6 December 2000
Vertical fin attachment bracket cracking
A recent Service Difficulty Report (SDR) describes cracks on the bracket (P/N 0432004-9) which serves as the attachment for the vertical fin and the elevator centre bearing of the Cessna 152. The AME found the cracks while performing the inspection of the vertical fin attachment bolt nutplates, required by FAA AD 80-11-04. A search of the SDR database revealed over 20 other reports of similar cracking on these Cessna 150 and 152 brackets.
According to the Cessna 150 and 152 parts manuals, the P/N 0432004-9 bracket was introduced in the 1974 production year and was installed on Cessna 150 and A150 aircraft starting at aircraft S/Ns 15075505 and A1500479 respectively. It was used until the end of production of the 150 series. The parts manuals also show that the -9 bracket was used on all the Cessna 152 and A152 models up to S/Ns 15284541 and A1520943 respectively. Prior to the introduction of the -9 bracket in 1974, P/N 0432004-1 was used during production. The difference between the two brackets is that the -9 bracket has a reinforcement plate welded across the forward face (the side of the bracket that is in contact with the rear spar web of the horizontal stabilizer, see diagram) of the assembly.
If a -1 bracket has been replaced since 1974 on earlier 150 aircraft, it may have been replaced with a -9 bracket. Cessna cross reference lists show that the -1 bracket is superseded by a -9 bracket, which means that a -9 bracket may be installed on any post-1965 (swept tail) 150 or A150, even though the aircraft was originally built with a -1 bracket.
The FAA has published an article in Aviation Maintenance Alert No. 267 (AC 43-16A, October 2000) recommending that the bracket and surrounding areas on all Cessna Model 150/152 airplanes built between 1966 and 1980 be inspected, initially within the next 100 hours time in service and every 100 hours thereafter or during inspections required by AD 80-11-04. The FAA notes that the prevalent crack location is along the edge of the plate welded to the forward face of the attachment bracket, with some cracks running diagonally across the plate. To help find these cracks, the use of mirrors and extra light to look through the lightening holes in the back face is recommended.
Cracks in both the stabilizer spar P/N 0432001-56 and its reinforcement P/N 0432001-15 are also being reported to the FAA. The subject vertical fin attachment bracket is attached to this spar and reinforcement, and the FAA recommends that the spar and reinforcement be inspected at the intervals described above.
A number of SDR submitters commented that cracks in the bracket were extremely difficult to see while the bracket was still installed on the aircraft. Many cracks were only found after the bracket had been removed for other reasons, such as heavy corrosion or for replacement of cracked nutplates as required by AD 80-11-04. Some reports also indicated that cracking of the spar assembly under the bracket was evident once the bracket had been removed.
Transport Canada recommends that these brackets be inspected for cracks or corrosion at the next maintenance interval and at subsequent inspections of the empennage area. In addition to the extra lighting mentioned by the FAA, thorough cleaning of the area is recommended prior to inspection.
Any defects or further occurrences should be reported by sending a Service Difficulty Report to Transport Canada, Continuing Airworthiness, Ottawa.
For further information, contact a Transport Canada Centre, or Mr. Mark Stephenson, Continuing Airworthiness, Ottawa, telephone (613) 952-4363, facsimile (613) 996-9178 or e-mail firstname.lastname@example.org.
For Director, Aircraft Certification
Chief, Continuing Airworthiness