Sealing in aviation is not limited to hydraulic or fuel systems: numerous seals are installed at critical points of the aircraft to maintain safety, performance and component longevity. On the diagram of an aircraft, we can identify several specific areas where each seal plays a precise role, whether it's to resist pressure, heat or exposure to various fluids.
1. Radome and front end
Radome seal
The radome is the nose of the aircraft, which protects the radar (navigation and detection system). The seal around the radome must :
Resist aerodynamic stress, rain, hail and insects.
Withstand temperature variations between ground level and cruising altitude.
Preserve radar accuracy by preventing the ingress of water or other contaminants.
2. Landing gear and undercarriage structures
Landing gear seal
Landing gear doors open and close with every flight. Associated seals:
Prevent water, dust and debris from entering the fuselage.
They are subject to repeated cycles, hence the need for fatigue-resistant materials.
Belly fairing gasket (membrane under fuselage)
The belly fairing is an important area for aerodynamics. The seal plays a dual role here:
Improving aerodynamic drag by connecting structural elements as closely as possible.
Prevent any flow of water or fluids from the fuselage to the outside (or vice versa).
3. Nacelles and motor
Motor mast and nacelle seal
The engine mast connects the engine to the wing or fuselage. Here, the seals face :
Strong vibrations, as the motor generates oscillations and jolts.
High temperatures and residues of fuel, oils or exhaust gases.
Significant pressure differences during ascent and descent phases.
For the engine nacelle, which envelops and protects the turbojet engine, the seals must :
Resist heat from hot engine parts.
Avoid fluid leaks (fuel, oil).
Preserve the aerodynamic performance of the engine block.
4. Moving wing surfaces
Slat seal (leading edge)
Slats are movable parts located at the front of the wing. During take-off or landing, they deploy to increase lift. The slat seal :
Withstands repeated rubbing with every movement.
Maintains optimum air circulation around the leading edge.
Resists rain or icing at altitude.
Spoiler and flap seals
Spoilers are panels on the wing used for braking and control. Flaps, on the other hand, are flaps at the rear of the wing to modify lift. In both cases :
Joints must tolerate significant angle differences when spoilers or flaps are actuated.
They prevent the ingress of water or dust, which could impair kinematics.
Their elastomer composition is specially adapted to remain flexible despite variations in temperature and pressure.
Aileron seal
Theaileron is the lateral control surface used to turn the aircraft about its longitudinal axis (roll). The aileron joint :
Maintains aerodynamic seal between wing and aileron.
Must be flexible enough to follow steering movements.
Ensures that the area remains free of impurities that could block the mechanism.
5. Empennage and rear surfaces
Tailplane seal (control surfaces and stabilizers)
At the rear of the aircraft, the empennage comprises the vertical fin and horizontal stabilizer, each fitted with a control surface (rudder, elevator). The corresponding joints :
Maintain the seal between the different sections to avoid parasitic turbulence.
Resistant to high aerodynamic loads, especially when maneuvering.
Prevent water and ice infiltration in the rear fuselage areas.
6. Common challenges and technical features
Joints installed in these different areas share common constraints:
Chemical resistance: Fuel (Jet A-1), hydraulic oil, de-icing products.
Wide temperature range: from high-altitude cold (down to -50°C) to engine heat.
Flexibility and endurance: withstand vibration, aerodynamic pressure and deformation cycles.
Regulatory requirements: traceability of materials, fatigue testing, approval by bodies such as the EASA or FAA.
7. Maintenance and inspection
To maintain a high level of safety and performance, aeronautical maintenance includes :
Regular joint checks by MRO (Maintenance, Repair & Overhaul) teams.
Preventive replacement of seals after a certain number of flight cycles or hours.
The use of approved materials and lubricants when installing seals.
8. Conclusion
Aeronautical seals are not confined to a single area, but are found in many critical points: radome, gear doors, engine nacelle, movable wings, empennage, etc. Each of these locations is subject to specific constraints (temperature, pressure, vibration, etc.). Each of these locations has its own particular constraints (temperature, pressure, vibration). Yet they all share the same objective: to ensure the safety, reliability and efficiency of an aircraft in flight.
A good understanding of these roles, and careful inspection of each area, enables airlines and maintenance workshops to guarantee the longevity of the aircraft. In an age of advanced materials and innovation in the aerospace industry, seals remain key components in protecting the aircraft's electronics, passengers and structure, while preserving its performance at altitude.