364 

14 CFR Ch. I (1–1–19 Edition) 

Pt. 60, App. C 

lllllllllllllllllllllll

B

EGIN

I

NFORMATION

 

3. G

ENERAL

 

a. If relevant winds are present in the ob-

jective data, the wind vector should be clear-
ly noted as part of the data presentation, ex-
pressed in conventional terminology, and re-
lated to the runway being used for test near 
the ground. 

b. The reader is encouraged to review the 

Airplane Flight Simulator Evaluation Hand-
book, 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 Cat-
egory Airplanes, and AC 23–8, as amended, 
Flight Test Guide for Certification of Part 23 
Airplanes, for references and examples re-
garding flight testing requirements and tech-
niques. 

4. C

ONTROL

D

YNAMICS

 

a. General. The characteristics of a heli-

copter flight control system have a major ef-
fect on the handling qualities. A significant 
consideration in pilot acceptability of a heli-
copter is the ‘‘feel’’ provided through the 
flight controls. Considerable effort is ex-
pended on helicopter feel system design so 
that pilots will be comfortable and will con-
sider 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 deter-
mined by comparing a recording of the con-
trol feel dynamics of the FFS to actual heli-
copter 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 prop-
erties as a result of only being able to esti-
mate 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 sys-
tem is essential. The required dynamic con-
trol tests are described in Table C2A of this 
attachment. 

(2) For initial and upgrade evaluations, the 

QPS requires that control dynamics charac-
teristics be measured and recorded directly 
from the flight controls (Handling Quali-
ties—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 con-

trol 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 ef-
fects. Thus, one may suffice for another. If 
either or both considerations apply, engi-
neering validation or helicopter manufac-
turer rationale should be submitted as jus-
tification 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 ini-
tial and upgrade evaluations if the QTG 
shows both test fixture results and the re-
sults of an alternate approach (e.g., com-
puter plots that were produced concurrently 
and show satisfactory agreement). Repeat of 
the alternate method during the initial eval-
uation satisfies this test requirement. 

b. Control Dynamics Evaluations. The dy-

namic properties of control systems are 
often stated in terms of frequency, damping, 
and a number of other classical measure-
ments. In order to establish a consistent 
means of validating test results for FFS con-
trol loading, criteria are needed that will 
clearly define the measurement interpreta-
tion and the applied tolerances. Criteria are 
needed for underdamped, critically damped 
and overdamped systems. In the case of an 
underdamped system with very light damp-
ing, the system may be quantified in terms 
of frequency and damping. In critically 
damped or overdamped systems, the fre-
quency and damping are not readily meas-
ured from a response time history. There-
fore, 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 con-
trols) 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 re-
sponse. The NSPM will consider the merits 
of testing methods based on reliability and 
consistency. One acceptable method of eval-
uating the response and the tolerance to be 
applied is described below for the under-
damped and critically damped cases. A spon-
sor using this method to comply with the 
QPS requirements should perform the tests 
as follows: 

(a) Underdamped Response. Two measure-

ments are required for the period, the time 
to first zero crossing (in case a rate limit is 
present) and the subsequent frequency of os-
cillation. It is necessary to measure cycles 
on an individual basis in case there are non- 
uniform periods in the response. Each period 
will be independently compared to the re-
spective period of the helicopter control sys-
tem and, consequently, will enjoy the full 
tolerance specified for that period. The 
damping tolerance will be applied to over-
shoots on an individual basis. Care should be 

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