What is a lamp?
The light source in a lamp-based fixture. A hot filament inside a sealed glass bulb makes the light, and the optics shape it into a beam, so the lamp must be the right type and sit in the right place.
Every airfield light needs a source of light small enough for its optics to shape into a beam. In a lamp-based fixture, the lamp is that source.
1It makes the light
A halogen lamp has a small tungsten filament inside a sealed glass envelope filled with halogen gas. Current from the secondary circuit heats the filament until it glows, and the halogen gas keeps the glass clearer for longer than a plain bulb.
2It must sit at the focus
The lens or reflector shapes the beam from a lamp at its focus. The lamp is held by its base and holder so the filament lands in the same place each time. A shifted, tilted or wrong-type lamp distorts the beam and changes the intensity.
3It ages, and is replaced
Lamps lose output as the filament wears and the glass blackens, then fail when the filament breaks. A failed lamp leaves an open circuit on the transformer secondary, and the series circuit carries on, but a dark lamp should be replaced promptly because an open secondary stresses the transformer. Replace with the correct type, handled by the base, not the glass, and seated as specified.
| Element | Detail |
|---|---|
| Lamp | The light source in a lamp-based fixture, usually halogen |
| Parts | Tungsten filament, glass envelope with halogen gas, support wires, base |
| Powered by | The secondary circuit of the isolation transformer |
| Must sit | At the optical focus of the lens or reflector |
| Ages by | Filament wear, glass blackening, falling output, failure |
| Check | Correct type, glass condition, seating, contacts, clean handling |
Frequently Asked Questions
Q1What is the lamp in an airfield light fixture?
The light source in a lamp-based fixture, usually a halogen lamp: a small glass envelope with a tungsten filament that glows when current passes through it.
Q2Why must the lamp sit at the right position?
The lens or reflector shapes the beam from a lamp placed at its focus. A lamp that is shifted, tilted or the wrong type moves the filament off the focus and distorts the beam.
Q3What happens when a lamp fails?
The filament breaks and the lamp becomes an open circuit on the transformer secondary. In a series circuit the isolation transformer lets the rest of the circuit keep running; an open secondary stresses the transformer, so replace the lamp promptly. Replace the lamp with the correct type, handled as the manufacturer specifies.
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