Narrative:

We (a B7S) were cleared for takeoff from sea runway 16L approximately 1 to 2 min after an MD80. During our initial climb beginning at approximately 3000 ft MSL we began getting what appeared to be light chop and light yawing movements which then increased slightly in intensity. As we continued to climb for the next 30 seconds or so, the turbulence became more noticeable until I was aggressively using aileron to counter significant uncommanded rolling movements of our aircraft. As I wondered aloud to the captain where this was coming from, I noticed the brown jetwash trail from the preceding MD80 was directly in line with our intended flight path on the departure. It appeared that were in the remnants of its jetwash and wake turbulence. I would estimate that I made 3 to 4 significant roll corrections in both directions until I turned slightly right to exit the jetwash/wake, whereupon the rolling movements ceased almost immediately. We attempted to get the actual time difference in takeoff clrncs from tower, but they were unable to provide that information. This is not the first instance recently where I've encountered this on takeoff or landing, just the first one I've reported since hearing of your interest in this subject. What was particularly unusual about this encounter was the somewhat insidious onset of the indications, followed by their quickly increasing intensity until I intentionally altered my heading to escape the trail of jetwash. I believe that departing aircraft who are cleared for takeoff with short intervals, say less than 2 min, should be given divergent headings to preclude this situation. In sea this presents a problem because of the need to closely track the sea 158 degree radial to the SID turn point at 11 NM to avoid noise complaints. This forces all aircraft to virtually follow the same lateral flight path. In my opinion, this is probably a classic case of flight safety being potentially compromised by mandated adherence to a single narrow departure track solely to accommodate noise complaints. Sea NOTAMS indicate that plus/minus 4 degrees is the tolerance on departure tracks to avoid noise complaints. Callback conversation with reporter revealed the following information: the reporter stated he was flying the boeing 737-300. He has experience flying F4's, F101's, F16's, the 727 and numerous corp and personal aircraft. He said he has of course experienced wake before but nothing like this. This started out as the insidious normal nibble. Then the left wing picked up to about 15 degrees and he was able to counter it. Then the wake picked the left wing up 20 degrees before he was able to counter it. He elected to fly the airplane off to the right to get away from the wake before the problem got worse. The momentary hesitation to abandon the in trail was due to noise abatement constraints at this airport that indicate penalties for exceeding 3 degrees from assigned departure path. The reporter stated he thought the wake was a vortex generated phenomena and not from the engines. He said if the departures are going to be so close behind each other then the path should be divergent and noise abatement should not prevail over safety considerations.

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Original NASA ASRS Text

Title: FLC ENCOUNTERS WAKE ON INITIAL CLB.

Narrative: WE (A B7S) WERE CLRED FOR TKOF FROM SEA RWY 16L APPROX 1 TO 2 MIN AFTER AN MD80. DURING OUR INITIAL CLB BEGINNING AT APPROX 3000 FT MSL WE BEGAN GETTING WHAT APPEARED TO BE LIGHT CHOP AND LIGHT YAWING MOVEMENTS WHICH THEN INCREASED SLIGHTLY IN INTENSITY. AS WE CONTINUED TO CLB FOR THE NEXT 30 SECONDS OR SO, THE TURB BECAME MORE NOTICEABLE UNTIL I WAS AGGRESSIVELY USING AILERON TO COUNTER SIGNIFICANT UNCOMMANDED ROLLING MOVEMENTS OF OUR ACFT. AS I WONDERED ALOUD TO THE CAPT WHERE THIS WAS COMING FROM, I NOTICED THE BROWN JETWASH TRAIL FROM THE PRECEDING MD80 WAS DIRECTLY IN LINE WITH OUR INTENDED FLT PATH ON THE DEP. IT APPEARED THAT WERE IN THE REMNANTS OF ITS JETWASH AND WAKE TURB. I WOULD ESTIMATE THAT I MADE 3 TO 4 SIGNIFICANT ROLL CORRECTIONS IN BOTH DIRECTIONS UNTIL I TURNED SLIGHTLY R TO EXIT THE JETWASH/WAKE, WHEREUPON THE ROLLING MOVEMENTS CEASED ALMOST IMMEDIATELY. WE ATTEMPTED TO GET THE ACTUAL TIME DIFFERENCE IN TKOF CLRNCS FROM TWR, BUT THEY WERE UNABLE TO PROVIDE THAT INFO. THIS IS NOT THE FIRST INSTANCE RECENTLY WHERE I'VE ENCOUNTERED THIS ON TKOF OR LNDG, JUST THE FIRST ONE I'VE RPTED SINCE HEARING OF YOUR INTEREST IN THIS SUBJECT. WHAT WAS PARTICULARLY UNUSUAL ABOUT THIS ENCOUNTER WAS THE SOMEWHAT INSIDIOUS ONSET OF THE INDICATIONS, FOLLOWED BY THEIR QUICKLY INCREASING INTENSITY UNTIL I INTENTIONALLY ALTERED MY HDG TO ESCAPE THE TRAIL OF JETWASH. I BELIEVE THAT DEPARTING ACFT WHO ARE CLRED FOR TKOF WITH SHORT INTERVALS, SAY LESS THAN 2 MIN, SHOULD BE GIVEN DIVERGENT HDGS TO PRECLUDE THIS SIT. IN SEA THIS PRESENTS A PROB BECAUSE OF THE NEED TO CLOSELY TRACK THE SEA 158 DEG RADIAL TO THE SID TURN POINT AT 11 NM TO AVOID NOISE COMPLAINTS. THIS FORCES ALL ACFT TO VIRTUALLY FOLLOW THE SAME LATERAL FLT PATH. IN MY OPINION, THIS IS PROBABLY A CLASSIC CASE OF FLT SAFETY BEING POTENTIALLY COMPROMISED BY MANDATED ADHERENCE TO A SINGLE NARROW DEP TRACK SOLELY TO ACCOMMODATE NOISE COMPLAINTS. SEA NOTAMS INDICATE THAT PLUS/MINUS 4 DEGS IS THE TOLERANCE ON DEP TRACKS TO AVOID NOISE COMPLAINTS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED HE WAS FLYING THE BOEING 737-300. HE HAS EXPERIENCE FLYING F4'S, F101'S, F16'S, THE 727 AND NUMEROUS CORP AND PERSONAL ACFT. HE SAID HE HAS OF COURSE EXPERIENCED WAKE BEFORE BUT NOTHING LIKE THIS. THIS STARTED OUT AS THE INSIDIOUS NORMAL NIBBLE. THEN THE L WING PICKED UP TO ABOUT 15 DEGS AND HE WAS ABLE TO COUNTER IT. THEN THE WAKE PICKED THE L WING UP 20 DEGS BEFORE HE WAS ABLE TO COUNTER IT. HE ELECTED TO FLY THE AIRPLANE OFF TO THE R TO GET AWAY FROM THE WAKE BEFORE THE PROB GOT WORSE. THE MOMENTARY HESITATION TO ABANDON THE IN TRAIL WAS DUE TO NOISE ABATEMENT CONSTRAINTS AT THIS ARPT THAT INDICATE PENALTIES FOR EXCEEDING 3 DEGS FROM ASSIGNED DEP PATH. THE RPTR STATED HE THOUGHT THE WAKE WAS A VORTEX GENERATED PHENOMENA AND NOT FROM THE ENGS. HE SAID IF THE DEPS ARE GOING TO BE SO CLOSE BEHIND EACH OTHER THEN THE PATH SHOULD BE DIVERGENT AND NOISE ABATEMENT SHOULD NOT PREVAIL OVER SAFETY CONSIDERATIONS.

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.