75HFE
75cc Single-Cylinder FlexDI™ Fully Integrated HFE Propulsion System for UAVs

Field Proven
Mission Ready

solar
cold
dust
rain
Built for endurance, the 75HFE uses FlexDI™ to deliver efficient heavy-fuel combustion
with minimal vibration and simplified integration. Field-proven with over 700,000+ hours
of multiple operating environments across the globe.
75HFE brochurestart with sales

Plug-and-fly integration, faster to flight

Compact form, direct coupling and integrated Engine Management System mean faster install, cleaner wiring and lower integration risk.

~345 g/kWh, multi-fuel longer missions,
no re-tune

Efficient and seamless operations across fuels and altitudes - no downtime for re-tuning.

5+ hp in a 4.4 kg, low-vibration package

For cleaner sensor data, more endurance or more payload from every litre.

Proven in 700,000+ operating hours

Multiple Tier 1 Defence customers and a proven record in numerous operating environments worldwide.

FlexDI™ Fuel Injection

8-micron precision, mission-level efficiency

Orbital’s FlexDI™ atomises fuel to ~8 µm droplets (vs ~120 µm conventional), delivering a cleaner, more complete burn. The result is >30% lower cruise fuel use, high specific power (>70 kW/L), and assured starts in –30 °C conditions with automatic altitude compensation to high density altitudes.

FlexDI™ runs JP-5/JP-8/Jet A/Jet A-1 or gasoline with no calibration change, meets MIL-STD-1474D noise targets, and uses electronic oil metering for consistent lubrication.

FlexDI™ turns advanced combustion control into tangible mission advantage.

FlexECU™

Advanced Engine Management System

Intelligent electronic propulsion management system
Hardware designed and validated for aero applications
Black-box logging
Fault monitoring and “return to base” logic
Advanced control strategies for UAV applications:
Anti-stall
Power management
Speed control
Engine protection

Textron Aerosonde 4.7HQ

The Textron Aerosonde 4.7HQ uses Orbital's 75HFE Integrated Propulsion System. Orbital worked closely with Aerosonde team to design and engineer to meet their exacting performance and reliability standards.

Proven Over Decades
Optimised for Today

CPI from 30+ years of missions
→ Tighter combustion control
→ Cleaner integration
→ Lower cost of ownership over the life of the programme.

Lifetime Value, Engineered In

UAV-specific design, FlexDI™ efficiency and mission-grade support cut fuel, maintenance and downtime - reducing total cost from development to through-life support.

Designed for UAV duty cycles (not repurposed motorcycle engines): thrives in high-hot-heavy profiles; higher MTBO → fewer removals, fewer spares, less downtime.

Lower fuel burn (FlexDI™ / OCS): 30%+ cruise reduction unlocks longer missions on the same fuel or more payload - compounds across time.

Proven reliability, engineered improvement: 30+ years of data driving Continuous Product Improvement (CPI); essential for single-engine platforms and BVLOS/LoS extensions.

Mission Assurance, not ad-hoc S&R: spares, overhaul, diagnostics, and SLAs sized to your tempo - shifts lifecycle risk off your team and protects availability.

How we reduce total cost of ownership

Fewer removals & teardowns: Long MTBO from UAV-specific architecture → lower maintenance labour and logistics.

Less fuel per flight hour: FlexDI™ efficiency → reduced opex or increased commercial yield (more data per tank).

Faster integration, fewer surprises: IPS + EMS + diagnostics → compressed development costs and quicker time-to-revenue.

Predictable sustainment: Support packages align cost to use; overhaul cycles planned, not reactive.

Orbital’s Integrated Propulsion Systems

From 50–350cc FlexDI™ heavy-fuel engines and PMS, Orbital delivers proven reliability, efficient combustion, and straightforward integration - backed by decades of mission experience.

