Squawk Box: 01/05


The following information is derived from the FAAs Service Difficulty Reports and Aviation Maintenance Alerts.


American General Model AG-5B
Seatbelt Plate Installation

While replacing the rear passenger seatbelts, a technician discovered the reinforcement plate (P/N 5102330-6) had been installed on the forward side of the aft seat bulkhead under the seatbelt attach bracket. The -6 plate should have been installed on the aft side of the bulkhead in accordance with AGAG drawing 5102299. Furthermore, MS20364-1032 (thin sheer nut) was used to secure the AN3-5A retaining bolts. MS20365-1032 or MS21042-3 nuts should have been installed as indicated on the drawing. According to the submitter, this arrangement resulted in reduced seatbelt attachment strength when compared with the design configuration. He reported the aircraft appeared to have the original seatbelts installed, and it is likely this improper installation was accomplished during assembly.Part total time: 1960 hours.

Beech Model F33A
Autopilot Bridle Cable

The submitter found one side of the bridle cable broken at the capstan pin. The other side of the bridle cable had back lashed and tangled in the capstan bridle cable guard pins, which restricted up-elevator control. This problem was addressed in the Century Flight Systems Service Bulletin CSB 2003-01. This Service Bulletin can be found at: www.centuryflight.com/services/frame/services.htm. The bulletin states: It has come to the attention of Century Flight Systems that a situation occurred involving a bridle cable that came loose from the servo capstan and caused some control wheel friction. Upon investigation it was determined that the locking pin on the bridle cable had not been secured by the set screw located on the front side of the capstan. The cable guard was also clocked wrong and the bridle cable was not wound and attached to the main pitch cable correctly.Century Flight Systems recommends a physical examination of the set screw and locking pin on any Roll, Pitch and Rudder Servo to insure locking pin is secure in the capstan. Also check the bridle cable wrap on the capstan and travel when the control wheel is moved from mechanical limit to limit. The submitter feels that an Airworthiness Directive would possibly ensure compliance.Part total time: unknown.

Cessna Models 172 and 175
Horizontal Stabilizer Spar

Maintenance technicians have found cracks in the forward horizontal stabilizer spar on Cessna 172 /175 series airplanes. A search of the FAA Service Difficulty Reporting System database revealed 76 separate reports of these occurrences during the past 30 years. The following quote is from Cessna Mandatory Service Bulletin No. SEB94-8, released on April 29, 1994: Service experience indicates the possibility of cracks/buckles developing in the area aft of the center lightening hole in the horizontal stabilizer forward spar. An inspection for cracks/buckles in this area should be conducted. If a crack or buckle is found, the spar shall be repaired or replaced depending upon the extent of crack propagation. To assist in preventing this condition from occurring, a new strengthened one-piece forward spar reinforcement is available. Non-compliance with this service bulletin may result in failure of the horizontal stabilizer.Cessna models 172R and 172S airplanes, built since 1996, incorporate the front spar reinforcement. Improper ground handling can cause cracking and deformation of the horizontal stabilizer structure. It is recommended that a tow/steering bar be used whenever the airplane is to be manually positioned on the ground. Do not steer the airplane by pushing down on the horizontal stabilizer. Adherence to Cessna Mandatory Service Bulletin No. SEB94-8 and to the Cessna Service Manual for 172 series airplanes is strongly recommended. Avoid steering these airplanes on the ground using the empennage.

Piper Model PA-28R-201
Loose Wing Attach Bolt

During a scheduled inspection, the technician discovered the left wing attach bolt (P/N NAS8206-6X) was loose. One year earlier, the technician replaced the same bolt in accordance with an engineering order issued by the manufacturer. The submitter indicated three other aircraft in the fleet had similar problems. He notified the manufacturer, and they are working on a repair.Part total time: 773.7 hours.

Lycoming Model O-360-A1H6
Fractured Intake Valve

During cruise flight, the pilot experienced surging manifold pressure on the left hand engine and a vibration was noticed on final approach. An inspection revealed the number 2 cylinder intake valve was fractured with pieces in the number 2 and 3 combustion chambers. The cylinder head and piston tops were damaged from contact with broken valve pieces.Part total time: 1521.6 hours.


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