(d)
Within thefree return speed range speci.edinparagraph(b) of this section,itis permissible for the airplane, without control forces, to stabilize on speeds above or below the desired trim speeds if exceptional attention on the part of the pilot is not required to return to and maintain the desired trim speed and altitude.]

Amdt. 25-7, E.. 11/14/65
FAR 25.175 : Demonstration of static longitudinal stability.
Static longitudinal stability must be shown as follows :
(a)
Climb. The stick force curve must have a stable slope at speeds between 85 and 115 percent of the speed at which the airplane–

(1)
Is trimmed, with–

(i)
Wing .aps retracted;

(ii)
Landing gear retracted;

(iii) Maximum takeo. weight; and
(iv) 75 percent of maximum continuous power for reciprocating engines or the maximum power or thrust selected by the applicant as an operating limitation for use during climb for turbine engines; and

(2)
Is trimmed at the speed for best rate-of-climb except that the speed need not be less than[1.3 VSR1].

(b)
Cruise.Staticlongitudinal stability mustbe showninthe cruise condition asfollows:

(1) With thelandinggearretracted athigh speed,the stickforcecurvemusthave a stable slope at all speeds within a range which is the greater of 15 percent of the trim speed plus the resulting free return speed range, or 50 knots plus the resultingfree returnspeed range,aboveandbelowthetrim speed(except thatthe speed range need notinclude speedslessthan[1.3 VSR1], nor speeds greater than VFC/MFC, nor speeds that require a stick force of more than 50 pounds), with–
(i)
The wing .aps retracted;

(ii)
The center ofgravity inthe most adverseposition(seeSec.25.27);

(iii) The most critical weight between the maximum takeo. and maximum landing weights;
(iv)
75 percent of maximum continuous power for reciprocating engines or, forturbine engines, the maximum cruisingpower selectedbythe applicant as an operating limitation(seeSec.25.1521),exceptthatthepower need not exceed that required at VMO/MMO ; and

(v)
Theairplanetrimmedforlevel.ightwiththepowerrequiredinparagraph (b)(1)(iv)above.

′
Elodie Roux. Septembre 2003
Subpart B : Flight
(2)
With the landing gear retracted at low speed, the stick force curve must have a stable slope at all speeds within a range which is the greater of 15 percent of the trim speed plus the resulting free return speed range, or 50 knots plus the resultingfree returnspeed range,aboveandbelowthetrim speed(except that the speed range need notinclude speedslessthan[1.3 VSR1],nor speeds greater than the minimum speed of the applicable speed range prescribed in paragraph (b)(1), nor speeds that require a stick force of more than 50 pounds), with–

(i)
Wing.aps,centerofgravityposition,andweight asspeci.edinparagraph (b)(1)ofthis section;

(VMO+1.3VSR1)

(ii)
Powerrequiredforlevel.ightataspeed equal to[]and

(iii) The airplane trimmed for level .ight with the power required in para-graph(b)(2)(ii) of this section.

(3)
With thelandinggearextended,the stickforcecurvemusthavea stableslope at all speeds within a range whichis thegreater of15percent of the trim speed plus the resulting free return speed range, or 50 knots plus the resulting free return speedrange,aboveandbelowthetrim speed(exceptthatthe speed range need notinclude speedsless than[1.3 VSR1] , nor speeds greater than VLE, nor speeds that require a stick force of more than 50 pounds), with–

(i)
Wing .ap,centerofgravityposition,and weight asspeci.edinparagraph (b)(1)ofthis section;

(ii)
75percentof maximum continuouspowerfor reciprocating engines or,for turbine engines, the maximum cruising power selected by the applicant as an operating limitation, except that the power need not exceed that required for level .ight at VLE ; and
　
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