Federal Aviation Administration May 26, 2006 – Federal Register Recent Federal Regulation Documents

The FAA is revising an earlier NPRM for an airworthiness directive (AD) that applies to certain Airbus Model A330 airplanes and Model A340-200 and -300 series airplanes. The original NPRM would have required repetitive detailed inspections for cracking in the aft web of support rib 6 between certain bottom skin stringers on both wings; high frequency eddy current inspections for cracking of the attachment holes of the fuel pipes, and repair if necessary. The original NPRM also would have provided for an optional modification, which would extend a certain inspection threshold. The original NPRM resulted from a report of significant cracking found in the aft web of support rib 6 on both wings. This action revises the original NPRM by mandating, for certain airplanes, a new modification of support rib 6 on both wings, which would end the repetitive inspection requirement. This action also reduces the applicability in the original NPRM. We are proposing this supplemental NPRM to prevent cracking in the aft web of support rib 6, which could result in overloading of adjacent ribs and the surrounding wing structure and consequent reduced structural integrity of the wing.

The FAA is revising an earlier proposed airworthiness directive (AD) for certain Boeing Model 737-300, -400, -500, -600, - 700, -700C, -800, and -900 series airplanes. The original NPRM would have required modifying the wiring for the master dim and test system. For certain airplanes, the original NPRM also proposed to require related concurrent actions as necessary. The original NPRM resulted from a report that the master dim and test system circuit does not have wiring separation of the test ground signal for redundant equipment in the flight compartment. This action revises the original NPRM by adding a new concurrent action for certain airplanes, extending the compliance time, and removing certain airplanes from concurrent requirements. We are proposing this supplemental NPRM to prevent a single fault failure in flight from simulating a test condition and showing test patterns instead of the selected radio frequencies on the communications panels, which could inhibit communication between the flightcrew and the control tower, affecting the continued safe flight of the airplane.

This document revises an earlier proposed airworthiness directive (AD), applicable to certain Boeing Model 737-300, -400, -500, -600, -700, -700C, -800, and -900, and 747-400 series airplanes; and Model 757, 767, and 777 airplanes. The original NPRM would have required modifying the static inverter by relocating resistor R170 of the static inverter bridge assembly. This new action revises the original NPRM by adding a new requirement for modifying the static inverter by replacing resistor R170 with a new resistor and relocating the new resistor. The actions proposed by this supplemental NPRM are intended to prevent a standby static inverter from overheating, which could result in smoke in the flight deck and cabin and loss of the electrical standby power system. This action is intended to address the identified unsafe condition.

The FAA is adopting a new airworthiness directive (AD) for all Boeing Model 767 airplanes. This AD requires repetitive measurements of the rudder and elevator freeplay, repetitive lubrication of rudder and elevator components, and related investigative/corrective actions if necessary. This AD results from reports of freeplay-induced vibration of the rudder and the elevator. The potential for vibration of the control surface should be avoided because the point of transition from vibration to divergent flutter is unknown. We are issuing this AD to prevent excessive vibration of the airframe during flight, which could result in loss of control of the airplane.

The FAA is superseding an existing airworthiness directive (AD), which applies to certain Boeing Model 757 series airplanes. That AD currently requires revising the Airworthiness Limitations section of the maintenance manual (757 Airworthiness Limitations Instructions (ALI)) to incorporate certain inspections and compliance times to detect fatigue cracking of principal structural elements (PSEs). This new AD requires incorporating a new revision to the Airworthiness Limitations section of the Instructions of Continued Airworthiness to mandate certain repetitive inspections for fatigue cracking of PSEs, and adds airplanes to the applicability in the existing AD. This AD results from a new revision to the ALI. We are issuing this AD to ensure that fatigue cracking of various PSEs is detected and corrected; such fatigue cracking could adversely affect the structural integrity of these airplanes.