23.1419 Ice protection
There is no corresponding rule in CAR 3.
The corresponding rule in the Airship Design Criteria, FAA-P-8110-2, Change 2, is section 6.37.
The § 23.1419 guidance in this AC is focused on the ice protection systems at the component and system level. For information about airplane performance and handling in icing conditions please refer to AC 23.1419-2B, “Certification of Part 23 Airplanes for Flight In Icing Conditions,” and AC 20-73, “Aircraft Ice Protection.”
Original Issue and Subsequent
Icing Policy for Small Airplanes
The CAR 3 airplanes and 14 CFR, part 23 airplanes with a certification basis preceding Amendment 23-14, are allowed to fly in known icing conditions if their TCs do not include a prohibition against this operation. Some of these airplanes may be placarded against flight into known icing because they lack de-ice/anti-ice equipment specified in the type design data. Installation of equipment required for icing approval per type design data is justification for removing the placard.
However, the part 91 and part 135 operating rules in icing have limitations for these aircraft.
If the airplanes type design data prohibits flight into known icing, then these airplanes can be approved for flight into known icing only if compliance is shown to part 23, § 23.1419, Amendment 23-14, and subsequent.
Amendment 23-14 and Subsequent To certificate a single-engine airplane for flight in icing conditions, part 21, § 21.101 would require the same criteria to be applied as in VFR, IFR, day and night flight, which is to keep the airplane in the air and flying even if performance is compromised. This may require redundancy in ice protection system components to minimize hazards to the airplane if a probable malfunction or failure occurs.
There is no requirement or allowance for making adjustments in the icing certification program for the frequency of encountering icing conditions. A likelihood of one is to be used for encountering discrete environmental conditions such as instrument meteorological conditions. Icing conditions are environmental conditions, and an encounter frequency of less than one for compliance with §§ 23.1093 and 23.1419 is not appropriate.
Amendment 23-43 and Subsequent See ACs 23.1419-2, 23-143-1, 23-8 and 20-73.
EASA AMC 23.1419 accepts FAA AC 23.1419-2 as an AMC to CS 23.1419.
MISCELLANEOUS EQUIPMENT
23.1431 Electronic equipment
The corresponding rule in CAR 3 is CAR 3.721.
There is no corresponding rule in the Airship Design Criteria.
Original Issue and Subsequent
Mercury cell battery packs for use in Emergency Locator Transmitters (ELT) should be manufactured by controlled processes. Service experience has shown that ELT mercury cell battery packs fabricated by individuals without a controlled process can result in the following:
a. Degradation of the cell seal causing leaks and a shorter shelf life.
b. Creation of internal shorts.
c. Internal corrosion.
d. Creation of explosive mercury fulminate.
The possibility of adverse interaction between communication and navigation equipment should be evaluated. Momentary indicator deflection or flicker is acceptable. However, loss of a required function because of interaction of assignable frequencies in the NAS is not acceptable.
Guidance for TCAS II installations is given in AC 20-131A, “Airworthiness Approval of Traffic Alert and Collision Avoidance Systems (TCAS II) and Mode S Transponders.”
Automatic Air Navigation Facility (NAVAID) selection tuning (Auto-tune) of VHF Omnirange Station/Distance Measuring Equipment (VOR/DME) for flight management or multisensor navigation systems is designed to improve the navigation accuracy for enroute flight. Under certain conditions, and depending on the particular implementation, the auto-tune function can cause a hazard if auto-tune remains operative during VOR and ILS operations. In this case, automatic selection of a NAVAID different from that wanted by the flight crew is a possibility. Visual cues indicating the auto-tune is still active may be subtle and may go unnoticed during a high workload period. If the auto-tune NAVAID is reasonably in line with the projected track, the anomaly can go undetected—causing the airplane to fly an erroneous track based on the auto-tune NAVAID. This may occur either when steering manually or when the flight guidance system has been engaged. System 304
installations that employ auto-tune should be mechanized in a manner that addresses these safety issues. An acceptable method of auto-tune implementation is to automatically inhibit the auto-tune feature when a navigation function other than the one using auto-tune has been selected for display on the Horizontal Situation Indicator/Electronic Horizontal Situation Indicator (HSI/EHSI).
