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F-18 High Alpha Research Vehicle (HARV) - Description - Configuration

The F-18 High Alpha Research Vehicle (HARV), figure 1, is a full-scale development twin-engine, single-place, fighter/attack (F/A) airplane. The F-18 HARV was built for the U.S. Navy by the McDonnell Douglas Corp. (St. Louis, Missouri) and the Northrop Corp. (Newbury Park, California). The F-18 HARV is powered by two modified General Electric (Lynn, Massachusetts) F404-GE-400 afterburning turbofan engines rated at approximately 16,000 lb static thrust at sea level. The aircraft was modified by adding externally mounted engine thrust vanes for the deflection of the exhaust to provide additional pitching and yawing moments. The engines were modified to accommodate the thrust vectoring vane installation by the removal of the divergent flap portion of the nozzle. The thrust vectoring capability is provided by controlled deflection of the vanes (three for each engine), which move into the engine exhaust plume.

The F-18 HARV features a midwing configuration with a wing-root leading-edge extension that extends from the forward portion of the fuselage and blends into the wing. The F-18 HARV carries no stores or missiles and is highly instrumented for research purposes. The wingtip launching rails and missiles were replaced with specially designed camera pods and airdata sensors. A pilot-actuated spin chute is onboard in case an uncontrolled spin is entered. The in-flight refueling capability and tail arresting hook were retained. In addition, a thrust vectoring vane system was added. A comparison of the unmodified and modified F-18 HARV is presented below.

Table 1

Comparison of physical characteristics of the unmodified and modified F-18 HARV.
Parameter Unmodified* Modified*
Weight, lb 31,980 36,099
Reference wing are, ft2 400 400
Reference m.a.c., ft 11.52 11.52
Reference span, ft 3OB7.4 37.4
Center of gravity    
    Percent m.a.c. 21.9 23.8
    Fuselage reference station 454.33 456.88
    Waterline 105.24 105.35
Roll inertia, slug-ft2 22,040 22,789
Pitch inertia, slug-ft2 124,554 176,809
Yaw inertia, slug-ft2 139,382 191,744
Product of inertia, slug-ft2 -2,039 -2,305
Overall length, ft 56 56
Wing aspect ratio 3.5 3.5
Stabilator span, ft 21.6 21.6
Stabilator area, ft2 88.26 86.48

The weight specified above reflects a difference of 4119 lb between the unmodified and modified F-18 HARV. The weight of the thrust vectoring vane system installation was approximately 2200 lb. With the addition of the spin chute, emergency systems, and ballast an additional 1500 lb were added for a thrust vectoring vane system weight increase of approximately 3700 lb. The remaining 419 lb in the weight difference represents the inclusion of equipment and wiring not directly associated with the thrust vectoring vane system. With the addition of the aforementioned items, the maximum symmetric limit load factor has been reduced to 5.4 g. The asymmetric limit load factor is 4.3 g.