Sukhoi Civil Aircraft (SCAC) expects to complete work to resolve a tail stabilizer defect discovered in Sukhoi SSJ100s during a routine inspection on December 22 by the end of January, according to the Russian regional jet manufacturer.

As 2016 drew to a close, the Russian civil aviation authority (the Federal Agency of Air Transportation or FATA, locally known as Rosaviatsiya) approved methods suggested by the manufacturer to fix the earlier discovered defects related to stabilizer attachments points. It also authorized the plan to conduct the work necessary.

The authority issued two Airworthiness Directives on the subject, on December 23 and December 28. The first directive recommended by air safety inspectors who discovered faulty force bearing elements on several airframes repairs sticking of attachment points in the area of upper and lower stiffeners of the tail stabilizer. Inspection of the Russian-registered SSJ100s revealed problems with six aircraft operated by Aeroflot and one by Irkutsk-based regional airline IrAero.

The second directive calls for replacement of the attachment stiffeners with new ones.

According to the manufacturer, the defect does not relate to construction material quality or manufacturing methods; rather, inspectors have traced the problem to incorrect installation of stiffeners. SCAC further said the defect does not amount to a critical issue because the attachment of the stabilizer incorporates “a multilevel redundancy system and a large amount of excessive strength, twice exceeding loadings observed in flight operation.” Work on a single aircraft takes several days.

According to the Russian authority, the SSJ100 fleet can operate normally–without restrictions on flight envelope--while the manufacturer performs work to eliminate the defects discovered. At the same time, the authority has prescribed weekly checks of the stabilizer attachment points-- instead of the daily checks recommended now--upon completion of the work.

Among Russian SSJ100 operators, the largest—Aeroflot—appears the least affected by the directives, as its Superjets continued flying regular services. Among Western operators, Interjet of Mexico had to temporarily ground half of its 22-strong SSJ100 fleet until it completed checks and defect-rectification work. Dublin-based CityJet, which now flies three SSJ100s, continued flying its airplanes as usual after performing requisite checks on December 24 and finding no anomalies.