Federal Aviation Administration, DOT

Pt. 60, App. A

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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 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 an airplane flight control system have a major effect on handling qualities. A significant consideration in pilot acceptability of an airplane is the  - feel -  provided through the
flight controls. Considerable effort is expended on airplane feel system design so that
pilots will be comfortable and will consider
the airplane desirable to fly. In order for an
FFS to be representative, it should  - feel - 
like the airplane being simulated. Compliance with this requirement is determined by
comparing a recording of the control feel dynamics of the FFS to actual airplane measurements in the takeoff, cruise and landing
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 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 airplane system is
essential. The required dynamic control
tests are described in Table A2A 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 A2A). 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 takeoff, cruise and
landing flight conditions and configurations.
(3) For airplanes 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 airplanes, takeoff,
cruise, and landing configurations have like
effects. Thus, one may suffice for another. In
either case, engineering validation or airplane 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 Evaluation. 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 Level C and D simulators. Tests to
verify that control feel dynamics represent
the airplane should show that the dynamic
damping cycles (free response of the controls) match those of the airplane 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 airplane 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
taken when applying the tolerance to small

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