B737 flight crew reported an overspeed situation while on descent to ord.

Attributes
ACN	1594888
Time
Date	201811
Local Time Of Day	0601-1200
Place
Locale Reference	ORD.Airport
State Reference	IL
Environment
Flight Conditions	VMC
Aircraft 1
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Descent
Route In Use	STAR WATSN3
Flight Plan	IFR
Component
Aircraft Component	Autopilot
Person 1
Function	Captain Pilot Not Flying
Qualification	Flight Crew Multiengine Flight Crew Commercial Flight Crew Air Transport Pilot (ATP) Flight Crew Instrument
Experience	Flight Crew Total 5881
Person 2
Function	Pilot Flying First Officer
Qualification	Flight Crew Commercial Flight Crew Multiengine Flight Crew Instrument Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Total 4196
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Procedural Published Material / Policy Deviation - Speed All Types Inflight Event / Encounter Weather / Turbulence

Narrative:

While on watsn arrival at FL250 and expecting to cross hulls at 120 [heading]; we were issued a descent to cross prise intersection at 12;000 [feet]. Aircraft was level flight; VNAV / LNAV engaged with autopilot on; utilizing good CRM. At approximately 35 miles from prise; pilot monitoring noticed we should have begun our descent (3 miles per 1;000 feet at normal descent speeds); but verified the path at our increased speed (310 KIAS) that we still had a few miles of level flight remaining. Pilot monitoring made PA to cabin and upon return ATC asked whether we would make our crossing restriction at prise. At that point; both pilot flying and pilot monitoring realized we were no longer in VNAV and pilot flying selected lvl chg and we began a high speed descent in accord with ATC instructions to maintain 310 or greater. Pilot flying increased airspeed to 320 and extended speed brakes to make the crossing at 12;000 [feet].when within 5 kts of barber pole; both pilots expected the autopilot to slowly pitch up when there was a sudden increase in airspeed due to unexpected turbulence and the high speed alert sounded and we exceed vmo by 15-20 kias. Both pilots announced upset and pilot flying disengaged autopilot and slowly made the upset recovery to desirable state. We flew the rest of the arrival and landed in ord without incident. We made a mx entry and talked to maintenance personnel upon arrival at gate.

Original NASA ASRS Text

Title: B737 flight crew reported an overspeed situation while on descent to ORD.

Narrative: While on WATSN arrival at FL250 and expecting to cross HULLS at 120 [heading]; we were issued a descent to cross PRISE intersection at 12;000 [feet]. Aircraft was level flight; VNAV / LNAV engaged with autopilot on; utilizing good CRM. At approximately 35 miles from PRISE; Pilot Monitoring noticed we should have begun our descent (3 miles per 1;000 feet at normal descent speeds); but verified the path at our increased speed (310 KIAS) that we still had a few miles of level flight remaining. Pilot Monitoring made PA to cabin and upon return ATC asked whether we would make our crossing restriction at PRISE. At that point; both Pilot Flying and Pilot Monitoring realized we were no longer in VNAV and Pilot Flying selected LVL CHG and we began a high speed descent in accord with ATC instructions to maintain 310 or greater. Pilot Flying increased airspeed to 320 and extended speed brakes to make the crossing at 12;000 [feet].When within 5 kts of barber pole; both pilots expected the autopilot to slowly pitch up when there was a sudden increase in airspeed due to unexpected turbulence and the high speed alert sounded and we exceed Vmo by 15-20 kias. Both pilots announced upset and Pilot Flying disengaged autopilot and slowly made the upset recovery to desirable state. We flew the rest of the arrival and landed in ORD without incident. We made a MX entry and talked to maintenance personnel upon arrival at gate.

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.