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Williams EJ22
Williams EJ22
Williams EJ22
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EJ22
Type Turbofan
National origin United States
Manufacturer Williams International
First run 2000

The Williams EJ22 was a small turbofan engine that was being developed by Williams International for very light jet (VLJ) aircraft applications.

Development

[edit]

Williams International had been building small turbofan engines for cruise missile applications since the 1960s, and had successfully entered the general aviation market in 1992 with the FJ44 engine. That same year, NASA initiated a program, Advanced General Aviation Transport Experiments (AGATE), to partner with manufacturers and help develop technologies that would revitalize the sagging general aviation industry. In 1996, Williams joined AGATE's General Aviation Propulsion (GAP) program to develop a clean-sheet fuel-efficient turbofan engine that would be even smaller than the FJ44 and designated the FJX-2 engine. This provided $100 million in research and development funding for the new engine.[1]

Initially, Williams contracted with Burt Rutan's Scaled Composites to design and build the Williams V-Jet II, a Very Light Jet (VLJ) to use as a testbed and technology demonstrator to showcase the new engine. The aircraft, powered by two interim FJX-1 man-rated version of Williams' cruise-missile engine, debuted at the 1997 Oshkosh Airshow. Development of the FJX-2 engine progressed, most of the design work was completed during 1998 with initial prototype parts being delivered in the second quarter of that year. The program ultimately culminated with altitude testing at the NASA Glenn Research Propulsion Systems Laboratory from March - April 2000.

In 2000, Williams joined with Eclipse Aviation to develop an FAA-certified version of the FJX-2, designated the EJ22, to be used on the Eclipse 500 VLJ due for first flight in June 2002. The new EJ22 powered the Eclipse 500 prototype on its first flight in the summer of 2002, but never flew with the EJ22 again and Eclipse terminated their contract in late 2002, stating: "The EJ22 is not a viable solution for the Eclipse 500 aircraft, and Williams International has not met its contractual obligations", while Williams acknowledged "a number of challenges" with the EJ22 but viewed its obligations as accomplished, implying that the aircraft was too heavy.[1] Eclipse switched to the more powerful Pratt & Whitney Canada PW600 series.[2] Following termination of the contract, development work and FAA certification was halted shortly thereafter.[3] Eclipse initially required the engine to produce 770 lbf (3,400 N) thrust, exceeding the 700 lbf (3,100 N) rating of the FJX-2 by 10%.

Design

[edit]

The FJX-2 engine was designed with many experimental systems and manufacturing processes to minimize parts count, lower production costs and have a bypass ratio of 4:1.[4] As a result, there were many technical difficulties and failures of the initial prototype hardware. However, subsequent re-designs and the incorporation of more conventional systems resulted in the engine eventually meeting the NASA requirement of 700 lbf (3,100 N) thrust.

To achieve the required thrust-specific fuel consumption, the EJ22 turbofan was designed as a three spool engine having a fan, two axial compressors and three expansion turbines. As a result, the engine was significantly more complicated than any prior Williams International engine. While very impressive on the test stand, the EJ22 proved quite temperamental during the two years of its development process and it was frequently subject to problems starting, overheating, part failures and various subsystem issues.

Specifications

[edit]

Data from NASA[4]

General characteristics

  • Type: 3-spool medium-bypass ratio turbofan[1]
  • Length: 41 in (104 cm)[5]
  • Diameter: 14.5 in (37 cm)[5]
  • Dry weight: 96 lb (44 kg): 16 

Components

  • Compressor: 1 fan, nine stages of axial compression,: 6  5-stage HP: 19 
  • Combustors: annular: 7 
  • Turbine: LP, IP and HP axial turbines
  • Fuel type: aviation kerosene

