A33N UAV Engine System


The A33N UAV Engine System is Cobra Aero’s initial entrant in the A33 family of engines. The A33N engine is an all-new purpose designed UAS engine.

  • High power to weight
  • Low acoustic signature
  • Fits a typical 3W-28i footprint
  • 3D-printed aluminum head and cylinder improves engine repeatability
  • Hardware, electronics, and software all designed specifically for UAS applications
  • Machined crankcase with integrated belt driven generator
  • Passed FAR33 150-hour endurance test

Endurance Report:


Engine Type: Air-cooled 2-stroke single
Displacement: 33 cc (2.0 ci)
Weight: 2.25 kg (5 lbs) (Includes core engine, exhaust, ECU, fuel pump, injector, ignition, generator, harnesses)
Fuel Delivery: Fuel injection at 3 bar (gasoline 50:1 premix)
Power Output: 2.0 kW (2.7 HP) at 8200 RPM
Fuel Consumption: 500 g/kW-hr (0.82 lbs/HP-hr) at cruise
Generator output: 250W (500W intermittent duty cycle)

The engine package includes

  • Power4Flight IntelliJect ECU
  • Currawong self priming fuel pump
  • All required EFI sensors and wire harnessing
    • CHT, MAT, and fuel pressure
    • Baro and MAP
    • CDI module
  • Fuel pressure accumulator
  • Full induction and exhaust system
  • Electric power generator with start capability
  • Cooling duct with active control


  • Altitude compensation
  • Cold start compensation
  • Superior throttle response compared to carbureted engines
  • Onboard log-booking and maintenance tracking
  • Onboard data logging
  • Plug n’ Play with Piccolo autopilot
  • Free communications ICD and software developers kit for CAN and serial
  • Free user interface for engine and configuration development

EFI Engine with Integrated Generator

The A33N engine is a purpose designed UAS engine. It features a 3D-printed cylinder and high quality machined crankcases that overcome porosity issues, provide a more precise path for internal fuel/air circulation and incorporate an integrated generator system. The 3D printed cylinder head minimizes engine-to-engine variability. This simplifies fleet management, allowing a ‘tighter’ fleet ECU calibration for improved performance and fuel economy.

Maxon Generator

The A33N engine is equipped with a 3-phase Maxon brushless motor used as a generator. The generator is driven by a toothed belt from the engine output shaft and produces 250 watts (500 watts intermittent) of electrical power. The generator includes sensors which allow it to be used to start the engine from a 24V supply (Power conditioning and starting electronics are a separate package).

Exhaust System

The exhaust system on the A33N dramatically reduces the acoustic signature of the engine as compared to conventional side-mount exhaust.