Overspeed Event with Crew Take-over and OEB49 Application

While flying at FL380, an A340 aircraft encountered a strong and abrupt tailwind decrease that triggered significant MMO overshoot and overspeed warning.The crew disconnected the AP, took over and inappropriately applied OEB49 (ADR2 & ADR3 set to OFF).This article describes this event and presents two main aspects from its analysis: the management of an overspeed situation and the inappropriate OEB49 application.It details the rationale for the OEB49 (on A330/A340 aircraft) and OEB48 (on A320 family) and their conditions of application. It explains why they must not be trained on simulator and recalls the aircraft modifications allowing to cancel the OEB.