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Safety Recommendation Details

Safety Recommendation A-09-047
Details
Synopsis: On June 28, 2008, about 2215 Pacific daylight time, an ABX Air Boeing 767-200, N799AX, operating as flight 1611 from San Francisco International Airport (SFO), San Francisco, California, experienced a ground fire before engine startup. The captain and the first officer evacuated the airplane through the cockpit windows and were not injured, and the airplane was substantially damaged. The cargo flight was operating under the provisions of 14 Code of Federal Regulations (CFR) Part 121. At the time of the fire, the airplane was parked near a loading facility, all of the cargo to be transported on the flight had been loaded, and the doors had been shut.
Recommendation: TO THE FEDERAL AVIATION ADMINISTRATION: Require airplane manufacturers and operators to ensure that oxygen system tubing in proximity to electrical wiring is made of, sleeved with, or coated with nonconductive material or that the tubing is otherwise physically isolated from potential electrical sources.
Original recommendation transmittal letter: PDF
Overall Status: Closed - Acceptable Alternate Action
Mode: Aviation
Location: San Francisco, CA, United States
Is Reiterated: No
Is Hazmat: No
Is NPRM: No
Accident #: DCA08MA076
Accident Reports: Ground Fire Aboard Cargo Airplane, ABX Air Flight 1611, Boeing 767-200, N799AX
Report #: AAR-09-04
Accident Date: 6/28/2008
Issue Date: 7/8/2009
Date Closed: 3/26/2013
Addressee(s) and Addressee Status: FAA (Closed - Acceptable Alternate Action)
Keyword(s): Hazmat

Safety Recommendation History
From: NTSB
To: FAA
Date: 3/26/2013
Response: The FAA’s requirement for electrical wiring interconnection system (EWIS) maintenance programs, effective March 10, 2011, completes the FAA’s actions to satisfy these recommendations in an alternate manner; consequently, Safety Recommendations A-09-46 and -47 are classified CLOSED—ACCEPTABLE ALTERNATE ACTION.

From: FAA
To: NTSB
Date: 1/15/2013
Response: -From Michael P. Huerta, Administrator: The FAA provided information related to the applicable regulations and guidance associated with these two safety recommendations in our previous letter of July 13, 2011. The Board stated that an additional regulation specifically requiring the separation of oxygen equipment from electrical is not necessary and also noted that the existing regulations described in the FAA letter did not prevent the wiring problems that were found on the ABX Air airplanes. The Board asked that we describe additional actions we intend to take to ensure compliance with existing regulations regarding the separation of oxygen lines from potential ignition sources. In addition to the airworthiness standards and associated guidance described in the FAA letter dated July 13, 20 II , we have added new operational requirements for electrical wiring interconnection system (EWIS) maintenance programs. Title 14, Code of Federal Regulations (14 CFR) 121.1111 and 129.111 require that after March 10, 2011 no certificate holder or foreign air carrier may operate an applicable airplane unless the maintenance program for that airplane includes inspections and procedures for EWIS. The intent of the new operating regulations and airworthiness standards is to help ensure the continued safety of commercial airplanes by improving the design, installation, and maintenance of electrical wiring systems. Guidance used for compliance to the new operating regulations is provided in AC 120-102 dated July 29, 2010. Although the operating regulations noted above had been published and were in effect during inspection of the ABX airplanes, operators were not yet required to comply. At the time of the ABX inspections, design approval holders were still developing their instructions for continued airworthiness (ICA) for the EWIS maintenance programs. As of March 10, 2011, pan 121 and 129 operators have included inspections and procedures for EWIS, based on those ICA, in their maintenance program. The maintenance program improvements are intended to increase the overall level of safety related to electrical wiring systems. I believe that the FAA has effectively addressed Safety Recommendations A-09-46 and -47 and consider our actions complete.

