Langley 16-Foot Transonic Tunnel Research Articles

Transonic Free-To-Roll Analysis of the F-35 (Joint Strike Fighter) Aircraft

The free-to-roll technique is used as a tool for predicting areas of uncommanded lateral motions. Recently, the NASA/Navy/Air Force Abrupt Wing Stall Program extended the use of this technique to the transonic speed regime. Using this technique, this paper evaluates various wing configurations on the Joint Strike Fighter (F-35) aircraft. The configurations investigated include leading- and trailing-edge flap deflections, leading-edge flap gap seals, and vortex generators. These tests were conducted in the NASA Langley 16-Foot Transonic Tunnel. The analysis used a modification of a figure of merit developed during the Abrupt Wing Stall Program to discern configuration effects. The results showed how the figure of merit can be used to schedule wing flap deflections to avoid areas of uncommanded lateral motion. The analysis also used both static and dynamic wind-tunnel data to provide insight into the uncommanded lateral behavior. The dynamic data were extracted from the time history data using parameter identification techniques. In general, sealing the gap between the inboard and outboard leading-edge flaps on the Navy version of the F-35 eliminated uncommanded lateral activity or delayed the activity to a higher angle of attack.

Transonic Free-to-Roll Analysis of Abrupt Wing Stall on Military Aircraft

Transonic free-to-roll and static wind-tunnel tests for four military aircraft-the AV-8B, the F/A-18C, the preproduction F/A-18E, and the F-16C-have been analyzed. These tests were conducted in the NASA Langley 16-Foot Transonic Tunnel as a part of the NASA/Navy/Air Force Abrupt Wing Stall Program. The objectives were to evaluate the utility of the free-to-roll test technique as a tool for predicting areas of significant uncommanded lateral motions and for gaining insight into the wing-drop and wing-rock behavior of military aircraft at transonic conditions. The analysis indicated that the free-to-roll results agreed well with flight data on all four models. A wide range of motions-limit-cycle wing rock, occasional and frequent damped wing drop/rock and wing-rock divergence-were observed

High-alpha vectoring characteristics of the F-18/HARV

An investigation was conducted in the Langley 16-Foot Transonic Tunnel (16FTT) to determine the multiaxis thrust vectoring characteristics of the F-18 high-alpha research vehicle (HARV). A 0.10-scale model of the F-18 airplane was modified with hardware to simulate the three-vane thrust vectoring system of the F-18/HARV. This investigation was conducted at Mach numbers ranging from 0.30 to 0.70, angles of attack from 0 to 70 deg, and nozzle pressure ratios from 2.0 to approximately 5.0. Results indicate that the thrust vectoring system of the F-18/HARV can generate useful levels of multiaxis thrust vectoring. During vectoring, resultant thrust vector angles were always less than the corresponding geometric vane deflection angle and were accompanied by large thrust losses. Significant external flow effects that were dependent on Mach number and angle of attack were noted during vectoring.