23.1443 Minimum mass flow of supplemental oxygen
There are no corresponding rule or airworthiness criteria in CAR 3 or the Airship Design Criteria.
Original Issue and Subsequent
When there is full compliance to this regulation, there is no need to consider the likelihood of a pressurization failure or to require an immediate descent in altitude if a failure occurs. Compliance should include the consideration of a rapid explosive decompression to ambient pressure with a pilot recognition and reaction time of 17 seconds to initiate a descent.
1. The airplane may be altitude-lim ited to meet this requirement, or
2. The applicant may provide an ELOS finding.
Amendment 23-9 and Subsequent
This amendment adopted a proposed revision in NPRM 67-30 that stated: “In connection with the standards for minimum mass flow of supplemental oxygen, the proposed Sec. 23.1443 contains requirements for continuous flow but not for demand flow oxygen equipment. The requirements of the more commonly used continuous flow systems are thus covered, while the mass flow of demand systems, where such systems are used, would be approved on a case-by-case basis as before.”
This amendment is clarified by Final Rule, Docket 8281, as follows: “One commentator suggested incorporating a provision in Sec. 23.1443 which would require compliance with the proposed graph (depicting oxygen mass flow rates) only up to the cruising altitude for which type certification of the airplane is desired. The recommendation is premised on the contention that it is unnecessary and economically unreasonable to install oxygen equipment capable of a specified mass flow rate at 40,000 feet if the airplane will be operated at a much lower altitude. The purpose of Sec. 23.1443 is to show the minimum oxygen mass flow rates which would be required for each occupant of an airplane at the corresponding cabin pressure altitudes. The applicant for a type certificate would not be required to install oxygen equipment capable of supplying the minimum oxygen mass flow rates for the entire range of cabin pressure altitudes shown in the graph unless his airplane is capable of operating through the entire range. Accordingly, Sec. 23.1443 is revised to state that the oxygen equipment installed in the airplane must be capable of supplying to each occupant the appropriate flow of oxygen for all altitudes up to and including the maximum operating altitude of the airplane.”
333 Amendment 23-43 and Subsequent
This amendment adopted a proposed revision in NPRM 90-23 that stated: “This proposal modifies the oxygen flow rates for small airplanes. These new requirements are needed for current and future airplanes that will be certificated to higher altitudes where oxygen is required.
Conference proposal 472 recommended revising Section 23.1443 by designating the present paragraph as paragraph (a) and adding a new paragraph (b) to read essentially the same as Section 25.1443(b). The justification given was that "The oxygen flow rate requirements of parts 23 and 25 are different. However, both regulations provide requirements needed to ensure continuous flow rates up to cabin pressure altitudes of 40,000 feet. Proposed Section 23.1443 is a combination of these requirements. Proposed Section 23.1443(a) contains current Section 23.1443 with regard to continuous flow requirements, and Section 23.1443(b) is derived from Section 25.1443 for demand system requirements. The language of the recommended change would allow Section 23.1443 to cover both continuous flow oxygen and demand systems without interpretation from part 25."
“Conference proposal 473 recommended revising § 23.1443 essentially as shown in this proposal since the oxygen flow rate requirements of parts 23 and 25 are different. However, both regulations provide requirements needed to assure continuous flow rates up to cabin pressure altitudes of 40,000 feet. Proposed § 23.1443 is a combination of these requirements. Sections 23.1443 (a)(1) and (a)(2) contain the continuous flow requirements of part 25 and allow the applicant to comply with those requirements or with paragraph (a)(3), which is the current continuous flow requirement of part 23. Demonstrating compliance with proposed § 23.1443(a)(3) is easier, but results in a larger volume of oxygen and more weight.
Demonstrating compliance with § 23.1443 (a)(1) and (a)(2) is harder, but results in a lesser volume of oxygen. By allowing the applicant to choose either method of compliance, this requirement permits freedom of design.
When presented for comment at the conference, the FAA confirmed that this conference proposal would allow alternatives of continuous flow oxygen equipment or demand oxygen equipment. With a good face-fitting mask, less oxygen will be used with a demand system than with a continuous flow system. Studies on altitude sickness and the impairment of ability to function on continuous flow equipment at altitudes above 25,000 feet leads the FAA to reconsider this issue, especially for flight crews.
