B787 Dreamliner Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Flight Crew Last 90 Days 141.83; Flight Crew Total 11102.03; Flight Crew Type 1016.48
Deviation - Altitude Excursion From Assigned Altitude; Deviation - Speed All Types; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Loss Of Aircraft Control; Inflight Event / Encounter Weather / Turbulence
Flight Crew FLC complied w / Automation / Advisory; Flight Crew Regained Aircraft Control
Human Factors; Weather
During cruse at FL400 mountain wave was encountered.  The airspeed exceeded Vmo/Mmo with accompany EICAS alert; Master Caution Alert and audible alert.  I was the pilot flying and the FO was Pilot monitoring.  The FO extended the speed breaks to full extend and reduced the throttles immediately to idle.  The aircraft descended 500 feet.  The airspeed reduced below Vmo/Mmo; the warnings stopped.  The FO retracted the speed breaks and the autothrottles increased to maintain VNAV programed speed.  This all occurred within 10-20 seconds.  I was attempting to determine what was happening as the FO accomplished the above items.  ATC was notified of the mountain wave and altitude excursion.We briefed the mountain waive and actions which were taken.  I reviewed the Flight Manual regarding high altitude overspeed situations.  It was determined that the actions taken deviated from FM directed guidance.  We reviewed CRM items on what went right; what went wrong and what we would do in the future.  It was a great discussion.It became apparent to me that the 4 hour departure delay and all the associated tasks had taken a toll on my ability to process information in a timely manner.  I was slow to react to the overspeed.  As a result; the FO used CRM skill of leadership to deploy the speed break and reduce the throttles.  We had a conversation about the FO acting too quickly and me not acting quickly enough.  Maintenance Control was contact to determine what items needed to be included in the report regarding the overspeed.  An electronic logbook write up was submitted.
Air carrier Captain reported that an airspeed exceedance and altitude excursion occurred when the aircraft encountered a mountain wave.