Mass Estimation of Folding Wings

Purpose – Review of mass increase of folding wings applied to passenger aircraft. --- Methodology – Data is obtained from literature (Yarygina and Popov). Data is reworked to build new, simple equations. --- Findings – Wing folds on passenger aircraft are intended to reduce wingspan at the gate. This keeps new, more efficient large-span aircraft in the original wingspan category according to the ICAO Aerodrome Reference Code. A wing fold cuts off part of the wing. The structural loads in the cut are larger if the cut is further inboard. A wing fold at the tip (is basically no fold and) adds no mass. The additional mass of a wing fold increases in good approximation linearly from tip to root. A wing fold at half-span position increases wing mass by about 33%. A one-sided fold is possible. A one-sided fold e.g. 20% from the tip has the same wing mass increase as a fold on both sides 10% from the tip (resulting in the same remaining span after folding). Stowage of an unsymmetrical aircraft with a one-sided fold is more complicated but one such fold may be mechanically simpler than two. --- Research Limitations – Calculating a fold more inboard than 32% of half span is extrapolating given data. --- Practical Implications – Approximating wing mass increase due to a fold can be estimated easily. The equations can be used in a spreadsheet for aircraft design optimization.