The pylon is a structure on the aircraft aft fuselage to which the engine attaches. The pylon includes the engine mounts and the connections between the aircraft and the engine.

The pylon is found between FS694.00 and FS839.00. It is a structure between the engine and the fuselage which has an aerodynamic shape. There are access panels for inspection and maintenance. The pylon also has vent and drain holes.

The pylon primary structure transmits the load from the engines to the fuselage structure.

The Primary Structure description includes:

Nose Structure

The nose structure extends between FS694.00 and FS722.10, which has three webs, one birdstrike support beam and two formers. The three webs are made from aluminum-alloy and attached to the fuselage skin at FS700.00, FS707.15 and FS717.82. The birdstrike support beam is installed at the outboard of the nose structure and made from the machined aluminum-alloy. Two formers are found between the birdstrike support beam and the fuselage skins, at FS700.00 and FS707.15. They are made from the clad aluminum-alloy sheets.

Center Structure

The center structure extends between FS722.10 and FS779.12, which has four webs, two thermal plates and four pieces of fireproof seals. The four webs are found at FS732.00, FS740.30, FS749.22 and FS756.25. They are made from aluminum-alloy sheets and attached to the pylon and the fuselage skin with angles. The two thermal plates are attached to the webs at FS732.00 and FS756.25 with bolts for heat protection and made from titanium-alloy sheets. There are four pieces of fireproof seals around the forward engine-mount frame for heat protection. They are attached to the adjacent structure with bolts and sealed with high-temperature sealant.

The forward engine mount frame is found at FS724.70 and made from die aluminum-alloy. The rear engine mount frame is found at FS772.19. It is made of the machined aluminum-alloy and attached to the fuselage with tension bolts.

The engine thrust link extends from FS729.00 to FS763.00. It is attached to the forward engine-mount frame with bolts and connected with the fuselage by the attachment fitting. The engine thrust link is made from machined titanium-alloy and the attachment fitting is made from machined aluminum-alloy.

Rear Structure

The rear structure is found between FS779.12 and FS839.00, which includes an inner and an outer part of the trailing edge. The outer part is the detachable trailing-edge. The inner part has four webs found at FS779.12, FS788.50, FS804.87 and FS821.22. Those are made from aluminum-alloy sheets and attached to the fuselage skin with angles.

The pylon secondary structure has a smooth aerodynamic surface for air to flow around the pylon primary structure. The pylon secondary structure includes the leading edge and trailing edge structures. It also has the access panels to give access for maintenance and inspection.

The Secondary Structure description includes:

Leading Edge Structure

The leading edge structure is found between FS694.00 and FS722.10. There is a firewall structure on the outboard of the leading edge. It is made from titanium-alloy sheets. The angles and doublers add more strength to the firewall structure. The skins are made from the chemically milled aluminum-alloy and are attached to the fuselage with angles. The aerodynamic seal is made from silicone rubber and is attached to the Z-angle and the web of the leading edge.

Center Structure

The center structure is found between FS722.10 and FS779.12, and has a top skin and a bottom skin. The bottom skin has cutouts for the installation of three access panels. The top and bottom skins are made from the chemically milled aluminum–alloy and are attached to the fuselage with angles.

Trailing Edge Structure

The trailing edge structure is made from the fiberglass with honeycomb core. It is found between FS779.12 and FS839.00. It has a detachable trailing edge fairing and it is attached to the rear structure of the primary structure. The aerodynamic seal is made from silicone rubber and is attached to the U-channel of the trailing edge.

Pylon Access Panels

There are three access panels on the leading edge structure:

• One at the top
• Two at the bottom

They are made from chemically milled aluminum-alloy. These access panels give access to the anti-icing, hydraulic, fuel and the wiring systems for maintenance.

There are three access panels on the bottom of the center structure. They are made from chemically milled aluminum-alloy. These access panels give access to the environmental control system (ECS) and to the thrust link fitting for maintenance.

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