Source: http://www.regulations.gov/?_escaped_fragment_=submitComment;D=USPS-2012-0087-0001
Timestamp: 2013-05-25 02:37:15
Document Index: 617861299

Matched Legal Cases: ['art 25', 'art 33', '§ 25', '§ 25', 'art 25', 'art 33', 'art 33', '§ 25', '§ 33', 'arts 91', 'art 121', 'art 23', 'art 121', '§ 25', '§ 25', 'art 25', 'art 33', 'art 33', 'art 33', 'art 33', 'art 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', 'art 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', 'art 25', '§ 25', 'art 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', 'art 33', '§ 33', 'art 33', '§ 25', '§ 25', '§ 25', 'art 25', 'art 33', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 33', '§ 25', '§ 25', 'art 33', 'arts 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 21', '§ 25', '§ 25', '§ 25', '§ 25', 'art 25', 'art 25', 'art 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', 'art 33', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', 'art:\n19', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', '§ 25', 'art 33', '§ 33', '§ 33', '§ 33', '§ 33', '§ 33', 'art 33', '§ 135', '§ 121', '§ 25', '§ 25']

Airplane and Engine Certification Requirements: Supercooled Large Drop, Mixed Phase, and Ice Crystal Icing Conditions
This Rule document was issued by the Federal Aviation Administration
[Docket No. FAA-2010-0636; Notice No. 10-10]
and follow the online instructions for sending your comments electronically.
Send comments to Docket Operations, M-30; U.S. Department of Transportation, 1200 New Jersey Avenue, SE., Room W12-140, West Building Ground Floor, Washington, DC 20590-0001.
Bring comments to Docket Operations in Room W12-140 of the West Building Ground Floor at 1200 New Jersey Avenue, SE., Washington, DC, between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.
For more information on the rulemaking process, see
theSUPPLEMENTARY INFORMATIONsection of this document.
The FAA will post all comments we receive, without change, to http://www.regulations.gov,
including any personal information you provide. Using the search function of our docket Web site, anyone can find and read the electronic form of all comments received into any of our dockets, including the name of the individual sending the comment (or signing the comment for an association, business, labor union, etc.). You may review DOT's complete Privacy Act Statement in theFederal Registerpublished on April 11, 2000 (65 FR 19477-78) or you may visit http://DocketsInfo.dot.gov.
To read background documents or comments received, go to http://www.regulations.gov
at any time and follow the online instructions for accessing the docket. Or, go to Docket Operations in Room W12-140 of the West Building Ground Floor at 1200 New Jersey Avenue, SE., Washington, DC, between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.
New safety requirements that are necessary for the design, production, and operation of those airplanes, and for other practices, methods, andprocedures relating to those airplanes and engines.
The FAA proposes to revise certain regulations in Title 14, Code of Federal Regulations (14 CFR) part 25 (Airworthiness Standards: Transport Category Airplanes) and part 33 (Airworthiness Standards: Aircraft Engines) related to the certification of transport category airplanes and turbine aircraft engines in icing conditions. We also propose to create new regulations: § 25.1324—Angle of attack systems; § 25.1420 SLD icing conditions; part 25, appendix O (SLD icing conditions); part 33, appendix C (this will be intentionally left blank as a placeholder); and part 33, appendix D (Mixed phase and ice crystal icing conditions). To improve the safety of transport category airplanes operating in SLD, mixed phase, and ice crystal icing conditions, the proposed regulations would:
Smaller & Medium Airplanes
$249,580,915
$69,994,259
Larger Airplanes
156,004,884
29,498,469
405,585,799
99,492,728
Engine Cert Cost
6,931,610
Engine Capital Cost
5,240,632
13,936,000
12,172,242
Smaller Airplane Certification Cost
24,999,039
21,835,129
New Larger Airplane Certification Cost
3,154,600
2,755,350
Derivative Larger Airplane Certification Cost
10,438,800
9,117,652
5,842,024
Fuel Burn All
8,046,676
2,261,941
70,965,115
53,984,338
In the 1990s, the FAA became aware that the types of icing conditions considered during the certification of transport category airplanes and turbine aircraft engines needed to be expanded to increase the level of safety during flight in icing. The FAA determined that the revised icing certification standards should include supercooled large drops (SLD), mixed phase, and ice crystals. (1)
As a result of this accident and consistent with related NTSBrecommendations (2)
the FAA tasked the Aviation Rulemaking Advisory Committee (ARAC), (3)
through its Ice Protection Harmonization Working Group (IPHWG), to do the following:
Study the effects icing requirement changes could have on §§ 25.773, Pilot compartment view; 25.1323, Airspeed indicating system; and 25.1325, Static pressure systems.
Currently, the certification regulations applicable to transport category airplanes for flight in icing conditions require that: “The airplane must be able to operate safely in the continuous maximum and intermittent maximum icing conditions of appendix C.”
The certification regulations also require minimum performance and handling qualities in these icing conditions and methods to detect airframe icing and to activate and operate ice protection systems. (5)
Icing regulations applicable to engines are in §§ 33.68 and 33.77. Operating regulations in parts 91 (General Operating and Flight Rules) and 135 (Operating Requirements: Commuter and On Demand Operations) address limitations in icing conditions for airplanes operated under these parts. (6)
Part 121 (Operating Requirements: Domestic, Flag and Supplemental Operations) addresses operations in icing conditions that might adversely affect safety and requires installing certain types of ice protection equipment and wing illumination equipment. (7)
The NTSB issued NTSB Safety Recommendation Numbers A-96-54 (8)
and A-96-56 (9)
as a result of the Roselawn accident previously discussed. This rulemaking activity partially addresses the NTSB recommendations because there are separate rulemaking activities associated with revisions to 14 CFR part 23 regulations for small airplanes and 14 CFR part 121 operational regulations. The NTSB recommendations are as follows:
Address when ice protection systems must be activated.
The proposed new AC and revisions to existing ACs would provide guidance material for one acceptable means, but not the only means, of demonstrating compliance with the proposed regulations contained in this NPRM. The guidance provided in these documents is directed at airplane manufacturers, modifiers, foreign regulatory authorities, and FAA transport airplane type certification engineers, flight test pilots, and their designees. The proposed ACs will be posted on the “Aircraft Certification Draft Documents Open for Comment” Web site, http://www.faa.gov/aircraft/draft_docs,
after this NPRM is published in theFederal Register
We also propose to create a new: § 25.1324—Angle of attack systems; § 25.1420—Supercooled large drop icing conditions; part 25, appendix O (supercooled large drop icing conditions; part 33, appendix C (intentionally left blank); and part 33, appendix D (Mixed phase and ice crystal icing conditions). Part 33, appendix C, is intentionally left blank and retained as a placeholder for non-icing related regulations so that part 33, appendix C, would not be confused with the icing conditions defined in part 25, appendix C.
The FAA has issued airworthiness directives (ADs) to address the unsafe conditions associated with operating certain airplanes in severe icing conditions, which can include SLD icing conditions. These ADs are applicable to airplanes equipped with both reversible flight controls in the roll axis and pneumatic deicing boots. The ADs require the flightcrews to exit icing when visual cues are observed that indicate the conditions exceed the capabilities of the ice protection equipment. In addition, for new certifications of airplanes equipped with unpowered roll axis controls and pneumatic deicing boots, the airplanes are evaluated to ensure the roll control forces are acceptable if the airplane operates in certain SLD conditions. However, the scope of these actions is limited because they do not address all transport category airplanes and do not address the underlying safety concern of the unknown performance and handling qualities safety margins for airplanes and engines operating in freezing drizzle, freezing rain, mixed phase, and ice crystal conditions. The IPHWG concluded there is a need to improve the regulations to ensure safe operationof airplanes and engines in these conditions.
