Significant Regulatory Activity

Safety in icing conditions: NPRM -- Airplane performance and handling qualities in icing conditions

Nov. 4 FR Doc 05-21793 Docket No. 2005-22840 Notice No. 05-10

The Federal Aviation Administration (FAA) proposes upgraded airworthiness standards, to be applied to new aircraft designs, to increase the level of safety in icing conditions and to harmonize U.S. regulations with those of Europe. This is an extensive document, running some 57 pages.

The executive summary covers much of the rationale for this initiative:

"Part 25 [of the code of Federal Regulations] does not currently include specific requirements for airplane performance or handling qualities for flight in icing conditions. Although part 25 requires airplanes with approved ice protection features to be able to operate safety in icing conditions, there is no standard set of criteria defining what 'to safely operate' in icing conditions means in terms of airplane performance and handling qualities. Further, because the existing icing regulations only address airplanes with ice protection provisions, it is unclear what requirements apply in cases where the applicant is seeking to have an airplane without an ice protection system certificated for flight in icing conditions.

"This notice proposes to amend part 25 by adding a comprehensive set of airworthiness requirements that must be met to receive certification approval for flight in icing conditions, including specific performance and handling qualities requirements, and the ice accretion (that is, the size, shape, location, and texture of the ice) that must be considered for each phase of flight. These proposed revisions would ensure that minimum operating speeds determined during the certification of all future transport category airplanes would provide adequate maneuver capability in icing conditions for all phases of flight and all airplane configurations.

"This notice proposes to require the same airplane handling characteristics that apply in non-icing conditions to continue to apply in icing conditions. Additionally, a specific evaluation for susceptibility to tailplane stall in icing conditions would be added.

"This proposal, if adopted, would harmonize the U.S. and European airworthiness standards for flight in icing conditions. It would benefit the public interest while retaining or enhancing the current level of safety for operation in icing conditions.

"If adopted, this rulemaking would affect manufacturers, modifiers, and operators of transport category airplanes (but only for new designs or significant changes to current designs that would affect the safety of flight in icing conditions). ...

"Service history shows that flight in icing conditions may be a safety risk for transport category airplanes. There have been nine accidents since 1983 that may have been prevented if this proposed rule had been in effect. ...

"The NTSB [National Transportation Safety Board] has issued several safety recommendations related to airframe icing, some of which are addressed, at least in part, by this notice. If adopted, this rulemaking would require, during type certification, that manufacturers of transport category airplanes:

• Investigate the susceptibility of their airplanes to ice-contaminated tailplane stall (ICTS);
• Provide for adequate warning on the flight deck of an impending stall in icing conditions;
• Show that their airplanes meet the same maneuvering capability and handling characteristics requirements in icing conditions as in non-icing conditions; and
• Show that their airplanes have adequate performance capability in icing conditions. ...

"The FAA has determined that this rulemaking would have the following costs and benefits over a 45-year analysis period. The cost of the proposed rule would be $22.0 million ... the potential benefit ... would be $89.9 million ..."

Also in the docket is a related advisory circular (AC) outlining the means by which applicants can comply with the new requirements (see below).

Comments due Feb. 6, 2006.

Safety in icing conditions: Notice of availability of proposed AC 25.21-1X, "Performance and Handling Characteristics in the Icing Conditions Specified in Part 25, Appendix C," and request for comments -- Airplane performance and handling qualities in icing conditions

Nov. 4 FR Doc 05-21791

The FAA publishes a draft 37-page AC indicating how an applicant can comply with the new certification standards alluded to in the above item. The draft AC's provisions are based not only on research, but on past accidents and the price paid in broken aluminum and dead bodies. For example, its discussion about takeoff performance involving aircraft without leading edge high lift devices, or the so-called hard wing, are based on numerous accidents on takeoff of early-model DC-9s, which featured hard wings. Extracts from the draft AC as follows:

"In determining the probability of a failure condition, it should be assumed that the probability of entering icing conditions is one." (Emphasis in original)

"For probable failure conditions that are annunciated to the flightcrew, and the associated operating procedure requires the airplane to leave the icing conditions as soon as practicable, it should be shown that the airplane's resulting performance and handling characteristics with the failure ice accretion are commensurate with the hazard level as determined by a system safety analysis ... The operating procedures and related speeds may restrict the airplane's operating envelope, but the size of the restricted envelope should be consistent with the safety analysis."

