The F-22 Raptor incorporates Pratt & Whitney's F119-PW-100 engine. Designed for efficient supersonic operation without afterburner use and with increased durability over today's engines, the F119 is a very high thrust-to-weight ratio engine. Advanced technologies in the F119 include integrated flight-propulsion controls and two-dimensional, thrust-vectoring engine nozzles. The F119 incorporates technology advances developed and verified in joint U.S. Air Force/Pratt &Whitney research programs and for other advanced fighter engines. It was designed using the "integrated product development" approach to ensure a balance between performance, safety and reliability, maintainability and low life-cycle cost. In addition, it has significantly fewer and more durable components than previous fighter engines.
In the 1980s Pratt & Whitney, a unit of United Technologies Corporation, developed the YF119 prototype engine to meet US Air Force and US Navy requirements for the Advanced Tactical Fighter Demonstration/Validation program. In 1990 it flew in both the Lockheed / General Dynamics / Boeing YF-22 and the Northrop / McDonnell Douglas YF-23 prototype aircraft. To reduce maintenance Pratt & Whitney designed the engine to use 40 percent fewer parts when compared to the then current operational engines. The YF119 engine allows supersonic flight of the aircraft without using the afterburner, resulting in fuel savings and increased combat radius and effectiveness. In April 1991 the Air Force selected the F119 engine for the F-22, Advanced Tactical Fighter.
AEDC engineers and technicians supported development for the Air Force's next-generation fighter, the F-22 Raptor, since 1988. This support included the Demonstration and Validation phase of the F-22 program and later the Engineering and Manufacturing Development (E&MD) phase.
The AEDC and Pratt & Whitney team completed a critical phase of support with successful completion of the Preliminary Flight Qualification test in 1997. Through the end of 1998, the engine has completed 3,500 air-on hours of testing at AEDC to support altitude assessment of the engine's performance, operability, aeromechanical and durability characteristics. All planned objectives for this phase of the engine's development were achieved by the AEDC-P&W project team.
During FY97 and continuing into FY98, Pratt & Whitney's F119 E&MD engine underwent testing in AEDC's Propulsion Development Test Cells C-1 and J-2. AEDC supported the F-22 program in evaluating the engine's aeromechanical performance, combustor and augmentor operability, vectored and non-vectored nozzle performance, fan performance, compressor stall margin and air start capability.
At the request of Pratt & Whitney, the AEDC team used a new test support system to provide immediate, on-line structural dynamic test results for the latest series of tests. The Center's Computer Assisted Dynamic Data Monitoring and Analysis System (CADDMAS) was used to process and analyze aeromechanical data on-line during the testing, rather than the traditional approach days after the test, allowing completion of testing two months ahead of the original plan. (See related story on page 22.) Testing was accomplished in AEDC's C-1 test cell to confirm elimination of vibratory stress levels discovered earlier in the program. During the 10-hour test, the engine was operated at varying altitudes and speeds, exposing it to the maximum pressures and temperatures possible during flight. Vibratory stress levels were taken at two flight conditions through strain gages mounted on the blades and then relayed to CADDMAS.
The F119 passed an important milestone in 1997 with the successful completion of both an Accelerated Mission Test (AMT) and Preliminary Flight Qualification altitude performance and operability clearance test. Successful completion of these tests are the final engine requirements for flight clearance.
During the AMT, the F119 engine completed 919 TAC cycles simulating more than 300 Air Force combat missions and included more than 13 hours in augmentation and more than 40 hours of hot time. Each cycle involves multiple settings of the engine's thrust vectoring exhaust nozzles, which totaled more than 12,000 vectored transients. The altitude testing, which verifies engine performance and operability, took the engine to all extremes of the fighter envelope. These extensive test programs included performance and operability testing at 15 different flight conditions, certifying the engine was cleared for flight testing in the F-22.
F-22 flight testing began in September 1997 at the Air Force Flight Test Center at Edwards AFB, Calif.
United Technologies Corp., West Palm Beach, Fla., was awarded on August 25, 1997 a $232,871,029 face value increase to a cost-plus-award-fee contract to provide for restructure of the Engineering and Manufacturing Development contract for the F119 engine applicable to the F-22 aircraft. This restructure includes extension of the F119 program by fifteen months, revision of the flight test engine delivery schedule, deletion of one flight test engine, addition of two developmental engines, and additional testing. Aeronautical Systems Center, Wright-Patterson Air Force Base, Ohio, is the contracting activity (F33657-91/C-0007, P00153).
