(1)
The vertical reactions must be combined with horizontal drag reactions of 50 percent of the vertical reaction applied at the ground.
(2)
Theresultantgroundloadsmust equal theverticalload speci.edinparagraph (b)of this section.
(i)
Equal tothe verticalload speci.edinparagraph(b) of this section; and
(ii)
Directedthrough the center ofgravity.
(d)
Sideloads in the level landing attitude. In the level attitude, and with the rotorcraft contacting the ground along the bottom of both skids, the following apply :
(1)
The verticalground reaction mustbe–
(i)
Equalto the verticalloads obtainedin the condition speci.edinparagraph (b)ofthis section; and
(ii)
Divided equally among the skids.
(2)
The verticalground reactions mustbe combined with ahorizontal sideload of 25 percent of their value.
(3)
[The total sideload must be applied equally between the skids and along the length of the skids.]
(4)
The unbalanced moments are assumed to be resisted by angular inertia.
(5)
The skid gear must be investigated for–
(i)
Inward acting sideloads; and
(ii)
Outward acting sideloads.
(e)
One-skid landing loads in the level attitude. In the level attitude, and with the ro-torcraft contacting the ground along the bottom of one skid only, the following apply :
(1)
The verticalloadon theground contact side mustbe the same as that obtained onthat sideinthe condition speci.edinparagraph(b) of this section.
(2)
The unbalanced moments are assumed to be resisted by angular inertia.
(f)
Special conditions.In additiontothe conditions speci.edinparagraphs(b) and(c) of this section,the rotorcraftmustbedesignedforthefollowingground reactions:
(1)
A ground reaction load acting up and aft at an angle of 45 degrees to the longitudinal axis of the rotorcraft. This load must be–
(i)
Equal to 1.33 times the maximum weight;
(ii)
Distributed symmetrically among the skids;
(iii) Concentrated at theforward end of the straightpart of the skid tube; and
(iv) Applied only to the forward end of the skid tube and its attachment to the rotorcraft.
(2)
With the rotorcraft in the level landing attitude, a vertical ground reaction load equal to one-half of the verticalloaddetermined underparagraph(b) of this section. This load must be–
(i)
Applied only to the skid tube and its attachment to the rotorcraft; and
(ii)
[Distributed equally over 33.3 percent of the length between the skid tube attachments and centrally located midway between the skid tube attachments.]
Amdt. 27-26, E.. 4/5/90
′
Elodie Roux. Septembre 2003
Subpart C : Strength Requirements
FAR 27.505 : Ski landing conditions
If certi.cation for ski operation is requested, the rotorcraft, with skis, must be de-signed to withstand the following loading conditions (where P is the maximum static weight on each ski with the rotorcraft at design maximum weight, and nzcl is the limit load factor determined under Sec. 27.473(b)).
(a) Up-load conditions in which–
(1) A vertical load of Pnzcl and a horizontal load of P nzcl are simultaneously
4
applied at the pedestal bearings; and
(2) A vertical load of 1.33P is applied at the pedestal bearings.
(b)
A side-load condition in which a side load of 0.35Pnzcl is applied at the pedestal bearingsin ahorizontalplaneperpendiculartothe centerline ofthe rotorcraft.
(c)
A torque-load condition in which a torque load of 1.33P (infootpounds)is applied to the ski about the vertical axis through the centerline of the pedestal bearings.
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 4(80)
