Scheduled maintenance
Summary¶
libdrone maintenance is interval-based: specific tasks are triggered by flight count, flight hours, elapsed time, or crash events. The most safety-critical intervals are floating motor mount O-ring replacement (every 20–30 flight hours) and post-crash arm inspection (every crash, regardless of apparent damage). Battery condition is assessed after every flight using resting voltage per cell. A simple logbook — even a notes file — tracking flight count, battery cycles, and any maintenance performed is the minimum required to maintain situational awareness of the platform's condition.
Concept¶
Why intervals matter¶
A drone that has flown 50 hours has worn O-rings, fatigued solder joints, and accumulated vibration stress in the frame that a drone with 5 hours does not. Visual inspection at each pre-flight catches visible damage; interval-based maintenance catches the invisible degradation that pre-flight inspection misses. The silicone O-rings in the floating motor mounts are the highest-replacement- frequency item: they harden and crack with UV and heat exposure, and degraded O-rings transmit more vibration to the gyroscope, degrading flight quality before they fail visibly.
Crash-triggered vs flight-interval maintenance¶
Some maintenance tasks are triggered by an event (crash) rather than an interval. After any hard landing or crash, even one that appears minor, the post-crash inspection is mandatory. Hairline cracks in PCCF layers are not visible from outside the frame and only become apparent under load — in the air. The cost of a ground inspection is 10 minutes; the cost of an in-flight structural failure is the drone.
Reference¶
Maintenance schedule¶
| Component | Task | Interval |
|---|---|---|
| Props | Visual inspection for cracks, chips, looseness | Every flight |
| Props | Balance check on magnetic balancer | Every 10 flights or after any tip strike |
| Motor mount O-rings | Visual inspect for cracking or deformation | Every 5 flights |
| Motor mount O-rings | Replace complete set (O-rings + sleeves) | Every 20–30 flight hours |
| Motor mount screws | Re-torque to 0.4–0.5 N·m | Every 10 flights |
| Arm T-locks | Press each arm, check for lateral play | Every flight (pre-flight) |
| Sandwich bolts | Re-torque to 0.3 N·m | Every 20 flights |
| CF rods | Acoustic ping — confirm ring tone | Every 20 flights |
| FC connectors | Visual inspect for corrosion or looseness | Every 20 flights |
| Conformal coating | Visual inspect for chips or peeling | Every 20 flights; after rain |
| Battery | Resting voltage per cell, check for swelling | After every flight |
| Battery | Storage charge/discharge if not flying within 3 days | As needed |
| Battery | Full cycle (charge + fly + measure capacity) | Every 20 charge cycles |
| GX12 connectors | Inspect pins, verify lock rings | Every 10 flights |
Post-crash inspection sequence¶
Inspect in order from the most to least likely damaged:
- Props: inspect all 4. Replace any with visible damage.
- Arm shafts: flex each by hand. Any play = fractured shaft. Replace.
- Arm tabs and T-slots: remove shaft (4× M2 screws). Inspect T-lock root on each tab for cracking. Inspect T-slot walls in PCCF for cracking.
- Motor mount O-rings: inspect for tearing. Replace if torn.
- CF rods: acoustic ping all 4. Dull sound = rod loose. Re-seat.
- Sandwich bolts: re-torque all to 0.3 N·m.
- Electronics: check all connector seating. Visual inspect for impact damage. Review Blackbox on next flight for anomalies.
- Battery: inspect for swelling, deformation, puncture. Retire if any.
Motor mount O-ring replacement procedure¶
- Remove motor (4× M3 motor mount screws). Disconnect MR30.
- Remove passive cover.
- Remove old O-rings and sleeves. Discard — never reuse degraded isolators.
- Clean arm head surface with IPA. Allow to dry fully.
- Apply thin film of Super Lube 52004 to new sleeves and O-rings.
- Insert sleeves into motor bolt holes. Place O-rings in arm head counterbores.
- Reinstall motor and passive cover. Torque to 0.4–0.5 N·m cross-pattern.
- Verify: passive cover does not contact arm head except at O-ring bosses.
Procedure¶
Maintaining a flight logbook¶
Minimum entries per session: - Date - Flight count (increment each flight) - Total flight time (running total) - Battery cycles used (by pack identifier) - Any maintenance performed - Any anomalies noted
A simple notes app or spreadsheet is sufficient. The logbook answers: "When did I last replace the O-rings? How many flights on this battery? Was there a hard landing recently that I should inspect for?" — questions that are impossible to answer reliably from memory after 50 flights.
Rationale¶
Why O-ring replacement is on a flight-hour interval rather than calendar time¶
O-ring degradation is driven by heat cycles (from motor temperature), UV exposure, and mechanical compression/release cycles — all proportional to flight hours, not calendar time. A drone flown intensively for 20 hours in a month degrades O-rings more than the same drone flown for 20 hours over a year. The interval is hours-based because hours are the relevant stress measure.
Calendar time is a secondary trigger: if the drone has been stored for more than 6 months without flying, inspect the O-rings regardless of flight hours — silicone ages, especially in warm storage conditions.
Connections¶
requires: - floating-motor-mounts - failure-hierarchy related: - preflight-checklist - arm-shaft - lipo-batteries - winter-protocol leads_to: - piloting-operations