Structural members — function and critical aspects
| Member | German | Function | Critical aspects |
|---|---|---|---|
| Spar | Holm | Main spanwise beam of the wing, carries bending | Primary structural item. Fatigue and corrosion at spar attachment are the most common findings at annual inspection. |
| Rib | Rippe | Transverse member, shapes the airfoil; transfers aerodynamic load to the spar | Inspect after hard landings or hail for deformations |
| Stringer | Längsträger | Longitudinal stiffener, prevents skin buckling | Replace on dents or corrosion |
| Frame / former | Spant | Transverse member in the fuselage, defines cross-section | Hard landings can cause deformation |
| Skin | Beplankung | Outer covering; in stressed-skin construction carries shear and compression | Point loads, hail dents, corrosion |
| Doubler / reinforcement | Verstärkung | Local thickening at high-load points (attachment, cut-outs) | Renew on cracks |
Spar constructions
Three common designs:
- Solid spar — simple but heavy
- I-beam spar — caps top and bottom, web between; lighter
- Box spar — four caps, four webs; highest torsional stiffness; modern
Pilot duties
The pre-flight inspection includes a visual check of the main structural items: dents, cracks, corrosion, loose rivets/screws. Suspicious findings must be evaluated before flight by a licensed maintenance technician (Part-66).