Federal Aviation Administration, DOT

Section 27.1321

in a timely manner after the rotorcraft
is exposed to lightning.
(b) For rotorcraft approved for instrument 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 operating condition, must be designed
and installed so that the function recovers normal operation in a timely
manner after the rotorcraft is exposed
to lightning.

spaschal on DSK3GDR082PROD with CFR

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

Section 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 function whose failure would prevent the
continued safe flight and landing of the
rotorcraft must be designed and installed so that - 
(1) The function is not adversely affected during and after the time the
rotorcraft is exposed to HIRF environment I, as described in appendix D to
this part;
(2) The system automatically recovers normal operation of that function,
in a timely manner, after the rotorcraft 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 affected during and after the time the
rotorcraft is exposed to HIRF environment II, as described in appendix D to
this part; and
(4) Each function required during operation under visual flight rules is not
adversely affected during and after the
time the rotorcraft is exposed to HIRF
environment III, as described in appendix 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 ability of the flightcrew to respond to an
adverse operating condition must be
designed and installed so the system is
not adversely affected when the equipment 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 system that performs a function whose
failure would reduce the capability of
the rotorcraft or the ability of the
flightcrew to respond to an adverse operating condition, must be designed
and installed so the system is not adversely affected when the equipment
providing these functions is exposed to
equipment HIRF test level 3, as described in appendix D to this part.
(d) Before December 1, 2012, an electrical or electronic system that performs a function whose failure would
prevent the continued safe flight and
landing of a rotorcraft may be designed
and installed without meeting the provisions of paragraph (a) provided - 
(1) The system has previously been
shown to comply with special conditions for HIRF, prescribed under Section 21.16,
issued before December 1, 2007;
(2) The HIRF immunity characteristics of the system have not changed
since compliance with the special conditions was demonstrated; and
(3) The data used to demonstrate
compliance with the special conditions
is provided.
[Doc. No. FAA-2006-23657, 72 FR 44026, Aug. 6,
2007]

INSTRUMENTS: INSTALLATION
Section 27.1321

Arrangement and visibility.

(a) Each flight, navigation, and powerplant instrument for use by any pilot
must be easily visible to him.
(b) For each multiengine rotorcraft,
identical powerplant instruments must
be located so as to prevent confusion as
to which engine each instrument relates.
(c) Instrument panel vibration may
not damage, or impair the readability
or accuracy of, any instrument.
(d) If a visual indicator is provided to
indicate malfunction of an instrument,

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