Proposed § 25.1420 would add safety requirements that must be met in SLD icing conditions for certain transport category airplanes to be certified for flight in icing conditions. This change would require evaluating the operation of these airplanes in the SLD icing environment; developing a means to differentiate between different SLD icing conditions, if necessary; and developing procedures to exit all icing conditions.
The SLD icing conditions described in the proposed appendix O would be those in which the airplane must be able to either safely exit following the detection of any or specifically identified appendix O icing conditions, or safely operate without restrictions. Specifically, the proposed § 25.1420 would allow three options:
Detect appendix O conditions and then operate safely while exiting all icing conditions (§ 25.1420(a)(1)).
Safely operate in a selected portion of appendix O conditions, detect when the airplane is operating in conditions that exceed the selected portion, and then operate safely while exiting all icing conditions (§ 25.1420(a)(2)).
Operate safely in all of the appendix O conditions (§ 25.1420(a)(3)).
As discussed below in the section titled “Differences from the ARAC Recommendations,” the proposed § 25.1420 would apply to airplanes with either: (1) a takeoff maximum gross weight of less than 60,000 pounds, or (2) reversible flight controls.
To establish that an airplane could operate safely in the proposed appendix O conditions described above, proposed § 25.1420(b) would require both analysis and one test, or more as found necessary, to establish that the ice protection for the various components of the airplane is adequate. The words “as found necessary” would be applied in the same way as they are applied in § 25.1419(b). During the certification process, the applicant would demonstrate compliance with the rule using a combination of analyses and test(s). The applicant's means of compliance would consist of analyses and the amount and types of testing it finds necessary to demonstrate compliance with the regulation. The applicant would choose to use one or more of the tests identified in paragraphs § 25.1420(b)(1) through (b)(5). Although the applicant may choose the means of compliance, it is ultimately the FAA that determines whether the applicant has performed sufficient test(s) and analyses to substantiate compliance with the regulation. Similarly, the words “as necessary,” which appear in § 25.1420(b)(3) and (b)(5), would result in the applicant choosing the means of compliance that is needed to support the analysis, but the FAA would make a finding whether the means of compliance is acceptable. If an applicant has adequate data a similarity analysis may be used in lieu of the testing required by § 25.1420(b). For an airplane certified to operate in at least a portion of proposed appendix O icing conditions, proposed § 25.1420(c) would extend the requirements of § 25.1419(e), (f), (g), and (h) (10)
to include activation and operation of airframe ice protection systems in the appendix O icing conditions for which the airplane is certified. Proposed § 25.1420(c) would not apply to airplanes certified to proposed § 25.1420(a)(1) because proposed § 25.1420(a)(1) would require a method to identify and safely exit all appendix O conditions.
The proposed appendix O defines SLD conditions. It was developed by the ARAC IPHWG, which included meteorologists and icing research specialists from industry, FAA/FAA Tech Center, Meteorological Services of Canada, National Aeronautics and Space Administration (NASA), and Transport Canada/Transport Development Center. The IPHWG collected and analyzed airborne measurements of pertinent SLD variables, developed an engineering standard to be used in aircraft certification, and recommended thatstandard to the FAA. The FAA concurs with the recommendation.
The ice accretion definitions in proposed appendix O, part II, and the proposed revisions to the performance and handling qualities requirements for flight in icing conditions are similar to those required for flight in appendix C icing conditions. The proposals address the three options allowed by proposed § 25.1420(a). Proposed appendix O, part II, would contain definitions of the ice accretions appropriate to each phase of flight. The proposed appendix O, part II(b), would define the ice accretions used to show compliance with the performance and handling qualities requirements for any portion of appendix O in which the airplane is not certified to operate. The proposed appendix O, part II(c), would define the ice accretions for any portion of appendix O in which the airplane is certified to operate.
Proposed appendix O, part II(d), would define the ice accretion in appendix O conditions before the airframe ice protection system is activated and is performing its intended function to reduce or eliminate ice accretions on protected surfaces. This ice accretion would be used in showing compliance with the controllability and stall warning margin requirements of §§ 25.143(j) and 25.207(h), respectively, that apply before the airframe ice protection system has been activated and is performing its intended function. Even if the airplane is certified to operate only in a portion of the appendix O icing conditions, the ice accretion used to show compliance with §§ 25.143(j) and 25.207(h) must consider all appendix O icing conditions since the initial entry into icing conditions may be into appendix O icing conditions in which the airplane is not certified to operate.
To reduce the number of ice accretions needed to show compliance with § 25.21(g), the proposed appendix O, part II(e), would allow the option of using an ice accretion defined for one flight phase for any other flight phase if it is shown to be more critical than the ice accretion defined for that other flight phase.
Existing § 25.21(g)(1) (11)
requires that the performance and handling qualities requirements of part 25, subpart B, with certain exceptions, (12)
be met in appendix C icing conditions. (13)
Proposed § 25.21(g)(3) would identify the performance and handling qualities requirements that must be met to ensure that an airplane certified to either the proposed § 25.1420(a)(1) or (a)(2) could safely exit icing if the icing conditions of proposed appendix O, for which certification is not sought, are encountered. Such an airplane would not be approved to take off in proposed appendix O icing conditions and would only need to be able to detect and safely exit those icing conditions encountered en route. Therefore, it is proposed that, in addition to the exceptions identified in the existing § 25.21(g)(1), such an airplane would not need to meet certain requirements (14)
for appendix O icing conditions.
With one exception, for an airplane certified under proposed § 25.1420(a)(1) or (a)(2), the same handling qualities requirements that must currently be met for flight in appendix C icing conditions are proposed for flight in appendix O icing conditions for which certification is not sought. That exception is § 25.143(c)(1), which addresses controllability following engine failure during takeoff at V 2
. Compliance with that rule would not be necessary since the airplane would not be approved for takeoff in appendix O icing conditions. No justification for a relaxation of other handling qualities requirements could be identified.
The requirements for safe operation in all or any portion of proposed appendix O icing conditions under proposed § 25.21(g)(4) are similar to those currently required for appendix C icing conditions. With one exception, the list of part 25, subpart B requirements that currently do not have to be met for flight in appendix C icing conditions would not have to be met in proposed appendix O icing conditions. The exception is that compliance with § 25.121(a), Climb: One-engine-inoperative
would be required for appendix O icing conditions because, unlike for appendix C icing conditions, the FAA cannot justify an assumption that the ice accretion in this flight phase can be assumed insignificant. In practice, it is expected that some applicants may use an operating limitation to prohibit takeoff in appendix O icing conditions. Otherwise, the same rationales behind the requirements are used for both appendix C and appendix O icing conditions. For continued operation in appendix O icing conditions, there should effectively be no degradation in handling qualities, and any degradation in performance should be no greater than that allowed by the regulations for appendix C icing conditions.
In certification programs, both the airplane as a whole and its individual components are evaluated for flight in icing conditions. There are several rules in part 25 (15)
that contain icing related requirements for specific components. We propose to revise those rules to ensure the airplane can safely operate in the new icing conditions established in this proposed rule.