On March 31, 2003 Pratt & Whitney received a $481 million supplement to its U.S. Air Force contract to produce F119-PW-100 engines that power the F/A-22 Raptor fighter aircraft. The supplement represents the third production contract for F119 engines. It covers 40 engines for delivery in 2004, along with associated spares and support services to be delivered in 2003. The supplement was added to an existing $150 million long lead production contract issued in January 2002, making the overall contract value more than $631 million.
Pratt & Whitney's F119 turbofan engine, the world's most technologically advanced aircraft engine in production, meets the need for greater speed and lower weight for new military weapon systems. The engine is a dual spool, counter-rotating turbofan. The F119 is equipped with a number of advanced technologies for unmatched operational performance and reliability. Its three-stage fan has shroudless titanium fan blades and is powered by a single-stage low-pressure turbine. The engine's core has an aerodynamically efficient six-stage compressor driven by a single-stage high-pressure turbine featuring the next generation of single-crystal superalloy blades with improved cooling management. The robust, but compact, high-pressure compressor features integrally bladed rotor disks for improved durability and three-dimensionally designed airfoils.
The engine delivers unparalleled aircraft maneuverability with its unique two-dimensional thrust vectoring exhaust nozzle. This convergent/divergent nozzle vectors thrust 20 degrees either up or down. Nozzle position management is automatically controlled by the full-authority digital electronic control (FADEC), which controls hundreds of other engine and aircraft operating parameters. The FADEC also features advanced diagnostic and on-condition management systems for maintenance awareness, autonomic logistics support, and automatic field data and test systems.
The F119 engine develops more than twice the thrust of current engines under supersonic conditions and more thrust without afterburner than conventional engines with afterburner. Each F-22 is powered by two of these 35,000-pound-thrust-class engines. By comparison, the engines powering the Air Force's current F-15 and F-16 fighters have thrust ratings ranging from 23,000 to 29,000 pounds. Jet engines achieve additional thrust by directly injecting fuel at the engine exhaust. The process, called afterburner, gives the aircraft a rocket-like boost as the fuel ignites in the exhaust chamber. The tradeoff is higher fuel consumption, a greater amount of heat and consequently, greater visibility to the enemy. The F119 can push the F-22 to supersonic speeds above Mach 1.4 even without the use of afterburner, which gives the fighter a greater operating range and allows for stealthier flight operation. The product of more than 40 years' research into high-speed propulsion systems, the F119 is proof that high-technology doesn't have to be complicated.
The F119-PW-100, was developed by a team of engineers in the Air Force Propulsion Development System Office (DSO). The F119 engine acquisition team adopted many of the Acquisition Reform and Lean Aircraft initiatives. As a result, the F119 Program achieved many successes. The development and flight clearance of new engine designs has been a slow, burdensome, and costly process due in part to oppressive contractual and data requirements. In addition, aircraft flight test programs have typically encountered extensive delays as a result of engine technical shortfalls that have gone undetected during ground testing.
By utilizing the principles of Acquisition Reform and Lean Aircraft initiatives, the F-22 engine team in ASC/LPR streamlined the F119 program to achieve substantial cycle time reductions for technical information flow and configuration upgrades. These streamlined processes enhanced the implementation of the F119 Propulsion and Power Systems Integrity Program (PPSIP), to substantially improve the systems engineering process for the F119 engine. As a result, F119 design weaknesses were exposed earlier in development and corrective actions were implemented prior to manifesting themselves at flight test, providing for a more efficient and successful F-22 flight test program.
The F119 team set the standard for the F-22 SPO in promoting Acquisition Reform and the use of best practices. Eighty-eight percent (164) of the F119 Program contract military specifications and standards were eliminated. The number of F119 Program contract data requirements list (CDRLs) was reduced by 72 percent. The F119 Statement of Work page count was reduced 50 percent. The cycle time for contractor/government contract technical information flow was reduced from 60 days to 2 weeks. The F119 team implemented the use of a shared government/contractor real-time electronic data exchange system to capitalize on the benefits of CDRL reductions and to facilitate the reduction in cycle time for technical information flow. Extensive use of video conferencing has also enhanced the technical information flow process and reduced travel by over 75 percent.
