Although wing removal was necessary to provide adequate access for effective visual and magnetic particle inspections of M18 wing attachment fittings, the aircraft manufacturer’s service bulletin E/02.170/2000 allowed the wings to remain attached during these inspections.
The improved clarity for operators/maintainers in Service Letter M19/034/2016 should significantly reduce the likelihood, and therefore risk, of an organisation attempting to develop a system whereby the wings are not removed and an inappropriate inspection method used.
On 16 September 2015, PZL Mielec reported to the ATSB that:
PZL Mielec will issue a Service Letter … in which it will be stated that if during executing the Service Bulletin no. E/02.170/2000 its executor is not sure that a bore in the PZL M18 wing attachment fitting is correctly inspected for the lack of cracks, he should disassemble the outer wing.
Inspection of the wing attachment fittings with the current inspection processes does not appear to ensure an adequate inspection without removal of the wings. However, the ATSB accepts that a suitable non-destructive inspection procedure that can adequately examine the wing attachment fittings without removing the wings may be developed in the future.
The ATSB has assessed the proposed safety action and considers that it should adequately address the identified safety issue. However, the ATSB will reconsider this assessment when the proposed safety action has taken place to determine if it remains adequate.
PZL advised that on 22 February the proposed Service Letter was released. The body of that service letter, No. M18/034/2016 stated:
The Service Bulletin No. E/02.170/2000 issued in 2000 and concerning the inspection of joints attaching the outer wings to the centerwing contains the procedure of detection of corrosion and cracks and the way of conduct after their detection.
The only acceptable method of inspection of joints that is referred to in this Bulletin is the magnetic particle inspection method.
The general guidelines for conducting inspection of holes (ø36 mm) of fittings using the magnetic particle inspection method, included in the Bulletin allow for the possibility of conducting the tests without disconnecting the outer wing, after removal of the pin from the inspected hole.
This method of inspection is allowable only in the case when the person conducting the inspection has the highly advanced equipment and large experience. Then, this person can with full responsibility confirm the technical condition of joints.
In case of any doubts, it is required to disconnect the outer wing and to inspect the fittings of the centerwing and the outer wing individually. It refers particularly to airplanes performing operations in the overloaded configuration.