Section 25.1419 requires that an airplane be able to safely operate in all of the conditions specified in appendix C, whereas the proposed § 25.1420 would not require an airplane to safely operate in all of the appendix O icing conditions. Proposed § 25.1420(a)(1) and (a)(2) only require an airplane to be capable of safely exiting icing conditions after encountering an appendix O icing condition for which that airplane will not be certified. The existing regulations for pilot compartment view, airspeed indicationsystem, and static pressure system (16)
contain requirements for operation in icing conditions. These sections would be revised to add requirements for operation in appendix O icing conditions. Section 25.1323, Airspeed indicating system,
would also be revised to include and define mixed phase and ice crystal conditions. New proposed § 25.1324 includes an icing requirement for angle of attack systems. This would be similar to the icing requirements for airspeed indication systems. The proposed section would require the angle of attack system to be heated to prevent malfunction in appendices C and O icing conditions and in the mixed phase and ice crystal conditions defined in § 25.1323.
In the proposed revisions to the requirements for pilot compartment view, airspeed indication system, and static pressure system, (17)
and the new proposed requirements for angle of attack systems, an airplane certified in accordance with § 25.1420(a)(1) or (a)(2) would not be required to be evaluated for all of appendix O. For airplanes certified in accordance with § 25.1420(a)(1), the icing conditions that the airplane is certified to safely exit following detection must be considered. For airplanes certified in accordance with § 25.1420(a)(2), the icing conditions that the airplane is certified to safely operate in, and to safely exit following detection, must be considered. For airplanes certified in accordance with § 25.1420(a)(3) and for airplanes not subject to § 25.1420, all icing conditions must be considered. Airplanes not certified for flight in icing need not consider appendix O.
The engine induction system icing section (§ 25.1093) and propeller deicing section (§ 25.929) contain requirements for operation in icing conditions. As a conservative approach to ensure safe operation of an airplane in an inadvertent encounter with icing, the existing language in § 25.1093 contains requirements for operation in icing conditions, even for an airplane that is not approved for flight in icing. Since proposed appendix O defines icing conditions that also may be inadvertently encountered, § 25.1093 would be revised to reference appendix O in its entirety. This would maintain the FAA's conservative approach for this section. Section 25.929 (propeller deicing) would also be revised to reference appendix O in its entirety.
Sections 25.929 and 25.1323 generically reference icing instead of specifically mentioning appendix C. Historically, the icing conditions specified in appendix C have been applied to these rules. For clarity, we are revising §§ 25.929 and 25.1323 so they specifically reference appendix C, as well as appendix O. The proposed revisions to icing regulations for pilot compartment view, propellers, engine induction system icing protection, airspeed indication system, static pressure system, and angle of attack system would be applicable to all transport category airplanes to ensure safe operation during operations in icing conditions.
The proposed revisions to § 25.903 would retain the existing regulations and add new subparagraphs to be consistent with the proposed part 33 changes in § 33.68. These revisions would allow for approving new aircraft type certification programs with engines certified to earlier amendment levels. The proposed revisions would make it clear that the proposed part 33 changes would not be retroactively imposed on an already type certified engine design, unless service history indicated that an unsafe condition was present.
The proposed revision to § 25.929 clarifies the meaning of the words “for airplanes intended for use where icing may be expected.” The intent has been for the rule to be applicable to airplanes certified for flight in icing.
The proposed revisions to §§ 25.1093, 33.68, and 33.77 would change the icing environmental requirements used to evaluate engine protection and operation in icing conditions. The reason for these changes is that the incident history of some airplanes has shown that the current icing environmental requirements are inadequate. The effect of the change would be to require an evaluation of safe operation in the revised icing environment. The proposed revision to § 25.1093 restructures paragraph (b) and adds a new Table 1—Icing Conditions for Ground Tests. The proposed rules would require engines and engine installations to operate safely throughout the SLD conditions defined in proposed new part 25, appendix O, and the newly defined mixed phase and ice crystal conditions defined in proposed new part 33, appendix D. (18)
The proposed appendix D was developed by the ARAC Engine Harmonization Working Group and the Power Plant Installation Harmonization Working Group, which included meteorologists and icing research specialists from industry, FAA/FAA Tech Center, Meteorological Services of Canada, National Aeronautics and Space Administration (NASA), and Transport Canada/Transport Development Center. The ARAC recommended appendix D and the FAA concurs with the recommendation.
The proposed revision to § 25.1521 would retain the existing regulations and add anew subparagraph that would require an additional operating limitation for turbine engine installations during ground operation in icing conditions defined in § 25.1093(b)(2). That operating limitation would address the maximum time interval between any engine run-ups from idle and the minimum ambient temperature associated with that run-up interval. This limitation is necessary because we do not currently have any specific requirements for run-up procedures for engine ground operation in icing conditions. The engine run-upprocedure, including the maximum time interval between run-ups from idle, run-up power setting, duration at power, and the minimum ambient temperature demonstrated for that run-up interval proposed in § 25.1521, would be included in the Airplane Flight Manual in accordance with existing § 25.1581(a)(1) and § 25.1583(b)(1).
The engine run-up procedure from ground idle to a moderate power or thrust setting is necessary to shed ice build-up on the fan blades before the quantity of ice reaches a level that could adversely affect engine operation if ice is shed into the engine. The proposed revision to § 25.1521 would not require additional testing. The ice shedding demonstration may be included as part of the § 33.68 engine icing testing.
The proposed revision to § 25.1533 would establish an operating limitation applicable to airplanes that are not certified in accordance with proposed § 25.1420(a)(1) or (a)(2). The flightcrews of these airplanes would be required to exit all icing conditions if they encounter appendix O icing conditions that the airplane has not been certified to operate in.
The proposed regulations (19)
for the airspeed indicating system and angle ofattack system would address the operation of those systems in specific mixed phase and ice crystal conditions, as defined in proposed Appendix O. During the drafting of this NPRM the FAA became aware of airspeed indicating system malfunctions in environmental conditions that may not be addressed by these proposed regulations. The FAA is reviewing the malfunctions and is considering the need to change the proposed mixed phase and ice crystal parameters to include freezing rain. The maximum mixed phase and ice crystal parameters that we are considering are those defined in the proposed part 33, appendix D. The freezing rain parameters that we are considering are based on standards some manufacturers have used for airdata probes. The maximum freezing rain parameters that we are considering are:
Droplet MVD
(nmiles)
0 to 10 000
The IPHWG recommended changes to parts 25 and 33 to ensure the safe operation of airplanes and engines in icing conditions. The FAA concurs with the recommendations, but has determined it is necessary to revise to which airplanes the new airplane icing certification requirements in the proposed § 25.1420 would apply. The proposed § 25.1420 in this NPRM would apply to airplanes with either: (1) a takeoff maximum gross weight of less than 60,000 lbs (27,000 kg), or (2) reversible flight controls. An airplane with reversible flight controls in any axis (pitch, roll, or yaw), even if these flight controls are aerodynamically boosted and/or power-assisted, would be considered to have reversible flight controls under this proposed rule. An airplane with flight controls that are irreversible under normal operating conditions, but are reversible following a failure, would not be considered to have reversible flight controls under this proposed rule. Reversible, aerodynamically boosted, and power-assisted flight controls are defined in Appendix 1 to the preamble of this NPRM. The ADs described above in section B. “Prior FAA Actions to address the Safety Concern” are only applicable to airplanes equipped with both reversible flight controls in the roll axis and pneumatic deicing boots.
