An erj-170 captain reported encountering moderate wake turbulence following a heavy jet into iad.

Attributes
ACN	1006317
Time
Date	201204
Local Time Of Day	0001-0600
Place
Locale Reference	IAD.Airport
State Reference	DC
Environment
Flight Conditions	IMC
Aircraft 1
Make Model Name	EMB ERJ 170/175 ER/LR
Operating Under FAR Part	Part 121
Flight Phase	Descent
Route In Use	STAR PRTZL3
Flight Plan	IFR
Aircraft 2
Make Model Name	Heavy Transport
Operating Under FAR Part	Part 129
Flight Phase	Descent
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Inflight Event / Encounter Wake Vortex Encounter

Narrative:

While descending through 10;000 on the PRTZL3 into iad we got moderate wake turbulence from a heavy jet in front of us. As a result I climbed and turned 20 degrees off course. We were able to get delay vectors back on course and returned on the arrival. ATC said that we were 12 miles in trail and asked if maybe it was just some turbulence. I had the TCAS band on 5 miles. I estimated the heavy jet to be about 7 miles ahead of us. I'm 100% sure it was wake turbulence. Give us more separation and let us know when we are following heavy traffic. I find that wake turbulence is more of a problem on descents and not so much on approach. Seven miles with a 20 knot head wind is not enough space.

Original NASA ASRS Text

Title: An ERJ-170 Captain reported encountering moderate wake turbulence following a heavy jet into IAD.

Narrative: While descending through 10;000 on the PRTZL3 into IAD we got moderate wake turbulence from a heavy jet in front of us. As a result I climbed and turned 20 degrees off course. We were able to get delay vectors back on course and returned on the arrival. ATC said that we were 12 miles in trail and asked if maybe it was just some turbulence. I had the TCAS band on 5 miles. I estimated the heavy jet to be about 7 miles ahead of us. I'm 100% sure it was wake turbulence. Give us more separation and let us know when we are following heavy traffic. I find that wake turbulence is more of a problem on descents and not so much on approach. Seven miles with a 20 knot head wind is not enough space.

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.