Pt. 60, App. C

14 CFR Ch. I (1-1-19 Edition)

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BEGIN INFORMATION
3. GENERAL
a. If relevant winds are present in the objective data, the wind vector should be clearly noted as part of the data presentation, expressed in conventional terminology, and related to the runway being used for test near
the ground.
b. The reader is encouraged to review the
Airplane Flight Simulator Evaluation Handbook, Volumes I and II, published by the
Royal Aeronautical Society, London, UK,
and FAA AC 25-7, as amended, Flight Test
Guide for Certification of Transport Category Airplanes, and AC 23-8, as amended,
Flight Test Guide for Certification of Part 23
Airplanes, for references and examples regarding flight testing requirements and techniques.

kpayne on VMOFRWIN702 with $$_JOB

4. CONTROL DYNAMICS
a. General. The characteristics of a helicopter flight control system have a major effect on the handling qualities. A significant
consideration in pilot acceptability of a helicopter is the  - feel -  provided through the
flight controls. Considerable effort is expended on helicopter feel system design so
that pilots will be comfortable and will consider the helicopter desirable to fly. In order
for an FFS to be representative, it should
 - feel -  like the helicopter being simulated.
Compliance with this requirement is determined by comparing a recording of the control feel dynamics of the FFS to actual helicopter measurements in the hover and cruise
configurations.
(1) Recordings such as free response to an
impulse or step function are classically used
to estimate the dynamic properties of
electromechanical systems. In any case, it is
only possible to estimate the dynamic properties as a result of only being able to estimate true inputs and responses. Therefore, it
is imperative that the best possible data be
collected since close matching of the FFS
control loading system to the helicopter system is essential. The required dynamic control tests are described in Table C2A of this
attachment.
(2) For initial and upgrade evaluations, the
QPS requires that control dynamics characteristics be measured and recorded directly
from the flight controls (Handling Qualities - Table C2A). This procedure is usually
accomplished by measuring the free response
of the controls using a step or impulse input
to excite the system. The procedure should
be accomplished in the hover and cruise
flight conditions and configurations.
(3) For helicopters with irreversible control systems, measurements may be obtained
on the ground if proper pitot-static inputs
are provided to represent airspeeds typical of

those encountered in flight. Likewise, it may
be shown that for some helicopters, hover,
climb, cruise, and autorotation have like effects. Thus, one may suffice for another. If
either or both considerations apply, engineering validation or helicopter manufacturer rationale should be submitted as justification for ground tests or for eliminating
a configuration. For FFSs requiring static
and dynamic tests at the controls, special
test fixtures will not be required during initial and upgrade evaluations if the QTG
shows both test fixture results and the results of an alternate approach (e.g., computer plots that were produced concurrently
and show satisfactory agreement). Repeat of
the alternate method during the initial evaluation satisfies this test requirement.
b. Control Dynamics Evaluations. The dynamic properties of control systems are
often stated in terms of frequency, damping,
and a number of other classical measurements. In order to establish a consistent
means of validating test results for FFS control loading, criteria are needed that will
clearly define the measurement interpretation and the applied tolerances. Criteria are
needed for underdamped, critically damped
and overdamped systems. In the case of an
underdamped system with very light damping, the system may be quantified in terms
of frequency and damping. In critically
damped or overdamped systems, the frequency and damping are not readily measured from a response time history. Therefore, the following suggested measurements
may be used:
(1) For Levels C and D simulators. Tests to
verify that control feel dynamics represent
the helicopter should show that the dynamic
damping cycles (free response of the controls) match those of the helicopter within
specified tolerances. The NSPM recognizes
that several different testing methods may
be used to verify the control feel dynamic response. The NSPM will consider the merits
of testing methods based on reliability and
consistency. One acceptable method of evaluating the response and the tolerance to be
applied is described below for the underdamped and critically damped cases. A sponsor using this method to comply with the
QPS requirements should perform the tests
as follows:
(a) Underdamped Response. Two measurements are required for the period, the time
to first zero crossing (in case a rate limit is
present) and the subsequent frequency of oscillation. It is necessary to measure cycles
on an individual basis in case there are nonuniform periods in the response. Each period
will be independently compared to the respective period of the helicopter control system and, consequently, will enjoy the full
tolerance specified for that period. The
damping tolerance will be applied to overshoots on an individual basis. Care should be

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