Proposed paragraph (c) provides the flow rate requirements for first-aid oxygen equipment if installed, but does not require its installation. These requirements are identical to the first-aid oxygen flow rate requirements in part 25. With the recent addition on commuter category airplanes in part 23, first-aid oxygen equipment is more likely to be installed in part 23 airplanes.
334 Proposed paragraph (d) is clarifying by providing definitions of the term "BTPS" and "STPD" as used in this section.
Post conference review of these comments and the oxygen requirements of parts 91, 121, and 135 led to the conclusion that (1) adding the equivalent of the part 25 oxygen requirements to part 23 will provide adequate protection for both flight crew and passengers; and (2) that crewmembers should have demand oxygen equipment for operations above 25,000 feet.”
This amendment is clarified by Final Rule, Docket 26344, as follows: “This proposes to amend Sec. 23.1443 to modify the oxygen flow rates for part 23 airplanes by providing alternate procedures that may be used to substantiate satisfactory continuous flow oxygen equipment. One commenter requested that the FAA make it clear that the 40,000 foot altitude limit in this proposal is not an absolute altitude limit for part 23 airplanes. The FAA agrees. The altitude limit in this proposal does not constitute an absolute altitude limit for the approval of part 23 airplanes;
however, the approval of individual airplanes would be limited to those altitudes where safe occupant protection is provided.”
Amendment 23-62 and Subsequent
In Docket No. FAA-2009-0738, the Discussion of the Regulatory Amendments stated: Currently FAA addresses oxygen systems for airplanes operating above 41,000 feet using special conditions derived from part 25. A large number of new jet and high performance airplanes entering part 23 certification will operate at higher altitudes than previously envisioned for part 23 airplanes. FAA proposes revisions to §§ 23.1443, 23.1445, and 23.1447 to establish requirements for oxygen systems that would eliminate the need for special conditions for airplanes operating above 41,000 feet.
This amendment requires supplemental oxygen be supplied to passengers by a continuous flow system if the service ceiling exceeds 41,000 feet.
The Final Rule adopts a comment that the proposed rule conflicted with another rule for crew oxygen equipment since a continuous oxygen system is not acceptable for the crew at that altitude. The FAA agrees. Section 23.1443(a) is modified to apply continuous flow oxygen systems only to passengers for operations above 25,000 feet, as required by § 23.1441(d).
23.1445 Oxygen distribution system
There are no corresponding rule or airworthiness criteria in CAR 3 or the Airship Design Criteria.
Amendment 23-43 and Subsequent
This amendment adopted a proposed revision in NPRM 90-23 that stated: “This proposal will establish standards for oxygen distribution systems not heretofore required. These requirements will prevent installation of plastic hoses in pressurized oxygen systems.
Conference proposal 474 recommended adopting equipment standards for oxygen systems essentially the same as proposed here. The justification given was that several accidents have occurred in airplanes where nylon tubing was used in an oxygen system pressurized to 70 psi. Because oxygen can support vigorous combustion, oxygen system installations warrant special attention in certification programs.
When presented for comment at the conference, the two commenters agreed that pressurized plastic tubing is inappropriate for oxygen system but did not completely agree with the proposal because they believed the rules should not specifically preclude all nonmetallic tubing. Some composite airplanes may need nonmetallic oxygen lines for lightning strike protection. In view of these comments, a phrase that allows a showing of suitability to the installation was added to the proposal.”
The guidance in this AC for § 23.1441, Amendment 23-9 and subsequent, for plastic lines is applicable to this regulation.
Amendment 23-62 and Subsequent
In Docket No. FAA-2009-0738, the Discussion of the Regulatory Amendments stated: Currently FAA addresses oxygen systems for airplanes operating above 41,000 feet using special conditions derived from part 25. A large number of new jet and high performance airplanes entering part 23 certification will operate at higher altitudes than previously envisioned for part 23 airplanes. FAA proposes revisions to §§ 23.1443, 23.1445, and 23.1447 to establish requirements for oxygen systems that would eliminate the need for special conditions for airplanes operating above 41,000 feet.
This amendment requires the flightcrew be able to reserve the minimum supply they need if they share a common source of oxygen with passengers.
The Final Rule is adopted as proposed.
