Change 1 AC 23-17C 7/16/2012
80 Amendment 23-49 and Subsequent
The intent of the proposed revision in NPRM 94-21 is given as follows: “Section
23.735(a) would be revised to state plainly that wheel brakes must be provided. A proposed new Sec. 23.735(c) would require the brake system to be designed so that the brake manufacturer's specified brake pressures are not exceeded during the landing distance determination required by Sec. 23.75. Proposed new Sec. 23.735(e), applicable to commuter category airplanes, would require establishing the minimum rejected takeoff brake kinetic energy capacity rating of each main wheel brake assembly. Section 23.45 provides that the determination of the accelerate-stop distance for commuter category airplanes be made in accordance with the applicant's procedures for operation in service. The proposed requirement is needed to ensure that the brakes will perform safely under accelerate-stop conditions.”
EASA AMC effective February 12, 2009, AMC 23.735(c) is acceptable for FAA certification.
Amendment 23-62 and Subsequent
In Docket No. FAA-2009-0738, the Discussion of the Regulatory Amendments stated: FAA revised the commuter category rejected takeoff requirements for all multiengine jet airplanes over 6,000 pounds. The higher takeoff speeds and distances for these aircraft make the ability to stop in a specified distance a safety issue.
Therefore, FAA revised the requirements in § 23.735(e) to apply to all multiengine jet airplanes over 6,000 pounds as well as all commuter category airplanes.”
This amendment changes the requirement for the wheel/brakes to meet § 23.735(e) if the airplane must comply with § 23.55. That section requires the accelerate-stop distance be determined and is applicable to normal, utility, and acrobatic category multiengine jet airplanes of more than 6,000 pounds maximum weight as well as commuter category airplanes.
The Final Rule adopted Section 23.735 as proposed.
23.737 Skis
The corresponding rule in CAR 3 is CAR 3.364.
There is no corresponding airworthiness criteria in the Airship Design Criteria.
Amendment 23-45 and Subsequent
See § 23.505, Supplementary conditions for ski-planes, for additional guidance about aircraft skis.
23.745 Nose/tail wheel steering
No policy available as of December 31, 2007.
There are no corresponding rule or airworthiness criteria in CAR 3 or the Airship Design Criteria.
83 Section 3. Floats And Hulls
23.751 Main float buoyancy
The corresponding rule in CAR 3 is CAR 3.371.
There is no corresponding airworthiness criteria in the Airship Design Criteria.
Original Issue and Subsequent
For a twin float seaplane or amphibian aircraft, the 80 percent excess buoyancy requirement should be applied to both rather than each float.
The rules for twin float aircraft do not address water stability or capsizing. They only require the aircraft remain afloat with any two compartments of the main floats flooded. The history does not support the position the aircraft will remain afloat indefinitely without capsizing with two compartments flooded. However, if an unsafe condition exists, certification should be denied under part 21, § 21.21(b)(2).
An example of an unsafe condition could be capsizing so rapidly the occupants could not safely exit. Capsizing that is delayed long enough to permit taxi to the shore or dock is not an unsafe condition. The time to capsize should be listed in the Emergency Procedures Section of the AFM.
Amendment 23-45 and Subsequent
This amendment adopted a proposed revision to NPRM 90-18 that stated: “This proposal revises Section 23.751 to clarify the buoyancy requirements for main floats in paragraph (a)(1) by specifying an 80 percent excess in buoyancy for each main float above the buoyancy required by that float to support the maximum weight of the seaplane. Additionally, the words "without capsizing" are added to paragraph (a)(2) to clarify the extent of flotation necessary after main float compartment flooding.
A strict interpretation of existing Section 23.751(a)(1) results in a buoyancy excess of 80 percent of the maximum weight of the seaplane when the design consists of only one main float, or a total of 180 percent of the maximum weight. However, on seaplanes having two main floats, each float would be required to have buoyancy of 80 percent in excess of that necessary to support the seaplane, or 180 percent of the maximum weight of the seaplane; for a total of 360 percent of the maximum weight.
For designs having three floats, each float would be required to support 180 percent of the maximum weight for a total of 440 percent. This is neither the intent of the rule nor the practice of industry.