A group of IPHWG members (Boeing, Airbus, and Embraer, supported by Cessna) held a minority position in their belief that the applicability of the proposed § 25.1420 should exclude airplanes with certain design features. Their rationale for the position is that large transport airplanes still in production have not experienced any accidents or serious incidents as a result of flying in SLD icing conditions. These manufacturers proposed that airplanes having all three of the following design features should be excluded from compliance with § 25.1420:
The IPHWG majority (Air Line Pilots Association, International (ALPA), Civil Aviation Authority for the United Kingdom (CAA/UK), FAA/FAA Tech Center, Meteorological Services of Canada, National Aeronautics and Space Administration (NASA), SAAB, Transport Canada/Transport Development Center) did not accept the exclusion of airplanes with the three aforementioned design features because one cannot predict with confidence that the past service experience of airplanes with these specific design features will be applicable to future designs. The IPHWG majority recommended applying the new SLD airplane certification requirements proposed in the new § 25.1420 to all future transport category airplane type designs.
Excluding airplanes with wing leading edge high-lift devices was opposed, in part, because there are many different designs for such devices, which may not all be equally effectivein mitigating the negative effects of SLD ice accretions. The designs for those devices include:
The complete minority and majority positions are discussed in the working group report, which is available in the public docket. (20)
The FAA continues to agree with the IPHWG majority position that the presence (or conversely, the absence) of leading edge high lift devices should not be used as a basis for determining the applicability of the proposed § 25.1420. There is insufficient data to conclude either that every type of leading edge high lift device, or that a specific leading edge high lift device design will affect (positively or negatively) an airplane's ability to operate in SLD atmospheric icing conditions. Also, leading edge high lift devices are only deployed in certain phases of flight (for example, takeoff and landing), and their deployment may differ for different flap configurations. For example, a leading edge slat may be sealed in one flap configuration, but slotted (that is, with a gap opened up between the trailing edge of the slat and the wing) in others. Therefore, the applicability of the proposed § 25.1420 is not affected by the presence or absence of leading edge high lift devices.
We request comment on whether this proposed rule, if adopted, should be applied to airplanes larger than 60,000 pounds MTOW or airplanes with other design features whose presence or absence would result in the airplane being susceptible to safety problems while operating in the SLD icing conditions defined in the proposed appendix O, as well as the economic analysis associated with these decisions. (21)
This NPRM also differs from the ARAC recommendation by proposing a revision to § 25.1533 for airplanes not certified to operate in all of the SLD atmospheric icing conditions specified in the proposed new appendix O (that is, airplanes certified in accordance with proposed § 25.1420(a)(1) or (a)(2)). The proposal would establish an operating limitation that requires the flightcrews to exit all icing conditions if they encounter appendix O icing conditions in which the airplane has not been certified to operate.
The FAA considers these ARAC recommended requirements to add significant complexity to the proposed rule to address an issue that may not arise. The FAA considers it unlikely that future airplane designs will include means to increase the stall warning margin and airplane controllability upon detection of appendix O icing conditions in addition to the means that are incorporated in many current transport category airplane designs to change the stall warning device activation point upon activation of the ice protection system. Therefore, these ARAC recommendations are not included in this NPRM. If needed, the FAA can issue special conditions, in accordance with § 21.16, to provide adequate safety standards in the unlikely event that such design features are included in a future transport category airplane.
Another difference between this NPRM and the ARAC recommendation concerns the requirements for pilot compartment view, airspeed indication system, angle of attack system and static pressure system. (22)
For these rules the ARAC recommendation would have required airplanes certified in accordance with § 25.1420(a)(1) or (a)(2) to consider all appendix O icing conditions. However, the ARAC recommended advisory circular material allowed these airplanes to consider less than the full appendix O icing conditions. The FAA is not proposing that these airplanes must meet the performance and handling qualities requirements for all of the icing conditions specified in appendix O. Therefore, for pilot compartment view, airspeed indication system, angle of attack system and static pressure system, (23)
the agency concurs that it would only be necessary to show compliance under the applicable conditions in appendix O.
2. Whether airplanes with certain design features should be exempt from the recommendation for § 25.1420.
3. Whether it is acceptable to certificate an airplane to a portion of appendix O, as proposed in the recommendation for § 25.1420(a)(2).
A detailed discussion of the IPHWG's minority and majority opinions on these issues is included in the working group report. A copy of the working group report is in the public docket. (24)
The FAA predominantly concurred with the ARAC's recommendations, but determined it was necessary to revise the applicability of the recommendation for § 25.1420, as discussed previously.
First, we develop an annual risk of a catastrophic SLD event per aircraft and assume a uniform annual likelihood. Next, we multiply the total annual affected aircraft by the annual risk per aircraft. Lastly, we multiply the total annual risk by the estimated cost of an average SLD event. When summed over time, the total estimated benefits are$405.6 million ($99.5 million present value).
$6,931,610
Small Aircraft Certification Cost
New Large Aircraft Certification Cost
Amended Type Certificate Large Airplane Certification Cost
Because this proposed rule would apply to airplanes that have yet to be designed, there would be no immediate cost to small entities. However, as of 2007, there are at least 54 small entity operators with 1,500 or fewer employees who would qualify as small entities.
Please send your comments to the address specified in theADDRESSESsection of this preamble.
Do not file in the docket information that you consider to be proprietary or confidential business information. Send or deliver this information directly to the person identified in theFOR FURTHER INFORMATION CONTACTsection of this document. You must mark the information that you considerproprietary or confidential. If you send the information on a disk or CD ROM, mark the outside of the disk or CD ROM and also identify electronically within the disk or CD ROM the specific information that is proprietary or confidential.
1. Searching the Federal eRulemaking Portal (
2. Visiting the FAA's Regulations and Policies web page at http://www.faa.gov/regulations_policies/
a. Appendix C Icing Conditions:
The environmental conditions defined in appendix C of 14 CFR part 25.
b. Appendix O Icing Conditions:
The environmental conditions defined in appendix O of 14 CFR part 25.
c. Drizzle Drop:
A drop of water measuring 100 µm to 500 µm (0.1-0.5 mm) in diameter.
d. Freezing Drizzle (FZDZ):
Supercooled drizzle drops that remain in liquid form and freeze upon contact with objects colder than 0°C.
e. Freezing Rain (FZRA):
Supercooled rain drops that remain in liquid form and freeze upon contact with objects colder than 0°C.
f. Icing Conditions:
The presence of atmospheric moisture and temperature conducive to airplane icing.
g. Icing Conditions Detector:
A device that detects the presence of atmospheric moisture and temperature conducive to airplane icing.
h. Irreversible Flight Controls:
Flight controls in the normal operating configuration that have loads generated at the control surfaces of an airplane which are reacted against the actuator and its mounting and cannot be transmitted directly back to the flight deck controls. This term refers to flight controls in which all of the force necessary to move the pitch, roll, or yaw control surfaces is provided by hydraulic or electric actuators, the motion of which is controlled by signals from the flight deck controls.