Performance

References

[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Williams EJ22

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from Grokipedia
The Williams EJ22 is a compact, high-thrust engine developed by for (VLJ) aircraft applications, most notably as the intended powerplant for the twin-engine business jet. Originating from 's Propulsion (GAP) program in the mid-1990s, the EJ22 evolved from the experimental FJX-2 demonstrator through a collaborative effort between and , aimed at creating affordable, efficient propulsion for revitalizing the light aircraft market. The engine first ran on a test stand in August 1999 and featured an innovative three-spool design with independent axial compressors and turbines, achieving a of 9:1 at just 85 pounds dry weight while delivering over 770 pounds of thrust. This made it the smallest, lightest, and quietest commercial of its era, with low emissions and fuel consumption tailored for short-haul "point-to-point" operations from small . Under an exclusive manufacturing agreement with Eclipse Aviation Corporation, the EJ22 powered the prototype on its from Albuquerque Sunport on August 26, 2002, where the twin engines enabled a 50-minute test covering the planned . However, high-altitude testing revealed performance shortfalls, including less than 50% of rated thrust due to temperature limitations, along with reliability challenges such as faulty starters, seals, and fan blades that complicated field maintenance and extended certification timelines to an estimated 2-3 years. Despite these issues, abandoned the EJ22 in November 2002, switching to the heavier PW610F engines (900 pounds thrust each, 260 pounds weight) to meet FAA requirements and accelerate production, ultimately leading to the Eclipse 500's in 2006 without further pursuit of EJ22 . Though it never entered commercial service, the EJ22's groundbreaking design inspired the broader VLJ category and demonstrated advancements in small technology for personal and air-taxi .

Development

Origins in NASA programs

The origins of the Williams EJ22 trace back to 's efforts in the mid-1990s to revitalize through advanced propulsion technologies. In 1996, joined the program's General Aviation Propulsion (GAP) element, a collaborative initiative between , industry partners, and academia aimed at developing affordable, efficient small engines for very light jets (VLJs) and other aircraft. The consortium, launched earlier in 1994, secured over $100 million in matched government and industry funding over an eight-year period to support broad technology development, with the GAP program receiving additional dedicated resources to focus on propulsion advancements. Building on Williams' prior FJX-1 demonstrator, the FJX-2 engine emerged as the core output of the GAP program, targeting a thrust level of at least 700 lbf to enable lightweight, cost-effective VLJ designs. Key objectives included reducing engine weight to under 100 lb—ultimately achieving 96 lb—while attaining a high thrust-to-weight ratio exceeding 7:1, facilitated by simplified architecture, advanced materials such as titanium and nickel-based superalloys (e.g., CMSX-4 blades and Mar-M-247 turbine components), and innovative features like hybrid ceramic bearings to minimize lubrication needs and enhance efficiency. These goals addressed longstanding barriers in general aviation, such as high acquisition and operating costs, by prioritizing fuel efficiency and reduced maintenance through clean-sheet design principles developed under a NASA-Williams Cooperative Agreement (NCC3-514) effective from December 1996. Development progressed rapidly, with component testing commencing in the third quarter of 1997 and the first full FJX-2 engine assembly completed by late 1998. The inaugural engine run occurred on December 22, 1998, at Williams' facilities in , validating core functionality and setting the stage for further evaluation. Ground testing followed, culminating in altitude simulations at Glenn Research Center's Propulsion Systems Laboratory (PSL) from March to April 2000, where the engine demonstrated 770 lbf thrust at simulated 5,000 ft altitude, Mach 0.2, and -40°F conditions, confirming performance metrics like specific fuel consumption below 0.5 lb/lbf-hr and overall efficiency gains. These tests provided critical validation of the FJX-2's operability across a range of flight envelopes, highlighting its potential for commercial adaptation. This -funded research laid the groundwork for the FJX-2's evolution into the certified EJ22 through subsequent private-sector partnerships.

Partnership with

In 2000, entered into an exclusive agreement with to adapt the FJX-2 engine, originally developed under programs, into a commercial variant designated the EJ22 for powering the (VLJ). The partnership required Williams to increase the engine's from the FJX-2's 700 lbf to 770 lbf to meet the aircraft's performance needs. Development progressed with the EJ22 designation formalized around 2001, as Williams modified a Rockwell Sabreliner as a flying testbed and conducted initial ground runs. Initial production planning targeted FAA certification by late 2004, aligning with Eclipse's goal to deliver the first Eclipse 500 aircraft shortly thereafter. However, as the project advanced, technical challenges emerged, including the engine's inability to reliably deliver the required thrust amid the Eclipse 500's growing empty weight, which exceeded initial design assumptions and demanded higher power margins. Flight testing in August 2002 revealed the EJ22's immaturity, with issues such as reduced output at high altitudes due to temperature limits, overheating starters, leaking seals, and broken fan blades, rendering it unsuitable for . These reliability shortfalls, compounded by development delays, led to terminate the contract in late November 2002, as Williams could not meet contractual obligations for a viable engine. The termination had significant financial and developmental repercussions for Williams, which halted all EJ22-specific efforts and redirected resources to other projects, including simpler designs like the FJ33 series. This shift preserved the company's focus on and applications but marked the end of the EJ22's pursuit as a certified commercial .

