Aerospace Electric Motor Design: Where Every Gram Pays Twice
By the Turncircles engineering team · Published
In the air, a motor does not only have to be good. It has to be light, efficient where the aircraft actually flies, and honest about its limits. Aerospace electric motor design is mostly the art of removing everything that does not make torque.
This page explains the weight arithmetic behind that, how a coreless axial flux motor with a printed stator helps, and where our work on drones, VTOL and space concepts comes in.
Configure a lightweight motor Read about lightweight motorsWhy Weight Is the Whole Story in Flight
On the ground, a heavy motor costs money. In the air, it costs range, payload and flight time, and then charges interest. Every gram of motor has to be lifted by the thrust of the motors, which are themselves heavier because they lift heavier motors. Aircraft designers call this the snowball. Motor designers call it Monday.
A rough but useful illustration, using the ideal hover relationship where power grows with thrust to the power of 1.5: if a lighter motor design takes 12% out of the take-off mass of a multirotor, hover power falls to about 0.881.5 = 83% of the original, and on the same battery the hover time rises by roughly 21%. Idealised, and the real number depends on your propellers and losses, but the direction is why aerospace buyers talk about grams. The same logic is laid out in why we need lighter electric motors.
What an Aerospace Motor Is Asked to Do
- Torque density. Torque per gram of active mass, see the torque density guide.
- Efficiency where you fly. A multirotor spends most of its life near hover; a fixed-wing near cruise. A motor whose efficiency island sits over those points beats one with a higher peak somewhere you never go.
- Direct drive at propeller speed. No gearbox means fewer parts, less noise and less to fail.
- Heat removal in an airflow. Propeller wash and airframe structure can be part of the cooling, which is a good reason to integrate the motor.
- Environment. Operating temperatures of -40 to +60 °C and protection up to IP67 cover many missions.
How Axial Flux Helps
A coreless axial flux motor with a printed stator removes the heaviest parts of a conventional motor: the iron core, the bobbins and the winding overhang. Built as a naked motor, without housing and with the stator mounted straight into an airframe arm or wing structure, it removes the housing as well. The disc shape suits pods, ducted fans and flat propulsion layouts, and the large diameter gives torque at propeller speeds without a gearbox. Our platform offers up to 50% weight reduction compared with conventional motors of the same output.
From Concept to Motor: Examples on This Site
- VTOL cargo drone concept: propulsion for vertical take-off with efficient forward flight.
- Long-flight UAV with a thermal camera: endurance as the design driver.
- Mars mobile spacecraft: extreme temperatures and a very high price per kilogram launched.
- What is a drone: where the motors sit in the whole system.
Efficiency Island vs Mission Profile: A Quick Example
A datasheet quotes the best point of a motor. An aircraft does not fly at the best point of a motor. Imagine a multirotor whose mission energy splits 80% at hover and 20% at climb, and two candidate motors:
| Efficiency at hover | Efficiency at climb | Datasheet peak | Mission-weighted | |
|---|---|---|---|---|
| Motor A | 88% | 94% | 94% | 89.2% |
| Motor B | 93% | 90% | 93% | 91.2% |
Motor A wins the brochure. Motor B wins the flight, by two percentage points that translate directly into minutes in the air. This is why we ask for the mission profile rather than the maximum, and why the efficiency map in the configurator matters more than any single headline number.
Hypothetical motors and a simplified energy-weighted average, to show the principle.
What We Do Not Claim
Be wary of any motor supplier who says "aerospace" without a footnote. We supply motors and the data that goes with them. We do not supply flight certification: airworthiness, qualification and installation approval belong to your aircraft and your regulator. We will help you specify the motor so that it can pass your tests, and we will be clear about what has been simulated and what has been measured.
Design Process for an Aerospace Motor
- Define the propulsion point: thrust, propeller RPM, supply voltage and mass target.
- Configure the motor in the configurator and read the efficiency map against your hover and cruise points.
- Decide the construction: housed, naked or wet, and how it is mounted.
- Engineer, build and test, then iterate. How a custom motor is designed covers each step.
Frequently Asked Questions
What makes an electric motor suitable for aerospace use?
Low mass for the torque it delivers, high efficiency at the real operating points (hover, cruise), a thermal design that works in the available airflow, and a construction that suits the installation. Certification is a property of the aircraft system, not of a motor alone.
Why use axial flux motors in drones and eVTOL?
Their flat, disc-shaped design gives high torque per unit of mass and a short axial length, and a coreless printed stator removes iron, bobbins and winding overhang. Direct drive at propeller speed avoids a gearbox.
Can the motor be built without a housing?
Yes. A naked motor is delivered as rotor and stator only, and the stator is mounted into your structure. This removes housing and end-bell weight, but the application then provides bearings and structural support.
What temperature range do the motors cover?
The platform is specified from -40 to +60 degrees Celsius, with protection up to IP67 for housed variants.
Do you provide flight-certified motors?
No. We provide motors and supporting data; certification of an aircraft or propulsion system is the responsibility of the aircraft manufacturer and the relevant authority.
Take weight out of your propulsion
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