329
Federal Aviation Administration, DOT
Pt. 60, App. D
2.c.2.
......................
Static
Stability
................
Longitudinal Control Position:
±
10% of change from trim or
±
0.25 in. (6.3 mm) or Longitu-
dinal Control Force:
±
0.5 lb.
(0.223 daN) or
±
10%.
Cruise or Climb.
Autorotation. Aug-
mentation On and
Off.
Record results for a minimum of
two speeds on each side of the
trim speed. May be a series of
snapshot tests.
X X X
2.c.3.
......................
Dynamic Stability.
2.c.3.a.
...................
Long Term Response
...
±
10% of calculated period.
±
10%
of time to
1
⁄
2
or double ampli-
tude, or
±
0.02 of damping ratio.
For non-periodic responses, the
time history must be matched
within
±
3
°
pitch; and
±
5 kts air-
speed over a 20 sec period fol-
lowing release of the controls.
Cruise Augmentation
On and Off.
Record results for three full cy-
cles (6 overshoots after input
completed) or that sufficient to
determine time to
1
⁄
2
or double
amplitude, whichever is less.
For non-periodic responses, the
test may be terminated prior to
20 sec if the test pilot deter-
mines that the results are be-
coming uncontrollably diver-
gent. Displace the cyclic for
one second or less to excite
the test. The result will be ei-
ther convergent or divergent
and must be recorded. If this
method fails to excite the test,
displace the cyclic to the pre-
determined maximum desired
pitch attitude and return to the
original position. If this method
is used, record the results.
X
X
X
The response for certain
helicopters may be
unrepeatable throughout
the stated time. In these
cases, the test should
show at least that a di-
vergence is identifiable.
For example: Displacing
the cyclic for a given time
normally excites this test
or until a given pitch atti-
tude is achieved and
then return the cyclic to
the original position. For
non-periodic responses,
results should show the
same convergent or di-
vergent character as the
flight test data.
2.c.3.b.
...................
Short Term Response
...
±
1.5
°
Pitch or
±
2
°
/sec. Pitch
Rate.
±
0.1 g Normal Accelera-
tion.
Cruise or Climb. Aug-
mentation On and
Off.
Record results for at least two air-
speeds.
X
X
A control doublet inserted
at the natural frequency
of the aircraft normally
excites this test. How-
ever, while input doublets
are preferred over pulse
inputs for Augmentation-
Off tests, for Augmenta-
tion-On cases, when the
short term response ex-
hibits 1st-order or dead-
beat characteristics, lon-
gitudinal pulse inputs
may produce a more co-
herent response.
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