Abstract: In a turbofan jet engine installation including a low pressure area (48) located between a primary exhaust nozzle (20) and strut fairings (30), an improvement including a fencing assembly (66) for reducing interaction of fan air (52) with air in the low pressure area. The fencing assembly (66) includes two pairs (70), (72) of opposed flow control fences (68) connected to the primary exhaust nozzle (20) at locations laterally outboard of the strut fairings (30). A first pair (70) includes fences formed of a single piece connected directly to the primary nozzle (20). A second pair (72) includes fences formed of a number of longitudinally spaced-apart segments (82). The segments (82) are connected to one face of an elongated attachment strap (84) with the opposite strap face being connected to the nozzle. Each fence includes a foot portion (78) and an upright portion (80) extending outwardly from the foot portion.