On say a B737 or an A319 what % of the braking action upon landing is provided by reverse thrust under normal (dry) conditions?
Yes, a lot of variables but the simplest answer (for an A320) is a decrease in the landing distance required of between 2-8% on a dry runway. Main variables are:
a. Landing Config 3 or Full
b. With or without autobrake
c. Autobrake setting (Low/Medium) if used.
Hope that this helps,
YS