When turbine-powered aircraft land, the wheel brakes and the imposed aerodynamic drag loads (e.g., flaps, spoilers, etc.) of the aircraft may not be sufficient to achieve the desired stopping distance, therefore, most turbine-powered aircraft include thrust reversers. Turbine-powered aircraft typically include aircraft powered by turbofan engines, turbojet engines, or the like. Thrust reversers enhance the stopping power of these aircraft by redirecting the turbine engine exhaust airflow in order to generate reverse thrust. When stowed, the thrust reverser typically forms a portion the engine nacelle and forward thrust nozzle. When deployed, the thrust reverser typically redirects at least a portion of the airflow (from the fan and/or engine exhaust) forward and radially outward, to help decelerate the aircraft.
Various thrust reverser designs are commonly known, and the particular design utilized depends, at least in part, on the engine manufacturer, the engine configuration, and the propulsion technology being used. Thrust reverser designs used most prominently with turbofan engines fall into two general categories: (1) fan flow thrust reversers, and (2) mixed flow thrust reversers. Fan flow thrust reversers are typically positioned circumferentially around the engine core and affect only the bypass airflow discharged from the engine fan. Whereas, mixed flow thrust reversers typically reside aft of the engine core and affect both the fan bypass airflow and the airflow discharged from the engine core (core airflow).
Typically, deployment of the thrust reverser means translating aft one or more sleeves or cowls (“transcowls”) thereby creating a circumferential aperture and exposing a plurality of rows and columns of cascade vanes disposed therein. Some thrust reversers use a blocking mechanism, such as two or more pivoting doors that simultaneously rotate, blocking the forward thrust flow path as the transcowl translates aft. The blocking mechanism redirects engine airflow, generally forcing it to discharge through the aforementioned plurality of cascade vanes disposed within the aperture. Redirecting the engine airflow in this manner causes the engine and thrust reverser to produce a net force in a direction substantially parallel with the thrust reverser centerline, and substantially opposite the direction of aircraft velocity, in order to decelerate the aircraft. Thrust produced in this manner is generally referred to as “reverse thrust”.
While the above described thrust reversers produce a reverse thrust that is desirable for decelerating the aircraft, these thrust reversers can also cause an undesirable nose-up pitch moment to be generated. This pitch moment occurs due to the vertical separation between the thrust reverser centerline and the aircraft center of gravity. This pitch moment can be particularly severe on aircraft with engines mounted relatively high on the fuselage or empennage. This pitch moment is undesirable because it reduces the effectiveness of the nose wheel steering, and can thereby reduce the ability of the pilot to control the aircraft. In some instances, the nose-up pitch moment may even lift the nose gear off the ground. To avoid these hazards, the reverse thrust may have to be limited, but this reduces the benefit of using thrust reversers.
Hence, there is a need for a thrust reverser system that is capable of reducing or eliminating this nose-up pitch moment. The desirable thrust reverser system employs asymmetric vane geometry that, in addition to producing reverse thrust, also produces a vertical thrust component that induces a nose-down pitch moment on the aircraft. The desirable thrust reverser also minimizes weight and material cost by employing a single row asymmetric vane geometry.