FAA 107 Aircraft Maintenance & Pre-flight Inspection 3 — Questions and Answers
Question 1: What is the function of an Electronic Speed Controller (ESC) in a multirotor sUAS?
- It stores energy for the motors during peak demand
- It regulates the speed of each motor based on flight controller commands (Correct answer)
- It converts AC power to DC for motor use
- It stabilizes the gimbal during rapid movements
Correct answer: It regulates the speed of each motor based on flight controller commands
ESCs receive signals from the flight controller and regulate the electrical power delivered to each motor to achieve the desired speed and direction.
Question 2: During pre-flight, you discover that the Return-to-Home (RTH) altitude is set lower than the tallest obstacle in your operating area. What should you do?
- Fly anyway since RTH is a backup function only
- Increase the RTH altitude above the tallest obstacle before flight (Correct answer)
- Disable RTH to prevent automatic altitude errors
- Only operate within line of sight to avoid needing RTH
Correct answer: Increase the RTH altitude above the tallest obstacle before flight
If RTH altitude is lower than surrounding obstacles, an automatic RTH event could cause the drone to collide with buildings, trees, or terrain.
Question 3: Which of the following maintenance actions requires logging in the maintenance record for a sUAS under Part 107?
- Part 107 does not require any maintenance records
- Only repairs done by an FAA-certified repair station
- Any maintenance or alteration that the remote pilot deems significant (Correct answer)
- Only engine overhauls and major component replacements
Correct answer: Any maintenance or alteration that the remote pilot deems significant
While Part 107 does not mandate specific maintenance record formats, remote pilots are responsible for determining and documenting maintenance they consider significant to airworthiness.
Question 4: Why is it important to let LiPo batteries cool down before recharging them after a flight?
- Warm batteries charge faster and may overcharge
- Charging warm LiPo batteries increases the risk of swelling, fire, or reduced cell life (Correct answer)
- The charger cannot detect cell voltage accurately when warm
- Cool batteries hold a higher charge capacity
Correct answer: Charging warm LiPo batteries increases the risk of swelling, fire, or reduced cell life
Charging a LiPo battery while it is still warm from flight stresses the cells and significantly increases the risk of thermal runaway, swelling, or fire.
Question 5: A remote pilot notices the sUAS drifts consistently to the left when hovering with no control inputs. What is the most likely cause?
- Low battery voltage
- Compass or accelerometer miscalibration or a motor/prop imbalance (Correct answer)
- GPS signal interference
- Incorrect flight mode selected
Correct answer: Compass or accelerometer miscalibration or a motor/prop imbalance
Consistent drift in hover usually indicates sensor calibration issues, a motor running slower than the others, or a damaged/imbalanced propeller.
Question 6: What does inspecting the gimbal for proper operation during pre-flight include?
- Verifying battery voltage at the gimbal connector only
- Checking that the gimbal self-levels correctly, moves freely, and shows no physical damage (Correct answer)
- Ensuring the gimbal is locked in place for takeoff
- Calibrating the gimbal motors using the remote controller
Correct answer: Checking that the gimbal self-levels correctly, moves freely, and shows no physical damage
A functional gimbal pre-flight check confirms it initializes correctly, self-levels, moves through its full range without binding, and has no physical cracks or loose parts.
Question 7: Under what condition should a remote pilot ground a sUAS due to a battery issue discovered during pre-flight?
- Only if the battery is below 50% charge
- If the battery shows physical swelling, damage, or fails to reach normal voltage (Correct answer)
- Whenever the battery is more than 6 months old
- Only if the BMS reports a fault through the app
Correct answer: If the battery shows physical swelling, damage, or fails to reach normal voltage
Swollen, physically damaged, or under-performing batteries present a serious fire and flight-failure risk and must not be used until inspected or replaced.
FAA 107 Aircraft Maintenance & Pre-flight Inspection 3
What is the function of an Electronic Speed Controller (ESC) in a multirotor sUAS?