Data Sheet

Engine Type:           



Fuel Delivery:           

Power Output:         

Fuel Consumption: 

Generator output:  

The A33-N UAV Engine System is a 33cc single cylinder engine having a high power density and minimal maintenance requirements. The engine features an advanced function ECU, a positive displacement high-pressure fuel pump. a fuel pressure accumulator, a super-atomizing fuel injector, capacitive discharge ignition, and MAT and CHT sensors. The engine incorporates an integrated generator and generator drive system.  A custom muffler is fitted as standard.

The list of features of the engine include the following:

  • Low-noise exhaust design
  • Stall-resistant throttle response
  • Significantly expanded throttle-RPM envelope vs Carburetor
  • Full EFI suite including automotive-quality ECU processor, self-priming fuel pump, ignition, sensors, injector and custom intake, all with over 40,000 hours on UAS platforms.
  • Seamless CAN-bus autopilot integration, compatible with Piccolo.

Summary Specifications


A33N UAV Engine System

The A33N UAV Engine System is Cobra Aero’s initial entrant in the A33 family of engines. This unit combines high power-to-weight with low acoustic signature in a simple and reliable propulsion module that fits a typical 3W-28i footprint.

A33N UAV Engine System

Electronic Fuel Injection

The A33N UAV Engine System has the latest version of Currawong’s EFI system. CE has developed EFI systems for a number of engines for use in UAVs. CE’s conversions include the 3W-56 two-stroke engine used on the Honeywell T-Hawk MAV, with over 700 systems delivered to date. The Raytheon Silver Fox UAS, using a Robins/Fuji 34cc four-stroke engine, was refitted with CE EFI systems, with over 85 systems delivered to date.

Note: In the fourteen months following the Silver Fox refit there were no major engine faults during in-theater operations. We have been informed that in excess of 20,000 operating hours have been logged with this aircraft and its propulsion unit.

The Currawong EFI system is the most mature and reliable of any system currently available for small engine use in UAS.

The A33N UAV 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.

Engine Technology

Air-cooled 2-stroke single


2.25 kg (5 lbs) (Includes core engine, exhaust, ECU, fuel pump, injector, ignition, generator, harnesses)

Fuel injection at 3 bar

2.3 kW (2.5 HP) at 8000 RPM

500 g/kW-hr (0.82 lbs/HP-hr) at cruise

250W (500W intermittent duty cycle)

  • An ECU that is fully featured for aeronautical use and which has the ability to communicate with various avionic systems. When used with Cloud Cap Technology’s Piccolo Autopilot the connection is plug-and-play. The ECU has a proven record of reliability in extreme conditions of temperature and at a wide range of altitude. The ECU incorporates sensors for manifold air pressure and fuel pressure. External sensors are used for manifold air temperature and engine cylinder head temperature.

  • A high pressure positive displacement fuel pump, incorporating a fuel pressure accumulator in the lower flow applications, with extraordinary self-priming capability and unchallenged ability to maintain pressure, even in the event of aeration of the fuel.

  • A robust fuel injector that uses an automotive injector body with proprietary interior modifications that provide the very fine atomization that is essential for use on small engines.

  • A CE designed throttle body that is lightweight and accurately machined.

  • Wiring harnesses that are dedicated to the EFI system but which can be customized for individual applications.

Maxon Generator

The A33-N engine is an all-new purpose designed UAV engine. It features high quality fully machined crankcases that overcome porosity issues, provide a more precise path for internal fuel/air circulation and incorporate an integrated generator and generator drive system. Other improvements include a new propeller hub design, incorporating a more accurate crank angle sensing system. The ignition system is based on a Desert Aircraft CDI unit with modifications to facilitate control by the ECU. Furthermore, the cylinder ports are fully machined (patent pending) to minimize engine-to-engine power variability. This simplifies fleet management, and it allows a ‘tighter’ fleet ECU calibration for improved performance and fuel economy. The engine also offers a twin plug head, and extra cooling fins which integrate into the cowling for more precise air flow over the cylinder.

Key Features

Exhaust System

The exhaust system used on the A33N both maximizes performance and substantially reduces acoustic signature. It is also lightweight and rebuildable for simple field maintenance.