Visual Differences Observed In Stiffening Rings And Beads In Formed Aluminum Ribs

Van’s Aircraft says it has been questioned by several builders recently regarding variations in the depth of stiffening rings and beads in formed aluminum ribs.

While understanding the reason for the questions, Van’s says the variations have existed for years. The primary reason for the variances is that the parts were transitioned from T0 to T3 temper. The company also began forming the wing ribs in-house with a large hydraulic press. This allowed for increased production volume and reduced manufacturing time, and from time to time the pressure of the press has varied, resulting in the observed variations in the stiffening ribs and beads.

Van’s states that although the variations can be observed, they do not present any quality or safety issues. However based on concerns expressed by customers, the company will tighten the specifications for the depth and appearance of the stiffening beads to reduce visually observable differences.

The company mentioned by way of historical perspective that in earlier years of aluminum homebuilt aircraft, builders fabricated their own wing ribs. This was done by hand-forming them over wood blocks using a soft hammer bending process, and there were often no stiffening rings or beads in the ribs. Most ribs for homebuilts back then were made from usually 2024-T3 aluminum, including the RV-1 wing ribs. Many of those early homebuilts are still flying today.

The explanation above was provided by Rian Johnson, Chief Engineer, and Richard VanGrunsven, Founder. The full text of the response is available at the link below.

FMI:  www.vansaircraft.com/