Boeing Begins JAST Engine Tests

TULALIP, Wash., Sept. 14, 1995 -- At a remote site 60 miles north of Seattle, The Boeing Company is conducting an important series of tests to validate performance of an aircraft design for the Joint Advanced Strike Technology (JAST) program.

Using a ground test model powered by a Pratt & Whitney YF- 119 engine, Boeing is gathering data to demonstrate vertical flight performance to meet the U.S. Marine Corps' need for a superior high-performance, Short Take off and Vertical Landing (STOVL) aircraft. The Marine Corps plans to replace its AV-8Bs and F/A-18s and transition to an all-STOVL strike force early in the 21st century.

Under the Joint Advanced Strike Technology (JAST) program, Boeing Defense & Space Group, Military Airplanes Division, is developing affordable strike aircraft concepts to meet the post-2000 needs of the U.S. Air Force, Navy and Marines, as well as those of the international community. The STOVL concept is one aspect of the Boeing family of JAST aircraft designed to meet the needs of the services for a multi-role high-performance aircraft.

Boeing's STOVL aircraft work on the JAST program is funded by a $32 million research agreement Boeing signed on March 25, 1994 with the Advanced Research Projects Agency (ARPA). It called for Boeing to design, develop and test the direct- lift STOVL concept over a 26-month period of performance. Boeing is managing the JAST and ARPA ASTOVL activities in a single, integrated program.

The model used in the Tulalip tests is a 94-percent-scale representation of Boeing's STOVL design as it appears during vertical flight operations. More than 40 feet long and weighing more than 45,000 pounds, the model is constructed primarily of steel and aluminum.

Fabrication and final assembly of Boeing's JAST model was completed in the company's Kent, Wash., facilities using rapid prototyping processes. Modifications of the engine and other propulsion components were designed by the following Boeing teammates: Florida-based Pratt & Whitney and the United Kingdom's Rolls Royce. Rolls Royce is responsible for the propulsion/life system, including all lift-system components and the attitude-control system. Pratt & Whitney is responsible for the YF-119 engine, cruise nozzle and overall propulsion system integration.

The model was produced in just over 15 months. "Completion of our model in such a short time frame is a major engineering and manufacturing accomplishment," said Mickey Michellich, Boeing JAST program manager. "It proves our team's ability to work together under extremely tight schedules, across two continents, and eight time zones."

The Tulalip tests will simulate the STOVL aircraft during vertical landings similar to those accomplished by the Harrier aircraft used by the U.S. Marine Corps.

Michellich added that the JAST model will be tested from "free air conditions" simulating hover and vertical landing all the way to "wheels on the ground." The tests will determine vertical flight performance characteristics in and out-of-ground effect, inlet ingestion characteristics, aircraft surface temperatures, pressure and acoustic impact, as well as the 'footprint' made by the aircraft on the ground."

Work leading up to the Tulalip tests involved simulation of STOVL control laws, handling qualities and significant sub- scale model testing for both in- and out-of-ground effects.

Construction of a multi-million-dollar JAST test site began with site-clearing of a heavily forested area in January. As part of the program's emphasis on affordability, engineers at the Boeing Tulalip facility extensively recycled components previously used in structural testing of the Boeing 777 jetliner. The test rig itself occupies an area the size of several football fields and is as tall as an eight-story building. It can accommodate a powered test model weighing up to 60,000 pounds and has been specifically designed to measure vertical flight performance from a height of 45 feet down to wheels-on-the-ground.

To give the model the full range of motion, engineers studied the design of modern flight simulators Boeing uses to train its commercial customer flight crews. "We basically took the flight simulator concept and turned it upside down," said Tulalip site manager Dick Jablonski. "Flight simulators are supported by their hydraulic actuator legs but in our test rig, the model is suspended from the frame by the hydraulic legs."

In addition to the U.S. armed forces, a number of U.S. allies have voiced interest in the JAST program and Boeing believes there will be a substantial international market for a low-cost, high-performance strike aircraft.