Moving Map Displays (MMD) used for primary command guidance during IFR flight should be evaluated with the particular navigation receiver (GPS and LORAN-C) to be used. It should also be restricted to use with that particular type of receiver on that particular airplane. If a separate command or deviation indicator is used to certify the system for IFR use, the MMD should be placarded “For Reference Only”. It should be used only if it can be shown that failure of the MMD would not fail the navigation system.
An MMD to be used for and placarded for “VFR Only” guidance would need verification that it performs its intended function when used with a particular navigation receiver. It could then be used on any other airplane with the same type navigation receiver.
Amendment 23-43 and Subsequent
A proposed revision to NPRM 90-23 explains this amendment as follows: “This proposal would include electronic equipment that is being installed in part 23 airplanes as well as radio equipment. When the existing regulation was adopted, radio equipment was the primary electronic equipment installed. For standardization in the application of FAA requirements, this proposal is consistent with Section 25.1431(a) and (c). Section 23.1309(b)(1) and (2) that are referenced are the proposed regulations in Notice 5, Small Airplane Airworthiness Review Program.”
This amendment is clarified by Final Rule, Docket 26344, as follows: “This proposes to amend Sec. 23.1431 to revise the current rule that addresses radio equipment only by including other electronic equipment that is installed in a part 23 airplane. Two comments were received. One commenter asks for a definition of the words, "critical environmental conditions" used in proposed Sec. 23.1431(a).
Critical environmental conditions are those environmental conditions under which a piece of equipment will not perform its intended function. By including this requirement, conditions that may be critical to the operation of a piece of equipment must be considered. Consideration of such conditions would include, but not be limited to, temperature extremes, vibration levels, and humidity.
The other commenter agrees with the proposal and suggests that Sec. 23.1431 be expanded to cover communications between pilots, radio transmission switches, and the effectiveness of aural warnings when headsets are being worn. Because these suggested expansion items were not included in the notice, their addition would be beyond the scope of the NPRM. This proposal is adopted as proposed.”
Amendment 23-49 and Subsequent
A proposed revision to NPRM 94-21 explains this change to Amendment 23-49 as follows: “This proposal would add three new paragraphs to Sec. 23.1431. Proposed new paragraph (c) would require that airplanes required to be operated by more than one flightcrew member must be evaluated to determine if the flightcrew members can converse without difficulty when they are seated at their duty stations. Accident investigations have shown that, in some instances, conversation between the flightcrew members was severely hindered by the noise level in the cockpit and that the inability to communicate contributed to the accident. If the required evaluation shows that the noise level does not impair conversation, no further action is required.
However, if the evaluation shows that conversation will be difficult, an intercommunication system would be required.
Proposed new paragraph (d) would require that if installed communication equipment includes any means of switching from receive to transmit, the equipment must use "off-on" transmitter switching that will ensure that the transmitter is turned off when it is not being used. Transmitting equipment that remains in the transmit mode when not being used blocks the frequency being used and can create an unsafe condition by preventing other needed communication.
Proposed new paragraph (e) would require that if provisions for the use of communications headsets are provided, it must be demonstrated that flightcrew members can hear aural warnings when a headset is being used. Aural warnings are required to warn the pilot of a condition that necessitates the pilots taking action;
therefore, it is necessary to ensure that such warnings would be effective even when headsets are being used.
During the development of the proposed new requirements in paragraphs (c) and (e), the FAA considered proposing a requirement that compliance demonstrations should be conducted under actual cockpit noise conditions when the airplane is being operated. The FAA, however, ultimately determined that such a requirement could result in demonstrations conducted under more severe noise conditions than needed.
Accordingly, no such requirement is being proposed. If the FAA determines in the future that noise conditions for demonstrations need to be specified, the FAA will define these conditions in advisory material.”
