Narrative:

Flight to lax was delayed so at the time of the event it was xa:15 am EST and we had 1 leg before the lax flight; both of us were fatigued. While in VNAV on an idle descent approximately 4 miles prior to minza we had seen on TCAS an aircraft 8 miles in front of us. At that time we encountered moderate wake turbulence at approximately 12000 ft; we were not notified that a heavy aircraft was in front of us. At that time I switched the autopilot to vertical speed 500 ft min to avoid further upsets then increased our descent above the preceding aircraft flight path. As we continued the descent and approaching the restr at decor the PNF informed me that I was not going to make the restr so I increased my descent rate to meet the restr and thus I was above 250 KTS below 10000 ft. Once realized I slowed the aircraft to 250 KTS and continued the flight uneventfully. We were descending for a landing to runway 24R at lax. I was trying to make the crossing restr at decor which is to cross between 9800 ft and 9000 ft. At 9700 ft I was at approximately 280 KTS. I then slowed the aircraft to 250 KTS but was still in a very shallow descent. After successfully meeting the crossing restr I saw the speed deviation and corrected. Once identified I reduced pitch; remained at idle power and extended the flight spoilers to reduce speed. When encountering wake turbulence with crossing restrs between you and the runway ask ATC if you can deviate from those crossing restrs for wake turbulence. That would of solved our problem that morning.

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Original NASA ASRS Text

Title: AN ACR PLT APCHING LAX RPTS FLYING ABOVE THE PROFILE TO AVOID WAKE VORTEX BUT EXCEEDING 250 KTS BELOW 10000 FT WHILE SLOWING ON PROFILE.

Narrative: FLT TO LAX WAS DELAYED SO AT THE TIME OF THE EVENT IT WAS XA:15 AM EST AND WE HAD 1 LEG BEFORE THE LAX FLT; BOTH OF US WERE FATIGUED. WHILE IN VNAV ON AN IDLE DESCENT APPROX 4 MILES PRIOR TO MINZA WE HAD SEEN ON TCAS AN ACFT 8 MILES IN FRONT OF US. AT THAT TIME WE ENCOUNTERED MODERATE WAKE TURBULENCE AT APPROX 12000 FT; WE WERE NOT NOTIFIED THAT A HEAVY ACFT WAS IN FRONT OF US. AT THAT TIME I SWITCHED THE AUTOPILOT TO VERTICAL SPEED 500 FT MIN TO AVOID FURTHER UPSETS THEN INCREASED OUR DSCNT ABOVE THE PRECEDING ACFT FLT PATH. AS WE CONTINUED THE DSCNT AND APCHING THE RESTR AT DECOR THE PNF INFORMED ME THAT I WAS NOT GOING TO MAKE THE RESTR SO I INCREASED MY DSCNT RATE TO MEET THE RESTR AND THUS I WAS ABOVE 250 KTS BELOW 10000 FT. ONCE REALIZED I SLOWED THE ACFT TO 250 KTS AND CONTINUED THE FLT UNEVENTFULLY. WE WERE DESCENDING FOR A LNDG TO RWY 24R AT LAX. I WAS TRYING TO MAKE THE CROSSING RESTR AT DECOR WHICH IS TO CROSS BETWEEN 9800 FT AND 9000 FT. AT 9700 FT I WAS AT APPROX 280 KTS. I THEN SLOWED THE ACFT TO 250 KTS BUT WAS STILL IN A VERY SHALLOW DSCNT. AFTER SUCCESSFULLY MEETING THE CROSSING RESTR I SAW THE SPEED DEVIATION AND CORRECTED. ONCE IDENTIFIED I REDUCED PITCH; REMAINED AT IDLE POWER AND EXTENDED THE FLT SPOILERS TO REDUCE SPEED. WHEN ENCOUNTERING WAKE TURB WITH CROSSING RESTRS BETWEEN YOU AND THE RWY ASK ATC IF YOU CAN DEVIATE FROM THOSE CROSSING RESTRS FOR WAKE TURB. THAT WOULD OF SOLVED OUR PROBLEM THAT MORNING.

Data retrieved from NASA's ASRS site as of January 2009 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.