Narrative:

We encountered wake turbulence on our descent into washington dulles at 7;000 ft MSL and approximately 30 miles northwest of iad. The autopilot was engaged at the time and the aircraft began to roll uncommanded. I disconnected the autopilot; arrested the roll; and slowed the aircraft towards maneuvering speed. The encounter only lasted for a matter of seconds. The bank was never greater than 30 degrees and no limitations were exceeded. The pilot not flying contacted the cabin crew and they reported that everyone was ok. The seat belt sign was on and no passengers or flight crew were injured during the encounter. The pilot not flying reported the wake turbulence event to ATC and they responded by informing us for the first time that we were following a heavy boeing 777. I then noticed that my windscreen wiper had moved during the encounter. During a post flight inspection of the aircraft I found that the first officer's windscreen wiper was bent. The captain contacted maintenance and informed them of the situation. This event occurred because of the lack of communication from ATC and possible mishandling from the approach controller. We were never informed that we were following a heavy B777 and the controller descended us behind and below the B777. As a result we encountered wake turbulence. At no time was the B777 in sight.

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Original NASA ASRS Text

Title: Q400 flight crew reported a significant wake vortex encounter with a preceding B777 that ATC had not mentioned.

Narrative: We encountered wake turbulence on our descent into Washington Dulles at 7;000 FT MSL and approximately 30 miles northwest of IAD. The autopilot was engaged at the time and the aircraft began to roll uncommanded. I disconnected the autopilot; arrested the roll; and slowed the aircraft towards maneuvering speed. The encounter only lasted for a matter of seconds. The bank was never greater than 30 degrees and no limitations were exceeded. The pilot not flying contacted the cabin crew and they reported that everyone was ok. The seat belt sign was on and no passengers or flight crew were injured during the encounter. The pilot not flying reported the wake turbulence event to ATC and they responded by informing us for the first time that we were following a heavy Boeing 777. I then noticed that my windscreen wiper had moved during the encounter. During a post flight inspection of the aircraft I found that the First Officer's windscreen wiper was bent. The Captain contacted Maintenance and informed them of the situation. This event occurred because of the lack of communication from ATC and possible mishandling from the Approach Controller. We were never informed that we were following a heavy B777 and the Controller descended us behind and below the B777. As a result we encountered wake turbulence. At no time was the B777 in sight.

Data retrieved from NASA's ASRS site as of July 2013 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.