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.