# FPV Drone Blackbox Log Analysis: Reading Gyro, PID, and Motor Traces
Your drone oscillates on hard turns. Your motors come down hot. You’ve tried every PID slider position and nothing works. Stop guessing — start reading the data. Blackbox logging captures every sensor reading, PID calculation, and motor command during flight, giving you a crystal-clear picture of what’s actually happening versus what you think is happening.
## What Is Blackbox Logging?
Blackbox records flight data at high speed (typically 1-2kHz) directly from your flight controller. Every gyro reading, PID loop output, motor command, RC input, and accelerometer value is timestamped and saved. This data lets you diagnose tuning issues, electrical noise, and mechanical problems with scientific precision.
### Data Rate vs Flash Memory
| Logging Rate | Data per Minute | 16MB Flash Duration | What You Capture |
|—|—|—|—|
| 2kHz (500μs) | ~25MB | ~38 seconds | Full gyro detail for noise analysis |
| 1kHz (1ms) | ~13MB | ~75 seconds | Good for PID tuning analysis |
| 500Hz (2ms) | ~7MB | ~150 seconds | Basic tune verification |
| 250Hz (4ms) | ~4MB | ~300 seconds | Long flight overview only |
## Required Tools
– **Betaflight Blackbox Explorer** (Chrome app or standalone): The primary visualization tool
– **Plasmatree PID Analyzer**: Automated PID response analysis
– **Betaflight Configurator**: For enabling Blackbox and setting logging rate
## How to Read Key Traces
### 1. Gyro Traces (Noise Check)
The gyro trace shows raw rotational velocity. A clean quad shows smooth lines. Noise appears as high-frequency “fuzz”:
“`
Clean gyro: ─────────────────── (smooth)
Noisy gyro: ─╱╲╱╲╱╲╱╲╱╲╱╲╱╲─ (fuzzy, jittery)
“`
**What to look for:**
– **Band thickness**: The wider the trace “band” of noise, the more vibration
– **Spikes at specific throttle**: Frame resonance — change RPM filter frequency
– **Consistent noise**: Bent motor shaft, bad bearing, unbalanced prop
### 2. PID Sum / PID Error (Tuning Quality)
The PID sum trace shows total correction applied. A well-tuned quad shows quick, critically-damped corrections:
| Pattern | Meaning | Fix |
|—|—|—|
| PID overshoots, oscillates 3+ times | P gain too high | Reduce P by 10-15% |
| PID barely reaches target, slow correction | P gain too low | Increase P by 10% |
| PID reaches target, slow wobble after | I gain too high | Reduce I by 20% |
| Sharp noise spikes on PID trace | D gain amplifying gyro noise | Reduce D or add filtering |
| Large PID correction on punch-outs | I-term windup or low authority | Check motor/prop sizing |
### 3. Motor Traces (Desync and Saturation Detection)
Motor traces show commanded output from 0 to 100%. Critical diagnostics:
– **Motor saturation (100%)**: Motor is maxed out — you need higher KV or more voltage
– **Motor oscillation**: Traces oscillate opposite each other — classic P-term oscillation
– **Single motor spikes**: That motor has a problem — check ESC, solder joints, and bearings
– **Motor clipping at minimum**: Too low idle or dynamic idle needs adjustment
## Step-by-Step Analysis Workflow
1. **Arm and hover for 10 seconds** — this isolates gyro noise from prop/motor issues
2. **Do smooth pitch/roll moves** — check PID tracking quality
3. **Punch out to full throttle** — check motor saturation and noise under load
4. **Sharp 180-degree turn** — check for propwash oscillation
5. **Land, stop logging, download the log**
### In Betaflight Blackbox Explorer:
1. Open your log file
2. Select “GYRO_SCALED[0..2]” — check noise baseline in hover
3. Select “PID_P[0..2]” and “PID_D[0..2]” — watch PID behavior during maneuvers
5. Select “MOTOR[0..3]” — verify all motors responding evenly
6. Use the spectrogram view (frequency domain) to identify noise peaks at specific Hz
## Common Issues Found in Blackbox
| Problem | Blackbox Signature | Root Cause | Solution |
|—|—|—|—|
| Mid-throttle oscillations | Oscillation at 100-200Hz | Frame resonance excited at cruise | Move RPM filter center frequency |
| Hot motors | Motors running 60%+ in hover | Over-propped, low KV mismatch | Smaller props or higher KV motors |
| Propwash | PID overshoot after sharp moves | P or D gain too low | Increase P or D, try feed forward |
| Yaw twitch | Yaw gyro noise spikes | Bad gyro, noisy BEC, or frame twist | Check gyro mounting, add BEC cap |
| Motor desync | Single motor trace drops to zero | ESC desync or phase loss | Increase motor timing, check solder |
| Pitch wobble on throttle | I-term buildup in punch-out | I gain too high or wrong I-term relax | Reduce I gain or adjust relax cutoff |
## Equipment That Logs Well
Not all flight controllers log equally well. A quality FC with ample onboard flash memory like the [SpeedyBee F405 V4 with 16MB Blackbox](https://uavmodel.com) gives you enough logging duration for meaningful analysis without requiring an external OpenLager module. Combined with the BMI270 gyro’s low noise floor, your logs will be clean and actionable.