after Parsons and Stulen.