Narrative:

The flight was progressing normally until we updated weather prior to coast out. We were unable to maintain radio contact with stockholm radio to get a phone patch with the foo. But we knew that the weather at our ETOPS alternate had deteriorated and was unusable as an alternate. The flight path was discontinued and we went into holding at the direction of shanwick radio before the resno intersection. After a while; we were able to establish contact with iceland radio and we got a clear phone patch to the foo. After some discussion; it was determined that the flight could not continue and we were to turn back to ZZZZ. Clearance was obtained from shanwick and we were heading towards ZZZZ. We needed to burn a lot of fuel in order to land under the maximum landing weight. So a lower altitude was obtained to aid in burning fuel. The first officer needed to use the bathroom. Before the international relief officer could take the first officer (first officer) seat; the max airspeed warning sounded. I was very busy working with ATC to complete our route and program the FMC. During the programming sequence; the only speed in the FMC was the cruise altitude of M.80. The autopilot was engaged with LNAV and VNAV selected and the speed window closed. The FMA was indicating VNAV speed and the speed bug and airspeed indication were both over the vmo (maximum operating speed) by 3-5 knots. There was nothing in the descent page as the route and crossing altitudes were still being programmed. The vmo was exceeded by 3-5 knots at 20;000 ft. MSL. After a quick recovery from the overspeed; the remaining programing of the FMS was completed and the remainder of the flight progressed normally. The flight was completed and the overspeed was noted in the logbook.

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Original NASA ASRS Text

Title: Air Carrier Captain reported overspeed during descent.

Narrative: The flight was progressing normally until we updated weather prior to coast out. We were unable to maintain radio contact with Stockholm Radio to get a phone patch with the FOO. But we knew that the weather at our ETOPS alternate had deteriorated and was unusable as an alternate. The flight path was discontinued and we went into holding at the direction of Shanwick Radio before the RESNO intersection. After a while; we were able to establish contact with Iceland Radio and we got a clear phone patch to the FOO. After some discussion; it was determined that the flight could not continue and we were to turn back to ZZZZ. Clearance was obtained from Shanwick and we were heading towards ZZZZ. We needed to burn a lot of fuel in order to land under the maximum landing weight. So a lower altitude was obtained to aid in burning fuel. The First Officer needed to use the bathroom. Before the IRO could take the FO (First Officer) seat; the max airspeed warning sounded. I was very busy working with ATC to complete our route and program the FMC. During the programming sequence; the only speed in the FMC was the cruise altitude of M.80. The autopilot was engaged with LNAV and VNAV selected and the speed window closed. The FMA was indicating VNAV Speed and the speed bug and airspeed indication were both over the VMO (Maximum Operating Speed) by 3-5 knots. There was nothing in the descent page as the route and crossing altitudes were still being programmed. The VMO was exceeded by 3-5 knots at 20;000 ft. MSL. After a quick recovery from the overspeed; the remaining programing of the FMS was completed and the remainder of the flight progressed normally. The flight was completed and the overspeed was noted in the logbook.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.