GE Military Airway Beacon MS-25015-2
Airway Beacons were introduced in the 1930s to enable the visual identification of airfields, and were subsequently installed in vast numbers every few tens of kilometres to delineate major air routes around the world and facilitate night-time flying in the days before radio and GPS location signals. While the route markers are practically obsolete today, airport beacons are still commonplace and serve as a visual back-up in case of failure of the other systems.

This lamp was introduced in 1961 for the American MS-25444 miltary beacon and has an unusual axial filament, vs the planar grid filament of most air beacon lamps. It is known by its Military Stock number MS-25015-2 according to US Mil. Std. MIL-L-6363, or simply 1200T20/BP, and is internationally classified under NATO Inter-Service number 6240-00-556-8012. Each beacon comprises two rigid drum lanterns, one projecting a double white beam and the other a single green beam, the whole assembly rotating at six RPM to provide the characteristic fast white-white-green flashing signal for the identification of military airfields.

This lamp was made partly by the author at the GE Leicester factory, while setting up the production of Medium & Mogul Bi-Post lamps that had been transferred to the UK from Mattoon Lamp Plant in U.S.A. The filament is welded to nickel rods and supported by molybdenum wires held in a glass bridge, and is topped by a folded metal gauze to limit blackening of the bulb. The base consists of a pair of No.1869 feather-edged copper thimbles, glazed with borax and a glass bead, and Housekeeper-sealed into a pressed glass base. The flange of this base is fused to the leaded borosilicate bulb by a standard drop-seal technique.
Manufacturer: General Electric U.S.A. GE #22524
Lamp Power: 1200 Watts
Lamp Voltage: 115 Volts
Lamp Current: 10.44 Amperes
Cap Type: G38 Mogul Bi-Post, copper
Bulb Type: T-63 T-20 in eighths/inch
Bulb Finish: Clear GE772 leaded borosilicate
Filament Type: CC-8 Axial Segmented Coiled-Coil
Atmosphere: Argon-Nitrogen Aluminium-zirconium getter
Luminous Flux: 29,600 Lumens
Luminous Efficacy: 24.67 Lumens per Watt
Beam Intensity: N/A
Beam Distribution: N/A
Colour Temperature & CRI: CCT: 3000 Kelvin CRI: Ra 100
Chromaticity Co-ordinates: CCx: 0.452 CCy: 0.409
Rated Lifetime: 750 hours
Burning Position: Vertical base down
Overall Length: 235 mm 91/4 inches
Light Centre Length: 102 mm 4 inches
Factory: Leicester England
Date of Manufacture: November 1998 Date Code: 1193
Original Value: US $6.75 (1969)
References: 1) Department of the Army, USA, Technical Manual TM 5-811-5, Army Aviation Lighting, September 1989
2) GE Authorized Federal Supply Schedule Lamp Catalog FSC 6240 Electric Lamps, 1 Nov 1969 - 1 Nov 1970.