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Air combat simulator studies consistently show large fighter effectiveness payoffs due to thrust vectoring and/or thrust reversing exhaust nozzles. However, the air-to-air missile related kill ratios achieved during these evaluations vary considerably as a function of maximum missile launch angle-of-attack (AOA). This paper will review the ways thrust vectoring/reversing is used during air combat and then discuss some missile related multi-function nozzle survivability benefits. Typical air combat simulator fighter agility advantages and disadvantages attributable to vectoring/reversing nozzles will then be examined. These include relative antenna train (look) angles, capture times, and capture frequencies during close-in combat. The high AOA launch desirability will be defined along with the payoffs of attaining that capability. Nozzle max vector angles and utilization frequencies along with high AOA missile launch problems and potential solutions will also be addressed.

The benefits of pitch/yaw thrust vectoring and/or thrust reversing multi-function nozzles (MFN) for fighter type aircraft have been identified relative to the air-to-air mission in several previous papers. This paper will point out those previously noted payoffs which also apply to air-to-ground attack fighters. It will also present a detailed description of air-to-ground unique multi-function nozzle benefits. Specific treatment will be given to close air support, battlefield interdiction, suppression of enemy air defenses, and deep strike missions. MFN contributions to air-to-ground survivability and effectiveness will be emphasized relative to the critical aspects of basing, ingress, target attack, self defense, egress and recovery. Actual air-to-ground attack historical data will be employed as it is applicable to this discussion.

Two propulsion related drag correlation parameters have been developed. Existing or planned parametric jet aftbody drag data can therefore be reduced into a simple prediction technique for aircraft preliminary design studies. The drag due to the external nozzle geometry correlates with the average slope of the aftbody's area distribution (Integral Mean Slope), and the drag influence of the internal nozzle geometry/exhaust plume correlates with an effective plume inclination angle (Plume Correlation Parameter). The propulsion related drags of single, twin, and two-dimensional jet installations, and convergent, convergent-divergent, and plug nozzles are shown to correlate with the two parameters. An example of the prediction system utilization is also presented.

The Lockheed YF-12 aircraft uses a blow-in door ejector nozzle, which consists of a variable area, primary nozzle mounted on the afterburner of a Pratt & Whitney Aircraft J58 engine and blow-in doors, a convergent-divergent spool piece, and variable exit area free-floating flaps integrated into a Lockheed YF-12 airframe. Performance data from cold-flow, wind tunnel models and hot-flow, static stand models were correlated and compared with actual flight test data. It was found that these data showed agreement when both internal thermodynamic and external aerodynamic effects were considered.