The change to paragraph (a)(2) is intended to clarify the fact that the seaplane be afloat in the upright condition.”
23.753 Main float design
There is no policy available as of December 31, 2007.
There are no corresponding rule or airworthiness criteria in CAR 3 or the Airship Design Criteria.
23.755 Hulls
The corresponding rule in CAR 3 is CAR 3.372.
There is no corresponding airworthiness criteria in the Airship Design Criteria.
Original Issue
The discussion on capsizing and unsafe conditions in § 23.751 applies to this rule also.
Amendment 23-45 and Subsequent
This amendment changed the rule to prohibit capsizing in fresh water for planes over 5,000 pounds with two adjacent compartments flooded, and those between 1,500 and 5,000 pounds with any single compartment flooded.
23.757 Auxiliary floats
There is no policy available as of December 31, 2007.
This rule was adopted on February 1, 1965 as a recodification of CAR 3.373.
There is no corresponding airworthiness criteria in the Airship Design Criteria.
87 Section 4. Personnel And Cargo Accommodations
23.771 Pilot compartment
There is no policy available as of December 31, 2007.
The corresponding rule in CAR 3 is CAR 3.381.
The corresponding airworthiness criteria is section 4.28, Airship Design Criteria, FAA-P-8110-2, Change 2.
23.773 Pilot compartment view
The corresponding rule in CAR 3 is CAR 3.382.
The corresponding airworthiness criteria is section 4.29, Airship Design Criteria, FAA-P-8110-2, Change 2.
Amendment 23-14 and Subsequent
See AC 23-8C, “Flight Test Guide for Certification of Part 23 Airplanes,” for guidance on this regulation. EASA AMC effective February 12, 2009, AMC
23.773 references the CS-23 Flight Test Guide.
Amendment 23-45 and Subsequent
A proposed revision in NPRM 90-18 explains the rewrite of this section as follows:
“This proposal is based in part on conference recommendation 272, on conference comments, and on a post conference review of the adequacy of previous certifications, which establishes a precedent for compliance with existing Section
23.773. It is not the intent of this proposal to require windshield heat on all small airplanes, to preclude open cockpit designs or to prohibit the pilot from using a cloth to wipe the windows. It does, however, define requirements to assure that a means exists to remove or prevent the formation of fog or frost on the inside of the windshield, specifies the extent of credit to be given to pilot actions and defines the area of windshield and windows to be kept clear.
Paragraph (a)(1) of this proposal requires an extensive, clear, and undistorted view sufficient to enable the pilot to perform any maneuvers within the operating limitations of the airplane, and specifies particular operations, such as taxi, takeoff, approach and landing to clarify the extent of view necessary for safe operation.
Paragraph (b) of this proposal is included to address the condition where an airplane is operated at high altitudes, becomes cold-soaked, and is then descended into warm, moist air. Such conditions have resulted in the formation of frost on the inside surface of the windshield and crew compartment windows, which resulted in a limited or completely obscured view. Since, in such cases, compliance has been shown for the current Section 23.773(a)(3), a rule change is appropriate to address this condition. The FAA proposes to revise Section 23.773 to identify this condition and to clarify the extent of actions taken by the pilot to remove such moisture.”
The Final Rule 26269 for Amendment 23-45 states as follows: “The FAA proposed to revise the 23.773 requirements for the pilot compartment view to address the environment expected in all the operations requested for certification. The JAA states that it will consider this change for JAR 23 but that it proposes to retain present paragraph (b) relating to night flight tests. The GAMA contends that the words "must
89 be shown in all operations for which certification is requested," could be interpreted to mean that the same view must be provided for all operations.
The FAA does not agree with the GAMA interpretation. Section 23.773(a) and (a)(1) require the pilot compartment view to be sufficiently extensive, clear, and undistorted to allow the pilot to perform the various functions identified in this proposal. The word "sufficiently" is included because the FAA recognizes that the view needed for one operation may differ from the view needed for another. The intent is also shown by the words "sufficiently large" used in Section 23.773(b). The FAA adopts Section
23.773 as proposed.”
