AC 135- 9 DATE 5/30/u
ADVISORY- CIRCULAR
DEPARTMENT OF TRANSPORTATION Federal Aviation Adminirtration Wuhinpton, D.C.
FAR C;UIDANCE MATERIAL Su bject : FAR PAKI' 135 ICING LIMITATIONS
1. PURP0SE. l?o provide information and guidance to cwmnter air carriers and air taxi operators axcerning the requirements of Federal Aviation Regulations (FAR) Part 135, Section 135.227, Icing Conditions: -rating Limitations.
2. mcus. The information in this Advisory Circular (AC) applies to ertificate holders using aircraft that are rx& certificated for operations into icing conditions.
3. RELATED READING MATERIAL. Airman’s Information Manual: AC OO-45B, Aviation Weather Services, issued 1979; and AC.91-51, Airplane Deice and Anti-ice Systems, issued September 15, 1977.
4. BACKGROUND.
a. Part 135 was initially issued in 1964. It mntained requirements regarding operations in icing conditions in Section 135.85 for air taxi operations under both Visual Flight Rules (VFR) and Instrument Flight Rules (IFR). Section 135.85 did not contain references to operations for aircraft certificated for -rations in icing conditions. Flight into known or forecast heavy icing was prohibited.
b. In 1969, Section 135.85 was revised to include ice certification provisions as contained in Special Federal Aviation Regulation Number 23 (SFAR 23), issued the same year, for small airplanes and those ice certification rules that pertained to transport category aircraft. Flight into known or forecast severe icing conditions was permitted in airplanes that met these ice protection provisions.
c. Provisions for certification of ice protection equipment on snail airplanes were incorporated into Part 23 of the Federal Aviation Regulation in 1973. Prior to that year, ice protection type certification approvals for small airplanes were made by policy based on requirements in Civil Air Regulations, Part 3 and 4b.
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d. In the Part 135 Regulatory Review in 1977, a revised Section 135.85 was proposed that would require aircraft to meet ice certification standards to cperate under IF'R in forecast or known light or rrPderate icing oxditions. Aircraft rr>t meeting these standards wuld be limited to VFR operations in similar icing conditions.
e. The rxoposed &ange to Section 135.85 was not included in the revised Part 135 issued in 1978. Additional study of this problem was deemed appropriate.
The icing operating limitations in the revised air taxi rules (Section 135.227) are almost identical to old Section 135.85.
5. IME'LEMEWTATIoN OF REVISED PART 135. After revised Part 135 became effective in December 19n FAA Flight Standards Offices were informed that there had been no change in policy in the applicability of new Section 135.227. Therefore, aircraft could be operated in forecast or known light or rules if it was equipped as required in Section functioning , unless the aircraft was prohibited operating in icing conditions.
moderate icing under VFR-or IFR
135.227 and this eguipnent was by operating limitations from
6. OPERATMG LIMITATIaJS FOR ICING OPERATICNS.
a. When ice certification requirements were included in Part 23, the cperating limitations were shown in the limitation section of the flight manual or manual material. Placards were used to display these limitations.
b. Prior to the early 1960's, no criteria was available regarding ice certification for snall aircraft. Between that time and 1973, ice protection authorizations were based on FAA policy and regulations. Those aircraft were limited to flight into light or moderate icing conditions.
c. In 1973, new Part 23 ice certification rules became effective which contained a standard that the aircraft nust be capable of cperations into mntinuous maximum or intermittent rnaxinarm icing anditions, which was a mxe stringent requirement than the previous policy. However, many aircraft were being manufactured after 1973 and equipped with deicing or anti-icing equipnt under type certificates issued prior to 1973.
d. After 1973, some manufacturers continued to produce these aircraft with the previously approved quipnent installed rather than recertificate to meet the new icing certification standards. For those aircraft that did not meet the new icing certification standards, placards were installed prohibiting flight in icing conditions. 'Thus, of many aircraft of the same make and rrpdel with identical ice protection equipment, &me were placarded because they were manufactured after 1973 whereas those aircraft manufactured prior to 1973 were mt.
e. FAR 91.31(a) states that m person may rperate a civil aircraft without CaTlpliance with the operating limitations. Therefore, an aircraft containing a placard specified in the limitations of the aircraft type certificate, or as a limitation in the current operating limitation prescribed for that aircraft by the Administrator, must be operated in accordance with that limitation.
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f. FAR 135.3 provides that each person operating an aircraft under Part 135 shall conply with applicable rules of Title 14 of the Code of Federal Regulations which include FAR Parts 21, 23, 25, 43, 61, and 91 which are pertinent to this subject.
Some aircraft have -rating limitations prohibiting operation in known icing conditions. These aircraft may r-W operate in icing oMitions unless this operating limitation is removed. The icing limitation may be roved by anending the aircraft type certificate. The FAA mgineering and Manufacturing District Office can provide guidance to mend an aircraft type certificate.
7. OPERATICXJS IN ICING CoNDITImS UNDER PART 135. Comnuters and air taxi operators are utilizing aircraft with various operating Mutations in weather anditions where icing is a factor. Therefore, clarification of the pertinent operating requirements is necessary. The following is pertinent to the type of operations authorized:
a. Aircraft quipped with functioning equipment meeting Section 135.227(b) and not placarded restricting operations in icing conditions may fly under IFR or VFR xes in known or forecast light or moderate icing and continue flight in actual icing cx>nditions.
b. Aircraft equipped with functioning equipnent meeting Part 135.227(b) and a placard prohibiting operation in icing conditions may depart on a flight when light or moderate icing 1s forecast or reported to exist for the intended route to be flown. However, continued flight in actual icing conditions is not permitted since such flight does not cffnply with the placard or the operating limitation in the aircraft flight manual.
C. Airplanes that have the ice protection provisions that meet Section 34 of Appendix A of Part 135, that are type certificated with the ice protection provisions of Part 23, or those for transport category airplane type certification may be flown into known or forecast icing.
8. FLIGHT OPERATIONS ADVISORY INFWWATICN.
a. Preflight planning.
(1 ) Any flight involving operations into forecast or known icing conditions, under VFR or IFR, should be preceded by extensive flight planning and weather analysis with special attention to an alternate aurse of action in case actual icing is encountered.
(2) Flight in actual icing is authorized when the aircraft is equipped as specified in Section 135.227(b) and placards or operating limitations do nX restrict such an operation. However, continuous flight in actual icing is rot -nded, and the pilot should alter flightpath to an area where ice accumulation is rWz a factor.
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b. Operations in severe icing. Although aircraft that meet the ice protection requirements of Appendix A of Part 135, Part 23, or those for transport category airplanes are mt prohibited fran operating in severe icing, it is recmmended that such operations be avoided. Severe icing is described in the Aviation Weather Services, Advisory Circular (AC) 00-45B, and in the Aim's Information Manual as follows: the rate of accmulation is such that deicing/anti-icing quipent fails to reduce or amtrol the hazard. Imediate flight diversion is necessary.
9. AC 91-51, AIRPLANE DEICE AND AWI-ICE,SYSTEMS. It is r ecomnended this advisory circular be reviewed smce it contains guidance on the use of deice and anti-ice systems and flight procedures in icing conditions.
Kenneth S. Hunt Director of Flight Operations, AFO-1 4 Par 8