# 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

• S pinning (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 10 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