The proposal to include testing under actual noise conditions in paragraphs (c) and (e) was revised by Final Rule, Docket 27806, as follows: “This proposal would add three new paragraphs to Sec. 23.1431. Proposed new paragraph (c) would provide that airplanes required to be operated by more than one flightcrew member be evaluated to determine if the flightcrew members can converse without difficulty when they are seated at their duty stations. Proposed new paragraph (d) would require installed communication equipment to use "off-on" transmitter switching that will ensure that the transmitter is turned off when it is not being used. Proposed new 306
paragraph (e) would require that, if provisions for communication headsets are provided, the applicant must demonstrate that flightcrew members will receive all warnings when a headset is being used. The demonstration must be made under actual cockpit noise conditions. To clarify the conditions under which these evaluations should be conducted, not withstanding earlier harmonization agreements, these two paragraphs are being revised to include the phrase, "under actual cockpit noise conditions when the airplane is being operated."
EASA AMC 23.1431(e) is acceptable for FAA certification.
23.1435 Hydraulic systems
The corresponding rule in CAR 3 is CAR 3.3.726.
The corresponding rules in the Airship Design Criteria, FAA-P-8110-2, Change 2, are sections 6.4 and 6.38.
Amendment 23-7 and Subsequent
A proposed revision to NPRM 67-14 revised paragraph (c) to add the words "or propeller" after the words "part of an engine.”
Amendment 23-14 and Subsequent
A proposed revision to NPRM 71-13 explains this amendment as follows: “This proposal is appropriate because of increased reliance on hydraulic systems and the increasing complexity or such systems in Part 23 airplanes.”
The NPRM was revised by Final Rule, Docket 11011, as follows: “Sec.
23.1435(a)(2) has been revised to indicate that the required indication must be to the flight crew.”
Amendment 23-43 and Subsequent
A proposed revision to NPRM 90-23 explains this amendment as follows:
“Conference proposal 469 recommended adding to Section 23.1435(c) a requirement that propeller unfeathering accumulators be considered as an integral part of the propeller and small (1 quart max.) nonpressurized reservoirs be acceptable.
Propeller unfeathering accumulators have been accepted as an integral part of a propeller. The conference discussion supported clarification of the requirement and the allowance of some small accumulators, such as for the brake systems on singleengine airplanes. The FAA has further considered these issues and concludes such accumulators should be allowed provided their total capacity is limited to one quart or less.”
Amendment 23-49 and Subsequent
A proposed revision to NPRM 94-21 clarifies paragraph (c) with the following explanation: “Since the close of the comment period for the Small Airplane Airworthiness Review Program Notice No. 3 (55 FR 40598, October 3, 1990), now adopted by Amendment No. 23-43 (58 FR 18958, April 9, 1993), the FAA has been involved in discussions of the installation of hydraulic accumulators that are permitted by Sec. 23.1435(c). These discussions have shown that applicants are likely to find Sec. 23.1435(c) difficult to understand because of the way it is worded.
This notice would further revise Sec. 23.1435(c) to clarify under what circumstances a hydraulic accumulator and reservoir may be installed on the engine side of any firewall.”
23.1437 Accessories for multiengine airplanes
No policy available as of September 30, 2003.
This rule was adopted on February 1, 1965 as a recodification of CAR 3.725.
The corresponding rule in the Airship Design Criteria, FAA-P-8110-2, Change 2, is section 6.39.
23.1438 Pressurization and pneumatic systems
There is no corresponding rule in CAR 3.
The corresponding rule in the Airship Design Criteria, FAA-P-8110-2, Change 2, is section 6.40.
Amendment 23-20 and Subsequent
A proposed revision to NPRM 75-23 explains this rule as follows: “Components (such as ducts and couplings) of pressurization and pneumatic systems have failed at an unacceptable rate in service. The proposed standards for these components have been effective in preventing design deficiencies in the past.”
The rule proposed in NPRM 75-23 was revised by Final Rule, Docket 14625, and is explained as follows: “For comments related to the proposal to add a new Section
23.1438, and for an explanation of revisions made to proposed Section 23.1438, see Proposal 5-33. Proposal 5-33 includes: One commentator stated that if the term "components" in proposed Secs. 25.1438(a) and (b) included all parts of the system it would not be compatible with other Secs. of Part 25, which use the term "elements".
The FAA intended that the term "components" include all parts of the system.
Therefore, in order to be consistent with current Section 25.1435, which uses the term "elements", that term is substituted for the term "components" in proposed Secs. 25.1438(a) and (b).
