Cessna 340 model aircraft with STC SA4948NM installed - Service Difficulty Alert

AL 2007-01
03 October 2007

Installation Of Wing Spoilers

Transport Canada Civil Aviation (TCCA) has learned through the Service Difficulty Reporting (SDR) program where an Approved Maintenance Organization (AMO) was investigating a customer complaint of a noticeable bowing of the wing structure when the flaps were retracted.

The AMO identified that in 1995, STC4948NM (Installation of Spoilers) had been installed when this was a US registered aircraft.

The AMO also identified a discrepancy in the template #8005T and the installation instructions #SP8000 supplied with STC SA4948NM. The template and installation instruction contradicts each other as to the repositioning of the wing rib.

The template shows the rib has to be moved to a rivet line, which at this location interferes with the flap rib when the flaps are retracted. The installation instructions state to move the wing rib to the new location in accordance with the doubler supplied. Moving the wing rib to this location will not interfere with the flap rib when the flaps are retracted.

Incorrect relocation of the wing rib may result in flap asymmetry or structural damage should there be a jam between the wing rib and the flap rib.

Figure 1
Wing Rib and Flap Rib

The STC holder, Spoilers Inc, has since amended the template, which now reference the installation instructions.

Since the incorrect relocation of the wing rib on this aircraft went undetected during STC installation and subsequent inspections since 1995, similar discrepancies may exist on other aircraft that have incorporated this STC. Therefore, this Service Difficulty Alert strongly recommends owners and AMEs to review the STCs installed on their aircraft and inspect for the proper installation.

Any further defects or occurrences should be reported to Transport Canada, Continuing Airworthiness, Ottawa, via the Service Difficulty Reporting program.

For further information, please contact a Transport Canada Centre, or Mr. Steve Dudka, Continuing Airworthiness, Ottawa, telephone 613 952-4361, facsimile 613 996-9178 or e-mail dudkas@tc.gc.ca.

For Director, Aircraft Certification

B. Goyaniuk
Chief, Continuing Airworthiness