Boeing Propulsion System

Pratt & Whitney is developing the Boeing X-32 propulsion system. RR is responsible for the component design, development, fabrication, and testing of the lift system and spool duct. P&W is responsible for the component design, development, fabrication and testing of the engine; including the low-pressure spool, the remote augmentor, the 2-D convergent/divergent nozzle, the jet screen off-take, the primary engine controls (hardware and software), and the engine externals and accessories. P&W is under contract for the integration and qualification of all engine system components, including the RR developed items. Boeing is responsible for the component design, fabrication and testing of all airframe propulsion components. Boeing is also responsible for physically and functionally integrating the engine system provided by P&W and RR with the aircraft, thus forming the propulsion system. Boeing is then responsible for certifying the aircraft for flight. The Boeing X-32A aircraft will demonstrate CTOL and CV capabilities while the X-32B will demonstrate the STOVL capabilities.

X-32A in January 2000

The primary vertical lift of the X-32B propulsion system is from the two lift nozzles located between the turbine exhaust case and the augmentor of the SE614 engine, just aft of the aircraft center of gravity. The lift module consists of two vectoring lift nozzles with internal butterfly shutoff valves. The spool duct extends from the back of the lift module/transition duct to the augmentor. The nozzles can be rotated through a 55º arc from 45º aft of vertical to 10º forward of vertical. The lift nozzles are contained within the airframe near its center of gravity. When these nozzles are in operation, the main cruise nozzle is in the fully closed position.

The lift module consists of a double walled offtake case, two butterfly shutoff valves and two vectoring, fixed area convergent/divergent lift nozzles. The lift nozzles vector by rotating on bearings in a manner similar to the Harrier. The lift nozzles are stored at the 45º position behind STOVL bay doors when not in use. When the aircraft is hovering close to the ground, the engine inlet is shielded from the effects of hot gas ingestion by a curtain of cool air from the jet screen nozzle, which is located on the bottom of the fan duct.

X-32B Propulsion System

Pitch and yaw control during STOVL operations is maintained by separate auxiliary nozzles located in the aft section of the aircraft. Roll control is maintained through similar nozzles located in the wing tips, which, like the other auxiliary nozzles, are supplied by fan duct air. During conventional (i.e. wing-borne) flight, the lift system and ACS are not required. The butterfly valves on the lift module are closed and the air is directed to the cruise nozzle; the lift system nozzles and ACS nozzles are covered by actuated doors to reduce the drag on the air vehicle and to reduce the low observable signature.

Located just in front of the 2-D cruise nozzle are two twin roll tubes protruding from either side of the propulsion system. At the end of these roll tubes are the roll nozzles, which help to control the aircraft during semi-jet-borne and jet-borne (vertical/transitional) flight. Below the 2-D nozzle is a single pitch nozzle. The pitch and yaw nozzles are combined on the Preferred Weapon System Concept (PWSC) -374 design (i.e. the production configuration). The cruise exhaust nozzle is a structurally integrated 2D design derived from the F119/YF119; the convergent flaps control the nozzle throat and fully close during jet-borne operations. Besides conventional throat and exit area control, the nozzle provides ±20º pitch thrust vectoring during conventional operation. All of the STOVL specific hardware on the X-32B weighs approximately 600 pounds and is eliminated on the X-32A and PWSC CTOL and CV variants of the aircraft.

Boeing PWSC STOVL Propulsion System

The inlet system is diverterless and bleedless. The "bump" that is located on the top of the inlet is designed to provide compression of the supersonic flow ahead of the inlet cowl. The entire inlet is a single molded composite piece, which was manufactured using automated fiber placement technologies developed at Boeing's Phantom Works in St. Louis, Missouri. The cowling translates forward for the high airflow demands of jet borne operations.

In December 1995, Boeing successfully completed three months of engine and hover tests using a 94%-scale Large-Scale Powered Model (LSPM) at Boeing facilities in Washington. These LSPM tests verified the Boeing STOVL propulsion system and provided valuable data. During the following years, thousands of hours of sub-scale testing on both low-speed and high-speed aspects of the Boeing propulsion system - as well as STOVL ground effects testing - were also completed.

By August 1997, Boeing had completed several major nozzle tests of their STOVL propulsion system. The first test, conducted at the Boeing Nozzle Test facility in Seattle, evaluated the RR lift components. The 17% scale model was used to assess the performance and operability of the lift system and spool duct during conventional flight, STOVL operations, and transition from one flight mode to the other. The full range of JSF nozzle pressure ratios, mass flows and lift module positions were also evaluated. In wind tunnel tests at AEDC, Boeing conducted a three-week-long evaluation of the performance of the high-speed inlet/forebody compression system. The tests employed a 13% scale model and encompassed the full range of JSF flight speeds and attitudes.

X-32A flight test engine ready for delivery. The disk covering the front of the engine serves to hold the shaft in place while in transit.

On 28 February 2000, Boeing announced that the first flight of the X-32B would be delayed, this delay is due to technical challenges encountered in integrating the STOVL propulsion system with the flight control system. The strike by the Society of Professional Engineering Employees in Aerospace that ran for 40 days may also impact some JSF activities.

On 4 November 1999, the first flight test engine assembly was completed. Boeing received the first flight test engine from P&W on 6 March 2000. Boeing currently expects the first flight of the X-32B to take place in the fall of 2000.