# Betaflight Blackbox Log Analysis: Diagnose Tuning and Mechanical Issues
**Your FPV drone wobbles, oscillates, or flies unpredictably — but PID tuning by feel isn’t working. Blackbox logging reveals exactly what your gyro sees: noise, oscillations, and frame resonance. This guide teaches you to read Blackbox logs and fix the root cause.**
## What is Blackbox?
Betaflight’s Blackbox records gyro, accelerometer, RC command, and motor output data at up to 2kHz onto an SD card or onboard flash. It captures exactly what the flight controller “feels” — noise that you cannot see in HD footage.
## Hardware Requirements
| FC Type | Blackbox Storage | Capacity | Recommendation |
|———|—————–|———-|—————-|
| F4/F7 with SD Card Slot | MicroSD (FAT32, Class 10+) | 16-32GB | Best option, supports 2kHz logging |
| F4/F7 with Onboard Flash | 8-16MB SPI Flash | ~2-3 flights at 1kHz | OK for quick diagnosis |
| F411 (no SD slot) | OpenLager external logger | 16GB+ | Excellent upgrade option |
Enable Blackbox in Betaflight Configurator → Blackbox tab → set `Blackbox logging device` to your hardware and `Blackbox logging rate` to 1kHz or 2kHz.
## Reading a Blackbox Log in 5 Steps
### Step 1: Download and Open
Download Betaflight Blackbox Explorer from the Chrome Web Store or use the standalone version at `github.com/betaflight/blackbox-log-viewer`. Open your `.BFL` file.
### Step 2: Identify the Graph Lines
| Graph | Color | What It Shows |
|——-|——-|—————|
| Gyro (roll/pitch/yaw) | Blue/Red/Green | What the gyroscope measures — raw rotation rate |
| PID P | Cyan | Proportional term magnitude |
| PID D | Magenta | Derivative term magnitude (amplifies noise!) |
| RC Command | Orange | Your stick input |
| Motors | Multi-color | Motor output signals (0-100%) |
### Step 3: Look for Noise
Zoom into a hover or forward-flight section (not flips/rolls). The gyro trace should be smooth, not fuzzy. Switch to **spectral view** (FFT mode) to see noise frequencies:
– **0-50Hz**: Frame resonance, loose arms, bent props
– **50-150Hz**: Motor vibration, prop imbalance
– **150-300Hz**: D-term noise (reduce D gain, enable RPM filtering)
– **300Hz+**: Electrical noise, gyro harmonics
### Step 4: Diagnose Common Patterns
| Issue | Blackbox Signature | Fix |
|——-|——————-|—–|
| Excess D Noise | Gyro trace has high-frequency “fuzz,” motors run hot | Reduce D gain 5-10 points, ensure RPM filter enabled |
| P-term Oscillation | Sinusoidal gyro oscillation at ~30-60Hz | Reduce P gain 5-10 points on affected axis |
| I-term Windup | Motor output slowly climbs without stick input | Increase I-term relax cutoff, check CG |
| Frame Resonance | Sharp spike at one frequency in FFT (e.g., 180Hz) | Add notch filter at that frequency, soft-mount FC |
| Motor Desync | Motor trace drops to zero momentarily | Check ESC protocol, increase motor timing |
| Yaw Twitch | Brief yaw gyro spike coinciding with throttle punch | Increase yaw P, check motor/prop tightness |
### Step 5: Apply and Iterate
Make ONE change at a time. Flash new PIDs, fly, check the log again. Never change multiple settings between test flights.
## Pro Tips for Blackbox
– **Use a stick overlay command.** Assign a switch to trigger a log marker. Do a punch-out, flip, then a hover — mark each phase so you can find them in the log.
– **Set `debug_mode = GYRO_SCALED`** in CLI to log pre-filter gyro data. This shows raw noise before RPM filters remove it — invaluable for finding mechanical issues.
– **Compare before/after.** Save screenshots of bad logs. After tuning, open both side-by-side to verify improvement.
For reliable flight controllers with excellent Blackbox support, the F7 and H7 stacks at [uavmodel.com](https://uavmodel.com) feature SD card slots that make logging effortless.
## Watch: Blackbox Log Analysis Tutorial
## FAQ: Blackbox Debugging Questions