Williams FJ33 Turbofan Engine Overview

The Williams International FJ33 is a family of compact turbofan engines designed for very light jets (VLJs) and personal jet programs. Scaled from the widely adopted FJ44 series, the FJ33 brings modern turbofan efficiency to smaller airframes—delivering low weight, low fuel burn, and simplified maintenance in the ~1,000–1,900 lbf thrust class. Although the FJ33 is physically smaller than the FJ44, it shares the same design philosophy: reliable power with minimal complexity for private aviation’s entry-level jet category.

Development & Certification

Williams International developed the FJ33 in the early 2000s to support a new wave of very light jet concepts. Building on the success of the FJ44, engineers pursued aggressive weight reduction and part simplification while retaining durability and hot/high capability for real-world operations. The FJ33 achieved FAA type certification in the mid-2000s, opening the door for multiple VLJ and experimental programs.

Design & Key Features

• Architecture: Single-stage fan with axial compressor stages, annular combustor, and a two-stage turbine—optimized for compact diameter and low parts count.
• Thrust Class: Approximately 1,000–1,900 lbf (variant dependent), suitable for single-engine VLJs and lightweight twins.
• Efficiency Focus: Low specific fuel consumption and high bypass for the class, targeting economical cruise at typical VLJ altitudes.
• Maintainability: Modular design to simplify inspections and reduce time off wing.
• Noise/Emissions: Modern combustor and fan design aimed at community noise standards and cleaner operation.

Variants & Thrust Classes

The FJ33 family includes multiple dash numbers (e.g., -1, -2, -3A, -5A series) that differ in thrust rating, materials, and control logic refinements. Later variants deliver higher takeoff thrust (approaching ~1,900 lbf) and enhanced hot-day performance, while early variants emphasize minimum weight and simplicity for lighter prototypes.

Applications in Very Light Jets

The FJ33 has powered several notable VLJ programs and prototypes. One of the most visible in-service examples is the Cirrus Vision Jet SF50 (single-engine configuration), highlighting the FJ33’s compact size and thrust-to-weight appeal. Other programs include the Flaris LAR 01 and the Diamond D-Jet (prototype). For shoppers comparing VLJs with step-up light jets, note that the Cessna Citation M2 uses the larger Williams FJ44 family, while the HondaJet HA-420 uses the GE Honda HF120—illustrating the range of modern small-turbofan solutions in today’s market.

Where the FJ33 Fits in the Market

The FJ33 helped solidify the VLJ category by enabling smaller, lighter airframes with true jet performance and manageable operating costs. For owner-operators and corporate users stepping up from turboprops, FJ33-powered concepts promised jet speeds, pressurization, and simplified maintenance, often at lower acquisition and hourly costs than larger cabin aircraft. Operationally, VLJs shine on short- to medium-haul missions (roughly 300–900 nm legs), with occasional longer stages depending on payload, weather, and alternates.

FJ33 vs. FJ44 (At a Glance)

• Size & Weight: FJ33 is smaller/lighter for VLJ class; FJ44 targets light-jet and some midsize applications.
• Thrust: FJ33 ~1,000–1,900 lbf; FJ44 typically ~1,900–3,600+ lbf depending on variant.
• Use Cases: FJ33 for single-engine VLJs or ultra-light twins; FJ44 for aircraft like Citation CJ/M2 and other light jets.

Specifications (Representative, Variant-Dependent)

Legacy & Outlook

The FJ33 proved that a small, efficient turbofan could reliably power very light jets without the complexity or cost typically associated with larger engines. As VLJ airframes continue to evolve, the FJ33 remains an important benchmark—while the FJ44 continues to anchor the light-jet segment. For travelers, this means more choices across very light jets and light jets, depending on the mission profile, passenger count, and range needs.

Frequently Asked Questions

What jets use the Williams FJ33?
Prominent examples include the Cirrus Vision Jet SF50 (single-engine), plus additional VLJ/experimental programs such as the Flaris LAR 01 and Diamond D-Jet (prototype). Availability may vary by certification and market.

How much thrust does the FJ33 produce?
Depending on the variant, approximately 1,000 to 1,900 pounds of thrust at takeoff. Later dash numbers trend toward the higher end of that range.

How is the FJ33 different from the FJ44?
The FJ33 is smaller and lighter, optimized for VLJ applications and single-engine designs. The FJ44 is larger and powers many light jets (e.g., Citation CJ/M2) with thrust ratings typically from ~1,900 to over 3,000 lbf.

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