| Significance | Code | Meaning |
|---|
| FIR | EGTT | London FIR | | | / | | | Qualifiers | Q | | | | OL | Obstacle lights | | | AS | unserviceable | | | / | | | Traffic | I | IFR traffic affected | | | V | VFR traffic affected | | | / | | | Purpose | M | Miscellaneous | | | / | | | Scope | A | Aerodrome information | | | E | En-Route information | | | / | | | From flight level | 000 | Surface | | | / | | | Up to flight level | 004 | 400 feet QNE | | | / | | | Centre Latitude | 5128N | 51° 28' North' | | Centre Longitude | 00028W | 0° 28' West | | Radius of area affected | 001 | 1 nautical miles |
| | REDUCED RED OBSTACLE LIGHT DUE WORK IN PROGRESS,POSITION 512818.52N 0002755.44W ( HEATHROW CONTROL TOWER ) HEIGHT 285FT ABOVE GROUND LEVEL,364FT ABOVE MEAN SEA LEVEL. |
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