What is mechanical inspection?
The structured check of the physical condition of lights and signs — position and height, fasteners and torque, frangible parts, seals, alignment and the base and pavement around them.
Mechanical inspection checks that each light and sign is physically sound: in the right place, at the right height, aimed correctly, held by properly tightened fasteners and sealed against water. The sequence is prepared and permitted, checked in place first, then isolated and proved dead before anything is opened or lifted, followed by fasteners, frangible parts and seals, alignment and base condition, and finally restored and recorded.
Elevated units are frangible by design, so couplings and fixing details matter for safety as well as for the light. Opening a fixture or lifting it from its base can expose series circuit parts, so that work is done only when the circuit is isolated, locked out and proved dead under the airport’s permit-to-work. Torque values and tolerances come from the manufacturer, not from memory.
- Prepare. Obtain the permit, collect drawings and manufacturer torque values, and confirm tools and torque wrenches are in calibration.
- In place. Check position, height, tilt, visible damage, debris and vegetation without opening anything.
- Isolate. Switch off, lock out and prove the circuit dead before opening, lifting or moving any unit.
- Inspect. Examine fasteners and torque, frangible couplings, gaskets, seals, covers and cable entries for wear, corrosion and damage.
- Align & base. Verify aim, level and height, and check base cans, foundations and the pavement or sealant around them.
- Restore & log. Re-seal, re-energise, verify the lights, then record findings and raise corrective work.
Frequently Asked Questions
Q1What is mechanical inspection in airfield ground lighting?
It is the structured check of the physical condition of lights and signs: fixture position, height and alignment, fasteners and torque, frangible couplings, seals and gaskets, base cans and foundations, and the pavement around them. It makes sure each unit is secure, correctly aimed and protected against water and impact.
Q2Why do frangible parts need special attention?
Elevated lights and signs are designed to break away cleanly if an aircraft strikes them. A damaged, corroded, wrongly assembled or over-tightened frangible coupling may not break as intended, or may fail too easily. They are checked for condition, correct assembly and height within the limits that apply to the site.
Q3Why check fastener torque rather than just tightness by hand?
Loose fasteners let fixtures move, vibrate and lose alignment, while over-tightening can crack housings or damage frangible parts. Using the manufacturer's torque value with a calibrated tool gives a repeatable result. The value comes from the manufacturer's instructions, not from a generic figure.
Q4Why does mechanical inspection often need isolation?
Opening a fixture, lifting it from its base or disturbing connectors and cable entries can expose live series circuit parts. External checks in place can be done under the site procedure, but anything that opens or moves the unit is done with the circuit isolated, locked out and proved dead.
Q5What do seals and gaskets protect against?
They keep water, dirt and insects out of the fixture, base can and connector areas. Hardened, cracked, displaced or missing seals are a common route for moisture, which later shows up as corrosion, low insulation resistance or lamp failure.
Q6What limits and intervals apply?
Heights, tolerances, torque values and intervals come from the airport's maintenance programme, the regulator, the manufacturers' instructions and the applicable standard. Always use the values for your site rather than a generic figure.
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.