Multirotor Flight Training In Close 

Proximity of Structures, Vegetation, 

and Power Lines

• Pilot and observer procedures

• Anticipated aircraft behavior, updrafts, wind 

shear mechanical turbulence

• Anticipated autopilot behavior, GPS poor 

flight, Attitude, manual

© Alfred A. Gates, 2014 1
Pilot and Observer Procedures

• The observer has equal rolls in producing a safe and beneficial flight 

around structures

• When the plot maneuvers a multicopter to a safe distance away 

from the target he will stop and hold position. The observer will 

then guide the pilot to a closer position by observing the aircraft 

from different positions and by using the video feed to guide the 

pilot. 

• The pilot should not move from his view point once the observer is 

providing guidance. Also the pilot should only be looking at the 

aircraft and if he must look at the controller he should move the 

controller to his line of sight.

• In close proximity of structures, vegetation and lines, the observer 

will have a better understanding of the position of the aircraft. 

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Pilot and Observer Procedures

• During any stage of the 

flight

• The pilot will put the 

transmitter in the field of 

view to check the flight 

status, GPS signal strength, 

battery strength.

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Pilot and Observer Signals

• Pilot performs all preflight 

• Pilot takes off, hovers and 

performs inflight checks.

• Pilot maneuvers aircraft to a 

safe distance from structure 

and holds position in GPS hold 

mode ( provided the satellite 

signal strength is strong 

enough)

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 Pilot maneuvers multirotor to 

safe distance from structure

 Observer starts to advise and 

guide the pilot to the 

inspection position

 Pilot holds position at inspection 

point

 Observer operates camera, zoom, 

pan tilt, photo and video
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 Pilot: Eyes always on the multirotor

 Observer: Advises pilot during every position change

• Operates all camera functions

• Moves around to vide aircraft from different angles

• Uses video feed to advise pilot
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 Once all inspection is 

complete.

 Observer guids pilot away 

from structure to a safe 

position where the pilot can 

fly the aircraft unassisted

Pilot can now safely 

land the aircraft
Winds/ Weather

• On calm days the winds were stronger than anticipated 

requiring the pilot to manually fly the multirotor in close 

proximity to the structures and power lines.

• Biggest limiting factor is weather. Winds greater than 5KTS 

coupled with other factors that create wind require over 

riding the GPS mode.

• Can not fly in rain or snow showers.

• A highly experienced pilot is required.

• The observer has a higher work load than anticipated.

2015 AHS Specialist’ Meeting on 

Unmanned Rotorcraft and Network-Centric 

Operations Program

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Navigation

• It is safer to navigate around wires in GPS position hold 

mode provided the autopilot is capable of maintaining 

position in the winds. This allows the pilot time to slowly 

maneuver the aircraft into position. The observer is 

advising the pilot in close proximity of lines and structures.

• The pilot needs to be ready to switch modes if the aircraft 

is blown out of position or if the GPS signal becomes weak.

• The maximum pitch and roll angles are decreased in GPS 

mode when compared with the stabilize and altitude flight 

modes. 

2015 AHS Specialist’ Meeting on 

Unmanned Rotorcraft and Network-Centric 

Operations Program

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Or no wind

This will occur around tree canopies

Shear Zone: This will cause a multicopter to move in pitch and roll to maintain 

attitude control. 

Wind Top Zone: the aircraft can be blown out of view.

FAA Pilots Handbook

2015 AHS Specialist’ Meeting on 

Unmanned Rotorcraft and Network-Centric 

Operations Program

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Still air

Wind

Multirotor can be blown out of view

Wind shear event

2015 AHS Specialist’ Meeting on 

Unmanned Rotorcraft and Network-Centric 

Operations Program

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Anticipating 

• Flight in turbulence (aircraft will move around more)

• Aircraft will be blown in one direction. Pilot is ready 

to switch modes

Wind shear

Video: Wind at top of structure

Aircraft was being blown out of view

Above tree canopy. Pilot had 

seconds to switch modes

2015 AHS Specialist’ Meeting on 

Unmanned Rotorcraft and Network-Centric 

Operations Program

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Terrain turbulence

Mechanical Turbulence

2015 AHS Specialist’ Meeting on 

Unmanned Rotorcraft and Network-Centric 

Operations Program

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Convective Currents
Multirotor UAS Flight Modes Commonly 

Uses For Structural Inspection

• Stabilize, Manual: Keeps the aircraft level if the control 

sticks are released. Does not hold position or altitude (Pilot 

has the most control authority)

• Altitude: keeps the aircraft level and at the current altitude 

if the sticks are released. Does not hold position (Change 

and altitude is limited by the maximum/ minimum 

throttle setting programmed)

• GPS Hold/ Loiter: Holds position and yaw if the stick are 

released. Depends on a good GPS signal. (Change in 

altitude and attitude is limited by the maximum control 

settings for pitch, roll, yaw and altitude) Pilot has the least 

control authority

2015 AHS Specialist’ Meeting on 

Unmanned Rotorcraft and Network-Centric 

Operations Program

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Anticipated autopilot behavior, GPS poor 

flight, attitude, manual

• The pilot must anticipate that the GPS signal 

strength will decrease. (Be ready to switch 

modes)

• The pilot must anticipate wind shear, updrafts, 

wind gust and wind changes. (Be ready to 

switch modes)

• The pilot must anticipate what the multirotor 

will do in the event of wind shear, updrafts, 

wind gust and wind changes

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Updrafts

• Updraft: Multirotor will climb in position. 

Throttle min position will not be low enough 

to maintain altitude.

• Pilot response: 

• If structure is above switch to manual mode. 

Manual mode provides more altitude control 

authority

• If there is no structure above. Let the aircraft 

climb and wait and see it the updraft decays

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Wind Shear

• Wind Shear: Multirotor will pitch and roll and 

possibly move away from the hover position. 

• Pilot response: 

• If structure is close switch to Altitude mode. 

Altitude mode has the same pitch, roll and 

YAW min, max settings as the manual mode.

• If there is no structure close by. Let the aircraft 

move around and fly the aircraft through the 

wind shear zone.

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Wind Gust, Wind Increase

• Wind Shear: Multirotor will blown in one direction. 

• Pilot response: 

• If structure is close or if the multirotor is being 

blown out of view switch to Altitude mode. 

Altitude mode has the same pitch, roll and YAW 

min, max settings as the manual mode.

• If there is no structure close by. Let the aircraft 

move around and see if the wind gust will died 

down

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GPS Signal Strength Reduction or 

Signal Loss

• When the GPS signal becomes weak. The 

aircraft will chase a unknown GPS position at 

the maximum pitch and roll positions. The 

aircraft will maintain altitude.

• The pilot must immediately switch modes to a 

none GPS mode, Altitude or Manual.

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