Design

Core architecture

The Williams EJ22 is a compact three-spool engine, featuring a low-pressure (LP) spool that drives the single-stage fan, an intermediate-pressure (IP) spool connected to multiple stages, and a high-pressure (HP) spool powering the core and . This configuration employs concentric shafts to allow each spool to operate at its optimal rotational speed, enhancing overall efficiency in a small-scale design. The engine incorporates a medium of 4:1, which balances and core performance for (VLJ) applications, paired with an that burns . Physical dimensions include a of 41 inches (104 cm) and a of 14.5 inches (37 cm), contributing to its integration into slender nacelles. The dry weight stands at 85 pounds (39 kg), achieved through lightweight construction using advanced alloys such as for critical components like compressor stages. The overall emphasizes high efficiency at low altitudes typical of VLJ operations, with a prioritizing in layout and to minimize production costs. This approach supports fuel-efficient performance while maintaining a compact footprint suitable for twin-engine .

Compressor and turbine

The compressor of the Williams EJ22 is an all-axial design comprising a single fan stage followed by nine stages of axial compression, selected to provide compactness and high efficiency without relying on centrifugal stages common in many small turbofans. This configuration achieves an adiabatic efficiency of approximately 85% through features like abradable rub strips between blade and vane rows, rotors formed from electron beam welded forgings, and for the static vane structure and interstage housing. The section features a three- with single-stage low-pressure, intermediate-pressure, and high-pressure axial turbines, each driven by its own spool in the engine's three-shaft . Blades in the hot sections employ via holes and are constructed from single-crystal nickel-based superalloys, such as CMSX for the first stage, to endure elevated temperatures while minimizing weight and enhancing durability; the low-pressure turbine uses high-aspect-ratio shrouded blisks machined from forgings. Key innovations include the integration of a full-authority engine control () system, which interfaces with sensors for parameters like interstage temperature and spool speeds to enable precise fuel metering and operation across the . The three-spool design permits independent optimization of spool speeds, contributing to the engine's high . Despite these advances, the all-axial introduces design challenges, including greater sensitivity to inlet flow distortions that can impact stability at off-design conditions, and higher overall complexity relative to centrifugal compressors typically favored in small engines for their simpler manufacturing and broader operating margins.

Testing and applications

Ground and flight testing

Ground testing of the Williams EJ22 began in August 1999 at Williams International facilities, where the engine achieved its designed thrust of 770 lbf while weighing just 85 pounds, yielding a 9:1 thrust-to-weight ratio. By early 2000, four EJ22 engines had accumulated over 200 hours, including altitude simulations at NASA Glenn Research Center's Propulsion Systems Laboratory, where they operated at full power equivalent to 27,000 feet, validating core performance under simulated flight conditions. However, initial runs revealed starting difficulties, requiring fuel mixture adjustments, along with overheating in the starters and combustor components. Post-2000 testing at Williams facilities emphasized reliability, accumulating over 500 hours and nearly 900 starts across prototypes. These efforts uncovered part failures, including cracked shrouds, broken fan blades in the stages during prolonged operation, leaking seals, and fuel controller malfunctions. The engine's design, lacking field-serviceable components, necessitated shipping units back to the manufacturer 15 to 20 times within 90 days for repairs, highlighting maintenance challenges. The EJ22's first flight integration occurred on the prototype on August 26, 2002, from , lasting 50 minutes to assess handling and systems. While basic functionality was confirmed with no major in-flight anomalies, the engines delivered less than 50% of rated —attributed to high ambient temperatures, thin air, and adherence to operational limits—resulting in lethargic acceleration. Overall, testing demonstrated the EJ22's conceptual viability as a compact, high-ratio but exposed significant reliability gaps, including frequent starting issues akin to hot starts and accelerated component wear. These findings led to pause certification efforts in November 2002, effectively halting further development for commercial applications.