From: NTSB
To: FAA
Date: 10/17/2011
Response: The NTSB agrees with the FAA that, because of the numerous current regulations (some dating back to February 1965) that require the separation of oxygen sources from potential electrical ignition sources, an additional regulation specifically requiring the separation of oxygen equipment from electrical wiring is not necessary. The FAA indicated that it considers its actions in response to these recommendations to be complete. However, we remain concerned by the findings of our investigation of the ABX flight 1611 accident. In the letter issuing these recommendations to the FAA, we stated the following: During postaccident inspections of other ABX Air 767 airplanes that were modified by IAI [Israeli Aircraft Industries], some installations were found to have electrical wiring in proximity to the stainless steel oxygen supply tubing. Other installations (both in the cockpit and supernumerary compartment) were found to have electrical wiring that was routed above and in direct contact with the oxygen tubing, even though the supplemental type certificate [STC] provided for positive separation. The existing regulations reviewed by the FAA and described in your letter did not prevent the wiring problems that were found on the ABX Air airplanes. Before we close these recommendations, we ask that you describe what further actions the FAA will take to ensure compliance with its existing regulations regarding the separation of oxygen lines from ignition sources. Pending our receipt of that information, Safety Recommendations A-09-46 and -47 remain classified OPEN—ACCEPTABLE RESPONSE.

From: FAA
To: NTSB
Date: 7/13/2011
Response: CC# 201100278: - From J. Randolph Babbitt, Administrator: We conducted a review of current FAA guidance and concluded that an additional regulation specifically requiring separation of oxygen equipment from electrical wiring is not necessary. Applicable regulations and guidance include all of the following: • Section 25.1441(b) which states, "[t]he oxygen system must be free from hazards in itself, in its method of operation, and in its effect upon other components." • Advisory Circular (AC) 25-22 contains a brief history of § 25.1441, which has been in effect since February 1965. AC 25-22 provides general guidance on this regulation and identifies that industry practice has been to separate and isolate the oxygen system from sources of ignition. • AC 25-16 contains information on the importance of separating wiring from equipment whose subsequent failure, caused by arcing, could cause further damage. AC 25-16 specifically states, when referring to wiring installation clamps, "[t]he clamps should be a compression type and should be spaced so that, assuming a wire break, the broken wire will not contact hydraulic lines, oxygen lines, pneumatic lines, or other equipment whose subsequent failure caused by arcing could cause further damage." Electrical wiring interconnection systems (EWIS) rules were added to part 25, along with related requirements in parts 26, 121, and 129 to enhance the safety of airplane wiring systems in December 2007. These new rules codified the FAA's belief that airplane wiring must be viewed as an airplane system and not something that simply connects one airplane system to another. Section 25.1707(a) states, "[e]ach EWIS must be designed and installed with adequate physical separation from other EWIS and airplane systems so that a EWIS component failure will not create a hazardous condition. Unless otherwise stated, for the purposes of this section, adequate physical separation must be achieved by separation distance or by a barrier that provides protection equivalent to that separation distance." Regarding separation from oxygen systems, section 25.1707(g) states, "[e]xcept to the extent necessary to provide electrical collection to the oxygen systems components, EWIS must be designed and installed with adequate physical separation from oxygen lines and other oxygen system components, so that an EWIS component failure will not create a hazardous condition." • AC 25.1701-1 contains guidance for certification of EWIS on transport category airplanes. This AC contains a section on physical failure analysis which states it should be assumed that wires are carrying electrical energy and that in the case of an EWIS failure this energy may result in hazardous or catastrophic effects directly or when combined with other factors, for example fuel, oxygen, hydraulic fluid, or damage by passengers. We believe that existing regulations and guidance already require separation of oxygen equipment from ignition sources, which includes electrical wiring. The FAA considers separation of oxygen equipment from potential ignition sources, which includes electrical wiring, necessary for compliance to these regulations. During the airplane certification process we review the instructions for continued airworthiness to ensure appropriate cautionary notes and instructions are included in the maintenance documentation for the oxygen system, wiring, and other EWIS components. In addition, general aerospace standards, such as Aerospace Information Report (AIR) 825/12, Oxygen System Integration and Performance Precautions, contain information on the protection of oxygen equipment from potential ignition sources, separation from wiring, and protection from potential electrical current. I believe that the FAA has effectively addressed this safety recommendation, and I consider our actions complete.

