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B.4.4 Ground resonance
The helicopter shall have no dangerous tendency to oscillate
on the ground with the rotor turning.
SUB-PART C. STRUCTURE
C.l General
The helicopter structure shall be designed, manufactured and
provided with instructions for its maintenance with the objective
of avoiding catastrophic failure throughout its operational
life.
Note.- Structure includes the airframe, undercarriage,
control system, blades and rotorhead, rotor pylon and
auxiliary lifting surfaces.
accordance with A.2.1, shall be included in the flight manual
as part of the operating limitations (see G.2.3). When airspeed
limitations are a function of mass, mass distribution, altitude,
rotor speed, power or other factors, airspeed limitations based
on the critical combination of these factors shall be
established.
C.6 Main rotor@) rotational speed limits
A range of main rotor(s) speeds shall be established that:
C.2 Mass and mass distribution
Unless otherwise stated, all structural Standards shall be complied
with when the mass is varied over the applicable range
and is distributed in the most adverse manner, within the operating
limitations on the basis of which certification is sought.
C.3 Limit loads
Except as might be otherwise qualified, the external loads and
the corresponding inertia loads, or resisting loads obtained for
the various loading conditions prescribed in C.7, C.8 and C.9
shall be considered as limit loads.
C.4 Strength and deformation
In the various loading conditions prescribed in C.7, C.8 and
C.9, no part of the helicopter structure shall sustain detrimental
deformation at any load up to and including the limit load, and
the helicopter structure shall be capable of supporting the
ultimate load.
C.5 Airspeeds
C.5.1 Design airspeeds
Design airspeeds shall be established for which the helicopter
structure is designed to withstand the corresponding manoeuvring
and gust loads in accordance with C.7.
C.5.2 Limiting airspeeds
Limiting airspeeds, based on the corresponding design
airspeeds with safety margins, where appropriate, in
a) with power on, provides adequate margin to accommodate
the variations in rotor speed occumng in any
appropriate manoeuvre, and is consistent with the kind
of governor or synchronizer used; and
b) with power off, allows each appropriate autorotative
manoeuvre to be performed throughout the ranges of
airspeed and mass for which certification is requested.
C.7 Loads
C.7.1 The loading conditions of C.7, C.8 and C.9 shall
consider the range of mass and mass distributions prescribed
in (2.2, the main rotor rpm ranges established in C.6, and
airspeeds established in accordance with C.5.1. Asymmetrical
as well as symmetrical loading shall be taken into account.
The air, inertia and other loads resulting from the specific
loading conditions shall be distributed so as to approximate
actual conditions closely or to represent them conservatively.
C.7.2 Manoeuvring loads
Manoeuvring loads shall be computed on the basis of manoeuvring
load factors appropriate to the manoeuvres permitted by
the operating limitations. They shall not be less than values
that experience indicates will be adequate for the anticipated
operating conditions.
C.7.3 Gust loads
Gust loads shall be computed for vertical and horizontal gust
velocities that statistics or other evidence indicate will be
adequate for the anticipated operating conditions.
ANNEX 8 IVB-(2-1 13/12/07
Annex 8 - Airworthiness of Aircraft Part ZVB
C.8 Ground and water loads
C.8.1 The structure shall be able to withstand all the loads
due to the reactions of the ground or water surface, as applicable,
that arise during start-up, ground and water taxiing, liftoff,
touchdown and rotor braking.
C.8.2 Landing conditions
The landing conditions at the design take-off mass and at the
design landing mass shall include such symmetrical and asymmetrical
attitudes of the helicopter at ground or water contact,
such velocities of descent, and such other factors affecting the
loads imposed upon the structure as might be present in the
anticipated operating conditions.
C.9 Miscellaneous loads
In addition to or in conjunction with, the manoeuvering and
gust loads and with the ground and water loads, consideration
shall be given to all other loads (flight control loads, pilot
forces, engine torque, loads due to changes of configuration,
external loads, etc.) that are likely to occur in the anticipated
operating conditions.
C.10 Fatigue strength
The strength and fabrication technique of the helicopter
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附件8--航空器适航性 Airworthiness of Aircraft(55)