208
14 CFR Ch. I (1–1–24 Edition)
§ 25.31
§ 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.
(c) The means used to limit the low
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]
P
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
°
F.
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
r
/
s
=
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
(c) The performance must correspond
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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