Federal Aviation Administration, DOT

Section 25.1324

(1) From 0.8 of the minimum value of
V1 to the maximum value of V2, considering 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 Section 25.111 assuming that the
critical engine fails at the minimum
value of V1.
(c) The airspeed error of the installation, excluding the airspeed indicator
instrument calibration error, may not
exceed three percent or five knots,
whichever is greater, throughout the
speed range, from - 
(1) VMO to 1.23 VSR1, with flaps retracted; and
(2) 1.23 VSR0 to VFE with flaps in the
landing position.
(d) From 1.23 VSR 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 VMO to VMO + 2-3 (VDF Section
VMO), the IAS must change perceptibly
with CAS and in the same sense, and at
higher speeds up to VDF the IAS must
not change in an incorrect sense.
(f) There must be no indication of
airspeed that would cause undue difficulty 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 significant takeoff indicated airspeed bias, or
significant errors in takeoff or accelerate-stop distances.
(h) Each system must be arranged, so
far as practicable, to prevent malfunction 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 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 conditions
specified in Appendix O of this part:
(1) For airplanes certificated in accordance with Section 25.1420(a)(1), the icing
conditions that the airplane is certified
to safely exit following detection.
(2) For airplanes certificated in accordance with Section 25.1420(a)(2), the icing
conditions that the airplane is certified
to safely operate in and the icing conditions that the airplane is certified to
safely exit following detection.
(3) For airplanes certificated in accordance with Section 25.1420(a)(3) and for airplanes not subject to Section 25.1420, all icing
conditions.

TABLE 1 - HEAVY RAIN CONDITIONS FOR AIRSPEED INDICATING SYSTEM TESTS
Altitude range

Liquid water
content

(ft)

(m)

0 to 10 000 .........................

0 to 3000 ............................

spaschal on DSK3GDR082PROD with CFR

(km)

(g/m3)
1
6
15

(j) Where duplicate airspeed indicators are required, their respective pitot
tubes must be far enough apart to
avoid damage to both tubes in a collision 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]

Horizontal extent

Section 25.1324

Droplet MVD

(nmiles)
100
5
1

50
3
0.5

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1000
2000
2000

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 Section 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 conditions specified in Appendix O of this
part:

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