National Aeronautics and Space Administration

Glenn Research Center

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Turbofan Engines (1974 – 1979)
F-100 Turbofan ending on cart
F-100 Turbofan

The NASA Lewis aeronautics program was in full-swing when PSL No. 3 and 4 became operational in 1973. Following the end of the Apollo Program, the Center pushed even further into its aircraft propulsion work. Unlike Lewis’ previous research, the majority of the new engine studies would be for civilian aircraft and not the military. Since demand was still high for altitude testing, the Center decided to keep PSL No. 1 and 2 operating for several more years. The jumbo jet generation of airliners was emerging in the early 1970s. The Boeing 747, McDonnell Douglas DC-10, and Lockheed L-1011 were all powered by turbofan engines. During the mid-1970s PSL concentrated on making turbofan engines quieter and more efficient.

Documents:
     “Down to Earth Problems,” by Virginia Dawson

Full-Scale Engine Research
Mechanic installing engine in PSL No.2
Quiet Engine Test

In the mid-1970s, NASA Lewis and the Air Force collaborated on two broad programs that studied a variety of design problems on full-scale engines. The first, the Full-Scale Engine Research (FSER) program utilized surplus Air Force engines as testbeds for a variety of research purposes, including flutter, inlet distortion, and electronic controls. In the late 1970s Engineers from the Airbreathing Engines Division’s Engine Research Branch studied two Air Force engines for the FSER in PSL—the Pratt & Whitney F100 and the General Electric J85-21.

A General Electric J85-21 turbojet, a 5000-pound thrust variant of the J85-13, was obtained from the Air Force in early 1975 for the FSER program. The engine was used for two series of investigations—internal compressor aerodynamics and mechanical instability or flutter. The researchers focused on two types of stall flutter, choke flutter, and system-mode instability. The different variations of distortion was unique from the others. The researchers assembled a collection of data from each type of instability.

Documents:
     NASA/GE Quiet Engine “A” (PDF, 1.23MB)

J85 in PSL
J85 in PSL
Test Setup
Test Setup
Distortion Simulator
Distortion Simulator
Pratt & Whitney F-100
F-100 engine in PSL No.2
F-100 in PSL No.2

A full-scale turbofan engine was subjected to long-term study in PSL for the Full-Scale Engine Program. The Pratt & Whitney F-100 turbofan was the first engine analyzed for performance problems. Since the F-100 was similar to the TF30 recently studied in PSL No. 1 much of the test hardware that was purchased for the TF30 tests was adapted and used for the F-100. PSL No.2 had to be renovated to accommodate the large F-100.

The initial turbojet and turbofan engines used fixed-geometry components with fuel flow and nozzle areas as variables. The engines being developed in the 1970s implemented variable shaped compressor and fan blades. These new types of engines required greater control systems that could handle many parameters and additional variables while increasing the accuracy and response of the engine. One tool was the linear quadratic regulator. The Air Force asked NASA Lewis to develop and test the multivariable control system on an F-100 engine. A digital controller was devised and first tested using computer simulation. Afterward the system would be tested on an F-100 in PSL. Pratt & Whitney was asked provide the F-100 and its design information. Systems Control, Inc. developed the computer logic for the system. The project began in 1975 with the hybrid simulation in late 1976. Engine testing in PSL took place in mid-1977.

Documents:
     F-100 Full Scale Engine Program article (PDF, 1.78MB)
     F-100 Multivariable Control Synthesis Program (PDF, 3.66MB)
     Propulsion Controls, 1979 (PDF, 5.94MB)

Wiring of F-100
Wiring of F-100
Digital Controls
Digital Controls
F-100 in PSL No.3
F-100 in PSL No.3