Integration with Eclipse 500

The Williams EJ22 was selected for integration into the (VLJ) as a twin-engine configuration, with adaptations focused on achieving a rated of 770 lbf per to accommodate the aircraft's requirements. These modifications were necessary amid design changes that increased the Eclipse 500's weight, straining the engine's ability to deliver sufficient power for takeoff, climb, and cruise in the compact . The EJ22's at 85 lb per offered a high of approximately 9:1, aligning with Eclipse Aviation's goal of efficient, low-cost operation for owner-pilots and services. On August 26, 2002, the prototype conducted its maiden flight at , powered solely by two EJ22 engines for a 50-minute test that validated basic handling, systems, and takeoff performance. However, the demonstration was constrained by the engines' temperamentality, including difficulties in starting and achieving full thrust under hot, high-altitude conditions, where output was limited to about half the rated level. This single flight highlighted early integration challenges but did not lead to further aerial testing with the EJ22. The EJ22 program for the was discontinued in November 2002 due to the engine's inability to reliably scale beyond initial ratings, particularly as weight growth demanded higher output without compromising reliability or certification timelines. cited performance shortfalls and maturation delays in the EJ22, prompting a switch to the PW610F engine in early 2003, which provided 900 lbf at the cost of added weight and fuel consumption. This decision contributed to broader certification setbacks for the , delaying entry into service until 2006. The EJ22's brief integration underscored fundamental mismatches between its NASA-derived design assumptions—optimized for ultra-light experimental applications—and the practical demands of a production VLJ, including robustness for frequent operations and adaptability to evolving specifications. Ultimately, the program's termination ended prospects for the EJ22 in .

Specifications

General characteristics

The Williams EJ22 is a three-spool medium-bypass manufactured by , developed under U.S. designations FJX-2/EJ22. The unit cost was estimated at under $100,000 for production, though unachieved. It measures 41 in (1,040 mm) in length and 14.5 in (370 mm) in diameter, with a dry weight of 85 lb (39 kg). The engine uses Jet A or Jet A-1 as fuel, with potential compatibility for military if adapted. The features an axial flow path.

Performance

The Williams EJ22 engine achieved a maximum dry thrust of 770 lbf (3.4 kN) at sea level static conditions during ground testing, as targeted for integration with the . Specific fuel consumption for the EJ22 was targeted at approximately 0.5 lb/lbf·h (14 g/kN·s) during cruise conditions, with the design emphasizing efficiency for short-field (VLJ) operations. The engine's of 4:1 helped achieve lower fuel burn compared to contemporary small turbofans. The overall pressure ratio is 15:1. The engine exhibited a high of 9:1, attributable to the three-spool architecture.

References

  1. https://www.smithsonianmag.com/air-space-magazine/the-little-engine-that-couldnt-6865253/
  2. https://spinoff.nasa.gov/spinoff2002/t_1.html
  3. https://aviationweek.com/business-aviation/archives-eclipse-aviations-eclipse-500-completes-first-flight
  4. https://ntrs.nasa.gov/api/citations/20080031112/downloads/20080031112.pdf
  5. https://ntrs.nasa.gov/api/citations/20000011648/downloads/20000011648.pdf
  6. https://ntrs.nasa.gov/api/citations/19980010521/downloads/19980010521.pdf
  7. https://minijets.org/en/300-500/williams-fjx-2/
  8. https://ntrs.nasa.gov/citations/20020080313
  9. https://minijets.org/en/300-500/williams-ej-22/
  10. https://www.flightglobal.com/williams-dropped-from-eclipse-500/45993.article
  11. https://www.flightglobal.com/williams-prepares-sabreliner-testbed-for-ej22/41748.article
  12. https://www.ainonline.com/aviation-news/business-aviation/2008-01-04/eclipse-and-williams-part-ways-new-engine-selection
  13. https://www.nytimes.com/2002/11/29/business/eclipse-drops-williams-engine-for-new-jet.html
  14. https://www.aopa.org/news-and-media/all-news/2003/march/pilot/pilot-briefing-%283%29
  15. https://www.flightglobal.com/what-next-for-williams-as-it-starts-to-lose-market-grip/46744.article
  16. https://www.designnews.com/industry/engineers-drive-a-light-aircraft-revival
  17. https://www.aopa.org/news-and-media/all-news/2002/october/pilot/test-pilot-%2810%29
  18. https://ntrs.nasa.gov/api/citations/20020080313/downloads/20020080313.pdf
  19. https://ntrs.nasa.gov/citations/20050040787
  20. https://www.aopa.org/news-and-media/all-news/2000/june/pilot/turbine-pilot-%289%29
  21. https://avweb.com/uncategorized/power-vacuum/
  22. https://www.aopa.org/news-and-media/all-news/2001/february/pilot/turbine-pilot
  23. https://www.williams-int.com/
  24. https://www.aero-news.net/index.cfm?do=main.textpost&id=e0c5c572-35a9-403e-8278-95f67e836ed5
  25. https://ntrs.nasa.gov/api/citations/19980209647/downloads/19980209647.pdf
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