Airworthiness Directive · Amendment 39-17641 · Flight controls
Bombardier, Inc. Airplanes
This AD applies to Bombardier, Inc. Model DHC-8-400, -401, and -402 airplanes, certificated in any category, serial numbers (S/N) 4001, 4003 and subsequent, equipped with rudder feel trim unit (RFTU) part number (P/N) 399500-1007.
We are adopting a new airworthiness directive (AD) for certain Bombardier, Inc. Model DHC-8-400, -401, and -402 airplanes. This AD was prompted by reports of movement of the rudder pedals being impeded due to corrosion of the trunnion shaft of the rudder feel trim unit (RFTU). This AD requires an inspection to determine if certain RFTUs are installed, an operational check for signs of seizure of affected parts, repetitive lubrication of certain RFTUs, and replacement of the RFTU if necessary. Installing replacement RFTUs having conformal bushings terminates the repetitive lubrication requirements. We are issuing this AD to detect and correct any sign of rough movement or seizure of the trunnion shaft and its bushing, which could cause a rudder control jam or a large and rapid alternating rudder input leading to a structural failure of the vertical fin.
You are responsible for having the actions required by this AD performed within the compliance times specified, unless the actions have already been done.
Within 200 flight hours or two months after the effective date of this AD, whichever occurs first: Inspect the RTFU to determine whether the serial number is in the range from S/N 0008 through 0509 inclusive without a suffix `B,' in accordance with the Accomplishment Instructions of Bombardier Service Bulletin 84-27-60, dated July 12, 2012. A review of airplane maintenance records is acceptable in lieu of this inspection if the serial number of the RFTU can be conclusively determined from that review.
(1) If the RFTU's serial number is not in the range from S/N 0008 through 0509 inclusive, or if the serial number has a suffix `B,' no further action is required for this paragraph.
(2) If the RFTU's serial number is in the range from S/N 0008 through 0509 inclusive, including those with a suffix `A,' but not including those with suffix `B': Within 200 flight hours or 2 months, whichever occurs first after the effective date of this AD, perform an operational check of the RFTU for any sign of rough movement or seizure of the trunnion or center shaft, in accordance with the Accomplishment Instructions of Bombardier Service Bulletin 84-27-60, dated July 12, 2012.
(i) If rough movement or seizure of the RFTU trunnion or center shaft is found: Before further flight, replace the RFTU with a new or serviceable RFTU, in accordance with the Accomplishment Instructions of Bombardier Service Bulletin 84-27-60, dated July 12, 2012.
(ii) If no rough movement or seizure of the RFTU trunnion or center shaft is found: Before further flight, lubricate the RFTU, in accordance with the Accomplishment Instructions of Bombardier Service Bulletin 84-27-60, dated July 12, 2012. Repeat the lubrication of the RFTU at intervals not to exceed 600 flight hours or 3 months, whichever occurs first, until the RFTU is replaced with a unit that has a serial number outside the affected range or a serial number with a suffix `B.'
For airplanes having an RFTU identified in paragraph (g)(2) of this AD: Except as required by paragraph (g)(2)(i) of this AD, within 5,000 flight hours or 3 years after the effective date of this AD, whichever occurs first, replace all affected RFTUs with units that have a serial number outside the range from S/Ns 0008 through 0509 inclusive, or that have a serial number with a suffix `B,' in accordance with the Accomplishment Instructions of Bombardier Service Bulletin 84-27-60, dated July 12, 2012. Installing replacement RFTUs having conformal bushings terminates the repetitive lubrication requirements of paragraph (g)(2)(ii) of this AD for the affected RTFU.
As of the effective date of this AD, no person may install an RFTU P/N 399500-1007 with a serial number from S/N 0008 through 0509 inclusive, including serial numbers with suffix `A,' on any airplane, except that RFTUs having a serial number with suffix `B' may be installed.
