Amdt. 25-72, E.. 8/20/90
FAR 25.399 : Dual control system.
(a)
Each dual control system must be designed for the pilots operating in opposition, using individual pilot forces not less than–
(1)
0.75 times those obtained under Sec. 25.395; or
(2)
The minimum forces speci.ed in Sec. 25.397(c).
(b)
The control system must be designed for pilot forces applied in the same direction, using individual pilot forces not less than 0.75 times those obtained under Sec.
25.395.
′
Elodie Roux. Septembre 2003
Subpart C : Structure
FAR 25.405 : Secondary control system.
Secondary controls, such as wheel brake, spoiler, and tab controls, must be designed for the maximum forces that a pilot is likely to apply to those controls. The following values may be used :
Pilot Control Force Limits(Secondary Controls)
Control Limit pilot forces
Miscellaneous : .Crank, wheel, or lever. Twist Push-pull /1+R 3、 50 lbs., but not less than 50 lbs. nor more than 150 lbs. (R=radius). (Applicable to any angle within 20'of plane of control.) 133 in.-lbs. To be chosen by applicant.
.Limited to .ap, tab, stabilizer, spoiler, and landing gear operation controls.
FAR 25.407 : Trim tab e.ects.
The e.ects of trim tabs on the control surface design conditions must be accounted for only where the surface loads are limited by maximum pilot e.ort. In these cases, the tabs are considered to be de.ected in the direction that would assist the pilot, and the de.ections are–
(a) For elevator trim tabs, those required to trim the airplane at any point within the positiveportionofthepertinent .ight envelopeinSec.25.333(b),exceptaslimited by the stops; and
(b) For aileron and rudder trim tabs, those required to trim the airplane in the critical unsymmetricalpower andloading conditions, with appropriate allowancefor rigging tolerances.
FAR 25.409 : Tabs.
(a) Trim tabs. Trim tabs must be designed to withstand loads arising from all likely combinations of tab setting,primary controlposition, and airplane speed(obtai-nable without exceeding the .ight load conditions prescribed for the airplane as a whole), when the e.ect of the tab is opposed by pilot e.ort forces up to those speci.ed in Sec. 25.397(b).
(b) Balancing tabs. Balancing tabs must be designed for de.ections consistent with the primary control surface loading conditions.
(c) Servo tabs. Servo tabs must be designed for de.ections consistent with the primary control surface loading conditions obtainable within the pilot maneuvering e.ort, consideringpossible oppositionfromthetrimtabs.
FAR 25.415 : Ground gust conditions.
(a) The control system must be designed as follows for control surface loads due to groundgusts andtaxiing downwind :
(1) The control system between the stops nearest the surfaces and the cockpit controls must be designed for loads corresponding to the limit hinge moments H ofparagraph(a)(2) of this section.Theseloads need not exceed–
(i)
Theloadscorresponding tothe maximumpilotloadsinSec.25.397(c)for eachpilot alone; or
(ii)
0.75 times these maximum loads for each pilot when the pilot forces are applied in the same direction.
(2) [The controlsystem stops nearest the surfaces, the control system locks, and theparts of the systems(if any)between these stops andlocks and the control surface horns, must be designed for limit hinge moments, H, in foot pounds, obtained from the formula, H = .0034KV2cS, where–
V =65 :(wind speedinknots)
K : limit hinge moment factor for ground gusts derived in pa-
ragraph (b) of this section.
c : mean chord of the control surface aft of the hinge line (ft);
S : area of the control surface aft of the hinge line (sq ft);]
(b) The limit hinge moment factor K for ground gusts must be derived as follows : 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：FAA规章 美国联邦航空规章 Federal Aviation Regulations 3(54)