75HFE Specifications:

Engine Configuration
75cc, Air-cooled 2-stroke with Orbital Flex DI
Power
5.1hp (3.8Kw) @ 6,500rpm
Fuel Consumption (BSFC)
~345 g/kWh @ typical cruise
Fuel Compatibility
JP5, JP8, Jet A, Jet A1 (able to operate on gasoline)
Weight
~7.8kg Integrated Propulsion System (includes ECU, mount, pumps, harness, propeller)
Engine Management
Orbital FlexECU with CAN Communication
TBO
500 Hours
Thermal Management
Light weight aerodynamic cowls
Exhaust System
Light weight acoustic/power optimised
Vibration Isolation
Dynafocal tuned mounting system
Electrical Power
Configurable Engine Management System alternator (with remote-start capability)
Fuel and Oil System
Integrated pumps and lines with consumption monitoring
Propeller
Orbital OptiProp propeller simulation and selection
Max. Operating Altitude
20,000’ AMSL
Operating Temperature
-30 to 55 °C including start
IP Rating
MIL Spec. Sand, Dust, Rain, Salt Fog
Environmental Conditions
MILSTD810H

Why Heavy-Fuel Wins for Payload, Endurance & BVLOS

Orbital’s FlexDI™ heavy-fuel engines give you the payload headroom, endurance, and mission assurance electric struggles to match

When range, uptime and mission assurance matter, Orbital’s FlexDI™ heavy-fuel engines deliver higher energy on board, faster turnarounds, and proven reliability in harsh theatres.

Proven reliability and consistent power delivery across heat, cold, dust and wet - critical when crews lose direct visual control giving higher mission assurance for BVLOS corridors, maritime legs and remote operations.

More Payload on Board & Endurance That Scales

ISR payloads are getting heavier and smarter. BVLOS routes are longer and harsher.

Higher energy density per kg than batteries means you can carry more sensors, comms and compute - or keep the same payload and fly longer.

Orbital’s FlexDI™ Integrated Propulsion Systems with superior fuel efficiency allows for bigger ISR packages, cleaner data, and less compromise on airframe weight balance. Fly further and smarter with Orbital.

Explore the 3 Ways to Work with Orbital

All options deliver Orbital’s proven reliability, FlexDI™ efficiency, and mission assurance across all engines. Choose the engagement model that fits your programme, timeline, and budget.

Strategic Partnership Programme

For OEMs who need a system-level advantage with co-engineered propulsion that wins programmes.

We embed with your team to design and execute a bespoke Integrated Propulsion System (IPS), optimised for your airframe and mission profile - from requirements capture to flight test and beyond, we’re with you for the long run mission after mission.

Mission-Ready Engines

Orbital’s renowned power, efficiency, and reliability - ready to deploy.

Standardised configurations of Orbital’s renowned Integrated Propulsion Systems with the same reliability and performance built on a 20 year pedigree - delivered faster and at a lower price point for OEMs seeking market leading Over Line of Sight (OLS) propulsion.

Mission Assurance Support

Keep your fleet flying - every mission, every theatre.

Flexible service packages to maximise availability: spares & repairs, health monitoring, engine overhaul, and field support - tailored to your operating tempo.

News

The Role of Metrology in Orbital UAV’s Engine Crankcases

In the world of unmanned aerial vehicles, reliability begins long before the first flight.

Read more ...

At Orbital UAV, combustion efficiency begins with precise fuel atomisation

Our FlexDI™ air-assisted direct injection system atomises fuel to ~8 µm droplets, compared to ~120 µm in conventional systems.

Read more ...

Built for Extreme UAV Performance: OptiProp

Tactical UAVs are flying higher, faster, and into increasingly contested environments - leaving no margin for inefficiency

Read more ...

Let’s chat about your airframe and mission requirements?

Sales

Let’s scope your programme.

Share timelines, quantities, and target budgets - we’ll map the best path (Partnership or Mission-Ready).

start with sales

Technical

Let’s talk airframe and mission.

Bring your platform specs, payloads, and constraints - we’ll recommend the right engine/PMS configuration.

start with engineering

Downloads

50HFE brochure75HFE brochure150HFE brochure350HFE brochurepms brochure

Australia

4 Whipple Street, Balcatta,
Western Australia, 6021
+61 (08) 9441 2311
contact@orbitalcorp.com.au

USA

210 Wasco Loop, Hood River,
OR 97031 USA
+61 (08) 9441 2311
contact@orbitalcorp.com.au