208 

14 CFR Ch. I (1–1–19 Edition) 

§ 25.27 

compliance with each applicable re-
quirement of this part is shown) must 
be established so that it is not less 
than— 

(1) The lowest weight selected by the 

applicant; 

(2) The design minimum weight (the 

lowest weight at which compliance 
with each structural loading condition 
of this part is shown); or 

(3) The lowest weight at which com-

pliance with each applicable flight re-
quirement is shown. 

[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as 
amended by Amdt. 25–23, 35 FR 5671, Apr. 8, 
1970; Amdt. 25–63, 53 FR 16365, May 6, 1988] 

§ 25.27

Center of gravity limits. 

The extreme forward and the extreme 

aft center of gravity limitations must 
be established for each practicably sep-
arable operating condition. No such 
limit may lie beyond— 

(a) The extremes selected by the ap-

plicant; 

(b) The extremes within which the 

structure is proven; or 

(c) The extremes within which com-

pliance with each applicable flight re-
quirement is shown. 

§ 25.29

Empty weight and cor-

responding center of gravity. 

(a) The empty weight and cor-

responding center of gravity must be 
determined by weighing the airplane 
with— 

(1) Fixed ballast; 
(2) Unusable fuel determined under 

§ 25.959; and 

(3) Full operating fluids, including— 
(i) Oil; 
(ii) Hydraulic fluid; and 
(iii) Other fluids required for normal 

operation of airplane systems, except 
potable water, lavatory precharge 
water, and fluids intended for injection 
in the engine. 

(b) The condition of the airplane at 

the time of determining empty weight 
must be one that is well defined and 
can be easily repeated. 

[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as 
amended by Amdt. 25–42, 43 FR 2320, Jan. 16, 
1978; Amdt. 25–72, 55 FR 29774, July 20, 1990] 

§ 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. 

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