How is the correct grip length of a bolt used in an aircraft structure determined?

• A. The grip length equals the combined thicknesses of the materials being held by the bolt
• B. The grip length equals the thickness of the outer skin only
• C. The grip length equals the bolt length
• D. The grip length equals twice the material thickness

Answer: (A)

Grip length is the portion of the bolt shank that sits inside the parts being joined. It must equal the combined thickness of those parts so the entire clamped stack is captured by the bolt and can be tightened properly. If the grip is too short, the bolt won’t engage enough of the shank to develop the required tension, and the joint won’t clamp securely. If the grip is longer than the joint, excess bolt length sits outside the clamped area and the nut can’t pull the parts together evenly. Therefore, the grip length should match the total thickness of the materials being held by the bolt, ensuring proper clamping and load distribution.