Engineering topics

Johnson, Steven A.

Publications and source records attributed to Johnson, Steven A..

4 records

NASA NTRS1992

Aircraft ground test and subscale model results of axial thrust loss caused by thrust vectoring using turning vanes

The NASA-Dryden F/A-18 high alpha research vehicle was modified to incorporate three independently controlled turning vanes located aft of the primary nozzle of each engine to vector thrust for pitch and yaw control. Ground measured axial thrust losses were compared with the results from a 14.25 pct. cold jet model for single and dual vanes inserted up to 25 degs into the engine exhaust. Data are presented for nozzle pressure ratios of 2.0 and 3.0 and nozzle exit areas of 253 and 348 sq in. The results indicate that subscale nozzle test results properly predict trends but underpredict the full scale results by approx. 1 to 4.5 pct. in thrust loss.

Johnson, Steven A.↗

NASA NTRS1990

A simple dynamic engine model for use in a real-time aircraft simulation with thrust vectoring

A simple dynamic engine model was developed at the NASA Ames Research Center, Dryden Flight Research Facility, for use in thrust vectoring control law development and real-time aircraft simulation. The simple dynamic engine model of the F404-GE-400 engine (General Electric, Lynn, Massachusetts) operates within the aircraft simulator. It was developed using tabular data generated from a complete nonlinear dynamic engine model supplied by the manufacturer. Engine dynamics were simulated using a throttle rate limiter and low-pass filter. Included is a description of a method to account for axial thrust loss resulting from thrust vectoring. In addition, the development of the simple dynamic engine model and its incorporation into the F-18 high alpha research vehicle (HARV) thrust vectoring simulation. The simple dynamic engine model was evaluated at Mach 0.2, 35,000 ft altitude and at Mach 0.7, 35,000 ft altitude. The simple dynamic engine model is within 3 percent of the steady state response, and within 25 percent of the transient response of the complete nonlinear dynamic engine model.

Johnson, Steven A.↗

NASA NTRS1990

A simple dynamic engine model for use in a real-time aircraft simulation with thrust vectoring

A simple dynamic engine model was developed for use in thrust vectoring control law development and real-time aircraft simulation. Engine dynamics were simulated using a throttle rate limiter and low-pass filter. This paper includes a description of a method to account for axial thrust loss resulting from thrust vectoring and the development of the simple dynamic engine model and its incorporation into the F-18 high alpha research vehicle (HARV) thrust vectoring simulation. The simple dynamic engine model was evaluated at Mach 0.2, 35,000-ft altitude and at Mach 0.7, 35,000-ft altitude. The simple dynamic engine model is within 3 percent of the steady state response, and within 25 percent of the transient response of the complete nonlinear dynamic engine model.

Johnson, Steven A.↗

NASA NTRS1990

Water-tunnel study results of a TF/A-18 and F/A-18 canopy flow visualization

A water tunnel study examining the influence of canopy shape on canopy and leading edge extension flow patterns was initiated. The F/A-18 single-place canopy model and the TF/A-18 two place canopy model were the study subjects. Plan view and side view photographs showing the flow patterns created by injected colored dye are presented for 0 deg and 5 deg sideslip angles. Photographs taken at angle of attack and sideslip conditions correspond to test departure points found in flight test. Flight experience has shown that the TF/A-18 airplane departs in regions where the F/A-18 airplane is departure-resistant. The study results provide insight into the differences in flow patterns which may influence the resulting aerodynamics of the TF/A-18 and F/A-18 aircraft. It was found that at 0 deg sideslip, the TF/A-18 model has more downward flow on the sides of the canopy than the F/A-18 model. This could be indicative of flow from the leading edge extension (LEX) vortexes impinging on the sides of the wider TF/A-18 canopy. In addition, the TF/A-18 model has larger areas of asymmetric separated and unsteady flow on the LEXs and fuselage, possibly indicating a lateral and directional destabilizing effect at the conditions studied.

Johnson, Steven A.↗