Federal Aviation Administration, DOT

Pt. 60, App. C

taken when applying the tolerance to small
overshoots since the significance of such
overshoots becomes questionable. Only those
overshoots larger than 5 percent of the total
initial displacement should be considered
significant. The residual band, labeled T(Ad)
on Figure C2A is Section5 percent of the initial displacement amplitude Ad from the steady
state value of the oscillation. Only oscillations outside the residual band are considered significant. When comparing FFS data
to helicopter data, the process should begin
by overlaying or aligning the FFS and helicopter steady state values and then comparing amplitudes of oscillation peaks, the
time of the first zero crossing, and individual
periods of oscillation. The FFS should show
the same number of significant overshoots to
within one when compared against the helicopter data. The procedure for evaluating
the response is illustrated in Figure C2A.
(b) Critically damped and Overdamped Response. Due to the nature of critically
damped and overdamped responses (no overshoots), the time to reach 90 percent of the
steady state (neutral point) value should be
the same as the helicopter within Section10 percent. The simulator response must be critically damped also. Figure C2B illustrates the
procedure.
(c) Special considerations. Control systems
that exhibit characteristics other than classical overdamped or underdamped responses
should meet specified tolerances. In addition, special consideration should be given to
ensure that significant trends are maintained.
(2) Tolerances.
(a) The following summarizes the tolerances,  - T -  for underdamped systems, and
 - n -  is the sequential period of a full cycle of
oscillation. See Figure C2A of this attachment for an illustration of the referenced
measurements.

T(P0)
T(P1)
T(P2)
T(Pn)
T(An)

....................
....................
....................
....................
....................

T(Ad) ....................

Section10% of P0
Section20% of P1
Section30% of P2
Section10(n + 1)% of Pn
Section10% of A1, Section20%
of Subsequent
Peaks
Section5% of Ad = residual band

kpayne on VMOFRWIN702 with $$_JOB

Significant overshoots. First
and Section1 subsequent overshoots

(b) The following tolerance applies to critically damped and overdamped systems only.
See Figure C2B for an illustration of the reference measurements:

T(P0) ....................

Section10% of P0

END INFORMATION
lllllllllllllllllllllll
BEGIN QPS REQUIREMENT
c. Alternative method for control dynamics evaluation.
(1) An alternative means for validating
control dynamics for aircraft with hydraulically powered flight controls and artificial
feel systems is by the measurement of control force and rate of movement. For each
axis of pitch, roll, and yaw, the control must
be forced to its maximum extreme position
for the following distinct rates. These tests
are conducted under normal flight and
ground conditions.
(a) Static test - Slowly move the control so
that a full sweep is achieved within 95-105
seconds. A full sweep is defined as movement
of the controller from neutral to the stop,
usually aft or right stop, then to the opposite stop, then to the neutral position.
(b) Slow dynamic test - Achieve a full
sweep within 8-12 seconds.
(c) Fast dynamic test - Achieve a full
sweep in within 3-5 seconds.
NOTE: Dynamic sweeps may be limited to
forces not exceeding 100 lbs. (44.5 daN).
(d) Tolerances
(i) Static test - see Table C2A, FFS Objective Tests, Entries 2.a.1., 2.a.2., and 2.a.3.
(ii) Dynamic test - Section2 lbs (0.9 daN) or Section10%
on dynamic increment above static test.
END QPS REQUIREMENT
lllllllllllllllllllllll
BEGIN INFORMATION

overshoot

d. The FAA is open to alternative means
that are justified and appropriate to the application. For example, the method described
here may not apply to all manufacturers systems and certainly not to aircraft with reversible control systems. Each case is considered on its own merit on an ad hoc basis.
If the FAA finds that alternative methods do
not result in satisfactory performance, more
conventionally accepted methods will have
to be used.

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