What Causes Stutters?

Estimated Lesson Length: 30–40 Minutes

Lesson Overview

One of the most common questions in the Flight Simulator community is:

“Why is my simulator stuttering?”

Many people immediately assume they need a new graphics card or processor. However, stutters can have many different causes, and they don’t always mean your PC is underpowered.

A stutter is simply a moment where the simulator cannot deliver the next frame smoothly.

This might last:

• A fraction of a second.
• One second.
• Several seconds.

Even though these pauses are often very short, they can ruin the immersion of an otherwise smooth flight.

The good news is that once you understand what causes stutters, you’ll be much better equipped to solve them.

What Is A Stutter?

A stutter occurs when your simulator briefly fails to maintain smooth frame delivery.

Instead of the simulator updating evenly…

It suddenly pauses before continuing.

Think about watching a movie.

Normally the video plays continuously.

Now imagine someone presses the pause button for half a second every few minutes.

The movie still plays…

But those interruptions are obvious.

That’s exactly how a stutter feels inside Microsoft Flight Simulator.

CPU Spikes

The CPU constantly performs calculations.

Normally these calculations remain fairly consistent.

Occasionally…

The simulator suddenly has much more work to do.

This is called a CPU Spike.

Examples

Flying into London.

Photogrammetry loading.

Approaching a busy airport.

Large amounts of AI traffic.

Complex aircraft systems.

Loading scenery.

Each of these situations temporarily increases CPU workload.

If the CPU cannot finish its work quickly enough…

Frame delivery pauses.

You experience a stutter.

Symptoms

Small freeze.

Frame time suddenly increases.

GPU usage drops.

Developer Mode shows:

MainThread Limited

GPU Spikes

Just like the CPU…

The graphics card can suddenly receive much heavier workloads.

Examples include:

Flying into dense cloud.

Sunrise lighting.

Heavy rain.

Large reflections.

Looking towards a busy airport.

Changing camera views.

The GPU suddenly needs to render significantly more information.

If rendering takes longer than expected…

A small pause occurs.

Symptoms

GPU usage jumps close to 100%.

Frame times increase.

FPS drops.

Camera movement becomes less smooth.

Streaming Scenery

Microsoft Flight Simulator streams a large amount of scenery from Microsoft’s servers.

Instead of storing every city, road and building on your computer…

The simulator downloads scenery while you fly.

What Happens?

As you fly…

The simulator requests:

Terrain.

Roads.

Trees.

Buildings.

Photogrammetry.

Satellite imagery.

Weather information.

This happens continuously.

If your internet connection slows…

Or scenery takes longer to load…

The simulator may briefly pause while waiting for new data.

Symptoms

Blurry scenery.

Buildings appearing late.

Ground textures slowly sharpening.

Short pauses while flying.

Background Applications

Every program running on your computer uses system resources.

Examples include:

Google Chrome.

Discord.

Steam downloads.

Windows Update.

Antivirus scans.

OneDrive syncing.

Game launchers.

RGB software.

Screen recording software.

Even if these programs appear idle…

They may still be using:

CPU

RAM

Disk activity

Network bandwidth

Imagine trying to have a conversation while several other people are talking over you.

The CPU experiences something similar.

Too many programs competing for resources can cause performance interruptions.

Recommendation

Before launching Microsoft Flight Simulator:

Close unnecessary programs.

Pause large downloads.

Disable scheduled antivirus scans during flights if appropriate.

Keep essential applications only.

Add-ons

Add-ons make Flight Simulator amazing.

However…

Every add-on requires additional processing.

Examples include:

Complex aircraft.

Custom airports.

Weather engines.

Traffic injectors.

Toolbar utilities.

Camera tools.

Sound enhancements.

Navigation software.

Each one consumes CPU, GPU, RAM or storage resources.

A large Community Folder containing hundreds of add-ons may increase loading times and contribute to performance issues.

If you experience unexplained stutters, testing with a reduced set of add-ons can help identify whether an add-on is contributing to the problem.

Rolling Cache

Rolling Cache stores recently downloaded scenery on your storage drive.

Its purpose is to avoid downloading the same scenery repeatedly.

In theory…

This can improve efficiency.

However…

If the Rolling Cache becomes corrupted or fragmented…

The simulator may spend additional time reading or writing cached data.

This can contribute to loading delays or stutters on some systems.

Different users report different experiences, so it’s worth testing what works best for your setup.

