title-14-part-25-sec25-101

208

14 CFR Ch. I (1–1–24 Edition)

§ 25.31

Removable ballast.

Removable ballast may be used on

showing compliance with the flight re-
quirements of this subpart.

§ 25.33

Propeller speed and pitch lim-

its.

(a) The propeller speed and pitch

must be limited to values that will en-
sure—

(1) Safe operation under normal oper-

ating conditions; and

(2) Compliance with the performance

requirements of §§ 25.101 through 25.125.

(b) There must be a propeller speed

limiting means at the governor. It
must limit the maximum possible gov-
erned engine speed to a value not ex-
ceeding the maximum allowable r.p.m.

pitch position of the propeller blades
must be set so that the engine does not
exceed 103 percent of the maximum al-
lowable engine rpm or 99 percent of an
approved maximum overspeed, which-
ever is greater, with—

(1) The propeller blades at the low

pitch limit and governor inoperative;

(2) The airplane stationary under

standard atmospheric conditions with
no wind; and

(3) The engines operating at the take-

off manifold pressure limit for recipro-
cating engine powered airplanes or the
maximum takeoff torque limit for tur-
bopropeller engine-powered airplanes.

[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25–57, 49 FR 6848, Feb. 23,
1984; Amdt. 25–72, 55 FR 29774, July 20, 1990]

ERFORMANCE

§ 25.101

General.

(a) Unless otherwise prescribed, air-

planes must meet the applicable per-
formance requirements of this subpart
for ambient atmospheric conditions
and still air.

(b) The performance, as affected by

engine power or thrust, must be based
on the following relative humidities;

(1) For turbine engine powered air-

planes, a relative humidity of—

(i) 80 percent, at and below standard

temperatures; and

(ii) 34 percent, at and above standard

temperatures plus 50

Between these two temperatures, the
relative humidity must vary linearly.

(2) For reciprocating engine powered

airplanes, a relative humidity of 80 per-
cent in a standard atmosphere. Engine
power corrections for vapor pressure
must be made in accordance with the
following table:

Altitude

H (ft.)

Vapor

pressure e

(In. Hg.)

Specific humidity

w (Lb. moisture

per lb. dry air)

Density ratio

0.0023769

0 0.403 0.00849 0.99508

1,000 .354  .00773  .96672
2,000 .311  .00703  .93895
3,000 .272  .00638  .91178
4,000 .238  .00578  .88514
5,000 .207  .00523  .85910
6,000 .1805

.00472

.83361

7,000 .1566

.00425

.80870

8,000 .1356

.00382

.78434

9,000 .1172

.00343

.76053

10,000 .1010

.00307

.73722

15,000 .0463 .001710

.62868

20,000 .01978

.000896

.53263

25,000 .00778

.000436

.44806

to the propulsive thrust available
under the particular ambient atmos-
pheric conditions, the particular flight
condition, and the relative humidity
specified in paragraph (b) of this sec-
tion. The available propulsive thrust
must correspond to engine power or
thrust, not exceeding the approved
power or thrust less—

(1) Installation losses; and
(2) The power or equivalent thrust

absorbed by the accessories and serv-
ices appropriate to the particular am-
bient atmospheric conditions and the
particular flight condition.

(d) Unless otherwise prescribed, the

applicant must select the takeoff, en
route, approach, and landing configura-
tions for the airplane.

(e) The airplane configurations may

vary with weight, altitude, and tem-
perature, to the extent they are com-
patible with the operating procedures
required by paragraph (f) of this sec-
tion.

(f) Unless otherwise prescribed, in de-

termining the accelerate-stop dis-
tances, takeoff flight paths, takeoff
distances, and landing distances,
changes in the airplane’s configura-
tion, speed, power, and thrust, must be
made in accordance with procedures es-
tablished by the applicant for oper-
ation in service.

(g) Procedures for the execution of

balked landings and missed approaches

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§ 25.105

associated with the conditions pre-
scribed in §§ 25.119 and 25.121(d) must be
established.

(h) The procedures established under

paragraphs (f) and (g) of this section
must—

(1) Be able to be consistently exe-

cuted in service by crews of average
skill;

(2) Use methods or devices that are

safe and reliable; and

(3) Include allowance for any time

delays, in the execution of the proce-
dures, that may reasonably be expected
in service.

(i) The accelerate-stop and landing

distances prescribed in §§ 25.109 and
25.125, respectively, must be deter-
mined with all the airplane wheel
brake assemblies at the fully worn
limit of their allowable wear range.

[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25–38, 41 FR 55466, Dec. 20,
1976; Amdt. 25–92, 63 FR 8318, Feb. 18, 1998]

§ 25.103

Stall speed.

(a) The reference stall speed, V

, is a

calibrated airspeed defined by the ap-
plicant. V

may not be less than a 1-g

stall speed. V

is expressed as:

≥

MAX

where:
V

MAX

= Calibrated airspeed obtained when

the load factor-corrected lift coefficient

⎛
⎝⎜

⎞
⎠⎟

is first a maximum during the maneuver

prescribed in paragraph (c) of this section. In
addition, when the maneuver is limited by a
device that abruptly pushes the nose down at
a selected angle of attack (e.g., a stick push-
er), V

MAX

may not be less than the speed ex-

isting at the instant the device operates;
n

= Load factor normal to the flight path

at V

MAX

W = Airplane gross weight;
S = Aerodynamic reference wing area; and
q = Dynamic pressure.

(b) V

CLMAX

is determined with:

(1) Engines idling, or, if that result-

ant thrust causes an appreciable de-
crease in stall speed, not more than
zero thrust at the stall speed;

(2) Propeller pitch controls (if appli-

cable) in the takeoff position;

(3) The airplane in other respects

(such as flaps, landing gear, and ice ac-
cretions) in the condition existing in
the test or performance standard in
which V

is being used;

(4) The weight used when V

is being

used as a factor to determine compli-
ance with a required performance
standard;

(5) The center of gravity position

that results in the highest value of ref-
erence stall speed; and

(6) The airplane trimmed for straight

flight at a speed selected by the appli-
cant, but not less than 1.13V

and not

greater than 1.3V

condition, apply the longitudinal con-
trol to decelerate the airplane so that
the speed reduction does not exceed
one knot per second.

(d) In addition to the requirements of

paragraph (a) of this section, when a
device that abruptly pushes the nose
down at a selected angle of attack (e.g.,
a stick pusher) is installed, the ref-
erence stall speed, V

, may not be less

than 2 knots or 2 percent, whichever is
greater, above the speed at which the
device operates.

[Doc. No. 28404, 67 FR 70825, Nov. 26, 2002, as
amended by Amdt. 25–121, 72 FR 44665, Aug. 8,
2007]

§ 25.105

Takeoff.

(a) The takeoff speeds prescribed by

§ 25.107, the accelerate-stop distance
prescribed by § 25.109, the takeoff path
prescribed by § 25.111, the takeoff dis-
tance and takeoff run prescribed by
§ 25.113, and the net takeoff flight path
prescribed by § 25.115, must be deter-
mined in the selected configuration for
takeoff at each weight, altitude, and
ambient temperature within the oper-
ational limits selected by the appli-
cant—

(1) In non-icing conditions; and
(2) In icing conditions, if in the con-

figuration used to show compliance
with § 25.121(b), and with the most crit-
ical of the takeoff ice accretion(s) de-
fined in appendices C and O of this
part, as applicable, in accordance with
§ 25.21(g):

(i) The stall speed at maximum take-

off weight exceeds that in non-icing
conditions by more than the greater of
3 knots CAS or 3 percent of V

; or