i. Liquid Water Content (LWC):
The total mass of water contained in liquid drops within a unit volume or mass of air, usually given in units of grams of water per cubic meter (g/m 3
j. Mean Effective Diameter (MED):
The calculated drop diameter that divides the total liquid water content present in the drop size distribution in half. Half the water volume will be in larger drops and half the volume in smaller drops. This value is calculated, as opposed to being arrived at by measuring actual drop size. The MED is based on an assumed Langmuir drop size distribution. The fact that it is a calculated measurement is how it differs from median volume diameter, which is based on actual drop size.
k. Median Volume Diameter (MVD):
The drop diameter that divides the total liquid water content present in the drop distribution in half. Half the water volume will be in larger drops and half the volume in smaller drops. The value is obtained by actual drop size measurements.
l. Mixed Phase Icing Environment:
A combination of supercooled liquid and ice crystals.
m. Rain Drop:
A drop of water greater than 500 µm (0.5 mm) in diameter.
n. Reversible Flight Controls:
Flight controls in the normal operating configuration that have force or motion originating at the airplane's control surface (for example, through aerodynamic loads, static imbalance, or trim tab inputs) that is transmitted back to flight deck controls. This term refers to flight deck controls connected to the pitch, roll, or yaw control surfaces by direct mechanical linkages, cables, or push-pull rods in such a way that pilot effort produces motion or force about the hinge line.
o. Supercooled Large Drops (SLD):
Supercooled liquid water that includes freezing rain or freezing drizzle.
p. Supercooled Water:
Liquid water at a temperature below the freezing point of 0°C.
Aircraft, Aviation safety, Reporting and recordkeeping requirements, Safety, Transportation.
Part 25 Airworthiness Standards Transport Category Airplanes
49 U.S.C. 106(g), 40113, 44701, 44702 and 44704.
2. Amend § 25.21 by revising paragraphs (g)(1) and (g)(2) and adding paragraphs (g)(3) and (g)(4) to read as follows:
§ 25.21
(ii) The airplane is equipped with reversible flight controls.
(2) Each requirement of this subpart, except §§ 25.121(a), 25.123(c), 25.143(b)(1) and (2), 25.149, 25.201(c)(2), 25.207(c) and (d), 25.239, and 25.251(b) through (e), must be met in the icing conditions specified in appendix C of this part. Compliance must be shown using the ice accretions defined in part II of appendix C of this part, assuming normal operation of the airplane and its ice protection system in accordance with the operating limitations and operating procedures established by the applicant and provided in the Airplane Flight Manual.
(3) If the applicant does not seek certification for flight in all icing conditions defined in appendix O of this part, each requirement of this subpart, except §§ 25.105, 25.107, 25.109, 25.111, 25.113, 25.115, 25.121, 25.123, 25.143(b)(1), (b)(2), and (c)(1), 25.149, 25.201(c)(2), 25.207(c) and (d), 25.239, and 25.251(b) through (e), must be met in the appendix O icing conditions for which certification is not sought in order to allow a safe exit from those conditions. Compliance must be shown using the ice accretions defined in part II, paragraphs (b) and (d) of appendix O of this part, assuming normal operation of the airplane and its ice protection system in accordance with the operating limitations and operating procedures established by the applicant and provided in the Airplane Flight Manual.
(4) If the applicant seeks certification for flight in any portion of the icing conditions of appendix O of this part, each requirement of this subpart, except §§ 25.123(c), 25.143(b)(1) and (2), 25.149, 25.201(c)(2), 25.207(c) and (d), 25.239, and 25.251(b) through (e), must be met in the appendix O icing conditions for which certification is sought. Compliance must be shown using the ice accretions defined in part II, paragraphs (c) and (d) of appendix O of this part, assuming normal operation of the airplane and its ice protection system in accordance with the operating limitations and operating procedures established by the applicant and provided in the Airplane Flight Manual.
3. Amend § 25.105 by revising paragraph (a)(2) introductory text to read as follows:
§ 25.105
(2) In icing conditions, if in the configuration used to show compliance with § 25.121(b), and with the most critical of the takeoff ice accretion(s) defined in appendices C and O of this part, as applicable, in accordance with § 25.21(g):
4. Amend § 25.111 by revising paragraphs (c)(5)(i) and (c)(5)(ii) to read as follows:
§ 25.111
(i) With the most critical of the takeoff ice accretion(s) defined in appendices C and O of this part, as applicable, in accordance with § 25.21(g), from a height of 35 feet above the takeoff surface up to the point where the airplane is 400 feet above the takeoff surface; and
(ii) With the most critical of the final takeoff ice accretion(s) defined in appendices C and O of this part, as applicable, in accordance with § 25.21(g), from the point where the airplane is 400 feet above the takeoff surface to the end of the takeoff path.
5. Amend § 25.119 by revising paragraph (b) to read as follows:
§ 25.119
(b) In icing conditions with the most critical of the landing ice accretion(s) defined in appendices C and O of this part, as applicable, in accordance with § 25.21(g), and with a climb speed of V REF
determined in accordance with § 25.125(b)(2)(ii).
6. Amend § 25.121 by revising paragraphs (b)(2)(ii) introductory text, (c)(2)(ii) introductory text, and (d)(2)(ii) to read as follows:
§ 25.121
(ii) In icing conditions with the most critical of the takeoff ice accretion(s) defined in appendices C and O of this part, as applicable, in accordance with § 25.21(g), if in the configuration used to show compliance with § 25.121(b) with this takeoff ice accretion:
(ii) In icing conditions with the most critical of the final takeoff ice accretion(s) defined in appendices C and O of this part, as applicable, in accordance with § 25.21(g), if in the configuration used to show compliance with § 25.121(b) with the takeoff ice accretion used to show compliance with § 25.111(c)(5)(i):
(ii) In icing conditions with the most critical of the approach ice accretion(s) defined in appendices C and O of this part, as applicable, in accordance with § 25.21(g). The climb speed selected for non-icing conditions may be used if the climb speed for icing conditions, computed in accordance with paragraph (d)(1)(iii) of this section, does not exceed that for non-icing conditions by more than the greater of 3 knots CAS or 3 percent.
7. Amend § 25.123 by revising paragraph (b)(2) introductory text to read as follows:
§ 25.123
(2) In icing conditions with the most critical of the en route ice accretion(s) defined in appendices C and O of this part, as applicable, in accordance with § 25.21(g), if:
8. Amend § 25.125 by revising paragraphs (a)(2), (b)(2)(ii)(B), and (b)(2)(ii)(C) to read as follows:
§ 25.125
(2) In icing conditions with the most critical of the landing ice accretion(s) defined in appendices C and O of this part, as applicable, in accordance with § 25.21(g), if V REF
for icing conditions exceeds V REF
for non-icing conditions by more than 5 knots CAS at the maximum landing weight.
(B) 1.23 V SR0
with the most critical of the landing ice accretion(s) defined in appendices C and O of this part, as applicable, in accordance with § 25.21(g), if that speed exceeds V REF
selected for non-icing conditions by more than 5 knots CAS; and
(C) A speed that provides the maneuvering capability specified in § 25.143(h) with the most critical of the landing ice accretion(s) defined in appendices C and O of this part, as applicable, in accordance with § 25.21(g).
