Effective Date:
8/31/06
Cancellation Date:
8/31/07
SUBJ: GUIDANCE AND PROCEDURES FOR DISPATCHING DURING LIGHT ICE
PELLET AND IN HEAVY SNOW CONDITIONS
1. PURPOSE. This notice provides guidance to aviation safety inspectors (ASI) and to all air carrier operators for allowance times in light ice pellet conditions and procedures for dispatch in heavy snow conditions.
2. DISTRIBUTION. This notice is distributed to the division level in the Flight Standards Service in Washington headquarters; to the branch level in the regional Flight Standards divisions; to the Flight Standards District Offices; and to the Regulatory Standards Division at the Mike Monroney Aeronautical Center. This notice is also distributed electronically to the division level in the Flight Standards Service in Washington headquarters and to all regional Flight Standards divisions and district offices. This information is also available on the Federal Aviation Administration’s (FAA) employee Web site at http://fsims.avr.faa.gov/fsims/fsims.nsf/ and on the FAA Web site at http://www.faa.gov/library/manuals/examiners_inspectors/8000/.
3. CANCELLATION. This notice cancels notices N 8000.309, Dispatching During Precipitation Conditions of Ice Pellets, Snow Pellets, or Other Icing Events for Which No Holdover Times Exist, dated 10/05/05; and N 8000.313, Parts 121 and 135 Operations Specification for Deicing/Anti-Icing, Operations in Ice Pellets without Deice/Anti-Ice Fluids, dated 10/21/05.
4. BACKGROUND. In October 2005, the FAA issued Notices 8000.309 and 8000.313 to address dispatching during ice pellet, snow pellet, and other icing conditions for which no holdover times exist. As a result of these notices, industry requested the FAA conduct research to obtain data to support relief for certain icing conditions for which no holdover times exist. That research was conducted during the winter season of 2005-06. The following relief is a result of the data obtained from the research and from further review of existing data. Although the following allowances under the stated precipitation condition are provided, the general requirement that takeoffs not be attempted with any contaminate adhering to the critical surfaces of the aircraft still applies.
5. DISCUSSION.
a. Operations in Light Ice Pellets (Without any other Forms of Precipitation Present).
(1) Tests have shown that ice pellets generally remain in the frozen state when imbedded in Type IV anti-icing fluid and are not absorbed by the fluid in the same manner as other forms of precipitation. Using current guidelines for determining anti-icing fluid failure, the presence of a contaminate not absorbed by the fluid (remaining imbedded) would be an indication that the fluid has failed. Ice pellets imbedded in Type IV fluids are generally not detectable by the human eye during pre-takeoff contamination check procedures. Therefore, a pre-takeoff contamination check in light ice pellet conditions would not be of value and is not required.
(2) The research data has also shown that after proper deicing and anti-icing, the accumulation of light ice pellets in Type IV fluid will still sheer from the aerodynamic surfaces during takeoff. This sheering occurs with rotation speeds consistent with Type IV recommended applications for up to 25 minutes from the start of the Type IV anti-icing fluid application.
(3) Operators with a deicing program approved in accordance with Title 14 of the Code of Federal Regulations (14 CFR) part 121, section 121.629, will be allowed, in light ice pellet conditions with no other form of precipitation present, up to 25 minutes after the start of the anti-icing fluid application to commence the takeoff with the following restrictions:
(a) The aircraft critical surfaces must be free of contaminates before applying Type IV anti-icing fluid. Or, the aircraft must be properly deiced and free of contaminates before the application of Type IV anti-icing fluid.
(b) An allowance time, of up to 25 minutes, is valid only if the aircraft is anti-iced with undiluted Type IV fluid.
(c) Due to the sheer characteristics of Type IV fluids with ice pellets imbedded in it, the allowance is limited to aircraft with a rotation speed of 100 knots or greater.
(d) If the takeoff is not accomplished within the 25 minutes allowed, the aircraft must be completely deiced and, if freezing precipitation continues, anti-iced again before a subsequent takeoff.
(e) A pre-takeoff contamination check is not required. The allowance time of up to 25 minutes cannot be extended by an internal or external check of the aircraft critical surfaces.
(f) If ice pellet precipitation becomes heavier than light or is mixed with any other form of precipitation, the 25-minute allowance time cannot be used.