Insufficient RAM

RAM temporarily stores data the simulator needs immediately.

If RAM becomes full…

Windows starts moving data onto your SSD.

This process is called paging.

Although SSDs are fast…

They are still much slower than RAM.

This causes:

Small pauses.

Longer loading times.

Micro-stutters.

Example

Imagine your desk is full.

You now have to walk to a filing cabinet every time you need another document.

Work becomes much slower.

RAM works exactly the same way.

Thermal Throttling

Computers generate heat.

If components become too hot…

They automatically reduce their operating speed to protect themselves.

This is called Thermal Throttling.

CPU Thermal Throttling

If the processor becomes too hot…

Clock speeds decrease.

The CPU performs fewer calculations.

FPS drops.

Stutters appear.

GPU Thermal Throttling

The graphics card behaves similarly.

If temperatures exceed safe limits…

The GPU reduces its performance.

Rendering becomes slower.

Frame times increase.

Common Causes

Dust build-up.

Poor airflow.

Old thermal paste.

Blocked laptop vents.

Warm room temperatures.

Monitoring Temperatures

Utilities such as HWiNFO or MSI Afterburner can be used to monitor CPU and GPU temperatures during a flight.

If temperatures rise unusually high and clock speeds fall, thermal throttling may be occurring.

Driver Issues

Drivers allow Windows to communicate with your hardware.

If a driver is:

Outdated.

Corrupted.

Incompatible.

Poorly optimised.

Performance problems may occur.

Examples include:

Graphics drivers.

Chipset drivers.

Network drivers.

Audio drivers.

Not every new graphics driver improves Flight Simulator performance. If you experience issues after an update, it may be worth checking whether other users are reporting similar behaviour before deciding whether to roll back or wait for a fix.

Identifying Stutters

The first step in solving any performance problem is identifying when it happens.

Different stages of flight place different demands on your hardware.

Taxi

Watch for:

Ground vehicle movement.

Airport traffic.

Camera panning.

Loading nearby scenery.

Take-off

Observe:

Rapid scenery loading.

Weather effects.

Large draw distances.

Increasing Terrain LOD workload.

Cruise

Watch for:

Photogrammetry loading.

Cloud rendering.

Weather transitions.

Long-distance scenery streaming.

Approach

This is often the most demanding phase.

The simulator loads:

Airports.

AI traffic.

Airport vehicles.

Buildings.

Glass cockpit updates.

Navigation calculations.

Runway lighting.

Landing

Observe:

Touchdown.

Reverse thrust.

Ground traffic.

Airport scenery.

Taxi lighting.

Camera movement.

Many users notice stutters during landing because several demanding tasks happen at the same time.

Student Exercise

Today we’re going to identify when your simulator stutters.

Step 1

Choose a familiar aircraft and airport.

Step 2

Enable the Developer Mode FPS Counter.

Step 3

Complete a full flight or use a saved flight that includes multiple phases.

Step 4

During each phase, make notes in your Performance Worksheet.

Taxi

• Did any stutters occur?
• Were they linked to camera movement or airport activity?

Take-off

• Did scenery loading cause any pauses?
• Did frame times increase?

Cruise

• Was performance stable?
• Did clouds or streamed scenery affect smoothness?

Approach

• Did stutters begin as the airport loaded?
• Was the Main Thread or GPU the limiting factor?

Landing

• Were there pauses during touchdown, braking or taxi back to stand?

Step 5

Think about patterns rather than isolated events.

For example:

• Do stutters always happen at large airports?
• Do they only occur in bad weather?
• Are they worse in complex aircraft?
• Do they disappear when AI traffic is reduced?

Identifying patterns is often the key to finding the root cause.

Lesson Summary

Congratulations.

You now understand that stutters can have many different causes.

Remember:

CPU spikes can delay frame preparation.

GPU spikes can occur during demanding graphical scenes.

Streaming scenery depends on both your internet connection and local storage.

Background applications compete for system resources.

Add-ons increase CPU, GPU and memory workload.

m Rolling Cache may affect performance differently depending on the system.

 Insufficient RAM can force Windows to use slower storage as virtual memory.

Thermal throttling reduces hardware performance to protect components from overheating.

Driver issues can sometimes affect simulator stability and performance.

Most importantly, don’t guess. Observe when stutters occur, gather evidence, and make changes methodically. That approach is far more effective than changing multiple settings at once and hoping for the best.