Federal Aviation Administration, DOT

Section 25.1321

manner after the airplane is exposed to
lightning.

spaschal on DSK3GDR082PROD with CFR

[Doc. No. FAA-2010-0224, Amdt. 25-134, 76 FR
33135, June 8, 2011]

Section 25.1317 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
airplane must be designed and installed
so that - 
(1) The function is not adversely affected during and after the time the
airplane is exposed to HIRF environment I, as described in appendix L to
this part;
(2) The system automatically recovers normal operation of that function,
in a timely manner, after the airplane
is exposed to HIRF environment I, as
described in appendix L to this part,
unless the system-s recovery conflicts
with other operational or functional
requirements of the system; and
(3) The system is not adversely affected during and after the time the
airplane is exposed to HIRF environment II, as described in appendix L to
this part.
(b) Each electrical and electronic
system that performs a function whose
failure would significantly reduce the
capability of the airplane 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 1
or 2, as described in appendix L to this
part.
(c) Each electrical and electronic system that performs a function whose
failure would reduce the capability of
the airplane 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
the function is exposed to equipment
HIRF test level 3, as described in appendix L 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 an airplane 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 44025, Aug. 6,
2007]

INSTRUMENTS: INSTALLATION
Section 25.1321 Arrangement and visibility.
(a) Each flight, navigation, and powerplant instrument for use by any pilot
must be plainly visible to him from his
station with the minimum practicable
deviation from his normal position and
line of vision when he is looking forward along the flight path.
(b) The flight instruments required
by Section 25.1303 must be grouped on the instrument panel and centered as nearly
as practicable about the vertical plane
of the pilot-s forward vision. In addition - 
(1) The instrument that most effectively indicates attitude must be on
the panel in the top center position;
(2) The instrument that most effectively indicates airspeed must be adjacent to and directly to the left of the
instrument in the top center position:
(3) The instrument that most effectively indicates altitude must be adjacent to and directly to the right of the
instrument in the top center position;
and
(4) The instrument that most effectively indicates direction of flight
must be adjacent to and directly below
the instrument in the top center position.
(c) Required powerplant instruments
must be closely grouped on the instrument panel. In addition - 
(1) The location of identical powerplant instruments for the engines must
prevent confusion as to which engine
each instrument relates; and
(2) Powerplant instruments vital to
the safe operation of the airplane must

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