9. Amend § 25.143 by revising paragraphs (c) introductory text, (i)(1), and (j) introductory text to read as follows:
§ 25.143
(c) The airplane must be shown to be safely controllable and maneuverable with the most critical of the ice accretion(s) appropriate to the phase of flight as defined in appendices C and O of this part, as applicable, in accordancewith § 25.21(g), and with the critical engine inoperative and its propeller (if applicable) in the minimum drag position:
(1) Controllability must be demonstrated with the most critical of the ice accretion(s) for the particular flight phase as defined in appendices C and O of this part, as applicable, in accordance with § 25.21(g);
(j) For flight in icing conditions before the ice protection system has been activated and is performing its intended function, it must be demonstrated in flight with the most critical of the ice accretion(s) defined in appendix C, part II, paragraph (e) of this part and appendix O, part II, paragraph (d) of this part, as applicable, in accordance with § 25.21(g), that:
10. Amend § 25.207 by revising paragraphs (b), (e)(1) through (5), and (h) introductory text to read as follows:
(1) The most critical of the takeoff ice and final takeoff ice accretions defined in appendices C and O of this part, as applicable, in accordance with § 25.21(g), for each configuration used in the takeoff phase of flight;
(2) The most critical of the en route ice accretion(s) defined in appendices C and O of this part, as applicable, in accordance with § 25.21(g), for the en route configuration;
(3) The most critical of the holding ice accretion(s) defined in appendices C and O of this part, as applicable, in accordance with § 25.21(g), for the holding configuration(s);
(4) The most critical of the approach ice accretion(s) defined in appendices C and O of this part, as applicable, in accordance with § 25.21(g), for the approach configuration(s); and
(5) The most critical of the landing ice accretion(s) defined in appendices C and O of this part, as applicable, in accordance with § 25.21(g), for the landing and go-around configuration(s).
(h) The following stall warning margin is required for flight in icing conditions before the ice protection system has been activated and is performing its intended function. Compliance must be shown using the most critical of the ice accretion(s) defined in appendix C, part II, paragraph (e) of this part and appendix O, part II, paragraph (d) of this part, as applicable, in accordance with § 25.21(g). The stall warning margin in straight and turning flight must be sufficient to allow the pilot to prevent stalling without encountering any adverse flight characteristics when:
11. Amend § 25.237 by revising paragraph (a)(3)(ii) to read as follows:
§ 25.237
(ii) Icing conditions with the most critical of the landing ice accretion(s) defined in appendices C and O of this part, as applicable, in accordance with § 25.21(g).
12. Amend § 25.253 by revising paragraph (c) introductory text to read as follows:
§ 25.253
(c) Maximum speed for stability characteristics in icing conditions.
The maximum speed for stability characteristics with the most critical of the ice accretions defined in appendices C and O of this part, as applicable, in accordance with § 25.21(g), at which the requirements of §§ 25.143(g), 25.147(e), 25.175(b)(1), 25.177 and 25.181 must be met, is the lower of:
13. Amend § 25.773 by revising paragraph (b)(1)(ii) to read as follows:
§ 25.773
(A) For airplanes certificated in accordance with § 25.1420(a)(1), the icing conditions that the airplane is certified to safely exit following detection.
(B) For airplanes certificated in accordance with § 25.1420(a)(2), the icing conditions that the airplane is certified to safely operate in and the icing conditions that the airplane is certified to safely exit following detection.
(C) For airplanes certificated in accordance with § 25.1420(a)(3) and for airplanes not subject to § 25.1420, all icing conditions.
14. Amend § 25.903 by adding paragraph (a)(3) to read as follows:
§ 25.903
15. Amend § 25.929 by revising paragraph (a) to read as follows:
§ 25.929
16. Amend § 25.1093 by revising paragraph (b) to read as follows:
§ 25.1093
(1) Operate throughout its flight power range, including the minimum descent idling speeds, in the icingconditions defined in appendices C and O of this part, and appendix D of part 33 of this chapter, and in falling and blowing snow within the limitations established for the airplane for such operation, without the accumulation of ice on the engine, inlet system components or airframe components that would do any of the following:
(2) Idle for a minimum of 30 minutes on the ground in the following icing conditions shown in Table 1, unless replaced by similar test conditions that are more critical. These conditions must be demonstrated with the available air bleed for icing protection at its critical condition, without adverse effect, followed by an acceleration to takeoff power or thrust. During the idle operation the engine may be run up periodically to a moderate power or thrust setting in a manner acceptable to the Administrator. The applicant must document the engine run-up procedure (including the maximum time interval between run-ups from idle, run-up power setting, and duration at power) and associated minimum ambient temperature demonstrated for the maximum time interval, and these conditions must be used in establishing the airplane operating limitations in accordance with § 25.1521.
Water concentration(minimum)
(i) Rime ice condition
0 to 15 °F (−18 to −9 °C)
Liquid—0.3 g/m 3
By test, analysis or combination of the two.
(ii) Glaze ice condition
20 to 30 °F (−7 to −1 °C)
(iii) Large drop condition
15 to 30 °F (−9 to −1 °C)
100 microns (minimum)
17. Amend § 25.1323 by revising paragraph (i) to read as follows:
§ 25.1323
(1) For airplanes certificated in accordance with § 25.1420(a)(1), the icing conditions that the airplane is certified to safely exit following detection.
(2) For airplanes certificated in accordance with § 25.1420(a)(2), the icing conditions that the airplane is certified to safely operate in and the icing conditions that the airplane is certified to safely exit following detection.
(3) For airplanes certificated in accordance with § 25.1420(a)(3) and for airplanes not subject to § 25.1420, all icing conditions.
Liquid watercontent
Ice median massdimension
Liquid water MVD
(n miles)
0 to −20
3,000 to 9,000
5100500
4,500 to 12,000
520100500
31050300
18. Add § 25.1324 to read as follows:
§ 25.1324
Each angle of attack system sensor must be heated or have an equivalent means of preventing malfunction in the mixed phase and ice crystal conditions as defined in § 25.1323, the icing conditions defined in appendix C of this part, and the following icing conditions specified in appendix O of this part:
19. Amend § 25.1325 by revising paragraph (b) to read as follows:
§ 25.1325
(2) The correlation between air pressure in the static pressure system and true ambient atmospheric static pressure is not changed when theairplane is exposed to the icing conditions defined in appendix C of this part, and the following icing conditions specified in appendix O of this part:
(i) For airplanes certificated in accordance with § 25.1420(a)(1), the icing conditions that the airplane is certified to safely exit following detection.
(ii) For airplanes certificated in accordance with § 25.1420(a)(2), the icing conditions that the airplane is certified to safely operate in and the icing conditions that the airplane is certified to safely exit following detection.
(iii) For airplanes certificated in accordance with § 25.1420(a)(3) and for airplanes not subject to § 25.1420, all icing conditions.
20. Add § 25.1420 to read as follows:
§ 25.1420
(a) If certification for flight in icing conditions is sought, in addition to the requirements of § 25.1419, an airplane with a maximum takeoff weight less than 60,000 pounds or with reversible flight controls must be capable of operating in accordance with paragraphs (a)(1), (2), or (3), of this section.
(c) For an airplane certified in accordance with paragraph (a)(2) or (a)(3) of this section, the requirements of § 25.1419 (e), (f), (g), and (h) must be met for the icing conditions defined in appendix O of this part in which the airplane is certified to operate.
21. Amend § 25.1521 by redesignating paragraph (c)(3) as (c)(4) and revising it, and by adding new paragraph (c)(3) to read as follows:
§ 25.1521
(3) Maximum time interval between engine run-ups from idle, run-up power setting, duration at power, and the associated minimum ambient temperature demonstrated for the maximum time interval, for ground operation in icing conditions, as defined in § 25.1093(b)(2).
