Appendix I
Automatic Reserve Performance (ARP) System
I 25.1 General
(a) This Appendix specifies additional
requirements and limitations for aeroplanes
equipped with an engine control system that
automatically resets thrust or power on the
operating engine(s) when any engine fails during
take-off, and for which performance credit is
limited to that of paragraph 25.3 (b) of this
Appendix. When performance credit is not so
limited, Special Conditions will apply.
(b) With the ARP system and associated
systems functioning normally as designed, all
applicable requirements of JAR-25, except as
provided in this Appendix, must be met without
requiring any action by the crew to increase thrust
or power.
I 25.2 Definitions
(a) Automatic Reserve Performance (ARP)
System. An ARP system is defined as a system
which automatically resets thrust or power on the
operating engine(s) when any engine fails during
take-off. For the purpose of the requirements in
this Appendix, the ARP system comprises all
elements of equipment necessary for the control
and performance of each intended function,
including all devices both mechanical and
electrical that sense engine failure, transmit
signals and actuate fuel controls or power levers
of the operating engine(s) to achieve scheduled
thrust or power increases, the engine control
system and devices which furnish cockpit
information on system operation.
(b) Critical Time Interval. When conducting
an ARP take-off, the critical time interval is
between one second before reaching V1, and the
point on the gross take-off flight path with all
engines operating where, assuming a simultaneous
engine and ARP system failure, the resulting
flight path thereafter intersects the gross flight
path, determined in accordance with JAR 25.115,
at not less than 400 feet above the take-off
surface. This definition is shown in the following
figure:
I 25.3 Performance requirements
All applicable performance requirements of
JAR-25 must be met with the ARP system
functioning normally as designed, except that the
propulsive thrust obtained from each operating
engine after failure of the critical engine during
take-off, and the thrust at which compliance with
the one-engine-inoperative climb requirements in
JAR 25.121 (a) and (b) is shown, must be
assumed to be not greater than the lesser of –
(a) The actual propulsive thrust resulting
from the initial setting of power or thrust controls
with the ARP system functioning normally as
designed, without requiring any action by the
crew to increase thrust or power until the
aeroplane has achieved a height of 400 feet above
the take-off surface; or
(b) 111 percent of the propulsive thrust
which would have been available at the initial
setting of power or thrust controls in the event of
failure of the ARP system to reset thrust or power,
without any action by the crew to increase thrust
or power until the aeroplane has achieved a height
of 400 feet above the take-off surface.
Note 1. The limitation of performance credit for
ARP system operation to 111 percent of the thrust
provided at the initial setting is intended to –
Appendix I
Automatic Reserve Performance (ARP) System
(See JAR 25X20 (c)
I 25.2 (continued)
(i) Assure an adequate level of
climb performance with all engines
operating at the initial setting of power or
thrust controls, and
(ii) Limit the degradation of
performance in the event of a critical
engine failure combined with failure of
the ARP system to operate as designed.
Note 2. For propeller-driven aeroplanes, propulsive
thrust means the total effective propulsive force
obtained from an operating engine and its
propeller.
I 25.4 Reliability requirements
(See JAR 25.1309 and AMJ 25.1309)
(a) The occurrence of an ARP system failure
or a combination of failures in the ARP system
during the critical time interval which –
(1) Prevents the insertion of the
required thrust or power, must be shown to be
Improbable;
(2) Results in a significant loss or
reduction in thrust or power, must be shown to
be Extremely Improbable.
(b) The concurrent existence of an ARP
system failure and an engine failure during the
critical time interval must be shown to be
Extremely Improbable.
(c) The inadvertent operation of the ARP
system must be shown either to be Remote or to
have no more than a minor effect.
I 25.5 Thrust or power setting
The initial setting of thrust or power controls
on each engine at the beginning of the take-off
roll may not be less than the lesser of –
(a) That required to permit normal operation
of all safety-related systems and equipment
dependent upon engine thrust or power lever
position; or
(b) That shown to be free of hazardous
engine response characteristics when thrust or
power is increased from the initial take-off thrust
or power level to the maximum approved take-off
thrust or power.
I 25.6 Powerplant controls
(a) General
(1) In addition to the requirements of
JAR 25.1141, no single failure or malfunction,
or probable combination thereof, of the ARP
system, including associated systems, may
cause the failure of any powerplant function
necessary for safety.
(2) The ARP system must be designed
to perform accurately its intended function
without exceeding engine operating limits
under all reasonably expected conditions.
(b) Thrust or Power Lever Control. The
ARP system must be designed to permit manual
decrease or increase in thrust or power up to the
maximum thrust or power approved for use
following engine failure during take-off through
the use of the normal thrust or power controls,
except that, for aeroplanes equipped with limiters
that automatically prevent engine operating limits
from being exceeded, other means may be used to
increase thrust or power provided that the means
is located in an accessible position on or close to
the thrust or power levers, is easily identified, and
operated under all operating conditions by a
single action of either pilot with the hand that is
normally used to actuate the thrust or power
levers.
(c) System Control and Monitoring. The
ARP system must be designed to provide –
(1) A means for checking prior to takeoff
that the system is in an operable condition;
and
(2) A means for the flight crew to deactivate
the automatic function. This means
must be designed to prevent inadvertent deactivation.
I 25.7 Powerplant instruments
(a) System Control and Monitoring. A
means must be provided to indicate when the ARP
system is in the armed or ready condition.
(b) Engine Failure Warning. If the inherent
flight characteristics of the aeroplane do not
provide adequate warning that an engine has
failed, a warning system which is independent of
the ARP system must be provided to give the pilot
a clear warning of engine failure during take-off.
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