23.1447 Equipment standards for oxygen dispensing units
There are no corresponding rule or airworthiness criteria in CAR 3 or the Airship Design Criteria.
Amendment 23-9 and Subsequent
This amendment is clarified by Final Rule, Docket 8281, as follows: “It was recommended that paragraphs (b) and (c) of proposed Sec. 23.1447 be revised to specify that they are applicable only to pressurized airplanes. The commentator asserts that these proposals should not apply to nonpressurized airplanes, which are not subject to sudden-decompression occurrences. The FAA agrees and this has been made clear in the final rule. In addition, further FAA studies have shown that for those pressurized aircraft designed to operate at 25,000 feet MSL or below, the pilot will have sufficient time to descend to safer altitudes prior to the onset of any symptoms of hypoxia in the event of a sudden decompression. For this reason, the proposal in paragraph (b) of Sec. 23.1447, requiring an oxygen supply terminal and unit of oxygen dispensing equipment within reach of each member of the required minimum flight crew for those airplanes designed to operate at flight altitudes up to and including 25,000 feet, is unnecessary and has not been adopted.”
The Small Airplane Directorate was recently asked for applicable policy about the requirements for (1) operation above 25,000 feet, dispensing units be immediately available to each occupant wherever seated, and for (2) operation above 30,000 feet, dispensing units be automatically presented to each occupant before the cabin pressure altitude exceeds 15,000 feet. Item (1) was incorporated into part 23 by Amendment 23-9 and item (2) above by Amendment 23-20. These rules were based on seats that were fixed in location and orientation. The question arises from the use of swiveling and tracked seats where it is possible for some occupants to move their seat into an orientation where an automatically presented dispensing unit will not be in view.
The following guidance is applicable to an airplane with a certification basis of Amendment 23-9 or subsequent. This guidance is taken from AC 25-17, section 25.1447, where the issue of tracked and swiveled seats has been addressed.
Automatic presentation is acceptable if the dispensing unit (mask) is presented in front of the eyes when the person's head is resting on the seat back cushion with the seat in any position, either as upright, reclined, swiveled or tracked. The mask need not be presented in front of all people if there is sufficient “crowd awareness,” that is, the vast majority has proper presentation and the others can readily see the masks have been presented. These latter people should have a preflight briefing clearly showing them the location of their mask. The mask should be reachable with the seat belt fastened. In some seating arrangements, such as executive interiors, the various seating positions result in many different group combinations. Each combination
337 should have an adequate number of masks reachable by every person. Consideration should be given to minimizing the likelihood of people taking the wrong masks, thus depriving another person of their mask. If the mask must be pulled to initiate oxygen flow, the mask should be presented so that the person must pull the mask to don it.
The fifth percentile female and ninety-fifth percentile male should be considered.
Either as sleeper seats, bunks or lavatories a streamer of webbing attached to the mask is acceptable to enable the person to pull the mask down to them.
Amendment 23-30 and Subsequent
This amendment adopted a proposed revision in NPRM 75-23 that stated: “The proposal would require automatic presentation of oxygen dispensing units on airplanes certificated under Part 23 for operations above 30,000 feet. Should loss of pressurization occur at those altitudes, the time of useful consciousness varies between 90 seconds at 30,000 feet and 10-12 seconds at 40,000 feet, necessitating automatic presentation of oxygen dispensing units. It is also proposed to specify 14,000 feet as the cabin pressure altitude at which they must be automatically presented so that they would be ready for use not only when the cabin pressure altitude goes very rapidly to very high values but also in the event of a pressurization system failure or malfunction after which (under present Sec. 23.841(a)) the cabin pressure altitude may go to 15,000 feet. The 14,000-foot cabin pressure altitude for automatic presentation is also being proposed for Part 25.
In addition, since service experience has shown that the automatic presentation feature may fail, it is proposed that a manual means be provided to enable each occupant to gain access to his oxygen dispensing unit. This manual means is also being proposed for Part 25.”
