Air carrier widebody transport overspeed warning during descent.

Attributes
ACN	134644
Time
Date	199001
Day	Tue
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : aml
State Reference	VA
Altitude	msl bound lower : 28000 msl bound upper : 28000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zdc tower : iad
Operator	common carrier : air carrier
Make Model Name	Widebody, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	descent other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : cfi
Experience	flight time last 90 days : 210 flight time total : 27000 flight time type : 444
ASRS Report	134644
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Events
Anomaly	non adherence : far other anomaly
Independent Detector	aircraft equipment other aircraft equipment : unspecified
Resolutory Action	none taken : detected after the fact
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

During descent through approximately FL280, the aircraft entered an excessive rate of descent and an overspd condition occurred. Note: overspd warning in this aircraft occurs well below vmo/mmo and vmo/mmo were not exceeded. Conditions of aircraft confign were: 1) autoplt on, 2) autothrottles on, 3) managed speed, and 4) open descent. This is a widebody transport and has more than its share of computer glitches. 'Every flight is a proficiency check.' callback conversation with reporter revealed the following: this was not a computer malfunction. The aircraft had actually exceeded mmo at FL280 and the warning was appropriate. The PIC PF had selected a descent program very close to vmo, and when he selected 'open descent' to make an altitude crossing restriction, the aircraft pitched down momentarily activating the overspd warning.

Original NASA ASRS Text

Title: ACR WDB OVERSPEED WARNING DURING DESCENT.

Narrative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

Data retrieved from NASA's ASRS site as of July 2007 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.