Photograph of three men conducting tests on the Learjet 23 prototype, March 16, 1964.Inscription on verso: "Flight test instruction for ground test / T-76-3A / 3-16-64."
Photograph of the Learjet 23 prototype undergoing a fuselage side-bending test, February 25, 1964. Text on sign: "Fuselage side bending static test / 67% ultimate / 25 Feb. 2964."Inscription on verso: "Gene Koenig / middle white shirt / T-58-4E /…
Photograph of the Learjet 23 prototype undergoing a fuselage side-bending test, February 25, 1964. Text on sign: "Fuselage side bending static test / 0% ultimate / 25 Feb. 2964."Inscription on verso: "T-58-4C / 2-25-64."
Photograph of the Learjet 23 prototype undergoing a fuselage side-bending test, February 25, 1964.Text on sign: "Fuselage side bending static test / 0% ultimate / 25 Feb. 1964."Inscription on verso: "T58-4A / 2-25-64."
Photograph of men installing a new engine in the Learjet 23 prototype, February 21, 1964.Inscription on verso: "Installing new engine on Jet #1 / 2-21-64."
Photograph of the Learjet 23 prototype undergoing a fuselage down-bending test, February 18, 1964.Text on sign: "Fuselage down bending static test / 0% ultimate / 18 Feb. 1964."Inscription on verso: "T58-2-O / 2-18-64."
Photograph of two men looking at the door of the Learjet 23 prototype, February 18, 1964. A third man is visible inside the aircraft performing a test with an oscillograph.Inscription on verso: "Direct read out oscillograph loaned from Century…
Photograph of the Learjet 23 prototype undergoing a fuselage up-bending test, February 13, 1964.Text on sign: "Fuselage up bending static test / 100% ultimate / 13 Feb. 1964."Inscription on verso: "T58-1-C / 2-13-64."
Photograph of the Learjet 23 prototype at a Lear facility, September 10, 1963. Other aircraft undergoing construction and testing are visible in the background.Inscription on verso: "P 15-E / Sept. 10, 1963."