22. Amend § 25.1533 by adding paragraph (c) to read as follows:
§ 25.1533
(c) For airplanes certified in accordance with § 25.1420(a)(1) or (a)(2), an operating limitation must be established to require exiting all icing conditions if icing conditions defined in appendix O of this part are encountered for which the airplane has not been certified to safely operate.
Liquid water content (LWC) in grams per cubic meter (g/m 3
) based on horizontal extent standard distance of 17.4 nautical miles.
LWC in grams per cubic meter (g/m 3
(1) For an airplane certified in accordance with § 25.1420(a)(1), the ice accretions for each flight phase are defined in part II, paragraph (b) of this appendix.
(2) For an airplane certified in accordance with § 25.1420(a)(2), the most critical ice accretion for each flight phase defined in part II, paragraphs (b) and (c) of this appendix, must be used. For the ice accretions defined in part II, paragraph (c) of this appendix, only the portion of part I of this appendix in which the airplane is capable of operating safely must be considered.
(3) For an airplane certified in accordance with § 25.1420(a)(3), the ice accretions for each flight phase are defined in part II, paragraph (c) of this appendix.
(b) Ice accretions for airplanes certified in accordance with § 25.1420(a)(1) or (a)(2).
(1) En route ice
is the en route ice as defined by part II, paragraph (c)(3), of this appendix, for an airplane certified in accordance with § 25.1420(a)(2), or defined by part II, paragraph (a)(3), of appendix C of this part, for an airplane certified in accordance with § 25.1420(a)(1), plus:
(2) Holding ice
is the holding ice defined by part II, paragraph (c)(4), of this appendix, for an airplane certified in accordance with § 25.1420(a)(2), or defined by part II, paragraph (a)(4) of appendix C of this part, for an airplane certified in accordance with § 25.1420(a)(1), plus:
(3) Approach ice
is the more critical of the holding ice defined by part II, paragraph (b)(2) of this appendix, or the ice calculated in the applicable paragraph (b)(3)(i) or (ii) of part II of this appendix:
(i) For an airplane certified in accordance with § 25.1420(a)(2), the ice accumulated during descent from the maximum vertical extent of the icing conditions defined in part I of this appendix to 2,000 feet above the landing surface in the cruise configuration, plus transition to the approach configuration, plus:
(B) The ice accumulated during the transit at 2,000 feet above the landing surface of one cloud with a horizontal extent of 17.4 nautical miles in the most critical of the icing conditions defined in part I of this appendix and one cloud with a horizontal extent of 17.4 nautical miles in the continuousmaximum icing conditions defined in appendix C of this part.
(ii) For an airplane certified in accordance with § 25.1420(a)(1), the ice accumulated during descent from the maximum vertical extent of the maximum continuous icing conditions defined in part I of appendix C to 2,000 feet above the landing surface in the cruise configuration, plus transition to the approach configuration, plus:
(4) Landing ice
is the more critical of the holding ice as defined by part II, paragraph (b)(2) of this appendix, or the ice calculated in the applicable paragraph (b)(4)(i) or (ii) of part II of this appendix:
(i) For an airplane certified in accordance with § 25.1420(a)(2), the ice accretion defined by part II, paragraph (c)(5)(i) of this appendix, plus a descent from 2,000 feet above the landing surface to a height of 200 feet above the landing surface with a transition to the landing configuration in the icing conditions defined in part I of this appendix, plus:
(B) The ice accumulated during an exit maneuver, beginning with the minimum climb gradient required by § 25.119, from a height of 200 feet above the landing surface through one cloud with a horizontal extent of 17.4 nautical miles in the most critical of the icing conditions defined in part I of this appendix and one cloud with a horizontal extent of 17.4 nautical miles in the continuous maximum icing conditions defined in appendix C of this part.
(ii) For an airplane certified in accordance with § 25.1420(a)(1), the ice accumulated in the maximum continuous icing conditions defined in appendix C of this part, during a descent from the maximum vertical extent of the icing conditions defined in appendix C of this part, to 2,000 feet above the landing surface in the cruise configuration, plus transition to the approach configuration and flying for 15 minutes at 2,000 feet above the landing surface, plus a descent from 2,000 feet above the landing surface to a height of 200 feet above the landing surface with a transition to the landing configuration, plus:
(5) Pre-detection ice
is the ice accretion before detection of appendix O conditions that require exiting per § 25.1420(a)(1) and (a)(2). It is the pre-existing ice accretion that may exist from operating in icing conditions in which the airplane is approved to operate prior to encountering the icing conditions requiring an exit, plus the ice accumulated during the time needed to detect the icing conditions, followed by two minutes of further ice accumulation to take into account the time for the flight crew to take action to exit the icing conditions, including coordination with air traffic control.
(i) For an airplane certified in accordance with § 25.1420(a)(1), the pre-existing ice accretion must be based on the icing conditions defined in appendix C of this part.
(ii) For an airplane certified in accordance with § 25.1420(a)(2), the pre-existing ice accretion must be based on the more critical of the icing conditions defined in appendix C of this part, or the icing conditions defined in part I of this appendix in which the airplane is capable of safely operating. The pre-detection ice accretion applies in showing compliance with §§ 25.143(k) and 25.207(k), and as part of the ice accretion definitions of part II, paragraph (b)(1) through (b)(4) of this appendix.
(c) Ice accretions for airplanes certified in accordance with §§ 25.1420(a)(2) or 25.1420(a)(3).
For an airplane certified in accordance with § 25.1420(a)(2), only the portion of the icing conditions of part I of this appendix in which the airplane is capable of operating safely must be considered.
(1) Takeoff ice
is the most critical ice accretion on unprotected surfaces, and any ice accretion on the protected surfaces appropriate to normal ice protection system operation, occurring between liftoff and 400 feet above the takeoff surface, assuming accretion starts at liftoff in the icing conditions defined in part I of this appendix.
(2) Final takeoff ice
is the most critical ice accretion on unprotected surfaces, and any ice accretion on the protected surfaces appropriate to normal ice protection system operation, between 400 feet and either 1,500 feet above the takeoff surface, or the height at which the transition from the takeoff to the en route configuration is completed and V FTO
is reached, whichever is higher. Ice accretion is assumed to start at liftoff in the icing conditions defined in part I of this appendix.
(3) En route ice
is the most critical ice accretion on the unprotected surfaces, and any ice accretion on the protected surfaces appropriate to normal ice protection system operation, during the en route flight phase in the icing conditions defined in part I of this appendix.
(4) Holding ice
is the most critical ice accretion on the unprotected surfaces, and any ice accretion on the protected surfaces appropriate to normal ice protection system operation, resulting from 45 minutes of flight within a cloud with a 17.4 nautical miles horizontal extent in the icing conditions defined in part I of this appendix, during the holding phase of flight.
