Advanced Aircraft Flight Control Sealing Systems & Applications

Aircraft Flight Controls Sealing Systems

Aircraft Flight Control sealing systems are a Trelleborg Sealing Solutions specialty. With well over 50 years of experience in the aerospace industry, Trelleborg Sealing Solutions is your proven value, performance and technology company.

We have developed advanced sealing polymers and seal designs that are proven to satisfy requirements for flight control sealing applications. These include new wear-resistant, high-pressure polymer compounds, new spring-energized seal technology and active back-pumping* seal technology.

*For an explanation of the benefits of active back-pumping seals in unvented actuators, please consult your Trelleborg Sealing Solutions contact.

Primary Flight Controls


Most primary flight control surfaces are continuously activated to maintain safe aircraft control. Some of the primary flight control surfaces are servo-controlled systems. Characteristically a servo-controlled surface is fed constant data or commands electronically to correct flight surface position to maintain proper direction and ensure safe flight operations.

Since the signal is generated electronically and fed to the actuator there are continuous movements and adjustments taking place inside the actuator. This constant short-travel, high-frequency movement is known as dither. Dither strokes place unique demands on seals and seal components. The primary flight control surfaces are typically the elevators on the horizontal tail, which operate for pitch control; the rudder on the vertical tail for yaw control; and the ailerons outboard on the wing which operate differentially for roll control.

All of these surfaces are normally trailing-edge-type, meaning the control surface is on the rear of the wing. The elevators, rudder and ailerons are constantly controlled to maintain safe flight and aircraft stability.

Trelleborg Sealing Solutions has developed advanced sealing polymers and seal designs that are proven to satisfy requirements for flight control sealing applications. These include new wear-resistant, high-pressure polymer compounds, new spring-energized seal technology and active back-pumping* seal technology.

For an explanation on the benefits of active back-pumping seals in unvented actuators, please consult your Trelleborg Sealing Solutions contact. 

Typical Operating Environment

Typical operating pressure reaches up to 3,000 psi, with new developments reaching 5,000 psi in both commercial (Airbus A380 and Boeing 7E7) and military (Boeing V-22, F/A-18 E/F) aircraft applications. Temperatures range from -65°F to +275ºF, with new developments reaching +325ºF (Lockheed Martin JSF F-35).

Fluids are typically Mil-PRF-83282, Mil-PRF-87257 and Mil-H-5606 for military applications and low density (LD), high density (HD) and Type V phosphate ester fluids for commercial applications.

Recommended Products

  • Dual Piston Rings
  • Excluder DC
  • Plus Seal II, Piston
  • Plus Seal II, Rod
  • T-Seal, Piston
  • Turcon® VL Seal
  • Variseal® M (V-spring-energized rod seal)
  • Variseal® W (Slantcoil energized rod seal)

Preferred Solutions

Piston Sealing System 1

Where controlled leakage is acceptable, the Dual Piston Ring offers a good, reliable, low-friction solution in a narrow groove with minimum hysteresis.

Piston Sealing System 2

Where leakage is critical, the Grooved Plus Seal® II has excellent wear characteristics. Because flight control performance is critical, we recommend Back-up Rings with the Plus Seal® II for extra security.

High Frequency Rod System- Primary Flight Control

The tandem Turcon Vl Seal® combines low-friction and leak-tight performance. Using the patented design of active-backpumping for the primary and secondary seal positions provides excellent sealing system performance with low-friction and leak-tight operation. The Excluder® DC provides additional leakage control for low-pressure and static stand-by operations, if necessary.

Secondary Flight Controls


Secondary flight control surfaces are activated at different times during take off, flight and landing to maintain safe control of the aircraft during operation. Spoilers are used on very high lift/low drag aircraft like sailplanes, while spoilers are used to disrupt airflow over the wing and greatly reduce the amount of lift.

This allows a pilot to lose altitude without gaining excessive airspeed. Flaps are mounted on the back edge of each wing near the wing roots. They are deflected down to increase the effective curvature of the wing and produce additional lift, and they also reduce the stalling speed of the wing. They are used during low-speed, high-angle-of-attack flight like descent for landing. Slats are extensions to the front of a wing and are intended to reduce the stalling speed by altering the airflow over the wing.

Airbrakes are used on high-speed aircraft and are intended to increase the drag of an aircraft without altering the amount of lift. The secondary flight control surfaces are used at a much lower level or repeated cycles when compared to primary flight control surfaces. The secondary flight control surfaces include linear and rotary seal applications.

Aircraft Flight Control sealing systems are a Trelleborg Sealing Solutions specialty. With well over 50 years of experience in the aerospace industry, Trelleborg Sealing Solutions is your proven value, performance and technology company. 

We have developed advanced sealing polymers and seal designs that are proven to satisfy requirements for flight control sealing applications. These include new wear-resistant,high-pressure polymer compounds, new spring-energized seal technology and active back-pumping* seal technology.

*For an explanation on the benefits of active back-pumping seals in unvented actuators, please consult your Trelleborg Sealing Solutions contact.

Typical Operating Environment

Typical operating pressure reaches up to 3,000 psi, with new developments reaching 5,000 psi in both commercial (Airbus A380 and Boeing 7E7) and military (Boeing V-22, F/A-18 E/F) aircraft applications. Temperatures range from -65°F to +275ºF, with new developments reaching +325ºF (Lockheed Martin JSF F-35).

Fluids are typically Mil-PRF-83282, Mil-PRF-87257 and Mil-H-5606 for military applications and low density (LD), high density (HD) and Type V phosphate ester fluids for commercial applications.

Preferred Solutions

Pressure-Relieving Rod System 1

This system is designed to allow interstage pressure build-up to be relieved back into the system when the pressure drops. This solution features the Plus Seal® PR.

Pressure Relieving Rod System 2

This system is designed to allow interstage pressure build-up to be relieved back into the system when the pressure drops. This solution features the Variseal™ M.

Pressure Relieving Rod System 3

The Turcon® VL Seal® and Turcon® Wedgpak® system configuration offers the ideal pressure-relieving sealing system. Pressure trapped between the seals is prevented from leaking out of the system by the elastomer contact Wedgpak® secondary. During normal stroking operation the Turcon® VL Seal® tilts, allowing the oil back into the hydraulic circuit.