What is a gasket?
The compressible seal between two parts of a fixture. It fills the tiny gap between the lens, body and base so water and dirt stay out of the lamp, optics and electronics.
Two metal or glass faces never fit perfectly, and water finds the smallest gap. A gasket fills that gap, so the inside of the fixture stays dry and clean.
1It seals the joints
A flat gasket or O-ring sits between the lens and body, at covers, and at the base flange. When the fasteners compress it, it presses into the surface of both faces and blocks the path for water, dirt and insects.
2It has to last outdoors
A gasket is usually rubber or a similar material, chosen to resist heat, sunlight, weather and chemicals. Over time it can harden, crack or flatten, and then the seal fails and moisture reaches the optics and electronics.
3Seat it right, and replace it
Clean the faces, seat the gasket evenly, and tighten the fasteners to the specified torque, so it compresses evenly. Look for hardening, cracks, flattening, a pinched or displaced gasket and water inside. Replace the gasket whenever the seal is opened, and fit the correct manufacturer part.
| Element | Detail |
|---|---|
| Gasket | Compressible seal between two fixture parts |
| Used at | Lens to body, body covers, and base flange |
| Form | Flat ring or O-ring |
| Material | Rubber or similar, chosen for heat, sun and chemical resistance |
| Needs | Clean faces and even, specified tightening |
| Check | Hardening, cracking, flattening, displacement, water or dirt inside |
| Performance | Sealing is specified as an ingress-protection (IP) rating in the fixture specification |
| Reference | Fixture manufacturer’s manual; IEC 60529 (IP code); FAA AC 150/5345-46 (light fixtures); FAA AC 150/5340-26 (maintenance) |
Frequently Asked Questions
Q1What is a gasket in an airfield light fixture?
A compressible seal, usually a flat ring or O-ring made of rubber or similar material, that sits between two parts such as the lens and the body, or the body and the base, to keep out water and dirt.
Q2What causes a gasket to fail?
Age, heat, sunlight and chemicals harden or crack the material. Uneven or incorrect tightening, dirt on the sealing faces, or refitting a used gasket can also stop it sealing.
Q3Can a used gasket be refitted?
Usually not. A gasket takes a set once compressed, and a damaged or hardened one will not seal again. Replace it with the correct manufacturer part, and clean the sealing faces first.
Q4What is the difference between a gasket and an O-ring?
A flat gasket is a flat ring or cut shape compressed between two flat faces. An O-ring is a round-section ring that sits in a groove and seals as it is squeezed. Both do the same job, and the fixture design decides which is used.
Q5How can a failed gasket be recognised?
Look for moisture or fogging inside the lens, water marks or corrosion inside the fixture, and a gasket that is hardened, cracked, flattened or pinched when the joint is opened. A fixture that keeps taking in water may also have a blocked or failed pressure-equalization vent, so the seal and the vent are checked together.
See It. Understand It. Then Learn How to Engineer It.
Recognising an AGL system visually is the first step. The next step is knowing how to design, install, test, commission and maintain them correctly.
Build Practical AGL Engineering Skills
Go deeper with structured training from Precision AGL Academy, covering:
Learn how each light, sign and circuit works as part of a complete airport lighting system, not just as an isolated diagram.