Narrative:

Operating as the pilot flying to mia. Approaching tadpo level FL380 noticed aircraft on TCAS approximately 4000 ft below and 5-10 miles ahead. We queried ATC about the traffic and coordinated 280 KTS for the descent to provide additional spacing with the aircraft ahead. Miami center concurred and also cleared the aircraft ahead; a B747-400; to 'maintain 300 KTS or greater for spacing into mia'. We were subsequently cleared to descend to cross curso at 10000' and 250 KTS as was the aircraft ahead. Shortly after and stable at 280 KTS; ATC stated we were over taking the 747 at approximately 50 KTS. Descending through approximately FL260 in the vicinity of mth we encountered moderate wake turbulence from the 747; which caused alternating rapid rolls right and left approximately 30 degrees of bank. I disconnected the autopilot; regained control of the aircraft and offset from the 747's track. We notified miami center of the occurrence. Miami center then cleared us when able to curso and cross at 10;000'/250 KTS. We continued to offset a few more miles and then proceeded direct curso. Shortly afterward we began to encounter the wake again; although only light turbulence this time. We notified center and turned upwind again. No further encounters from the 747's wake. The first officer also chimed the flight attendants to let them know what happened and to take a moment and check the passengers and crew for injuries. They chimed us back a few minutes later and stated that everyone was ok and there were no injuries. They reported that everyone including the flight attendants had been seated at the time of the wake encounter. I would also like to commend the first officer and the flight attendants for their calm and professional response to the wake encounter.

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Original NASA ASRS Text

Title: An air carrier Flight Crew reported encountering wake vortex from preceding B747-400 on arrival to MIA.

Narrative: Operating as the pilot flying to MIA. Approaching TADPO level FL380 noticed aircraft on TCAS approximately 4000 FT below and 5-10 miles ahead. We queried ATC about the traffic and coordinated 280 KTS for the descent to provide additional spacing with the aircraft ahead. Miami Center concurred and also cleared the aircraft ahead; a B747-400; to 'maintain 300 KTS or greater for spacing into MIA'. We were subsequently cleared to descend to cross CURSO at 10000' and 250 KTS as was the aircraft ahead. Shortly after and stable at 280 KTS; ATC stated we were over taking the 747 at approximately 50 KTS. Descending through approximately FL260 in the vicinity of MTH we encountered moderate wake turbulence from the 747; which caused alternating rapid rolls right and left approximately 30 degrees of bank. I disconnected the autopilot; regained control of the aircraft and offset from the 747's track. We notified Miami Center of the occurrence. Miami Center then cleared us when able to CURSO and cross at 10;000'/250 KTS. We continued to offset a few more miles and then proceeded direct CURSO. Shortly afterward we began to encounter the wake again; although only light turbulence this time. We notified Center and turned upwind again. No further encounters from the 747's wake. The First Officer also chimed the Flight Attendants to let them know what happened and to take a moment and check the passengers and crew for injuries. They chimed us back a few minutes later and stated that everyone was ok and there were no injuries. They reported that everyone including the Flight Attendants had been seated at the time of the wake encounter. I would also like to commend the First Officer and the Flight Attendants for their calm and professional response to the wake encounter.

Data retrieved from NASA's ASRS site as of April 2012 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.