B767 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 100; Flight Crew Total 9000; Flight Crew Type 180
Distraction
Aircraft Equipment Problem Less Severe; Deviation - Speed All Types; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Wake Vortex Encounter
General None Reported / Taken
Aircraft; Environment - Non Weather Related; Human Factors
During final approach to runway 27L into EGLL; we were given instructions to maintain 160kt until 4 DME. On approach we experienced an Auto Throttle (A/T) failure; as it disconnected automatically. We attempted to reengage the A/T twice with no success. Also we started to experience wake turbulence from the heavy aircraft in front of us and separation looked close. The Captain instinctively slowed to target speed just prior to 4 DME to maintain safe operation of the approach. After landing Ground Control queried why we slowed down. We responded that we had experienced wake turbulence.     In my opinion; the distractions of the A/T; the wake turbulence with reduced separation; combined with a very late landing clearance inhibited us in reporting our reduction of speed just prior to 4 DME.
B767 First Officer reported deviating from assigned speed on approach to EGLL; citing wake turbulence and an autothrottle anomaly as contributing factors.