Preflight Inspection and Maintenance for Part 107 Pilots (2026)

Section 107.15 is one sentence long and it grounds more flights than any weather rule in Part 107: before each flight the remote pilot in command must check the small unmanned aircraft system to determine whether it is in a condition for safe operation. Maintenance and preflight inspection are also knowledge area (l) in 14 CFR 107.73.

Where the Rule Actually Lives

Section 107.15(a) requires the check before each flight; 107.15(b) forbids continuing once the pilot knows the system is no longer in a condition for safe operation. Section 107.49 lists the preflight actions themselves. Chapter 7 of AC 107-2A explains how to inspect and maintain a small UAS, and its Appendix C charts findings that may make an aircraft unairworthy.

Section 107.49 never mentions propellers, motors or batteries: it covers the environment, the crew briefing, control links, power, payload security and the over-people category. The hardware inspection comes from 107.15 and the AC. The AC also recommends calibrating the compass prior to any flight (item 19 of its preflight list), the exam answer even where an app calibrates only when prompted.

The 107.49 Duties Before Launch

Assess the operating environment: local weather, airspace and any flight restrictions, persons and property on the surface, other ground hazards. Brief everyone directly participating on conditions, emergency and contingency procedures, roles and hazards. Ensure all control links work. Ensure enough power for the intended operating time. Ensure anything attached is secure and does not degrade flight characteristics. Section 107.49(f) adds the category requirement over people.

Currency Is Not Airworthiness

Section 107.65 governs the pilot, not the aircraft: within the previous 24 calendar months the remote PIC must have passed the initial knowledge test, completed recurrent training, or completed the 107.74 training while holding a Part 61 certificate and meeting the flight review. A pilot can be perfectly current and grounded by a cracked arm. Registration runs on its own clock, expiring 3 years after the date of issue (48.100(c)).

Section 107.13 requires compliance with 91.203(a)(2), which calls for an effective U.S. registration certificate. Registration is required unless the aircraft weighs 0.55 pounds or less on takeoff including everything attached (48.15), and 48.205 requires the unique identifier to stay affixed and be legibly displayed on an external surface. A number under a battery hatch that needs a screwdriver fails that test. Our drone registration guide covers renewal.

A Workable Inspection Sequence

AC 107-2A suggests Part 43 Appendix D as a model: airframe, then flight controls, then batteries, then powerplant. For a small UAS: one direction, the same order every time, a hand on everything you inspect.

• Airframe and arms: cracks, delamination, stress whitening at the motor mounts, missing fasteners.
• Propellers: chips, nicks, cracks, delamination, bent blades, elongated hub holes.
• Motors: bearing roughness, shaft play, heat after a short hover.
• Battery: swelling, punctures, corroded contacts, cell voltage spread.
• Compass and IMU: calibration prompts, drift in a hover, heading error after an update.
• Control station: antennas, battery level, firmware match, latency, satellite count.
• Payload: mount tightness, gimbal limits, cables clear of the propellers.

Then run the AC's functional check: start the propellers to listen for imbalance, fly a low altitude lap, recheck controls and stability.

Propeller Damage Criteria

Propellers are the cheapest part and the one most likely to end a flight. Manufacturer guidance converges on one rule: a crack, chip, nick, gouge, delamination, bent blade or elongated hub hole means replacement, not trimming or glue. A blade that lost material is out of balance, and vibration travels into the motor bearings and the flight controller. Appendix C treats a noticeable change in the sound of the propulsion system as a condition that may make the aircraft unairworthy.

Battery Care and Storage Voltage

Appendix C names two battery findings: a casing that is distorted or bulging, and diminishing flight time capability. Either grounds the pack. A swollen pack has vented internally: a fire risk, and unrepairable. Charge to full on the morning of the flight, not a week before, because a lithium polymer pack stored at full charge ages faster. Manufacturer guidance, including DJI's battery documentation, puts storage at about 3.8 volts per cell, close to half charge, and warns against leaving a pack deeply discharged, where a cell drifting below roughly 2.6 volts takes permanent damage. If a pack that once flew 22 minutes now gives 16, plan on 16 and retire it.

Firmware, Geofence and the Control Station

AC 107-2A section 7.2.2 counts software updates as maintenance, and notes a manufacturer may require an unscheduled update to fix a problem; flight operations should not occur until it is corrected. Update at the desk, put aircraft and control station on the same version, fly a short function check. Then set the limits to the mission: altitude ceiling, distance limit, return to home altitude, no fly zone data. A geofence left at the legal maximum from a previous job is a liability beside a hospital helipad.

Site Survey and Control Station Setup

The first 107.49 duty is the environment. Look up for wires, guy lines and crane cables no chart shows. Look down for the launch surface and the footpath crossing the flight path. Check the sun: backlight turns the aircraft into a silhouette. Set the control station where the pilot sees aircraft and airspace without turning, keep antennas clear of the vehicle roof, and stand where a building will not shadow the link. Then brief who does what, and what word means stop.

When a Preflight Failure Becomes an In-Flight Emergency

Section 107.21 lets the remote PIC deviate from any rule of Part 107 to the extent necessary to meet an in-flight emergency, and requires a written report to the FAA on request. Most of those emergencies were visible on the ground. A nicked propeller becomes vibration and heat; a tired pack becomes voltage sag at 300 feet. The exam frames it as the second half of 107.15: once the pilot knows the system is no longer in a condition for safe operation, the flight may not continue. Deviating to land is protected; continuing because the client is watching is not. The ADM guide covers the decision loop.

Next Steps

Read 107.15 and 107.49 once, then write your checklist in the order you walk around the aircraft, and log repairs with the time in service. The loading and performance guide covers how payload changes performance, the Part 107 study guide maps the other knowledge areas, and a free practice question shows how the exam words a preflight scenario. Try the study checklist, then compare plan options.