| 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 | E | En-Route information | | | / | | | From flight level | 000 | Surface | | | / | | | Up to flight level | 012 | 1200 feet QNE | | | / | | | Centre Latitude | 5222N | 52° 22' North' | | Centre Longitude | 00406W | 4° 6' West | | Radius of area affected | 001 | 1 nautical miles |
| | AIR NAV OBSTACLE LIGHT UK0171A040F RTM RTM BLAENPLWYF MAST SINGLE UNSERVICEABLE POSITION 522138.45N 0040609.24W.ELEV / HEIGHT : 1144 FT / 561 FT |
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