Flight Stability Criteria - Standard
Flight Stability Criteria - Standard
The following exerpts from Gyroplane ASTM Standard F2352-11 is printed here with the permission of the ASTM. The full standard is copyrighted and may be purchased from the ASTM or is available to ASTM members (
ASTM)
4.5.1.2 The gyroplane must be able to be flown without
undue piloting skill, alertness, or strength in any normal
maneuver for a period of time as long as that expected in
normal operation.
4.5.1.3 Each requirement of this section must be met for the
most adverse combinations of engine power and airspeed
within which the gyroplane will be operated. Unless otherwise
specified, all requirements of this section shall be met at engine
power settings ranging from idle power to maximum allowed
engine power. Unless otherwise specified, all requirements of
this section shall be met at airspeeds ranging from MPRS to
VNE.
4.5.2.1 A power change from trimmed MPRS level flight at
MPRS power must result in a steady state trimmed airspeed not
to differ by more than 25 % from the initial trimmed MPRS
airspeed for the following conditions:
(1) In level flight, MPRS power increased to full power.
(2) In level flight, MPRS power reduced to engine off.
(3) Conducted with a cyclic stick fixed in pitch at the initial
MPRS stick position.
(4) Conducted with a the cyclic stick free in pitch at the
initial MPRS pitch trim.
4.5.2.2 Without trim adjustment, the cyclic pitch control
range must be adequate to reduce airspeed from trimmed VNE
to VMIN airspeed without excessive forces on the cyclic control
system at the following conditions:
(1) From VNE to VMIN with engine power off.
(2) From VNE to VMIN with engine at full power.
4.5.2.3 A rapid power change from trimmed MPRS level
flight at MPRS power must result in an airframe pitch attitude
rate of change not to exceed 5° per second for the following
conditions.
(1) MPRS power rapidly increased to full power.
(2) MPRS power rapidly reduced to idle power.
(3) Conducted with a cyclic stick fixed in pitch at the initial
MPRS stick position.
(4) Conducted with a the cyclic stick free in pitch at the
initial MPRS pitch trim.
4.5.3 Static Longitudinal Airspeed Stability:
4.5.3.1 The longitudinal control must be such that: (1) with
constant engine power, an aft force and movement of the cyclic
control is necessary to achieve an airspeed less than any
available trim airspeed; and (2) with constant engine power, a
forward force and movement of the control is necessary to
achieve an airspeed greater than any available trim airspeed.
The control force slope must not reverse during any progressive
application of control movement at airspeeds greater than
VMIN up to VNE. Static longitudinal airspeed stability must be
met at the following power and trimmed airspeed conditions:
(1) Steady altitude at MPRS,
(2) Full power at VNE,
(3) Full power at VMIN,
(4) Engine idle at MPRS,
(5) Engine idle at 80 % VNE, and
(6) Engine idle at VMIN.
4.5.3.2 The longitudinal control must be such that, with
constant engine power and with airspeed temporarily increased
at least 20 % above trimmed airspeed, upon release of the
cyclic pitch control the airspeed shall not diverge and shall
return to within 10 % of the following initially trimmed
airspeed condition with the cyclic pitch control free. Initial and
return trimmed conditions:
(1) Steady altitude at MPRS,
(2) Full power at 80 % VNE,
(3) Engine idle at MPRS, and
(4) Engine idle at 80 % VNE.
4.5.3.3 The longitudinal control must be such that: (1) with
constant engine power and with airspeed temporarily increased
at least 20 % above trimmed airspeed, upon return to the
following fixed stick conditions the airspeed shall return to
within 10 % of the initial fixed stick steady state airspeed; and
(2) with constant engine power and with airspeed temporarily
decreased at least 20 % below trimmed airspeed, upon return to
the following fixed stick conditions the airspeed shall return to
within 10 % of the initial fixed stick steady state airspeed.
Initial and return fixed stick conditions:
(1) Steady altitude at MPRS,
(2) Full power at 80 % VNE,
(3) Engine idle at MPRS, and
(4) Engine idle at 80 % VNE.
4.5.4 Static Longitudinal Maneuvering (G-Load) Stability:
4.5.4.1 The pitch control forces during turns or load factor
maneuvers greater than 1.0 g must be such that an increase in
load factor is associated with an increase in aft pilot control
force, and a decrease in load factor is associated with a
decrease in aft pilot control force for the following initial
trimmed conditions:
(1) Steady altitude at MPRS,
(2) Full power at the lesser of VH or VNE,
(3) Engine idle at MPRS, and
(4) Engine idle at 80 % VNE.
4.5.4.2 The airspeed during turns or load factor maneuvers
greater than 1.0g at a fixed cyclic pitch position must be such
that an increase in load factor is associated with an increase in
airspeed, and a decrease in load factor is associated with a
decrease in airspeed for the following initial fixed stick
conditions:
(1) Steady altitude at MPRS,
(2) Full power at the lesser of VH or of VNE,
(3) Engine idle at MPRS, and
(4) Engine idle at 80 % VNE.
4.5.5 Static Spiral Divergence:
4.5.5.1 For banked turns up to 1.5 g or 30° of bank with the
stick fixed, there must be no tendency for the gyroplane to
increase the turn rate rapidly at all allowable power settings for
the following conditions:
(1) Level 30° banking turn at straight and level MPRS
airspeed,
(2) 30° banking turn at full engine power, and
(3) Descending 30° turn at MPRS at engine idle.
4.5.7 Dynamic Longitudinal Stability:
4.5.7.1 The gyroplane under moderately turbulent air conditions
must exhibit no dangerous or divergent behavior with
cyclic pitch control fixed or with cyclic pitch control free for
the following conditions:
(1) Steady altitude at MPRS,
(2) Full power at VNE,
(3) Engine idle at MPRS,
(4) Engine idle at 80 % VNE, and
(5) Engine idle at VMIN.
4.5.7.2 Longitudinal Oscillation Damping:
(1) Any excitable longitudinal oscillations with periods less
than 5 s must damp to one half amplitude in not more than one
cycle with cyclic pitch control fixed or with cyclic pitch control
free. There should be no tendency for undamped small amplitude
oscillations to persist for more than 2 cycles with cyclic
pitch control fixed or with cyclic pitch control free.
(2) Any excitable longitudinal oscillations with periods
between 5 and 10 s should damp to one half amplitude in not
more than two cycles. There should be no tendency for
detectable undamped small oscillations to persist for longer
than 20 s.
(3) Any excitable longitudinal oscillations with periods
between 10 and 20 s should be damped, and in no circumstances
should a longitudinal oscillation having a period longer
than 20 s achieve more than double amplitude in less than 20 s.
Conditions:
(a) Steady altitude at MPRS,
(b) Full power at VNE,
(c) Engine idle at MPRS,
(d) Engine idle at 80 % VNE, and
(e) Engine idle at VMIN.