(5) Approach ice
is the ice accretion on the unprotected surfaces, and any ice accretion on the protected surfaces appropriate to normal ice protection system operation, resulting from the more critical of the:
(6) Landing ice
(i) Ice accretion defined by part II, paragraph (c)(5)(i), of this appendix, plus ice accumulated in the icing conditions defined in part I of this appendix during a descent from 2,000 feet above the landing surface to a height of 200 feet above the landing surface with a transition to the landing configuration, followed by a go-around at the minimum climb gradient required by § 25.119, from a height of 200 feet above the landing surface to 2,000 feet above the landing surface, flying for 15 minutes at 2,000 feet above the landing surface in the approach configuration, and a descent to the landing surface (touchdown) in the landing configuration; or
(iv) Failure of the critical engine occurs at V EF
(d) The ice accretion before the ice protection system has been activated and is performing its intended function is the critical ice accretion formed on the unprotected and normally protected surfaces before activation and effective operation of the ice protection system in the icing conditions defined in part I of this appendix. This ice accretion only applies in showing compliance to §§ 25.143(j) and 25.207(h).
(e) In order to reduce the number of ice accretions to be considered when demonstrating compliance with the requirements of § 25.21(g), any of the ice accretions defined in this appendix may be used for any other flight phase if it is shown to be more critical than the specific ice accretion defined for that flight phase. Configuration differences and their effects on ice accretions must be taken into account.
(f) The ice accretion that has the most adverse effect on handling qualities may beused for airplane performance tests provided any difference in performance is conservatively taken into account.
Part 33 Airworthiness Standards Aircraft Engines
25. Revise § 33.68 to read as follows:
§ 33.68
(c) In addition to complying with § 33.68(b), the following conditions shown in Table 1 of this section unless replaced by similar CPA test conditions that are more critical or produce an equivalent level of severity, must be demonstrated by an engine test:
Total airtemperature
Supercooled water concentrations(minimum)
Median volume drop diameter(±3 microns)
1. Glaze ice conditions
21 to 25 °F (−6 to −4 °C)
2 g/m 3
(a) 10 minutes for power below sustainable level flight (idle descent).
2. Rime ice conditions
−10 to 0 °F (−23 to −18 °C)
1 g/m 3
3. Glaze ice holding conditions (Turboprop and turbofan, only)
Turbofan, only: 10 to 18 °F (−12 to −8 °C)Turboprop, only: 2 to 10 °F (−17 to −12 °C)
Alternating cycle: 0.3 g/m 3
(6 minute) 1.7 g/m 3
Must show repetitive, stabilized operation (or 45 minutes max).
4. Rime ice holding conditions (Turboprop and turbofan, only)
Turbofan, only: −10 to 0 °F (−23 to −18 °C)Turboprop, only: 2 to 10 °F (−17 to −12 °C)
0.25 g/m 3
(d) The engine should be run at ground idle speed for a minimum of 30 minutes at each of the following icing conditions shown in Table 2 of this section with the available air bleed for icing protection at its critical condition, without adverse effect, followed by acceleration to takeoff power or thrust. During the idle operation the engine may be run up periodically to a moderate power or thrust setting in a manner acceptable to the Administrator. The applicant must document any demonstrated run ups and minimum ambient temperature capability during the conduct of icing testing in the engine operating manual as mandatory in icing conditions. The applicant must demonstrate, with consideration of expected airport elevations, the following:
Supercooled waterconcentrations(minimum)
1. Rime ice condition
0 to 15 °F (−8 to −9 °C)
By engine test.
2. Glaze ice condition
3. Snow ice condition
26 to 32 °F (−3 to 0 °C)
Ice—0.9 g/m 3
4. Large drop glaze ice condition
100 microns (minimum); 3000 microns (maximum)
26. Amend § 33.77 by adding paragraph (a) and by revising paragraphs (c) introductory text, (c)(1), (d), and (e)(1) through (4) to read as follows:
§ 33.77
Engine inlet hilite area(sq inch)
Appendix D to Part 33 Mixed Phase and Ice Crystal Icing Envelope Deep Convective Clouds
Within the envelope, total water content (TWC) in g/m 3
has been determined based upon the adiabatic lapse defined by the convective rise of 90% relative humidity air from sea level to higher altitudes and scaled by a factor of 0.65 to a standard cloud length of 17.4 nautical miles. Figure D2 displays TWC for this distance over a range of ambient temperature within the boundaries of the ice crystal envelope specified in Figure D1.
Temperaturerange—deg C
LWC—g/m 3
</= 50 miles
</=1.0
Appendix 1 of this preamble contains definitions of certain terms used in this notice of proposed rulemaking (NPRM).
NTSB recommendations A-96-54 and A-96-56; available in the Docket and on the Internet at: http://www.ntsb.gov/Recs/letters/1996/A96_48_69.pdf.
Published in theFederal Register, December 8, 1997 (62 FR 64621).
14 CFR 25.1419, Ice Protection.
For a complete discussion of the regulations see Amendment 25-121 (72 FR 44665, August 8, 2007), and Amendment 25-129 (74 FR 38328, August 3, 2009).
14 CFR 91.527, Operating in icing conditions; and § 135.227, Icing conditions: Operating limitations.
14 CFR 121.629(a), Operation in icing conditions and § 121.341, Equipment for operations in icing conditions.
NTSB recommendation A-96-54; available in the Docket and on the Internet at: http://www.ntsb.gov/Recs/letters/1996/A96_48_69.pdf.
NTSB recommendation A-96-56; available in the Docket and on the Internet at: http://www.ntsb.gov/Recs/letters/1996/A96_48_69.pdf.
These requirements were recently adopted in Amendment 25-129 (74 FR 38328, August 3, 2009). Generally, that amendment requires methods to detect airframe icing and to activate and operate ice protection systems.
14 CFR 25.21(g)(1) is proposed to be redesignated as § 25.21(g)(2).
The exceptions listed in this requirement are §§ 25.121(a), 25.123(c), 25.143(b)(1) and (b)(2), 25.149, 25.201(c)(2), 25.207(c) and (d), 25.239, and 25.251(b) through (e).
For a complete discussion of these requirements, see
Amendment 25-121 (72 FR 44665, August 8, 2007).
14 CFR 25.105, 25.107, 25.109, 25.111, 25.113, 25.121, and 25.123.
14 CFR 25.773, 25.929, 25.1093, 25.1323, and 25.1325.
14 CFR 25.773, 25.1323, and 25.1325.
FAA report DOT/FAA/AR-09/13, Technical Compendium from Meetings of the Engine Harmonization Working Group, March 2009 for details on appendix D and its development.
14 CFR 25.1323, and 25.1324.
The complete IPHWG working group report is available on the Internet at http://regulations.gov.
A copy will also be placed in the docket (FAA-2010-0636).
A copy of the Initial Regulatory Evaluation (dated October 5, 2009) can be found in the docket (FAA-2010-0636).
14 CFR 25.773, 25.1323, 25.1324, and 25.1325.
The docket number is FAA-2010-0636.
Due Aug 30 2010, at 11:59 PM ET
FAA-2010-0636-0001
This submission elaborates upon comments previously submitted by J. Marwitz. Please see the uploaded file.
Please disregard previous version of the document and consider this one.
Additional pages to Enclosure 2 (pp. 10-19) of Boeing Commercial Airplanes letter of comments (B-H300-10-DML-41) to Docket FAA-2010-0636.
U.S. DOT/FAA - Letter of Determination to Not Extend the...
Airbus - Request for Extension of Comments
Aerospace Industries Association & General Aviation...
You are viewing a non-interactive page that is intended for the crawler. You probably want to see this page: http://www.regulations.gov/#!submitComment;D=USPS-2012-0087-0001