Federal Aviation Administration, DOT

Section 121.631

fluid will prevent the formation of
frost or ice and the accumulation of
snow on the protected surfaces of an
aircraft. Holdover time begins when
the final application of deicing/antiicing fluid commences and expires
when the deicing/anti-icing fluid applied to the aircraft loses its effectiveness. The holdover times must be supported by data acceptable to the Administrator. The certificate holder-s
program must include procedures for
flight crewmembers to increase or decrease the determined holdover time in
changing conditions. The program
must provide that takeoff after exceeding any maximum holdover time in the
certificate holder-s holdover timetable
is permitted only when at least one of
the following conditions exists:
(i)
A
pretakeoff
contamination
check, as defined in paragraph (c)(4) of
this section, determines that the
wings, control surfaces, and other critical surfaces, as defined in the certificate holder-s program, are free of frost,
ice, or snow.
(ii) It is otherwise determined by an
alternate procedure approved by the
Administrator in accordance with the
certificate holder-s approved program
that the wings, control surfaces, and
other critical surfaces, as defined in
the certificate holder-s program, are
free of frost, ice, or snow.
(iii) The wings, control surfaces, and
other critical surfaces are redeiced and
a new holdover time is determined.
(4) Aircraft deicing/anti-icing procedures and responsibilities, pretakeoff
check procedures and responsibilities,
and pretakeoff contamination check
procedures and responsibilities. A pretakeoff check is a check of the aircraft-s wings or representative aircraft
surfaces for frost, ice, or snow within
the aircraft-s holdover time. A pretakeoff contamination check is a check
to make sure the wings, control surfaces, and other critical surfaces, as defined in the certificate holder-s program, are free of frost, ice, and snow. It
must be conducted within five minutes
prior to beginning take off. This check
must be accomplished from outside the
aircraft unless the program specifies
otherwise.
(d) A certificate holder may continue
to operate under this section without a

program as required in paragraph (c) of
this section, if it includes in its operations specifications a requirement
that, any time conditions are such that
frost, ice, or snow may reasonably be
expected to adhere to the aircraft, no
aircraft will take off unless it has been
checked to ensure that the wings, control surfaces, and other critical surfaces are free of frost, ice, and snow.
The check must occur within five minutes prior to beginning takeoff. This
check must be accomplished from outside the aircraft.
[Doc. No. 6258, 29 FR 19222, Dec. 31, 1964, as
amended by Amdt. 121-231, 57 FR 44942, Sept.
29, 1992; Amdt. 121-253, 61 FR 2615, Jan. 26,
1996]

Section 121.631 Original dispatch or flight release, redispatch or amendment of
dispatch or flight release.
(a) A certificate holder may specify
any regular, provisional, or refueling
airport, authorized for the type of aircraft, as a destination for the purpose
of original dispatch or release.
(b) No person may allow a flight to
continue to an airport to which it has
been dispatched or released unless the
weather conditions at an alternate airport that was specified in the dispatch
or flight release are forecast to be at or
above the alternate minimums specified in the operations specifications for
that airport at the time the aircraft
would arrive at the alternate airport.
However, the dispatch or flight release
may be amended en route to include
any alternate airport that is within the
fuel range of the aircraft as specified in
SectionSection 121.639 through 121.647.
(c) No person may allow a flight to
continue beyond the ETOPS Entry
Point unless - 
(1) Except as provided in paragraph
(d) of this section, the weather conditions at each ETOPS Alternate Airport
required by Section 121.624 are forecast to be
at or above the operating minima for
that airport in the certificate holder-s
operations
specifications
when
it
might be used (from the earliest to the
latest possible landing time); and
(2) All ETOPS Alternate Airports
within the authorized ETOPS maximum diversion time are reviewed and
the flight crew advised of any changes

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