365
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(A
d
)
on Figure C2A is
±
5 percent of the initial dis-
placement amplitude A
d
from the steady
state value of the oscillation. Only oscilla-
tions outside the residual band are consid-
ered significant. When comparing FFS data
to helicopter data, the process should begin
by overlaying or aligning the FFS and heli-
copter steady state values and then com-
paring 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 heli-
copter data. The procedure for evaluating
the response is illustrated in Figure C2A.
(b) Critically damped and Overdamped Re-
sponse. Due to the nature of critically
damped and overdamped responses (no over-
shoots), the time to reach 90 percent of the
steady state (neutral point) value should be
the same as the helicopter within
±
10 per-
cent. The simulator response must be criti-
cally damped also. Figure C2B illustrates the
procedure.
(c) Special considerations. Control systems
that exhibit characteristics other than clas-
sical overdamped or underdamped responses
should meet specified tolerances. In addi-
tion, special consideration should be given to
ensure that significant trends are main-
tained.
(2) Tolerances.
(a) The following summarizes the toler-
ances, ‘‘T’’ for underdamped systems, and
‘‘n’’ is the sequential period of a full cycle of
oscillation. See Figure C2A of this attach-
ment for an illustration of the referenced
measurements.
T(P
0
) ....................
±
10% of P
0
T(P
1
) ....................
±
20% of P
1
T(P
2
) ....................
±
30% of P
2
T(P
n
) ....................
±
10(n + 1)% of P
n
T(A
n
) ....................
±
10% of A
1
,
±
20%
of Subsequent
Peaks
T(A
d
) ....................
±
5% of A
d
= resid-
ual band
Significant overshoots. First overshoot
and
±
1 subsequent overshoots
(b) The following tolerance applies to criti-
cally damped and overdamped systems only.
See Figure C2B for an illustration of the ref-
erence measurements:
T(P
0
) ....................
±
10% of P
0
E
ND
I
NFORMATION
lllllllllllllllllllllll
B
EGIN
QPS R
EQUIREMENT
c. Alternative method for control dynam-
ics evaluation.
(1) An alternative means for validating
control dynamics for aircraft with hydrau-
lically powered flight controls and artificial
feel systems is by the measurement of con-
trol 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 oppo-
site 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.
N
OTE
: Dynamic sweeps may be limited to
forces not exceeding 100 lbs. (44.5 daN).
(d) Tolerances
(i) Static test—see Table C2A, FFS Objec-
tive Tests, Entries 2.a.1., 2.a.2., and 2.a.3.
(ii) Dynamic test—
±
2 lbs (0.9 daN) or
±
10%
on dynamic increment above static test.
E
ND
QPS R
EQUIREMENT
lllllllllllllllllllllll
B
EGIN
I
NFORMATION
d. The FAA is open to alternative means
that are justified and appropriate to the ap-
plication. For example, the method described
here may not apply to all manufacturers sys-
tems and certainly not to aircraft with re-
versible control systems. Each case is con-
sidered 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.
VerDate Sep<11>2014
16:30 Jun 25, 2019
Jkt 247047
PO 00000
Frm 00375
Fmt 8010
Sfmt 8002
Q:\14\14V2.TXT
PC31
kpayne on VMOFRWIN702 with $$_JOB