Thursday, December 1, 2005
SDRs and Mx Alerts
Boeing 737-7EL: A mechanic described a potential defect in this aircraft's anticollision light (P/N 30-0909-20) lens mount located on the tailcone. "While cleaning the lens, it appeared to be loose...a very gentle pull released the lens from its housing. The lens is thick glass that could be a runway hazard if it fell from the aircraft and broke. The probable cause is Skydrol (hydraulic fluid), which leaked from the rudder PCU (power control unit) and compromised the adhesive features of the sealant attaching the lens to the housing assembly. I recommend inspection of aircraft that have had rudder PCU Skydrol leakage problems. Some type of mechanical attachment of the lens to the housing should be considered." Part total time: 893.6 hours.
Cessna 421B: "This aircraft was here [repair station] for a complete exterior repaint," wrote the submitting technician. "After removing the rudder we complied with Cessna service bulletin SB MEB 00-4. It's just a visual inspection, but it does require removing the rudder. We found the rudder hinge assembly (P/N 5731026-1) was installed upside down. Being in the aircraft refurbishment business...[and working)]many of the affected model airplanes, we have found about 75 percent of these lower rudder hinge assemblies installed upside down and many with the bearings falling out and wearing on the rudder hinge brackets. I recommend a one time AD to inspect all affected aircraft.
Cessna 750: A repair station technician wrote: "The screw depicted in Cessna 750-0202 Interior Manual 25-10-06 (page 9, reference number 18) was found loose on both the pilot's and co-pilot's seats on two separate occasions, six months apart. These screws were retightened on both occasions. I feel this problem is significant due to the fact the possible failure mode could be loss of seat locking capability and the crew seat being free to move fore and aft. It has been recommended to Cessna Aircraft (using their Service Condition Report) some locking feature should be used for this screw, such as a lock washer or Loctite compound."
Raytheon Beech 300: A technician described finding a cable quadrant (P/N 101-530057-3) for the autopilot rudder servo--loose on the rudder torque shaft assembly (P/N 101-524012-15). This defect's repair included replacing the loose and working rivets with their next larger size. These fasteners were installed "...wet with EA9309 structural adhesive in accordance with Raytheon Aircraft technical support recommendations. [I] recommend this area be looked at closely on Beech 300 aircraft after accumulation of 3,000 hours or more." Fatigue and rudder servo torque were offered as cause for rivet loosening. Part total time: 4,974.1 hours.
Agusta A109E: An operator described finding a four-inch crack in the leading edge spar doubler of this helicopter's lower vertical fin. Further inspection revealed two additional cracks in the upper vertical fin with approximate measures of five and seven inches. "[Neither] a detail breakdown of this assembly...[or]...the part numbers of the individual cracked components are available to this operator. The approximate location of the damaged area is station 9141, WL [water line] 1625. This tail boom (P/N 109-0370-17-115) is being returned to the manufacture for repair evaluation." (See the next entry for similar defects and a drawing reference.) Part total time: 1391.6 hours.
Agusta A 119: A repair station mechanic submitted a similar defect report as the previous entry: "This is to report cracks in the frames on the vertical fin (P/N 109-0373-01) in the areas at WL 2145.0 and 2520.0. These cracks are occurring approximately between F.S. 9350.0 to 9850.0. Agusta Aerospace has a repair for these cracks in Agusta A119/A109 Series Structural Repair Manual, Chapters 4-2-23, 4-2-24."