21/10/2025
🎯 Understanding PAPI, VASI, and OLS: The Eyes That Guide Pilots to a Safe Landing ✈️
When an aircraft is coming in to land, pilots need to know whether they’re too high, too low, or perfectly aligned with the correct glide path (the invisible slope leading to the runway).
That’s where Visual Approach Slope Indicators (VASI), Precision Approach Path Indicators (PAPI), and Optical Landing Systems (OLS) come in — these light systems are like visual guides that help pilots maintain the right descent angle.
Breakdown 👇
🟥 1. PAPI (Precision Approach Path Indicator)
Found beside the runway, usually with four lights.
Each light shows red or white, depending on your altitude.
The color combination tells the pilot if they’re on the correct glide path.
💡 How to read PAPI:
⚪⚪⚪⚪ = Too High
⚪⚪⚪🔴 = Slightly High
⚪⚪🔴🔴 = On Glide Slope ✅
⚪🔴🔴🔴 = Slightly Low
🔴🔴🔴🔴 = Too Low (Climb immediately!)
⚪🔴 2. VASI (Visual Approach Slope Indicator)
Usually two light bars — one near and one far from the runway.
Each bar shows either red or white light.
The combination helps the pilot align correctly.
💡 How to read VASI:
White/White = Too High
White/Red = On Glide Path ✅
Red/Red = Too Low
This system is simpler and very common on smaller or regional runways.
🟢🟡🔴 3. OLS (Optical Landing System)
Commonly used on aircraft carriers or advanced runways.
Uses a "meatball" light (the moving amber dot in the middle).
The goal is to keep the meatball aligned with the green reference lights.
💡 How to read OLS:
Meatball above center = Too High
Meatball centered = On Glide Path ✅
Meatball below center = Too Low
🧠 In Summary:
These light systems are visual guides that ensure safe landings by giving instant visual feedback to pilots.
They’re like traffic lights in the sky — showing if you’re too high, too low, or just right to touch down safely.
👨✈️ Next time you’re at an airport or watching a landing video, look closely near the runway edge — you’ll probably spot these guiding lights in action!