Narrative:

On feb/09; work was in progress on aircraft X. I was working engineering authorization replacement of the aileron centering mechanism. To the best of my knowledge; installation is complete; tests are complete; and the aircraft is in service. While preparing to perform the same work on the next aircraft for service; I was looking in detail at the aircraft maintenance manual and component maintenance manual and noticed the quadrant assembly attach bolts. The illustrations showed the bolts installed one head aft; and the other head inboard. The aircraft maintenance manual did not state the bolts had to be installed this way; only the illustrations were drawn that way with no notes on the illustrations as to the direction of bolt installation. Aircraft has the quadrant bolts installed 1 head aft and 1 head outboard. As the next aircraft was being opened up for service; I went to look at the quadrant assembly on that aircraft. I found those quadrant bolts installed 1 bolt head forward and 1 bolt head outboard. I could see no obstruction to movement with the way the bolts were installed. If the bolts were installed in the opposite direction; I do not believe they would interfere with the operation of the aileron centering mechanism. I reported this information to my foreman. I am submitting this report because I am unsure if the bolt installation direction is critical or at the discretion of the mechanic. A clarification of bolt installation direction; or if the bolt installation direction is at the discretion of the mechanic; would help mechanics in the future. Callback conversation with reporter revealed the following information: reporter stated the engineering authorization (ea) was issued in response to pilot write-ups for stiff ailerons. After much troubleshooting; mechanics and engineering determined the problem involved the aileron feel and centering cam roller in the left forward well wheel. The aileron centering unit cam roller face that rides in the centering assembly was not completely aligned; or matched up; with the 3/8 inch face of the cam it was riding against. As a result; a portion of the roller bearing developed an edge from uneven wear against the cam; causing the stiff ailerons; because the cam roller would be slow to center in the cam. Reporter stated his engineering department decided to correct for this condition; which they consider a manufacturing misalignment of the cam and centering roller assembly; by installing a shim that raises the aileron input torque tube under the cabin floor boards. Raising the input torque tube would properly align the cam roller bearing to the centering cam assembly; allowing for smoother wear of the roller face. Reporter stated the input torque tube (shaft) upper bearing has to be removed and replaced with a shim added under the bearing. That procedure also requires the removal of the aileron upper quadrant; which is also under the cabin floorboards; just above the upper bearing. Two bolts attach the upper quadrant to the upper section of the input shaft. The problem is the seat track rails that attach to the floor beams and adjacent floor supports; are attached with fasteners that hang down below the supports; and were thought to possibly interfere; with the rotation of the aileron quadrant retaining bolts; depending on how they were installed. Reporter stated he has not seen any further clarification of which direction the bolt heads should face; when installing the upper quadrant. They have not seen any further problems with stiff ailerons on aircraft with the centering cam modifications.

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Original NASA ASRS Text

Title: While accomplishing an Engineering Authorization (EA) for replacement of the aileron centering unit on B737-800 aircraft; a Mechanic reports the illustrations for positioning two bolt heads that secure the upper quadrant were unclear.

Narrative: On Feb/09; work was in progress on Aircraft X. I was working Engineering Authorization replacement of the aileron centering mechanism. To the best of my knowledge; installation is complete; tests are complete; and the aircraft is in service. While preparing to perform the same work on the next aircraft for service; I was looking in detail at the Aircraft Maintenance Manual and Component Maintenance Manual and noticed the quadrant assembly attach bolts. The illustrations showed the bolts installed one head aft; and the other head inboard. The Aircraft Maintenance Manual did not state the bolts had to be installed this way; only the illustrations were drawn that way with no notes on the illustrations as to the direction of bolt installation. Aircraft has the quadrant bolts installed 1 head aft and 1 head outboard. As the next aircraft was being opened up for service; I went to look at the quadrant assembly on that aircraft. I found those quadrant bolts installed 1 bolt head forward and 1 bolt head outboard. I could see no obstruction to movement with the way the bolts were installed. If the bolts were installed in the opposite direction; I do not believe they would interfere with the operation of the aileron centering mechanism. I reported this information to my foreman. I am submitting this report because I am unsure if the bolt installation direction is critical or at the discretion of the Mechanic. A clarification of bolt installation direction; or if the bolt installation direction is at the discretion of the Mechanic; would help mechanics in the future. Callback conversation with reporter revealed the following information: Reporter stated the Engineering Authorization (EA) was issued in response to pilot write-ups for stiff ailerons. After much troubleshooting; mechanics and Engineering determined the problem involved the aileron feel and centering cam roller in the left forward well wheel. The aileron centering unit cam roller face that rides in the centering assembly was not completely aligned; or matched up; with the 3/8 inch face of the cam it was riding against. As a result; a portion of the roller bearing developed an edge from uneven wear against the cam; causing the stiff ailerons; because the cam roller would be slow to center in the cam. Reporter stated his Engineering department decided to correct for this condition; which they consider a manufacturing misalignment of the cam and centering roller assembly; by installing a shim that raises the aileron input torque tube under the cabin floor boards. Raising the input torque tube would properly align the cam roller bearing to the centering cam assembly; allowing for smoother wear of the roller face. Reporter stated the input torque tube (shaft) upper bearing has to be removed and replaced with a shim added under the bearing. That procedure also requires the removal of the aileron upper quadrant; which is also under the cabin floorboards; just above the upper bearing. Two bolts attach the upper quadrant to the upper section of the input shaft. The problem is the seat track rails that attach to the floor beams and adjacent floor supports; are attached with fasteners that hang down below the supports; and were thought to possibly interfere; with the rotation of the aileron quadrant retaining bolts; depending on how they were installed. Reporter stated he has not seen any further clarification of which direction the bolt heads should face; when installing the upper quadrant. They have not seen any further problems with stiff ailerons on aircraft with the centering cam modifications.

Data retrieved from NASA's ASRS site as of April 2012 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.