Narrative:

On jan/mon/05; I performed an ultrasonic inspection of the front spar; lower spar cap on aircraft X in ZZZ. The work was accomplished per twin commander service bulletin 208A. The purpose of this inspection is to detect corrosion between the spar cap lower surface and a steel strap. The lower wing skin is attached below the strap. There were areas where corrosion was detected; the most severe being inboard of the left nacelle; which will require a re-inspection every 12 months. Visible evidence of corrosion was noted in one area between the spar and the strap also inboard of the left nacelle. There were also visible signs of corrosion on both wings inboard of the nacelle between the strap and the skin. This area is not evaluated during the ultrasonic inspection. These conditions do not render the aircraft unairworthy; however; I believe the proper way to address the corrosion is to disassemble the skin and strap in the affected areas; remove the corrosion and treat with a corrosion inhibitor. It is my understanding that my customer is spraying the areas with acf 50 and re-inspecting in 12 months. I don't believe this will effectively arrest the advancement of the corrosion. This aircraft had been OTS for an extended amount of time and flown in from another country. Although I was contracted only to inspect the spar cap; I noticed other areas that require maintenance and feel it would be a good idea for an asi to take a look at this aircraft. Finally; this aircraft has no provision (access) to the spar cap just outboard of the fuselage for approximately 5 inches on either side and cold not be inspected. This condition was so noted on the customer's report. Callback conversation with reporter revealed the following information: the aircraft owner is presently spraying the areas of corrosion with corrosion inhibitor and will re-inspect in 12 months. The reporter believes this will not be effective and the corrosion will spread. After the ultrasonic inspection was complete; the owner was given a report on the areas of corrosion and the recommend repair. The reporter is caught between customer loyalty and the future of flight safety.

Related reports:

Google
 

Original NASA ASRS Text

Title: A TWIN COMMANDER 690 HAD AN ULTRASONIC INSPECTION OF THE FRONT SPAR LOWER SPAR CAP PER SVC BULLETIN. CORROSION FOUND ON STEEL STRAP.

Narrative: ON JAN/MON/05; I PERFORMED AN ULTRASONIC INSPECTION OF THE FRONT SPAR; LOWER SPAR CAP ON ACFT X IN ZZZ. THE WORK WAS ACCOMPLISHED PER TWIN COMMANDER SVC BULLETIN 208A. THE PURPOSE OF THIS INSPECTION IS TO DETECT CORROSION BTWN THE SPAR CAP LOWER SURFACE AND A STEEL STRAP. THE LOWER WING SKIN IS ATTACHED BELOW THE STRAP. THERE WERE AREAS WHERE CORROSION WAS DETECTED; THE MOST SEVERE BEING INBOARD OF THE L NACELLE; WHICH WILL REQUIRE A RE-INSPECTION EVERY 12 MONTHS. VISIBLE EVIDENCE OF CORROSION WAS NOTED IN ONE AREA BTWN THE SPAR AND THE STRAP ALSO INBOARD OF THE L NACELLE. THERE WERE ALSO VISIBLE SIGNS OF CORROSION ON BOTH WINGS INBOARD OF THE NACELLE BTWN THE STRAP AND THE SKIN. THIS AREA IS NOT EVALUATED DURING THE ULTRASONIC INSPECTION. THESE CONDITIONS DO NOT RENDER THE ACFT UNAIRWORTHY; HOWEVER; I BELIEVE THE PROPER WAY TO ADDRESS THE CORROSION IS TO DISASSEMBLE THE SKIN AND STRAP IN THE AFFECTED AREAS; REMOVE THE CORROSION AND TREAT WITH A CORROSION INHIBITOR. IT IS MY UNDERSTANDING THAT MY CUSTOMER IS SPRAYING THE AREAS WITH ACF 50 AND RE-INSPECTING IN 12 MONTHS. I DON'T BELIEVE THIS WILL EFFECTIVELY ARREST THE ADVANCEMENT OF THE CORROSION. THIS ACFT HAD BEEN OTS FOR AN EXTENDED AMOUNT OF TIME AND FLOWN IN FROM ANOTHER COUNTRY. ALTHOUGH I WAS CONTRACTED ONLY TO INSPECT THE SPAR CAP; I NOTICED OTHER AREAS THAT REQUIRE MAINT AND FEEL IT WOULD BE A GOOD IDEA FOR AN ASI TO TAKE A LOOK AT THIS ACFT. FINALLY; THIS ACFT HAS NO PROVISION (ACCESS) TO THE SPAR CAP JUST OUTBOARD OF THE FUSELAGE FOR APPROX 5 INCHES ON EITHER SIDE AND COLD NOT BE INSPECTED. THIS CONDITION WAS SO NOTED ON THE CUSTOMER'S RPT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE ACFT OWNER IS PRESENTLY SPRAYING THE AREAS OF CORROSION WITH CORROSION INHIBITOR AND WILL RE-INSPECT IN 12 MONTHS. THE RPTR BELIEVES THIS WILL NOT BE EFFECTIVE AND THE CORROSION WILL SPREAD. AFTER THE ULTRASONIC INSPECTION WAS COMPLETE; THE OWNER WAS GIVEN A RPT ON THE AREAS OF CORROSION AND THE RECOMMEND REPAIR. THE RPTR IS CAUGHT BTWN CUSTOMER LOYALTY AND THE FUTURE OF FLT SAFETY.

Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.