From: NTSB
To: FAA
Date: 7/9/2010
Response: The NTSB is pleased that the FAA has assembled an interdisciplinary team of technical specialists to address these safety issues and looks forward to reviewing the FAA's findings related to Safety Recommendations A-09-44 and A-09-46 through -53 and, more importantly, its plan for addressing the safety deficiencies identified in these recommendations. Pending the NTSB's review of this information, Safety Recommendations A-09-44 and A-09-46 through -53 are classified OPEN – ACCEPTABLE RESPONSE.

From: NTSB
To: FAA
Date: 12/4/2009
Response: Notation 8116C: The National Transportation Safety Board (NTSB) has reviewed the Federal Aviation Administration’s (FAA) notice of proposed rulemaking (NPRM) titled, “Airworthiness Directives; Boeing Model 757 Airplanes,” which was published in 74 Federal Register 49827 on September 29, 2009. This NPRM proposes an airworthiness directive (AD) requiring the inspection of certain Boeing 757 airplanes to verify the part number of the flight crew and supernumerary oxygen system low pressure flex-hoses installed under the oxygen mask stowage boxes to ensure that the hoses are of a nonconductive design. The AD would require replacement of the older electrically conductive hoses. This NPRM also notes that the FAA plans to issue similar rules applicable to Boeing 737, 747, and 767 airplanes. The proposed AD results from an August 1997 incident, in which a hole was created in a low pressure flex hose in the flight crew oxygen system due to an electrical short circuit in an adjacent audio select panel. Following the incident, Boeing released Service Bulletins 757-35A-0015, Revision 2 and 757-35-A0016, Revision 1, both dated June 15, 2000, addressing the replacement of electrically conductive hoses. This proposed rule is partially consistent with three NTSB safety recommendations that resulted from the investigation of a June 28, 2008, preflight ground fire, which destroyed an ABX Air Boeing 767-200, N799AX, at San Francisco International Airport, San Francisco, California. The NTSB determined that the probable cause of that fire was the design of the supplemental oxygen system hoses and the lack of positive separation between electrical wiring and electrically conductive oxygen system components, as well as the FAA’s failure to require the installation of nonconductive oxygen hoses after Boeing initially identified the safety issue concerning conductive hoses. The NTSB issued the following safety recommendations to the FAA: Require operators to replace electrically conductive combustible oxygen hoses with electrically nonconductive hoses so that the internal hose spring cannot be energized. (A-09-43) Prohibit the use of electrically conductive combustible oxygen hoses unless the conductivity of the hose is an intentional and approved parameter in the design. (A 09 44) Require airplane manufacturers and operators to ensure that oxygen system tubing in proximity to electrical wiring is made of, sleeved with, or coated with nonconductive material or that the tubing is otherwise physically isolated from potential electrical sources. (A 09 47) These recommendations are currently classified “Open—Await Response.” The FAA’s initial response, dated September 23, 2009, is currently under review by the NTSB. The NTSB fully supports NPRM FAA-2009-0795 and welcomes future rules that would address similar installations in other Boeing models. However, the NTSB notes that this proposed rule and the future rules mentioned in the NPRM would apply only to Boeing airplanes and that the NTSB’s recommendations above are not restricted to those airplanes. Suppliers provide other airplane manufacturers with low-pressure oxygen hoses that are nearly identical to those that this proposed AD seeks to identify and replace. Because the risk of fire from electrically conductive hoses is not restricted to Boeing models, the NTSB urges the FAA to widen the inspection and replacement of oxygen hoses beyond the airplanes cited in this proposed rule. Thank you for the opportunity to comment on this NPRM.

From: FAA
To: NTSB
Date: 9/23/2009
Response: Letter Mail Controlled 10/5/2009 12:30:33 PM MC# 2090617 - From J. Randolph Babbitt, Administrator: To comprehensively address Safety Recommendations A-09-44, and A-09-46 through -53, the FAA has assembled a team of specialists from various technical disciplines to review the recommendations and assess the underlying safety issues. Following this review we will develop a plan to address each recommendation.