355 

Federal Aviation Administration, DOT 

§ 25.1420 

the various components of the airplane 
is adequate, taking into account the 
various airplane operational configura-
tions; and 

(b) To verify the ice protection anal-

ysis, to check for icing anomalies, and 
to demonstrate that the ice protection 
system and its components are effec-
tive, the airplane or its components 
must be flight tested in the various 
operational configurations, in meas-
ured natural atmospheric icing condi-
tions and, as found necessary, by one 
or more of the following means: 

(1) Laboratory dry air or simulated 

icing tests, or a combination of both, of 
the components or models of the com-
ponents. 

(2) Flight dry air tests of the ice pro-

tection system as a whole, or of its in-
dividual components. 

(3) Flight tests of the airplane or its 

components in measured simulated 
icing conditions. 

(c) Caution information, such as an 

amber caution light or equivalent, 
must be provided to alert the 
flightcrew when the anti-ice or de-ice 
system is not functioning normally. 

(d) For turbine engine powered air-

planes, the ice protection provisions of 
this section are considered to be appli-
cable primarily to the airframe. For 
the powerplant installation, certain ad-
ditional provisions of subpart E of this 
part may be found applicable. (e) One 
of the following methods of icing detec-
tion and activation of the airframe ice 
protection system must be provided: 

(1) A primary ice detection system 

that automatically activates or alerts 
the flightcrew to activate the airframe 
ice protection system; 

(2) A definition of visual cues for rec-

ognition of the first sign of ice accre-
tion on a specified surface combined 
with an advisory ice detection system 
that alerts the flightcrew to activate 
the airframe ice protection system; or 

(3) Identification of conditions con-

ducive to airframe icing as defined by 
an appropriate static or total air tem-
perature and visible moisture for use 
by the flightcrew to activate the air-
frame ice protection system. 

(f) Unless the applicant shows that 

the airframe ice protection system 
need not be operated during specific 
phases of flight, the requirements of 

paragraph (e) of this section are appli-
cable to all phases of flight. 

(g) After the initial activation of the 

airframe ice protection system— 

(1) The ice protection system must be 

designed to operate continuously; 

(2) The airplane must be equipped 

with a system that automatically cy-
cles the ice protection system; or 

(3) An ice detection system must be 

provided to alert the flightcrew each 
time the ice protection system must be 
cycled. 

(h) Procedures for operation of the 

ice protection system, including acti-
vation and deactivation, must be estab-
lished and documented in the Airplane 
Flight Manual. 

[Amdt. 25–72, 55 FR 29785, July 20, 1990, as 
amended by Amdt. 25–121, 72 FR 44669, Aug. 8, 
2007; Amdt. 25–129, 74 FR 38339, Aug. 3, 2009] 

§ 25.1420

Supercooled large drop icing 

conditions. 

(a) If certification for flight in icing 

conditions is sought, in addition to the 
requirements of § 25.1419, an airplane 
with a maximum takeoff weight less 
than 60,000 pounds or with reversible 
flight controls must be capable of oper-
ating in accordance with paragraphs 
(a)(1), (2), or (3), of this section. 

(1) Operating safely after encoun-

tering the icing conditions defined in 
Appendix O of this part: 

(i) The airplane must have a means 

to detect that it is operating in Appen-
dix O icing conditions; and 

(ii) Following detection of Appendix 

O icing conditions, the airplane must 
be capable of operating safely while 
exiting all icing conditions. 

(2) Operating safely in a portion of 

the icing conditions defined in Appen-
dix O of this part as selected by the ap-
plicant: 

(i) The airplane must have a means 

to detect that it is operating in condi-
tions that exceed the selected portion 
of Appendix O icing conditions; and 

(ii) Following detection, the airplane 

must be capable of operating safely 
while exiting all icing conditions. 

(3) Operating safely in the icing con-

ditions defined in Appendix O of this 
part. 

(b) To establish that the airplane can 

operate safely as required in paragraph 
(a) of this section, an applicant must 

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