500
14 CFR Ch. I (1–1–14 Edition)
§ 25.1323
(b) Alerts must conform to the fol-
lowing prioritization hierarchy based
on the urgency of flightcrew awareness
and response.
(1) Warning: For conditions that re-
quire immediate flightcrew awareness
and immediate flightcrew response.
(2) Caution: For conditions that re-
quire immediate flightcrew awareness
and subsequent flightcrew response.
(3) Advisory: For conditions that re-
quire flightcrew awareness and may re-
quire subsequent flightcrew response.
(c) Warning and caution alerts must:
(1) Be prioritized within each cat-
egory, when necessary.
(2) Provide timely attention-getting
cues through at least two different
senses by a combination of aural, vis-
ual, or tactile indications.
(3) Permit each occurrence of the at-
tention-getting cues required by para-
graph (c)(2) of this section to be ac-
knowledged and suppressed, unless
they are required to be continuous.
(d) The alert function must be de-
signed to minimize the effects of false
and nuisance alerts. In particular, it
must be designed to:
(1) Prevent the presentation of an
alert that is inappropriate or unneces-
sary.
(2) Provide a means to suppress an
attention-getting component of an
alert caused by a failure of the alerting
function that interferes with the
flightcrew’s ability to safely operate
the airplane. This means must not be
readily available to the flightcrew so
that it could be operated inadvertently
or by habitual reflexive action. When
an alert is suppressed, there must be a
clear and unmistakable annunciation
to the flightcrew that the alert has
been suppressed.
(e) Visual alert indications must:
(1) Conform to the following color
convention:
(i) Red for warning alert indications.
(ii) Amber or yellow for caution alert
indications.
(iii) Any color except red or green for
advisory alert indications.
(2) Use visual coding techniques, to-
gether with other alerting function ele-
ments on the flight deck, to distin-
guish between warning, caution, and
advisory alert indications, if they are
presented on monochromatic displays
that are not capable of conforming to
the color convention in paragraph (e)(1)
of this section.
(f) Use of the colors red, amber, and
yellow on the flight deck for functions
other than flightcrew alerting must be
limited and must not adversely affect
flightcrew alerting.
[Amdt. 25–131, 75 FR 67209, Nov. 2, 2010]
§ 25.1323
Airspeed indicating system.
For each airspeed indicating system,
the following apply:
(a) Each airspeed indicating instru-
ment must be approved and must be
calibrated to indicate true airspeed (at
sea level with a standard atmosphere)
with a minimum practicable instru-
ment calibration error when the cor-
responding pitot and static pressures
are applied.
(b) Each system must be calibrated
to determine the system error (that is,
the relation between IAS and CAS) in
flight and during the accelerated take-
off ground run. The ground run calibra-
tion must be determined—
(1) From 0.8 of the minimum value of
V
1
to the maximum value of V
2
, consid-
ering the approved ranges of altitude
and weight; and
(2) With the flaps and power settings
corresponding to the values determined
in the establishment of the takeoff
path under § 25.111 assuming that the
critical engine fails at the minimum
value of V
1
.
(c) The airspeed error of the installa-
tion, excluding the airspeed indicator
instrument calibration error, may not
exceed three percent or five knots,
whichever is greater, throughout the
speed range, from—
(1)
V
MO
to 1.23
V
SR1
, with flaps re-
tracted; and
(2) 1.23
V
SR0
to
V
FE
with flaps in the
landing position.
(d) From 1.23 V
SR
to the speed at
which stall warning begins, the IAS
must change perceptibly with CAS and
in the same sense, and at speeds below
stall warning speed the IAS must not
change in an incorrect sense.
(e) From V
MO
to V
MO
+
2
⁄
3
(V
DF
¥
V
MO
), the IAS must change perceptibly
with CAS and in the same sense, and at
higher speeds up to V
DF
the IAS must
not change in an incorrect sense.
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