F-5 Agility Enhancement Kits

For customers that would like to improve the maneuverability of their F-5 aircraft, TCA has developed agility enhancement kits for the F-5 series that can be easily retrofitted.

All F-5 aircraft have included a wing-root leading edge extension (LEX) in their aerodynamic design. The original W1 LEX (designated by its wind tunnel model component number) was added to the F-5A/B wing design as a fairing over the leading edge flap actuator. Even though the W1 LEX was less than 2% of the wing area, it provided a 10% increase in the maximum lift capability of the wing, resulting in improved maneuverability. When the F-5E aircraft was developed, Northrop engineers increased the size of the LEX to approximately 5% of the wing area. This new LEX was designated W4 and provided a further 25% increase in maximum lift. Approximately 700 F-5E and 100 F-5F aircraft were delivered with the W4 LEX installed.

When the dual-seat F-5F was developed, it initially used the same W4 LEX as the single-seat F-5E. However, initial in-service experience with the F-5F uncovered some unfavorable stability characteristics at high angles of attack. In order to eliminate these problems, some design changes were made to the aircraft. The forebody was redesigned and new radome was developed that was designated “Shark Nose” due to its distinctive contour that resembled a shark. The wing flap control logic was changed to add angle of attack (AOA) as a scheduling parameter along with airspeed/Mach. The new flap system was designated “Auto Flaps”. One part of the design change resulted in a new, slightly larger LEX that was designated W6 LEX that is seen in the figure at the left. These three (3) design changes were certified by the USAF as the “Improved Handling Qualities - IHQ Package” and were incorporated in the production configuration of all F-5F aircraft built after 1979. For production commonality reasons (not to solve a stability problem), the IHQ package was incorporated into the production configuration of all F-5E aircraft after 1979 also.

Due to the fact that Northrop chose not to develop a retrofit kit for the IHQ package, none of the owners of previously delivered aircraft were offered the opportunity to upgrade their aircraft with the new design. In response to a market requirement from owners of F-5E/F aircraft built before 1979, TCA developed a wing leading-edge extension (W6 LEX) retrofit kit that is compatible with all configurations of the F-5E/F aircraft. The TCA W6 LEX kit is fully certified and is in daily operational service. The resigned shape of the W6 LEX provides a 10% increase in maximum lift over the W4 LEX. This increases instantaneous maneuverability, resulting in an improvement in mission effectiveness and survivability in close-in air-to-air combat. The W6 LEX also increases lateral-directional stability in the near-stall/post-stall angle-of-attack region resulting in improved spin resistance.

The benefits of the W6 LEX retrofit kit include:

  • Increases instantaneous maneuverability at all subsonic Mach numbers by 10%, resulting in increased combat effectiveness in close-in air-to-air combat
  • Increases lateral-directional stability in the near-stall/post-stall angle-of-attack region, resulting in improved overall departure and spin resistance

The Tiger Century W6 LEX retrofit kit is fully developed and qualified and is in series production. The installation kit includes step-by-step workbook instruction along with the required changes to the maintenance and Operational Technical Orders.