Overheating motors

Overview

Motors hot after flight — smell or discoloration.

FPV 5" racing, DJI Mavic in heat, BLHeli32 thermal protection.

Symptoms

Typical "Overheating motors" signs in flight, app or OSD:

• Motors too hot to touch
• Burning smell
• Shorter flight before thermal throttle
• Touch test after landing — should cool within 2–3 min.

Common causes

Before replacing parts, rule out software, mechanical and environmental causes:

• Aggressive full throttle
• Prop pitch too high
• Stuck motor / bad bearing

Tools needed

Prepare before diagnostics — saves time in the field:

• IR thermometer (optional)
• Stack ventilation
• Prop pitch spec sheet

Step-by-step fix

Work safely: battery off when working on ESC/motors; props removed; after repair — VLOS test flight.

• Cool down between flights.
• Lower prop pitch or lighter props.
• Replace motor if bearing rough.

Additional diagnostics

Touch test after landing — should cool within 2–3 min.

Reduce WOT time or prop pitch.

Check airflow — stack not covered.

When to contact service

If any of the following apply — do not fly and contact authorised service:

• Motors/discoloration after one flight.
• ESC shutdown in flight twice in a row.
• Burnt insulation smell.

Prevention

Prevention reduces failure risk and supports EASA Open / VLOS compliance:

• Touch test after landing

Frequently asked questions

Is it safe to fly with "Overheating motors"?

No if the fault affects navigation, power, ESC or link. Fix on the ground first, then conduct a VLOS test flight in open area.

How long does diagnosis take?

Most “Overheating motors” cases — 15–45 min on the ground. Complex ones (firmware, hardware) may need 1–2 h and service.

Must I register repair with the NAA?

No mandatory repair registration, but a maintenance log is recommended for commercial operations.