"The ice protection systems may not adequately perform their anti-ice or deice functions at some engine power or thrust settings. This may result in establishing a minimum useable power or thrust setting for operation in icing conditions, which can affect descent or approach capabilities. The effect of power or thrust settings should also be considered in determining the applicable ice accretions. For example, at low power or thrust, a thermal bleed air system may not be able to completely evaporate the liquid after melting the ice, resulting in the potential for runback ice."

"Any airspeed limitations associated with flight in icing conditions should be presented, such as the minimum airspeed for each normal airplane configuration in icing conditions."

"For turbojet airplanes without leading edge high lift devices [such as many regional jets now entering service], unless the applicant shows that the airplane retains sufficient stall and stall warning margins during takeoff with residual ice contamination, or that such contamination would otherwise be detected and removed before takeoff, the AFM [airplane flight manual] Limitations section should contain statements similar to the following:

Takeoff may not be initiated unless the flight crew verifies that a visual and tactile (hands on surface) check of the wing upper surfaces and leading edges have been accomplished, and the wings are free of frost, ice, or snow in conditions conducive to ice/frost/snow formation. Conditions conducive to ice/frost/snow formation exist whenever the outside air temperature is below 6 degrees C (42 degrees F) and either: (1) visible moisture is present in the air or on the wing, or (2) the difference between the dew point temperature and the outside air temperature is less than 3 degrees C (5 degrees F)."

"For turbojet airplanes without leading edge high-lift devices, unless the applicant shows that the airplane retains sufficient stall and stall warning margins during takeoff with residual ice contamination, the AFM normal operating procedures section should contain statements similar to the following along with the procedures to be followed to ensure that such contamination is detected and removed prior to takeoff:

WARNING

The Model XX airplane has a wing design with no leading edge high lift devices, such as slats. Wings without leading edge high lift devices are particularly susceptible to loss of lift and stall speed margin because of wing icing. Minute amounts of ice or other contamination on the leading edges or wing upper surfaces can result in a stall without warning, leading to loss of control on takeoff."

"The applicant should determine the effect of the 45-minute hold in continuous maximum icing conditions [the ATR-72 that crashed from icing at Roselawn, Ill., in 1994 was in a holding pattern]. The analysis should assume that the airplane remains in a rectangular 'race track' pattern, with all turns being made within the icing cloud. Therefore, no horizontal extent correction should be used for this analysis. The applicant should substantiate the critical mean effective drop diameter, LWC [liquid water content], and temperature that result in the formation of an ice accretion that is critical to the airplane's performance and handling qualities. The shape and texture of the ice are important and should be agreed to by the responsible aircraft certification office."

"Sandpaper ice is the most critical thin, rough layer of ice. Carborundum sandpaper no. 40 (that is, 40-grit) has been used in past certification programs to represent sandpaper ice. However ... the uniformly distributed roughness of carborundum grit may not result in aerodynamic effects similar to those of the actual intercycle ice surface roughness. The applicant should validate the use of uniformly distributed roughness to simulate sandpaper ice, particularly for intercycle ice accretions."

Comments due Jan. 3, 2006.

Aviation security: NPRM, reopening of comment period and notice of public meeting -- Special flight rules area (SFRA) for Washington, D.C., metropolitan area

Nov. 7 FR 05-22261 Docket No. FAA-2004-17005 Notice No. 05-12

FAA reopens the comment period on proposed security rules, which initially closed Nov. 2 (see ASW, Aug. 15). The FAA received over 18,000 comments on the proposed flight restrictions, and they are still coming in. "We will file in the docket all comments we receive," the FAA promises, indicating that the extension responds to requests from Congress and industry associations.

Comments are now due Feb. 6, 2006.

The FAA also announces that it will hold a public meeting on its proposed restrictions, at a time and place to be announced.

Source: U.S. Federal Register, see http://www.gpoaccess.gov/fr/index.html