Narrative:

A half hour prior to arrival, I received the ATIS information for the detroit metropolitan airport. Wind velocity was very light and therefore the captain and I briefed for the possibility of wake turbulence. As we approached the airport at 4000 ft MSL, dc-9 jet traffic above and ahead began to descend to land on runway 21R. We were instructed to follow traffic for a visual approach to the same runway. As we followed the traffic we remarked on the exhaust trail easily visible trailing from the dc-9 ahead. The trail was immediately ahead and above our flight path, but it was 'descending' into our flight path. As we flew into the exhaust we experienced a slight roll to the left, then a rapid roll to the right. Because we anticipated the turbulence we both fought the uncommanded roll immediately and regained control. During the encounter we rolled right about 30 degrees and gained 150 ft. I advised ATC of our encounter and then remained 2 dots above glide path for the remainder of the approach. The landing was performed without incident. Hindsight is always 20/20. In this case the crew anticipated correctly and prepared for the wake turbulence encounter. However, due to the rarity of encounters with this type of turbulence, we were 'reactive' to the situation instead of 'proactive.' perhaps the most valuable lesson learned from this encounter will be that your intuition should be listened to and treated as another crew member. Also, it should be known that flight into or through jet aircraft exhaust is not recommended. Callback conversation with reporter revealed the following: the reporter said that the flight crew expected that they may encounter wake on such a calm wind day. They saw the dc-9's engine smoke trail, but they made no maneuvers to avoid it. Their be-1900D rolled left 10 degrees then violently to the right about 30 degrees and a slight pitch up. There was no prior warning, other than the smoke trail, of the wake possibility. The first officer said that he will, in the future, steer around obvious wake trails.

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Original NASA ASRS Text

Title: WAKE ENCOUNTER -- ACR CREW OF A BE-1900D HITS THE WAKE OF A DC-9, AND AFTER PARTIALLY LOSING CTL, CONTINUES TO A SUCCESSFUL LNDG.

Narrative: A HALF HR PRIOR TO ARR, I RECEIVED THE ATIS INFO FOR THE DETROIT METRO ARPT. WIND VELOCITY WAS VERY LIGHT AND THEREFORE THE CAPT AND I BRIEFED FOR THE POSSIBILITY OF WAKE TURB. AS WE APCHED THE ARPT AT 4000 FT MSL, DC-9 JET TFC ABOVE AND AHEAD BEGAN TO DSND TO LAND ON RWY 21R. WE WERE INSTRUCTED TO FOLLOW TFC FOR A VISUAL APCH TO THE SAME RWY. AS WE FOLLOWED THE TFC WE REMARKED ON THE EXHAUST TRAIL EASILY VISIBLE TRAILING FROM THE DC-9 AHEAD. THE TRAIL WAS IMMEDIATELY AHEAD AND ABOVE OUR FLT PATH, BUT IT WAS 'DSNDING' INTO OUR FLT PATH. AS WE FLEW INTO THE EXHAUST WE EXPERIENCED A SLIGHT ROLL TO THE L, THEN A RAPID ROLL TO THE R. BECAUSE WE ANTICIPATED THE TURB WE BOTH FOUGHT THE UNCOMMANDED ROLL IMMEDIATELY AND REGAINED CTL. DURING THE ENCOUNTER WE ROLLED R ABOUT 30 DEGS AND GAINED 150 FT. I ADVISED ATC OF OUR ENCOUNTER AND THEN REMAINED 2 DOTS ABOVE GLIDE PATH FOR THE REMAINDER OF THE APCH. THE LNDG WAS PERFORMED WITHOUT INCIDENT. HINDSIGHT IS ALWAYS 20/20. IN THIS CASE THE CREW ANTICIPATED CORRECTLY AND PREPARED FOR THE WAKE TURB ENCOUNTER. HOWEVER, DUE TO THE RARITY OF ENCOUNTERS WITH THIS TYPE OF TURB, WE WERE 'REACTIVE' TO THE SIT INSTEAD OF 'PROACTIVE.' PERHAPS THE MOST VALUABLE LESSON LEARNED FROM THIS ENCOUNTER WILL BE THAT YOUR INTUITION SHOULD BE LISTENED TO AND TREATED AS ANOTHER CREW MEMBER. ALSO, IT SHOULD BE KNOWN THAT FLT INTO OR THROUGH JET ACFT EXHAUST IS NOT RECOMMENDED. CALLBACK CONVERSATION WITH REPORTER REVEALED THE FOLLOWING: THE RPTR SAID THAT THE FLC EXPECTED THAT THEY MAY ENCOUNTER WAKE ON SUCH A CALM WIND DAY. THEY SAW THE DC-9'S ENG SMOKE TRAIL, BUT THEY MADE NO MANEUVERS TO AVOID IT. THEIR BE-1900D ROLLED L 10 DEGS THEN VIOLENTLY TO THE R ABOUT 30 DEGS AND A SLIGHT PITCH UP. THERE WAS NO PRIOR WARNING, OTHER THAN THE SMOKE TRAIL, OF THE WAKE POSSIBILITY. THE FO SAID THAT HE WILL, IN THE FUTURE, STEER AROUND OBVIOUS WAKE TRAILS.

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.