Current Regulatory Activity

Air Safety Week, August 23, 2004

Note that just the four problems in this table affect more than 6,000 airplanes worldwide.

Date posted on Federal Register and Document Type: Aug. 6 Notice of Proposed Rulemaking (NPRM) FR Doc 04-17988 Docket No. FAA-2004-18788 Structural safety Summary of Situation: Boeing [BA] B737 classics. Federal Aviation Administration (FAA) proposes an airworthiness directive (AD) to detect and correct fatigue cracking on the forward and aft sides of the forward entry door, "which could result in loss of the forward entry door and rapid decompression of the airplane." Eleven operators reported finding cracking. Below, an example of stresses involved (see comments column):

Action Date & Comments: Comments due Sept. 20. Boeing Special Attention Service Bulletin (SB) applies (equivalent to alert SB?). Inspect within 4,500 flight cycles or before 15,000 total flights. These forward door-surround cracks may stem from the lack of continuous integrity support around a forward door after the main wheels have touched down and any residual pressurization differential is dumped - well before the pilot places the nose-wheel on the deck (firmly, gently or vigorously). Once the pressurization has gone, the door is no longer supporting the (doorway) hole - and the stress concentration of nosewheel touchdown (and nose-gear transmitted vibration) is on the door's surrounding spar webs, stringers and intercostals. It's a cumulative fatigue damage scenario. For evidence of the stresses involved on nosewheel placement. From the other viewpoint, when the differential is increasing, the fuselage is blowing up like a balloon - yet the plug door is a static entity - and so one might have yet

Date posted on Federal Register and Document Type: Aug. 6 NPRM FR Doc 04-17990 Docket No. FAA-2004-18729 Fuel system safety

Summary of Situation: Boeing B747-100 & -200 airplanes. Proposed AD requires installation of bonding clips and jumpers for the housing of each fuel pump to aircraft structure. Electrical bonding deemed inadequate. Of significant note in the NPRM: "On the affected airplanes, a special corrosion protection finish used on the fuel tank acts as a partial insulator. Given a lightning strike or pump electrical fault, arcing can occur at this existing interface, which is inside the fuel tank. This condition, if not corrected, could result in ignition [and] ... a fuel tank explosion."

Action Date & Comments: Comments due Sept. 20. Boeing alert SB applies. Inspect and fix within 60 months. This AD is an outcome of the SFAR 88-related fuel system safety review. As one observer quipped, seems like someone slept through Failure Modes and Effects Analysis (FMEA 101) and this one got through, a few decades ago. Action affects 158 planes worldwide.

Date posted on Federal Register and Document Type: Aug. 9 NPRM FR Doc 04-17985 Docket No. FAA-2004-18784 Fuel and powerplant system safety. ASW note: This one comes under the heading of truly adding fuel to the fire. Summary of Situation: Boeing B747-400, B767-200 & -300, and B777-200 & -300 airplanes. FAA is proposing an AD requiring installation of a jumper wire between the wiring of the fire extinguisher switch and the fuel shutoff switch. FAA says "a certain combination of conditions could cause the fuel spar shutoff valves to remain partially open when the engine fire switch is activated, which could result in fuel from the engine feeding an uncontrolled fire in the engine or the strut." "We are issuing this AD to prevent a latent open circuit that could leave the fuel spar shutoff valves to remain in a partially open position when the engine fire switch is activated," the NPRM explains. Action Date & Comments: Comments due Sept. 20. FAA says the AD is necessary to prevent a "latent open circuit." Boeing "Special Attention" SBs apply. SBs do not provide a compliance time. FAA is proposing 60 months. There are some things the NPRM does not say. For example, why would such a tricky trap spring up so late in the life of all these airplanes? The NPRM is not clear about the "latent" open circuit, but it may relate to the automatic generator/bus-tie switching that takes place on engine shutdown - during which the fuel shutoff switch would be energizing a solenoid that would drive the relevant fuel valve closed. That process of OPEN to CLOSED takes finite time. During that interval of a few milliseconds, if the power drops and that relay should (as a result) spring open, the solenoid's power would have been lost, so there would be no real assurance that the fuel valve would have been entirely closed. By inserting another source of relay and/or solenoid power from the fire extinguisher squibfiring relay, it appears

Date posted on Federal Register and Document Type: Aug. 9 Final Rule FR Doc 04-17979 AD 2004-16-09 Structural safety

Summary of Situation: B747 airplanes. Repetitive inspections and repairs are being mandated to prevent bulges (described as "oil cans") in the aft pressure bulkhead that can lead to explosive decompression, tail section damage and consequent loss of control of the airplane. An oil can is described as an area on the pressure dome that moves when pushed from the forward, or pressurized side.