This amendment is clarified by Final Rule, Docket 14625, as follows: “For comments related to the proposal to add new Secs. 23.1447(c) and (d), and for an explanation of the revisions made to proposed Secs. 23.1447(c) and (d), see Proposal
5-34. One commentator objected to the provision in proposed Section 25.1447(c)(1) which would require that oxygen dispensing units be automatically presented before the cabin pressure altitude exceeds 14,000 feet, contending that long-standing FAA policy has been that the altitude for automatic presentation should be 15,000 feet and service experience over the last 16 years has not shown a need to reduce that altitude.
The commentator further stated that the flight crew is given a warning when or before the cabin pressure altitude reaches 10,000 feet and is therefore alerted (in the event of a gradual increase in cabin pressure altitude) to the need for appropriate action either to maintain a safe cabin pressure altitude or manually deploy the dispensing units. Another commentator suggested that the presentation altitude be 14,500 feet, rather than 14,000 feet, to take equipment tolerances into account. In light of the comments received and after further review, the FAA believes that there is insufficient evidence at the present time to justify a requirement for the automatic presentation of oxygen dispensing units before the cabin pressure altitude exceeds 14,000 feet, and
338 that the widely-used value of 15,000 feet provides an adequate level of safety.
Proposed Section 25.1447(c)(1) is revised accordingly.
Several commentators disagreed with the provision in proposed Section
25.1447(c)(1) that would require that each occupant be provided with a manual means to make the oxygen dispensing unit immediately available, contending that manual back-up for the automatic presentation system should be provided for use by the crew only, to avoid tampering by the passengers. Another commentator stated that the average passenger would not be capable of operating such manual means properly and quickly, and that manual means are not feasible for ceiling or hatrack mounted dispensing units.
The FAA believes that a manual means must be provided to back up the automatic presentation system, but is persuaded that it may not be in the interest of safety to require that a manual means be provided for passengers. Accordingly, proposed Section 25.1447(c)(1) is revised to require only that a manual means for the development of the dispensing units be provided for the crew.”
This amendment allows the use of nasal cannulas for operation up to an altitude of 18,000 feet MSL. These are simple devices with no known service problems, and the FAA has not developed a design standard for them.
Section 23.1447(e) requires that oxygen masks be automatically presented to each occupant before the cabin pressure exceeds 15,000 feet for airplanes certificated for operation above 30,000 feet MSL. Before the cabin pressure altitude exceeds 15,000 feet, the oxygen mask should fall down automatically and present itself to a 95th percentile human occupant at mouth level within the visual periphery. All the occupant should have to do is pull the mask from the hanging position, don the mask, and start breathing.
Amendment 23-43 and Subsequent
In a proposed revision in NPRM 90-23, Amendment 23-43 adopted this change with the following explanation: “This proposal would add presentation requirements for the demand oxygen equipment required by Section 23.1441(d) and allow the option of quick-donning type oxygen dispensing units.”
Amendment 23-49 and Subsequent
This amendment adopted a proposed revision in NPRM 94-21 that stated:
“Proposed new Sec. 23.1447(a)(4) would require that if radio equipment is installed in an airplane, flightcrew oxygen dispensing units must be designed to allow the use of communication equipment when oxygen is being used. If radio equipment is installed, that equipment cannot perform its intended function if the flightcrew is not
339 provided the proper means for its utilization under all operating conditions, including operations when oxygen is being used.
This proposal would not require all flightcrew oxygen dispensing units to be equipped with communication equipment. Since an airplane may be operated in uncontrolled airspace, where two-way radio communication is not required and, at the same time, be at altitudes where oxygen is required for the flightcrew members, some airplanes have a crew oxygen system but no radio equipment. It would be inappropriate to require the flightcrew dispensing units of those airplanes to be equipped with communication equipment.
The proposed revisions to Sec. 23.1447(d) would require the flightcrew oxygen dispensing units to be automatically presented before the cabin pressure altitude exceeds 15,000 feet or be the quick-donning type if the airplane is certificated for operation above 25,000 feet. The requirement in paragraph (e) for the passenger dispensing units to be automatically presented if the airplane is approved for operation above 30,000 feet has not been revised. The revision to paragraph (d) would provide the flightcrew and the airplane passengers the same level of safety as provided by other airworthiness standards. This proposed revision is also consistent with the proposed revision of Sec. 23.841 in this notice.”
