Libelle 201B – Return to Flight
During the annual inspection of my Standard Libelle 201B S/N 181, a crack was discovered in the main spar spigot. This happened in March of this year. The following 5 months were filled with repairs and communication challenges with Germany. However the outcome was positive and the Libelle is now repaired, determined airworthy, and has been returned to flight. The following post is intended to benefit other Libelle owners so that they may inspect the area of concern in more detail during their next annual inspection.
A detailed drawing, shown in Figure 2, of the welded steel assembly of concern was provided by Glasfaser-Flugzeug-Service.
Figure 4 shows the area with paint removed and a stir stick inserted between the rapping plies and steel assembly. This is the area of concern regarding corrosion due to trapped moisture.
Figure 5a shows the assembly after the plies that rap the assembly have been removed. Figure 5b shows the removal of the pins that attach the assembly to the upper and lower spar caps. The best way to remove these pins is to use a pin of slight smaller diameter, a large C-clamp, and a large diameter deep socket. Use the pin and C-clamp to press the pin out with the socket as a backing plate that allows the pin to slide thru.
|Figure 5a and 5b|
Once the steel assembly has been removed the thickened resin used to bond the assembly in place was removed, shown in Figure 6. The important aspect of the step is to remove the non-load bearing thickened resin only, no fibrous spar cap material can be removed, or the structural integrity of the spar will be compromised.