344
14 CFR Ch. I (1–1–24 Edition)
§ 25.1324
(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.
(f) There must be no indication of
airspeed that would cause undue dif-
ficulty to the pilot during the takeoff
between the initiation of rotation and
the achievement of a steady climbing
condition.
(g) The effects of airspeed indicating
system lag may not introduce signifi-
cant takeoff indicated airspeed bias, or
significant errors in takeoff or accel-
erate-stop distances.
(h) Each system must be arranged, so
far as practicable, to prevent malfunc-
tion or serious error due to the entry of
moisture, dirt, or other substances.
(i) Each system must have a heated
pitot tube or an equivalent means of
preventing malfunction in the heavy
rain conditions defined in Table 1 of
this section; mixed phase and ice crys-
tal conditions as defined in part 33, Ap-
pendix D, of this chapter; the icing con-
ditions defined in Appendix C of this
part; and the following icing conditions
specified in Appendix O of this part:
(1) For airplanes certificated in ac-
cordance with § 25.1420(a)(1), the icing
conditions that the airplane is certified
to safely exit following detection.
(2) For airplanes certificated in ac-
cordance with § 25.1420(a)(2), the icing
conditions that the airplane is certified
to safely operate in and the icing con-
ditions that the airplane is certified to
safely exit following detection.
(3) For airplanes certificated in ac-
cordance with § 25.1420(a)(3) and for air-
planes not subject to § 25.1420, all icing
conditions.
T
ABLE
1—H
EAVY
R
AIN
C
ONDITIONS FOR
A
IRSPEED
I
NDICATING
S
YSTEM
T
ESTS
Altitude range
Liquid water
content
Horizontal extent
Droplet MVD
(ft) (m)
(g/m3)
(km) (nmiles) (
μ
m)
0 to 10 000 .........................
0 to 3000 ............................
1
100
50
1000
6 5 3
2000
15 1 0
.5 2000
(j) Where duplicate airspeed indica-
tors are required, their respective pitot
tubes must be far enough apart to
avoid damage to both tubes in a colli-
sion with a bird.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25–57, 49 FR 6849, Feb. 23,
1984; Amdt. 25–108, 67 FR 70828, Nov. 26, 2002;
Amdt. 25–109, 67 FR 76656, Dec. 12, 2002; Amdt.
25–140, 79 FR 65526, Nov. 4, 2014]
§ 25.1324
Angle of attack system.
Each angle of attack system sensor
must be heated or have an equivalent
means of preventing malfunction in the
heavy rain conditions defined in Table
1 of § 25.1323, the mixed phase and ice
crystal conditions as defined in part 33,
Appendix D, of this chapter, the icing
conditions defined in Appendix C of
this part, and the following icing con-
ditions specified in Appendix O of this
part:
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§ 25.1325
(a) For airplanes certificated in ac-
cordance with § 25.1420(a)(1), the icing
conditions that the airplane is certified
to safely exit following detection.
(b) For airplanes certificated in ac-
cordance with § 25.1420(a)(2), the icing
conditions that the airplane is certified
to safely operate in and the icing con-
ditions that the airplane is certified to
safely exit following detection.
(c) For airplanes certificated in ac-
cordance with § 25.1420(a)(3) and for air-
planes not subject to § 25.1420, all icing
conditions.
[Amdt. 25–140, 79 FR 65527, Nov. 4, 2014]
§ 25.1325
Static pressure systems.
(a) Each instrument with static air
case connections must be vented to the
outside atmosphere through an appro-
priate piping system.
(b) Each static port must be designed
and located so that:
(1) The static pressure system per-
formance is least affected by airflow
variation, or by moisture or other for-
eign matter; and
(2) The correlation between air pres-
sure in the static pressure system and
true ambient atmospheric static pres-
sure is not changed when the airplane
is exposed to the icing conditions de-
fined in Appendix C of this part, and
the following icing conditions specified
in Appendix O of this part:
(i) For airplanes certificated in ac-
cordance with § 25.1420(a)(1), the icing
conditions that the airplane is certified
to safely exit following detection.
(ii) For airplanes certificated in ac-
cordance with § 25.1420(a)(2), the icing
conditions that the airplane is certified
to safely operate in and the icing con-
ditions that the airplane is certified to
safely exit following detection.
(iii) For airplanes certificated in ac-
cordance with § 25.1420(a)(3) and for air-
planes not subject to § 25.1420, all icing
conditions.
(c) The design and installation of the
static pressure system must be such
that—
(1) Positive drainage of moisture is
provided; chafing of the tubing and ex-
cessive distortion or restriction at
bends in the tubing is avoided; and the
materials used are durable, suitable for
the purpose intended, and protected
against corrosion; and
(2) It is airtight except for the port
into the atmosphere. A proof test must
be conducted to demonstrate the integ-
rity of the static pressure system in
the following manner:
(i)
Unpressurized airplanes. Evacuate
the static pressure system to a pres-
sure differential of approximately 1
inch of mercury or to a reading on the
altimeter, 1,000 feet above the airplane
elevation at the time of the test. With-
out additional pumping for a period of
1 minute, the loss of indicated altitude
must not exceed 100 feet on the altim-
eter.
(ii)
Pressurized airplanes. Evacuate
the static pressure system until a pres-
sure differential equivalent to the max-
imum cabin pressure differential for
which the airplane is type certificated
is achieved. Without additional pump-
ing for a period of 1 minute, the loss of
indicated altitude must not exceed 2
percent of the equivalent altitude of
the maximum cabin differential pres-
sure or 100 feet, whichever is greater.
(d) Each pressure altimeter must be
approved and must be calibrated to in-
dicate pressure altitude in a standard
atmosphere, with a minimum prac-
ticable calibration error when the cor-
responding static pressures are applied.
(e) Each system must be designed and
installed so that the error in indicated
pressure altitude, at sea level, with a
standard atmosphere, excluding instru-
ment calibration error, does not result
in an error of more than
±
30 feet per 100
knots speed for the appropriate con-
figuration in the speed range between
1.23
V
SR0
with flaps extended and 1.7
V
SR1
with flaps retracted. However, the
error need not be less than
±
30 feet.
(f) If an altimeter system is fitted
with a device that provides corrections
to the altimeter indication, the device
must be designed and installed in such
manner that it can be bypassed when it
malfunctions, unless an alternate al-
timeter system is provided. Each cor-
rection device must be fitted with a
means for indicating the occurrence of
reasonably probable malfunctions, in-
cluding power failure, to the flight
crew. The indicating means must be ef-
fective for any cockpit lighting condi-
tion likely to occur.
(g) Except as provided in paragraph
(h) of this section, if the static pressure
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