If you’re learning to fly—or even just brushing up for your written—you’ll come across a small but powerful number on sectional charts: the Maximum Elevation Figure (MEF). It’s easy to overlook, but it can be one of the fastest ways to answer a critical question in flight:
“Am I high enough to safely clear everything around me?”
Let’s break down what MEFs are, how to read them, and how to actually use them in the cockpit.
What is a Maximum Elevation Figure?
A Maximum Elevation Figure (MEF) is the highest elevation of terrain or obstacle within a defined grid area on a sectional chart.
Each sectional is divided into rectangular quadrangles. Inside each one, you’ll see a large blue number—this is the MEF.
It represents the highest of:
- The highest natural terrain (mountains, ridges, hills), or
- The tallest man-made obstacle (towers, antennas, buildings)
They are not your maximum altitude, but rather the terrain's. Therefore, they actually help you determine a minimum altitude for terrain and obstacle clearance.
How to Read an MEF
MEFs are shown in hundreds of feet MSL, without the last two zeros.
- “92” → 9,200 feet MSL
- “125” → 12,500 feet MSL
Why the rounding?
MEFs are rounded up and include a built-in safety buffer:
- +100 ft for terrain
- +200 ft (or more) for obstacles
So the MEF isn’t just the highest thing—it’s the highest thing plus a margin of safety.
Why MEFs Matter (Especially for VFR)
As a VFR pilot, you don’t have terrain warning systems like airliners. MEFs give you a quick, visual safety check without needing detailed calculations.
They help you:
- Pick a safe cruising altitude
- Avoid terrain and obstacle collisions
- Maintain awareness when navigating off-course
- Make better decisions in unexpected situations (weather, reroutes, emergencies)
A simple rule of thumb:
If you’re flying above the MEF, you should be clear of terrain and obstacles in that grid.
A simple rule of thumb:
If you’re flying above the MEF, you should be clear of terrain and obstacles in that grid.
MEFs are incredibly useful—but not perfect.
- ❌ Data may be outdated (new towers can appear)
- ❌ Doesn’t account for your exact route within the grid
- ❌ Doesn’t include weather, winds, or aircraft performance
Think of MEFs as a fast, conservative estimate. They are not a guarantee.
How to Use MEFs in Real Flying
Here’s a practical workflow you can use:
During preflight:
- Scan your route across the sectional
- Note the highest MEFs along the way
- Choose a cruising altitude comfortably above them
In flight:
- Periodically check the MEF in your current grid
- Use it as a sanity check if you’re unsure of terrain clearance
In an emergency:
- Lost or disoriented?
→ Climb above the MEF to regain safe clearance
The Mental Model to Remember
If you take one thing away, make it this:
MEF = “Worst-case highest thing in this area… plus a buffer.”
It’s your quick safety floor for terrain and obstacles.