(a) Electrical system capacity. The required generating capacity
and the number and kind of power sources must --
(1) Be determined by an electrical load analysis; and
(2) Meet the requirements of §29.1309.
(b) Generating system. The generating system includes electrical
power sources, main power busses, transmission cables, and associated
control, regulation, and protective devices. It must be designed so that
--
(1) Power sources function properly when independent and when connected
in combination;
(2) No failure or malfunction of any power source can create a hazard
or impair the ability of remaining sources to supply essential loads;
(3) The system voltage and frequency (as applicable) at the terminals
of essential load equipment can be maintained within the limits for which
the equipment is designed, during any probable operating condition;
(4) System transients due to switching, fault clearing, or other causes
do not make essential loads inoperative, and do not cause a smoke or fire
hazard;
(5) There are means accessible in flight to appropriate crewmembers for
the individual and collective disconnection of the electrical power
sources from the main bus; and
(6) There are means to indicate to appropriate crewmembers the
generating system quantities essential for the safe operation of the
system, such as the voltage and current supplied by each generator.
(c) External power. If provisions are made for connecting
external power to the rotorcraft, and that external power can be
electrically connected to equipment other than that used for engine
starting, means must be provided to ensure that no external power supply
having a reverse polarity, or a reverse phase sequence, can supply power
to the rotorcraft's electrical system.
(d) Operation with the normal electrical power generating system
inoperative.
(1) It must be shown by analysis, tests, or both, that the rotorcraft
can be operated safely in VFR conditions for a period of not less than 5
minutes, with the normal electrical power generating system (electrical
power sources excluding the battery) inoperative, with critical type fuel
(from the standpoint of flameout and restart capability), and with the
rotorcraft initially at the maximum certificated altitude. Parts of the
electrical system may remain on if --
(i) A single malfunction, including a wire bundle or junction box fire,
cannot result in loss of the part turned off and the part turned on;
(ii) The parts turned on are electrically and mechanically isolated
from the parts turned off; and
(2) Additional requirements for Category A Rotorcraft.
(i) Unless it can be shown that the loss of the normal electrical power
generating system is extremely improbable, an emergency electrical power
system, independent of the normal electrical power generating system, must
be provided, with sufficient capacity to power all systems necessary for
continued safe flight and landing.
(ii) Failures, including junction box, control panel, or wire bundle
fires, which would result in the loss of the normal and emergency systems,
must be shown to be extremely improbable.
(iii) Systems necessary for immediate safety must continue to operate
following the loss of the normal electrical power generating system,
without the need for flight crew action. (Secs. 313(a), 601, 603,
604, and 605 of the Federal Aviation Act of 1958 (49 U.S.C. 1354(a), 1421,
1423, 1424, and 1425); and sec. 6(c), Dept. of Transportation Act (49
U.S.C. 1655(c)))