Federal Aviation Administration, DOT

Section 25.1093

(1) There must be means to prevent
hazardous quantities of fuel leakage or
overflow from drains, vents, or other
components of flammable fluid systems
from entering the engine or auxiliary
power unit intake system; and
(2) The airplane must be designed to
prevent water or slush on the runway,
taxiway, or other airport operating
surfaces from being directed into the
engine or auxiliary power unit air inlet
ducts in hazardous quantities, and the
air inlet ducts must be located or protected so as to minimize the ingestion
of foreign matter during takeoff, landing, and taxiing.
(e) If the engine induction system
contains parts or components that
could be damaged by foreign objects
entering the air inlet, it must be shown
by tests or, if appropriate, by analysis
that the induction system design can
withstand the foreign object ingestion
test conditions of SectionSection 33.76, 33.77 and
33.78(a)(1) of this chapter without failure of parts or components that could
create a hazard.

spaschal on DSK3GDR082PROD with CFR

[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25-38, 41 FR 55467, Dec. 20,
1976; Amdt. 25-40, 42 FR 15043, Mar. 17, 1977;
Amdt. 25-57, 49 FR 6849, Feb. 23, 1984; Amdt.
25-100, 65 FR 55854, Sept. 14, 2000]

Section 25.1093 Induction system icing protection.
(a) Reciprocating engines. Each reciprocating engine air induction system
must have means to prevent and eliminate icing. Unless this is done by other
means, it must be shown that, in air
free of visible moisture at a temperature of 30 F., each airplane with altitude engines using - 
(1) Conventional venturi carburetors
have a preheater that can provide a
heat rise of 120 F. with the engine at 60
percent of maximum continuous power;
or
(2) Carburetors tending to reduce the
probability of ice formation has a preheater that can provide a heat rise of
100 SectionF. with the engine at 60 percent of
maximum continuous power.
(b) Turbine engines. Except as provided in paragraph (b)(3) of this section, each engine, with all icing protection systems operating, must:
(1) Operate throughout its flight
power range, including the minimum

descent idling speeds, in the icing conditions 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:
(i) Adversely affect installed engine
operation or cause a sustained loss of
power or thrust; or an unacceptable increase in gas path operating temperature; or an airframe/engine incompatibility; or
(ii) Result in unacceptable temporary
power loss or engine damage; or
(iii) Cause a stall, surge, or flameout
or loss of engine controllability (for example, rollback).
(2) Operate at ground idle speed for a
minimum of 30 minutes on the ground
in the following icing conditions shown
in Table 1 of this section, 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 in accordance
with the procedures defined in the airplane flight manual. 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. Analysis may be
used to show ambient temperatures
below the tested temperature are less
critical. 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), the associated minimum ambient temperature,
and the maximum time interval. These
conditions must be used in the analysis
that establishes the airplane operating
limitations in accordance with Section 25.1521.
(3) For the purposes of this section,
the icing conditions defined in appendix O of this part, including the conditions specified in Condition 3 of Table 1
of this section, are not applicable to
airplanes with a maximum takeoff
weight equal to or greater than 60,000
pounds.

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