SUAS Crash Investigation

If you don’t figure out why your 

unmanned aircraft crashed then you 

will crash it the same way in the 

future.

© Alfred A. Gates, 2014

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Crash Investigation Tools

• Flight data recording 

– Video camera recording from flight

– On board SD card

– Recording through a ground control station link

• Weather

• Pilot control observations

• Observer observations

• Crash site

• Internet search on make model common crash's

© Alfred A. Gates, 2014 2
Crash Investigation

• Pilot: Did the aircraft operate as expected

• Observer: What happened prior to crash and 

what is the camera doing

• Weather: What are the winds and is it raining 

or snowing

© Alfred A. Gates, 2014 3
Crash Investigation, Aircraft Behavior 

Prior to Crash What to Look For

• Spinning (YAW) and pitch or roll in one direction: Loss of power to 

one or more control surface servos. Control surface connecting rod 

or control horn failure and control surface is locked in position.

• Controlled roll and or pitch in one direction and controlled flight 

by AP in that direction: GPS signal loss

• Slowly or quickly losing altitude: Battery low, loss of power

• Increasing pitch and or roll oscillations of aircraft: Autopilot tuning 

problem.

• Uncontrolled pitch and or roll and YAW, loss of attitude:

• Typically the aircraft will pitch and or roll to an angle and 

maintain the angle. The angle will be steep and the aircraft will 

dive External or onboard electromagnetic interference, autopilot 

problems.

• Control Surface Flutter: Vibration noise and control surfaces falling 

off aircraft. 

© Alfred A. Gates, 2014 4
Inflight Observations

© Alfred A. Gates, 2014 5

Dropping slowly 

or quickly

Loss of power

Spinning out of 

control

Failure of servo, 

linkage, or 

connection

Sharp angle 

and flight in a 

direction

GPS signal loss

Rapid increasing 

oscillation

Autopilot tuning 

problem

Observation and possible cause

Aircraft YAWs and rolls 

and attitude is lost: 

Electromagnetic 

interference, autopilot 

problems
Crash Site Investigation

• Debris field

– Wreckage in one location

• Human error, autopilot or electronics failure

– Wreckage spread over a large area

• Break up in flight inspect parts to determine point of 

failure

– Aircraft in one location with a missing component

• Missing component has something to do with the 

failure

© Alfred A. Gates, 2014 6
Aircraft Investigation, Crash Site

• Do not pick up the aircraft (Batteries may be 

connected and burning)

• Take pictures

• Locate: All control surfaces, rods, wing, motors 

and ESC

• Check: Propellers are they tight, motors lose 

or tight, are ESC plugged into the autopilot 

and motors, is the autopilot loose, is the 

battery connected

© Alfred A. Gates, 2014 7
Aircraft Crash Investigation

• Difficult to separate the actual crash from the cause

• Are props hubs tightly bolted on the motors

– (Props can be broken but the hubs should be tightly mounted)

• Are the motors securely mounted to the aircraft

– (Motors must be bolted down tightly)

• Dose the ESC look burnt or do they smell

– (They could burn out after impact)

• If the aircraft is intact are the ESC wires plugged in to the AP

• Is the battery pack damage is it plugged in

• Is the wing bolted on are the bolts tight

• Are the control surfaces locked or loose

• Is the autopilot loose

© Alfred A. Gates, 2014 8
Autopilot Failure

Inflight Observation: Steep bank and Yaw

Ground Observation: Wreckage at one location

What failed: Loss of Attitude Control

Cause: Electromagnetic Interference

Video: See directory 

© Alfred A. Gates, 2014

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Structural Failure

(Flutter)

Inflight Observation: Aircraft spinning and loss of control

Ground Observation: Wreckage at one location except for control surface

What failed: flutter of control surface

Cause: Improper aerodynamics of control surface and or control linkage too 

loose

Video: https://www.youtube.com/watch?v=0xRrCm0vbHM

Note: This can occur in less than a second. If it 

happens to an aileron you may be able to fly the 

aircraft. If this occurs throttle idle and land the 

aircraft

© Alfred A. Gates, 2014

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Prevention: Proper preflight
Aircraft Flyway

Inflight Observation: Aircraft will bank in a direction can 

continue to fly in that direction (typically)

Ground Observation: Wreckage at one location 

What failed: Loss of GPS signal and or transmitter signal

Cause: Improper autopilot programming, poorly trained 

pilot

Video:https://www.youtube.com/watch?v=oXrrIxWC64Q

Clamed signal loss:

Prevention: 

• Proper autopilot programming

• If signal loss occurs fly back to starting point and 

circle at a reduced throttle

• preflight inspection and radio testing

© Alfred A. Gates, 2014 11
After A Crash 

• Determine the cause

• Disassemble aircraft and inspect components

• Replace parts and assemble

• Bench test

• Flight test all modes all maneuvers

• Ready for service

• DO NOT FLY AIRCRAFT UNTILL THE CAUSE 

HAS BEEN IDENTIFIED

© Alfred A. Gates, 2014 12