Airworthiness Directive · Amendment 39-15566 · Boeing Model 747-400, 747-400D, and 747-400F Series Airplanes
Boeing Model 747-400, 747-400D, and 747-400F Series Airplanes
This AD applies to Boeing Model 747-400, 747-400D, and 747-400F series airplanes, certificated in any category, as identified in Boeing Alert Service Bulletin 747-27A2479, dated November 8, 2007.
The FAA is superseding an existing airworthiness directive (AD) that applies to all Boeing Model 747-400, 747-400D, and 747-400F series airplanes. That AD currently requires reviewing airplane maintenance records, doing repetitive inspections for cracking of the yaw damper actuator portion of the upper and lower rudder power control modules (PCMs), replacing the PCMs if necessary, and reporting all airplane maintenance records review and inspection results to the manufacturer. This new AD limits the applicability, reduces the initial inspection threshold and repetitive interval, removes the reporting requirement, and requires installation of a secondary retention device for the yaw damper modulating piston. Installation of the secondary retention device terminates the repetitive inspection requirements. This AD results from additional reports of failure or cracking of the PCM manifold in the area of the yaw damper cavity endcap at intervals well below the initial inspection threshold of the existing AD. We are issuing this AD to prevent an uncommanded left rudder hardover in the event of cracking in the yaw damper actuator portion of the upper or lower rudder PCMs, and subsequent failure of the PCM manifold, which could result in increased pilot workload, and possible runway departure upon landing.
You are responsible for having the actions required by this AD performed within the compliance times specified, unless the actions have already been done.
For any affected airplane, if it can be positively verified that any rudder PCM or PCM main manifold installed on that airplane has accumulated a different total of flight hours or flight cycles than the totals accumulated by that airplane, the flight cycles or flight hours accumulated by the rudder PCM or PCM main manifold will be acceptable as valid starting points for meeting the compliance times required by this AD.
Do an ultrasonic inspection for cracking of the yaw damper actuator portion of the upper and lower rudder PCMs at the applicable times specified in paragraph (g)(1) or (g)(2) of this AD in accordance with the Accomplishment Instructions of Boeing Service Bulletin 747-27A2397, Revision 2, dated September 1, 2005. Doing the installation required by paragraph (j) of this AD ends the inspection requirements of this paragraph for that PCM.
(1) For airplanes that have been inspected before the effective date of this AD in accordance with Boeing Alert Service Bulletin 747-27A2397, dated July 24, 2003; Revision 1, dated March 31, 2005; or Revision 2, dated September 1, 2005: Do the ultrasonic inspection at the later of the times specified in paragraphs (g)(1)(i) and (g)(1)(ii) of this AD. Repeat the inspection thereafter at intervals not to exceed 7,000 flight hours or 1,125 flight cycles, whichever occurs first, until the action required by paragraph (j) of this AD is accomplished.
(i) Within 7,000 flight hours or 1,125 flight cycles after the prior inspection, whichever occurs first.
(ii) Within 6 months after the effective date of this AD.
(2) For airplanes that have not been inspected before the effective date of this AD in accordance with Boeing Alert Service Bulletin 747-27A2397, dated July 24, 2003; Revision 1, dated March 31, 2005; or Revision 2, dated September 1, 2005: Do the ultrasonic inspection at the later of the times specified in paragraphs (g)(2)(i) and (g)(2)(ii) of this AD. Repeat the inspection thereafter at intervals not to exceed 7,000 flight hours or 1,125 flight cycles, whichever occurs first, until the action required by paragraph (j) of this AD is accomplished.
(i) Prior to the accumulation of 14,000 total flight hours or 2,250 total flight cycles, whichever occurs first.
(ii) Within 6 months after the effective date of this AD.
If no cracking is found during any inspection required by paragraph (g) of this AD: Before further flight, apply sealant and a torque stripe and install a lockwire on the rudder PCM in accordance with the Accomplishment Instructions, and Figure 1 or Figure 2, as applicable, of Boeing Service Bulletin 747-27A2397, Revision 2, dated September 1, 2005.
(i) If any cracking is found during any inspection required by paragraph (g) of this AD: Before further flight, do the action in paragraph (i)(1) or (i)(2) of this AD.
(1) Replace the affected PCM with a new or serviceable PCM in accordance with the Accomplishment Instructions of Boeing Service Bulletin 747-27A2397, Revision 2, dated September 1, 2005.
(2) Replace the PCM with a PCM that has the new secondary retention device installed as specified in paragraph (j) of this AD.
Within 24 months or 8,400 flight hours after the effective date of this AD, whichever occurs earlier: Install a new secondary retention device for the yaw damper piston assembly in both the upper and lower PCMs by either replacing the existing PCM with a new improved PCM that already has the new secondary retention device, or by modifying, testing, and re-identifying the existing PCM while the PCM is installed on the airplane. Do the installation in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 747-27A2479, dated November 8, 2007. Doing the installation terminates the inspection requirements of this AD.
Note 1: Boeing Alert Service Bulletin 747-27A2479 refers to Parker Service Bulletins 332700-27-312 and 333200-27-314, both dated September 13, 2007, as additional sources of service information for modifying the PCM.
Actions accomplished before October 13, 2006 (the effective date of AD 2006-18-17), in accordance with Boeing Alert Service Bulletin 747-27A2397, dated July 24, 2003; or Revision 1, dated March 31, 2005; are considered acceptable for compliance with the corresponding requirements of this AD.
As of October 13, 2006, no person may install on any airplane a rudder PCM having a top assembly part number (P/N) 332700-1003, -1005, or -1007; or P/N 333200-1003, -1005, or -1007; unless the PCM has been ultrasonically inspected and found to be without cracks; in accordance with the Accomplishment Instructions of Boeing Service Bulletin 747-27A2397, Revision 2, dated September 1, 2005, as specified by paragraph (g) of this AD.
