Abstract: In the helicopter engine lubricating oil system, malodorous gray resultant was found on the surface of Ag-Pb solder on the socket iron sheet. The socket is located at the end of the magnetic debris signal detector. The composition of the resultant was analyzed by infrared spectroscopy(FT-IR), X-ray fluorescence spectroscopy(XRF), energy dispersive spectrum (EDS) and pyrolysis gas chromatography combined with mass spectrum (PGC-MS). The aresults show that the major components are amides and esters. The amides content reached 29.4%, which caused a foul smell. The formation reason is that the viation lubricating oil flowed into the detector, and then reacted with Ag-Pb solder, generating complexes.