Born: United States of America
Primarily active in: United States of America

November 5, 1926 – August 19, 2013

Robert W. Metzger was a rotor stress engineer who led the rotor stress group at Bell for many years. He was one of the original transplants to Ft Worth from Buffalo, New York when, in 1952, the Bell Aircraft Corp. moved the helicopter division to Texas. His interests were always rotor system related. The first patent issued to him, in 1958, was for a way to over-mass-balance a wooden main rotor blade by adding weight to the leading edge near the tip and under a metallic abrasion strip, allowing for more weight in the form of stiffer wood to be added to the afterbody, thus creating higher chordwise stiffness for blade tuning. He was the co-inventor, along with Jan Drees, of the rotor hub concept used on the AH-1G Cobra, made famous in the Vietnam War. The rotor, known in Bell parlance as the “Door Hinge” rotor was Bell’s first stiff-in-plane flex-beam system to see production, introduced on the UH-1C “Charlie” gun ship, also used in Vietnam. The Cobra used the rotor until the model was upgraded with the Model 214ST dynamics to become the AH-1T.


Bob was always interested in research, particularly if it was rotor-related. He convinced management that there were advantages to tuning a rotor above 3/rev. He led the design, construction and test of a large rotor (for Bell). It had two blades (typical of Bell at the time), a diameter of 50 feet, a chord of 42.5 inches, and contained 100 lb of tip weight. Bell decided lighter might be better, as long as the rotor was still well mass-balanced. Bob continued researching and eventually, along with a few others, invented the Model 680 Rotor System. This research rotor flew on the model 222 and formed the basis for several models still in use today, most notably the Model 430, the AH-1Z Zulu and UH- 1Y Yankee.

Still rotor-related, but not specifically rotor structure, Bob co-invented the Mast Torque Measuring System used in the Model 412 today.
Bob joined AHS in 1951 and was an Emeritus member.

AHS Update: Vertiflite November/December 2014