119 

Federal Aviation Administration, DOT 

§ 121.321 

than one exit, provided the proximity 
of the exits allows unassisted verbal 
communication between seated flight 
attendants; 

(e) Is capable of operation within 10 

seconds by a flight attendant at each of 
those stations in the passenger com-
partment from which its use is acces-
sible; 

(f) Is audible at all passenger seats, 

lavatories, and flight attendant seats 
and work stations; and 

(g) For transport category airplanes 

manufactured on or after November 27, 
1990, meets the requirements of § 25.1423 
of this chapter. 

[Doc. No. 24995, 54 FR 43926, Oct. 27, 1989] 

§ 121.319

Crewmember interphone sys-

tem. 

(a) No person may operate an air-

plane with a seating capacity of more 
than 19 passengers unless the airplane 
is equipped with a crewmember inter-
phone system that: 

(1) [Reserved] 
(2) Is capable of operation inde-

pendent of the public address system 
required by § 121.318(a) except for 
handsets, headsets, microphones, selec-
tor switches, and signaling devices; and 

(3) Meets the requirements of para-

graph (b) of this section. 

(b) The crewmember interphone sys-

tem required by paragraph (a) of this 
section must be approved in accordance 
with § 21.305 of this chapter and meet 
the following requirements: 

(1) It must provide a means of two- 

way communication between the pilot 
compartment and— 

(i) Each passenger compartment; and 
(ii) Each galley located on other than 

the main passenger deck level. 

(2) It must be accessible for imme-

diate use from each of two flight crew-
member stations in the pilot compart-
ment; 

(3) It must be accessible for use from 

at least one normal flight attendant 
station in each passenger compart-
ment; 

(4) It must be capable of operation 

within 10 seconds by a flight attendant 
at those stations in each passenger 
compartment from which its use is ac-
cessible; and 

(5) For large turbojet-powered air-

planes: 

(i) It must be accessible for use at 

enough flight attendant stations so 
that all floor-level emergency exits (or 
entryways to those exits in the case of 
exits located within galleys) in each 
passenger compartment are observable 
from one or more of those stations so 
equipped; 

(ii) It must have an alerting system 

incorporating aural or visual signals 
for use by flight crewmembers to alert 
flight attendants and for use by flight 
attendants to alert flight crew-
members; 

(iii) The alerting system required by 

paragraph (b)(5)(ii) of this section must 
have a means for the recipient of a call 
to determine whether it is a normal 
call or an emergency call; and 

(iv) When the airplane is on the 

ground, it must provide a means of 
two-way communication between 
ground personnel and either of at least 
two flight crewmembers in the pilot 
compartment. The interphone system 
station for use by ground personnel 
must be so located that personnel 
using the system may avoid visible de-
tection from within the airplane. 

[Doc. No. 10865, 38 FR 21494, Aug. 9, 1973, as 
amended by Amdt. 121–121, 40 FR 42186, Sept. 
11, 1975; Amdt. 121–149, 43 FR 50602, Oct. 30, 
1978; Amdt. 121–178, 47 FR 13316, Mar. 29, 1982; 
Amdt. 121–253, 61 FR 2611, Jan. 26, 1996] 

§ 121.321

Operations in icing. 

After October 21, 2013, no person may 

operate an airplane with a certificated 
maximum takeoff weight less than 
60,000 pounds in conditions conducive 
to airframe icing unless it complies 
with this section. As used in this sec-
tion, the phrase ‘‘conditions conducive 
to airframe icing’’ means visible mois-
ture at or below a static air tempera-
ture of 5 

°

C or a total air temperature 

of 10 

°

C, unless the approved Airplane 

Flight Manual provides another defini-
tion. 

(a) When operating in conditions con-

ducive to airframe icing, compliance 
must be shown with paragraph (a)(1), 
or (2), or (3) of this section. 

(1) The airplane must be equipped 

with a certificated primary airframe 
ice detection system. 

(i) The airframe ice protection sys-

tem must be activated automatically, 
or manually by the flightcrew, when 

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