106
14 CFR Ch. I (1–1–19 Edition)
Pt. 60, App. A
overshoots since the significance of such
overshoots becomes questionable. Only those
overshoots larger than 5 per cent of the total
initial displacement should be considered.
The residual band, labeled T(A
d
) on Figure
A2A is
±
5 percent of the initial displacement
amplitude A
d
from the steady state value of
the oscillation. Only oscillations outside the
residual band are considered significant.
When comparing FFS data to airplane data,
the process should begin by overlaying or
aligning the FFS and airplane steady state
values and then comparing amplitudes of os-
cillation peaks, the time of the first zero
crossing and individual periods of oscilla-
tion. The FFS should show the same number
of significant overshoots to within one when
compared against the airplane data. The pro-
cedure for evaluating the response is illus-
trated in Figure A2A.
(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 airplane within
±
10 percent.
Figure A2B 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 table summarizes the tol-
erances, T, for underdamped systems, and
‘‘n’’ is the sequential period of a full cycle of
oscillation. See Figure A2A 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
.
T(A
d
) ..........
±
5% of A
d
= residual
band.
Significant overshoots, First overshoot
and
±
1 subsequent overshoots.
(b) The following tolerance applies to criti-
cally damped and overdamped systems only.
See Figure A2B 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 to 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 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 A2A, 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
such as the one described above. The alter-
natives should be justified and appropriate
to the application. For example, the method
described here may not apply to all manufac-
turers’ 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 per-
formance, more conventionally accepted
methods will have to be used.
VerDate Sep<11>2014
16:30 Jun 25, 2019
Jkt 247047
PO 00000
Frm 00116
Fmt 8010
Sfmt 8002
Q:\14\14V2.TXT
PC31
kpayne on VMOFRWIN702 with $$_JOB