The efforts of the F119 engineers paid huge dividends for F-22 flight test. Twenty-five F119 flight test engines were delivered to power the F-22 Raptors at flight test. The F119 engine performed flawlessly during flight test, enabling the F-22 to achieve key milestones. In more than 860 hours of flight test the F-22/F119 flew to 50,000 feet, supercruised in excess of 1.5 Mach, exceeded 7 G’s, and reached 60 degrees angle of attack.
A significant portion of the F119 development and verification testing was conducted in state-of-the-art test facilities at the Arnold Engineering and Development Center (AEDC). The F119 engine was tested extensively at various combinations of altitude and Mach number while being exposed to simulated F-22 maneuvers that produce engine inlet conditions of distorted, unstable, low-pressure air. In addition, the F119 engine underwent rigorous accelerated mission testing (AMT) in a one-of-a-kind dedicated AEDC sea level test facility at simulated F-22 high speed, high pressure inlet air conditions. The F119 engineers in the Propulsion DSO worked in concert with their counterparts at Pratt & Whitney and AEDC to continuously refine and streamline the AEDC testing to achieve test objectives at the lowest possible cost.
Since its inception, the F119 EMD program fully embraced the EN systems engineering process, with special emphasis on the integrity programs. The F119 Propulsion and Power Systems Integrity Program (PPSIP) was a key factor in the development and maturation of the F119 engine design. PPSIP broadened the integrity process beyond the historical engine structural integrity program (ENSIP). PPSIP expands the integrity process to encompass not only the structural but also the performance, operability, and functional aspects of the entire propulsion system, including engine controls, accessories, and external subsystems.
The PPSIP program’s development and verification methodology ensured that the F119 engine design is being thoroughly evaluated during the EMD phase of the program. As an example of the aggressive testing concepts embodied in the PPSIP program, the F119 accelerated mission testing accomplished over 75 percent of the full life hot time exposure in just 40 percent of the test time. The PPSIP program exposed several initial F119 design weaknesses and allowed for corrective action prior to the problems manifesting themselves at flight test, providing for a more efficient and successful F-22 flight test program.
A redesign of the F-22 Raptor's turbine exhaust case (TEC) on the F119 engine has been so successful the program is being considered for use on engines of other Air Force aircraft. The TEC on a jet engine is located just aft of the turbines, and directs the exhaust of the turbine in a particular flow pattern out the rear of the engine.
A priority of any ManTech program is the constant search for potential cost-saving measures within the manufacturing process. In this case, TEC vanes were an area believed to be one that improvements could be made with a fairly high degree of confidence in success. Original built up sheet metal components historically comprise a lot of the cost in the engine due to the need for laser cutting and drilling, welding, brazing, assembly and more. This has always made the TEC a labor-intensive section of each engine.
The Reproducible F119 TEC Castings Program was conducted under a contract between the Manufacturing Technology (ManTech) Division of the Air Force Research Laboratory's Materials and Manufacturing Directorate, and Pratt & Whitney (P&W). This program directly supports an alternate manufacturing approach for the F119 TEC making extensive use of thin wall casting technology in the Initial Service Release design.
Development and incorporation of thin wall castings, in place of the existing, complex, multi-walled and diffusion-bonded sheet metal assemblies, offer advantages. They eliminate many sub-assembly details and manufacturing processes by designing simplified cast details that serve the same function as the previously used sheet metal sub-assemblies.
The cast TEC consists of four vane panels, box assemblies and inner and outer diameter panels that are assembled into a vane section. A total of 16 vane airfoil segments are assembled around a ring-strut-ring configured frame to complete each TEC. The nickel based alloy used to create the cast TEC is an Equiaxed alloy (the grains of the alloy are roughly the same size, and go in all directions) that offers higher temperature capability over Waspalloy used in sheet metal construction.
Results of the Reproducible F119 TEC Castings Program not only provided a significant reduction in cost (ManTech predicts at least a 35 percent savings), but also improved the engine's durability, while maintaining weight parity with the former sheet metal design.