300 

14 CFR Ch. I (1–1–14 Edition) 

§ 23.1309 

affected when the equipment providing 
the function is exposed to equipment 
HIRF test level 3, as described in ap-
pendix J to this part. 

(d) Before December 1, 2012, an elec-

trical or electronic system that per-
forms a function whose failure would 
prevent the continued safe flight and 
landing of an airplane may be designed 
and installed without meeting the pro-
visions of paragraph (a) provided— 

(1) The system has previously been 

shown to comply with special condi-
tions for HIRF, prescribed under § 21.16, 
issued before December 1, 2007; 

(2) The HIRF immunity characteris-

tics of the system have not changed 
since compliance with the special con-
ditions was demonstrated; and 

(3) The data used to demonstrate 

compliance with the special conditions 
is provided. 

[Doc. No. FAA–2006–23657, 72 FR 44024, Aug. 6, 
2007] 

§ 23.1309

Equipment, systems, and in-

stallations. 

The requirements of this section, ex-

cept as identified in paragraphs (a) 
through (d), are applicable, in addition 
to specific design requirements of part 
23, to any equipment or system as in-
stalled in the airplane. This section is 
a regulation of general requirements 
and does not supersede any require-
ments contained in another section of 
part 23. 

(a) The airplane equipment and sys-

tems must be designed and installed so 
that: 

(1) Those required for type certifi-

cation or by operating rules perform as 
intended under the airplane operating 
and environmental conditions, includ-
ing the indirect effects of lightning 
strikes. 

(2) Any equipment and system does 

not adversely affect the safety of the 
airplane or its occupants, or the proper 
functioning of those covered by para-
graph (a)(1) of this section. 

(b) Minor, major, hazardous, or cata-

strophic failure condition(s), which 
occur during Type Inspection Author-
ization or FAA flight-certification 
testing, must have root cause analysis 
and corrective action. 

(c) The airplane systems and associ-

ated components considered separately 

and in relation to other systems, must 
be designed and installed so that: 

(1) Each catastrophic failure condi-

tion is extremely improbable and does 
not result from a single failure; 

(2) Each hazardous failure condition 

is extremely remote; and 

(3) Each major failure condition is re-

mote. 

(d) Information concerning an unsafe 

system operating condition must be 
provided in a timely manner to the 
crew to enable them to take appro-
priate corrective action. An appro-
priate alert must be provided if imme-
diate pilot awareness and immediate or 
subsequent corrective action is re-
quired. Systems and controls, includ-
ing indications and annunciations, 
must be designed to minimize crew er-
rors which could create additional haz-
ards. 

[Doc. No. FAA–2009–0738, 76 FR 75760, Dec. 2, 
2011] 

§ 23.1310

Power source capacity and 

distribution. 

(a) Each installation whose func-

tioning is required for type certifi-
cation or under operating rules and 
that requires a power supply is an ‘‘es-
sential load’’ on the power supply. The 
power sources and the system must be 
able to supply the following power 
loads in probable operating combina-
tions and for probable durations: 

(1) Loads connected to the system 

with the system functioning normally. 

(2) Essential loads, after failure of 

any one prime mover, power converter, 
or energy storage device. 

(3) Essential loads after failure of— 
(i) Any one engine on two-engine air-

planes; and 

(ii) Any two engines on airplanes 

with three or more engines. 

(4) Essential loads for which an alter-

nate source of power is required, after 
any failure or malfunction in any one 
power supply system, distribution sys-
tem, or other utilization system. 

(b) In determining compliance with 

paragraphs (a)(2) and (3) of this section, 
the power loads may be assumed to be 
reduced under a monitoring procedure 
consistent with safety in the kinds of 
operation authorized. Loads not re-
quired in controlled flight need not be 

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