Amendment 23-62 and Subsequent
In Docket No. FAA-2009-0738, the Discussion of the Regulatory Amendments stated: Currently FAA addresses oxygen systems for airplanes operating above 41,000 feet using special conditions derived from part 25. A large number of new jet and high performance airplanes entering part 23 certification will operate at higher altitudes than previously envisioned for part 23 airplanes. FAA proposes revisions to §§ 23.1443, 23.1445, and 23.1447 to establish requirements for oxygen systems that would eliminate the need for special conditions for airplanes operating above 41,000 feet.
While § 23.1441(d)(2) requires the crew have pressure demand equipment for operation above 41,000 feet, this amendment requires that equipment include a quick donning mask with a pressure demand, mask mounted regulator that can be donned and supplying oxygen with 5 seconds, and that does not adversely affect normal communication.
The Final Rule is adopted as proposed.
23.1449 Means for determining use of oxygen
No policy available as of December 31, 2007.
There are no corresponding rule or airworthiness criteria in CAR 3 or the Airship Design Criteria.
23.1450 Chemical oxygen generators
No policy available as of December 31, 2007.
There are no corresponding rule or airworthiness criteria in CAR 3 or the Airship Design Criteria.
23.1451 Fire protection for oxygen equipment
There are no corresponding rule or airworthiness criteria in CAR 3 or the Airship Design Criteria.
Amendment 23-49 and Subsequent
This amendment adopted a proposed revision in NPRM 94-21 that stated: “This proposed new section would specify that fire protection is needed for oxygen equipment installations. Section 23.1451(a) and (b) would, respectively, prohibit the installation of oxygen equipment in designated fire zones and require that oxygen system components be protected from the heat from designated fire zones.
Proposed Sec. 23.1451(c) would require oxygen equipment and lines to be separated from other equipment or to be protected in a manner that would prevent escaping oxygen from striking grease, fluids, or vapors. The impingement of pure oxygen on certain materials will lower their combustion point to a value where ignition will occur in ambient conditions thereby creating a potential source for an airplane fire.
In one instance, an airplane was destroyed by fire that resulted when escaping oxygen impinged on lubricating material during maintenance of the airplane. The proposed new section would ensure that oxygen systems are protected to prevent fire hazards that can result from escaping oxygen.”
23.1453 Protection of oxygen equipment from rupture
There are no corresponding rule or airworthiness criteria in CAR 3 or the Airship Design Criteria.
Amendment 23-49 and Subsequent
This amendment adopted a proposed revision in NPRM 94-21 that stated: “This proposed new section would clarify the rupture protection needed for oxygen system installation. Rupture protection for oxygen systems is currently required by the application of the structures load requirements of part 23. The addition of Sec. 23.1453(a) would clarify the application of these load requirements and would identify the need to consider maximum temperatures and pressures that may be present. Section 23.1453(b) would identify the protection to be provided for high pressure oxygen sources and the high pressure lines that connect such sources to the oxygen system shutoff valves.”
Amendment 23-49 is clarified by Final Rule, Docket 27806, as follows: “Proposed new Sec. 23.1453 would clarify the rupture protection needed for oxygen system installation. Rupture protection for oxygen systems is currently required by the application of the structure load requirements of part 23. The addition of Sec. 23.1453(a) would clarify the application of these load requirements and would identify the need to consider maximum temperatures and pressures that may be present. Section 23.1453(b) would identify the protection to be provided for high pressure oxygen sources and the pressure lines that connect such sources to the oxygen system shutoff valves.
The comments received on this proposal from the JAA and the Civil Aviation Authority (CAA). CAA noted that the word "high" in paragraph (b) could lead to confusion and require interpretation. Accordingly, they suggested that the words "High pressure oxygen sources" be revised to read as follows: "Oxygen pressure sources." This is the same text that is used in JAR 23.
The FAA agrees with the suggested wording change. When the proposal was originally drafted, the FAA was considering the oxygen source side of the oxygen regulator, the high pressure side, and the passenger dispensing side of the regulator, the low pressure side; thus, the word "high" was used.
The suggested change will not alter the requirements applicability and will be more clearly understood. It is also noted that the suggested text change will more closely align with the same requirement in Sec. 25.1453. Section 23.1453 is changed by revising the first four words of proposed paragraph (b) to read, "Oxygen pressure sources.
This section is adopted with the above change.”