23.775 Windshields and windows
The corresponding rule in CAR 3 is CAR 3.383.
The corresponding airworthiness criteria is section 4.30, Airship Design Criteria, FAA-P-8110-2, Change 2.
Original Issue and Subsequent
The rule requires the Luminous Transmittance (LT) be no less than 70 percent when the pilot is seated in a normal flight position. This rule does not specify how the LT is to be measured. Industry, federal practices, standards and airframe manufacturer specifications have specified a minimum LT measurement for Federal Standard 406, Method 3022 or equivalent.
Based on available data, FAA cannot determine that an LT of 70 percent is in itself an unsafe condition. There are other factors such as windshield/window inclination from vertical. The criterion to determine an unsafe condition is a qualitative pilot evaluation.
Nonsplintering material in this section refers to materials such as safety glass, which shatter into small fragments that can cause superficial injuries. Splintering materials are those that shatter into slivers, which can result in serious injuries.
Policy for 14 CFR, part 23, § 23.775, Temperature and Temperature Gradient Requirement Certification:
Section 23.775 requires the following:
“The design of windshields, windows, and canopies in pressurized airplanes must be based on factors peculiar to high altitude operation, including – The effects of temperatures and temperature gradients;” and
“If certification for operation above 25,000 feet is requested, the windshield, window panels, and canopies must be strong enough to withstand the maximum cabin differential loads combined with critical aerodynamic pressure and temperature effects, after failure of any load-carrying element of the windshield, window panel, or canopy.”
On-airplane testing is one acceptable Means of Compliance (MOC) to these requirements. Other acceptable MOCs are component level testing, a combination of tests and analyses, or an analysis based on known temperature and temperature gradient effects for a specific material and installation. Qualification by similarity is also acceptable.
91 NOTE: FAA is not aware of any case where an applicant has used an analysis without testing, but will consider this if an applicant proposes it.
The testing or analysis would have to consider pressurization loads or fail-safe loads with the temperature and temperature gradient effects. These would be in addition to the cyclic or fail-safe testing of the complete pressure cabin at ambient temperature.
Current practice is to superimpose the pressure loading and the thermal gradients in a test. The testing and conditions vary from full-scale test articles with environmental chambers around the windows and windshields to component tests. For fail-safe requirements, most manufacturers are using a “failed” article (cut before test) while running a test to fail-safe loads or better.
If the bird strike requirements in § 23.775(h)(1) are applicable (Amendment 23-49), the applicant should consider the effects of temperature and temperature gradients when showing compliance to the two-pound bird strike.
Amendment 23-7 and Subsequent
A proposed revision in NPRM 67-14 explains this amendment as follows: “Sudden decompression of small cabins due to transparency failure is potentially catastrophic.
Experience with transport category airplanes has shown that decompression has been averted in several cases because of the dual element design of transparencies. The value 25,000 feet is believed to represent a reasonable point of demarcation between the altitudes at which sudden decompression is and is not potentially catastrophic, considering the expected cabin sizes and operating altitudes of small airplanes.”
The preamble material for Final Rule, Docket 8083 is explained as follows: “The notice proposed to add a new Sec. 23.775(e) imposing a fail-safe requirement for windshields, window panels, and canopies of airplanes certificated for operation above 25,000 feet. One comment objected, stating that the proposed requirement is unnecessary and an arbitrary dictation of design; that windshields should not be singled out over control systems or other components, and that transport category airplane decompression experience does not apply to Part 23 airplanes because the differential pressures are not the same. Commentator also suggested that if the proposal is adopted, the prescribed load should be the ultimate load. The FAA does not agree. Windshield strength cannot be controlled to the same degree of precision as is achieved with other materials, consequently redundancy is particularly important. Part 23 airplanes operate at the same altitudes as transport airplanes, where windshields have been lost and where windshield failure can be extremely hazardous. There is no justification for Part 23 design standards for windshields to be lower than those required in Part 25. The prescribed loading cannot be considered the ultimate load because a partially failed windshield would have essentially no factor of safety. Another comment objected to the proposal because paragraph (e) would require a fail-safe determination for all canopies of pressurized airplanes operated above 25,000 feet in addition to the testing already required