Triebwerkspylon (Pylon)

Was ist ein Pylon?

A pylon is the structural fillet or strut that connects a jet engine's nacelle to the aircraft's wing, or in some configurations to the rear fuselage. The pylon is far more than a simple bracket: it is a primary load-bearing structure that must transmit the full thrust, weight, gyroscopic, and aerodynamic loads of the engine into the airframe throughout the entire flight envelope — including the extreme loads of a fan blade-out event, where a turbofan blade separates and creates enormous imbalance forces.

Funktion und Zweck

The pylon serves several interdependent functions. Structural: It carries engine thrust (which acts horizontally, forward) and engine weight (which acts vertically downward) into the wing box structure via a series of carefully designed attach fittings. Critically, modern pylons use a "fail-safe fuse pin" design: in the event of an extreme overload (e.g., a gear-up landing or severe turbulence), the pylon is designed to separate cleanly from the wing rather than transmitting catastrophic loads into the wing or fuel tanks, preventing fire or structural failure.

Systems routing: The pylon contains and protects the fuel supply lines running from the wing tanks to the engine, hydraulic lines for thrust reversers and engine-driven pumps, electrical wiring harnesses, bleed-air ducting, and fire detection/suppression lines. The pylon's interior is a dense bundle of aircraft systems that must be carefully routed and maintained.

Aerodynamic fairings: Smoothly shaped composite fairings cover the pylon structure, minimizing drag and managing the complex airflow interaction between the engine nacelle and the wing's lower surface.

Typen und Varianten

• Under-wing pylon: The dominant configuration on commercial jets. Engines hang below and forward of the wing leading edge on pylons that also act as ballistic protection — in the event of an uncontained engine failure, the pylon position minimizes the probability of debris striking the fuselage or opposite engine.
• Over-wing pylon: Used on some regional jets (e.g., HondaJet, VFW 614) for aesthetic, noise, or ground-clearance reasons. The aerodynamic interaction with the wing upper surface requires careful design to avoid excessive drag.
• Rear-fuselage pylon: On aircraft like the Boeing 727, McDonnell Douglas DC-9, and Bombardier CRJ family, pylons mount engines directly to the aft fuselage. This eliminates wing-engine aerodynamic interference but concentrates weight aft, requiring more complex balance and empennage design.

Bemerkenswerte Beispiele

The Boeing 737 MAX controversy centred in part on the LEAP-1B engine's larger diameter. To fit the engine under the 737's low-slung wing with adequate ground clearance, Boeing redesigned the pylon to mount the engine further forward and higher — a change that subtly altered the aircraft's handling characteristics and contributed to the MCAS (Maneuvering Characteristics Augmentation System) design decisions. The Airbus A380 pylons support four Engine Alliance GP7200 or Rolls-Royce Trent 970 turbofans, each weighing over 6,000 kg, requiring some of the most robust pylon structures in commercial aviation.

Verwandte Komponenten

The pylon interfaces directly with the engine's nacelle — the aerodynamic cowling that surrounds the engine — at the forward and aft mount points. All fuel and systems connections between the wing and the turbofan engine pass through the pylon. The entire assembly attaches to the primary structure of the fuselage via the wingbox, which must be designed to handle not only normal flight loads but also the emergency separation loads designed into the pylon fuse pins.