548 

14 CFR Ch. I (1–1–24 Edition) 

§ 27.1316 

(c) A means to alert the crew in the 

event of a failure must be provided 
when an unsafe system operating con-
dition exists and to enable them to 
take corrective action. Systems, con-
trols, and associated monitoring and 
crew alerting means must be designed 
to minimize crew errors that could cre-
ate additional hazards. 

(d) Compliance with the require-

ments of this section must be shown by 
analysis and, where necessary, by 
ground, flight, or simulator tests. The 
analysis must account for: 

(1) Possible modes of failure, includ-

ing malfunctions and misleading data 
and input from external sources; 

(2) The effect of multiple failures and 

latent failures; 

(3) The resulting effects on the rotor-

craft and occupants, considering the 
stage of flight and operating condi-
tions; and 

(4) The crew alerting cues and the 

corrective action required. 

[Amdt. 27–51, 88 FR 8737, Feb. 10, 2023] 

§ 27.1316

Electrical and electronic sys-

tem lightning protection. 

(a) Each electrical and electronic 

system that performs a function, for 
which failure would prevent the contin-
ued safe flight and landing of the rotor-
craft, must be designed and installed so 
that— 

(1) The function is not adversely af-

fected during and after the time the 
rotorcraft is exposed to lightning; and 

(2) The system automatically recov-

ers normal operation of that function 
in a timely manner after the rotorcraft 
is exposed to lightning. 

(b) For rotorcraft approved for in-

strument flight rules operation, each 
electrical and electronic system that 
performs a function, for which failure 
would reduce the capability of the 
rotorcraft or the ability of the 
flightcrew to respond to an adverse op-
erating condition, must be designed 
and installed so that the function re-
covers normal operation in a timely 
manner after the rotorcraft is exposed 
to lightning. 

[Doc. No. FAA–2010–0224, Amdt. 27–46, 76 FR 
33135, June 8, 2011] 

§ 27.1317

High-intensity Radiated 

Fields (HIRF) Protection. 

(a) Except as provided in paragraph 

(d) of this section, each electrical and 
electronic system that performs a func-
tion whose failure would prevent the 
continued safe flight and landing of the 
rotorcraft must be designed and in-
stalled so that— 

(1) The function is not adversely af-

fected during and after the time the 
rotorcraft is exposed to HIRF environ-
ment I, as described in appendix D to 
this part; 

(2) The system automatically recov-

ers normal operation of that function, 
in a timely manner, after the rotor-
craft is exposed to HIRF environment 
I, as described in appendix D to this 
part, unless this conflicts with other 
operational or functional requirements 
of that system; 

(3) The system is not adversely af-

fected during and after the time the 
rotorcraft is exposed to HIRF environ-
ment II, as described in appendix D to 
this part; and 

(4) Each function required during op-

eration under visual flight rules is not 
adversely affected during and after the 
time the rotorcraft is exposed to HIRF 
environment III, as described in appen-
dix D to this part. 

(b) Each electrical and electronic 

system that performs a function whose 
failure would significantly reduce the 
capability of the rotorcraft or the abil-
ity of the flightcrew to respond to an 
adverse operating condition must be 
designed and installed so the system is 
not adversely affected when the equip-
ment providing these functions is ex-
posed to equipment HIRF test level 1 
or 2, as described in appendix D to this 
part. 

(c) Each electrical and electronic sys-

tem that performs a function whose 
failure would reduce the capability of 
the rotorcraft or the ability of the 
flightcrew to respond to an adverse op-
erating condition, must be designed 
and installed so the system is not ad-
versely affected when the equipment 
providing these functions is exposed to 
equipment HIRF test level 3, as de-
scribed in appendix D to this part. 

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

trical or electronic system that per-
forms a function whose failure would 

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