CNN's Grumman X-29: The impossible fighter jet with inverted wings contains several interesting photos, and says:
It was unflyable -- literally -- without a digital flight computer on board, which made corrections to the flight path 40 times a second," said Christian Gelzer, chief historian at the NASA Armstrong Flight Research Center in southern California (where the plane was tested) in a phone interview.
"An F-18 fighter jet has an instability factor of only 5%. The X-29, on the other hand, was 35% unstable," said Gelzer.
Question: What is the "aircraft stability factor" and what does it mean exactly when an aircraft is "35% unstable"?
The Grumman X-29 had a wingspan of 27 feet and was 48 feet long. It could reach Mach 1.8 (1,100 mph). (NASA)