One commentator questioned the need to specify a higher burst pressure for pneumatic systems than for pressurization systems, contending that pneumatic systems do not necessarily operate at higher pressure and that some are derived from pressurization systems. The FAAs experience has been that pneumatic systems in airplanes are operated at higher pressures, even when a common pressure source is provided for both pneumatic and pressurization systems.
One commentator objected to the provision in proposed Section 25.1438(b) requiring a burst pressure test of 4.0 times maximum normal operating pressure, contending that the industry has historically designed and tested pneumatic systems to a burst pressure of 3.0 times maximum normal operating pressure and that service experience over millions of flight hours has proven the integrity of those systems.
Another commentator pointed out that pneumatic deicer boots in general use today cannot sustain a pressure of 4.0 times maximum normal operating pressure. The FAA agrees with these comments, and proposed Section 25.1438(b) is revised to specify a burst pressure of 3.0 times maximum normal operating pressure.
One commentator suggested revision of proposed Section 25.1438 to allow the use of analysis, or a combination of analysis and test, as an alternative method of compliance to eliminate unnecessary testing. The FAA agrees that there are 311
instances where an analysis, or a combination of analysis and test, may be equivalent to a test under proposed Section 25.1438(a) or (b). Accordingly, a new Section
25.1438(c) is added to provide this alternative.”
Burst and proof tests are required at multiples of the maximum normal operating pressure. Temperature effects are not required as part of these tests if pressurization and pneumatic system elements are constructed of materials that can withstand the operational pressures and temperatures. If enough overstrength material elements are part of a design, then reduced material strength because of temperature variations is not a concern and testing may be performed at ambient temperature. The “sufficiently overstrength” determination must consider temperature cycles/extremes for materials that may show structural property phenomenon and structural strength changes because of temperature changes. Certain composite materials may be characteristic of adverse performance in certain temperature environments. Also, the “sufficiently overstrength” determination must consider both the duct system and its attach/clamping/stabilization devices. This advice is consistent with §§ 23.1301, Function and Installation; 23.307, Proof of Structure; and 23.603(a), Materials and Workmanship.
23.1441 Oxygen equipment and supply
There is no corresponding rule in CAR 3 or the Airship Design Criteria.
Amendment 23-9 and Subsequent
A revision to NPRM 67-30 proposed this rule based on the following explanation:
“In a study concerning the physiological requirements for oxygen entitled "Oxygen in General Aviation" dated December 1964, the Office of Aviation Medicine of the FAA reported that, while individual oxygen requirements may be influenced by factors such as fatigue, age, use of drugs and tobacco, night, etc., nevertheless supplemental oxygen, dependent on altitude, is a physiological necessity for all humans. For this reason and because of the increasing number of small airplanes having high altitude capability, there appears to be a need for airplane airworthiness standards and for general operating rules relating to oxygen system requirements.
In the past, type certification of small airplanes with oxygen equipment installed has been handled on a case-by-case basis either by application of special conditions or under the general operating limitations of Sec. 23.1501. This amendment proposes uniform airworthiness standards for oxygen equipment and supply. It also proposes performance standards relating to oxygen mass flow and equipment standards for oxygen dispensing units.
Parts 121 and 135 of the Federal Aviation Regulations currently prescribed oxygen requirements for pilots and passengers. For consistency in the interest of safety, all other aircraft operating in the same airspace and environmental conditions should be under comparable standards. The FAA, therefore, considers it appropriate to propose general operating and flight rules governing the use of supplemental oxygen in pressurized and unpressurized cabin aircraft.
FAA studies have indicated that for any person in a pressurized cabin subjected to decompression at the higher altitudes, the short time available to don an oxygen mask before losing consciousness may be critical. In such case, the smaller the cabin volume, the more aggravated the situation becomes. As an added operational consideration, the FAA, therefore, believes it necessary for safety, at flight altitudes above 35,000 feet, that at least one pilot at the controls be required to wear an oxygen mask. The corresponding altitude for Part 121 operations had originally been established at 35,000 feet. However, it was subsequently raised, in steps, to 41,000 feet, on the basis of the extensive operating experience with the large transport-category airplanes. This satisfactory operating experience is attributable, in part, to the stringent Part 121 crew training and maintenance requirements. Such compensating conditions do not presently exist for operations conducted under Part 91 and the proposed cutoff altitude has been accordingly set at 35,000 feet.