DEPARTMENT OF CIVIL AVIATION
Airworthiness Notices
T/14
ELECTRICAL GENERATION SYSTEMS (AIRCRAFT NOT EXCEEDING
MAXIMUM CERTIFIED TAKE-OFF MASS OF 5700 KG)
1. Introduction
1.1. Investigation into accidents and incidents involving total loss of generated electrical
power to aircraft, the maximum certified take-off mass of which does not exceed
5700 kg, have shown certain inadequacies in the failure warnings and indications
provided. Experience has shown that the loss of generated electrical power can
remain undetected for a significant period of time, resulting in the serious depletion of
the available battery capacity and reduced duration of supplies to essential services
under these conditions.
1.2. The purpose of this Notice is to publish requirements for certain aircraft to ensure that
a clear and unmistakable warning of loss of generated electrical power is given, and to
preserve or provide sufficient electrical energy to operate essential services for an
adequate period of time in the event of such a loss occurring.
2. Requirement
2.1. For all multi-engined aircraft, the maximum certified take-off mass of which does not
exceed 5700 kg, compliance with paragraphs 2.2, 2.3, 2.4 and 2.5 of this Notice, or
with a DCA approved alternative providing an equivalent level of airworthiness, is
required.
2.1.1. Where it can be shown that an aircraft is fitted with such limited electrical and
radio equipment, or is certificated to operate under such limited conditions
(e.g. VMC day only) that the loss of generated electrical power would not
significantly prejudice safe flight, the DCA will, on application, waive the
requirements of this Notice where it is satisfied that compliance would not be
justified in the circumstances of a particular case.
2.2. Clear visual warning shall be provided, within the pilot's normal line of sight, to give
indication of either
(a) reduction of the generating system voltage to a level where the battery
commences to support any part of the main electrical load of the aircraft; or
(b) loss of the output of each engine driven generator at the main distribution point
or bus-bars.
2.3. The battery capacity shall be such that in the event of a complete loss of generated
electrical power, adequate power will be available for a period of not less than 30
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Airworthiness Notices
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minutes following the failure, to support those services essential to the continued safe
flight and landing of the aircraft, (see paragraph 3.1). This includes an assumed period
of not less than 10 minutes from operation of the warning specified in paragraph 2.2,
for completion of the appropriate drills. This delay may be reduced to not less than
five minutes if the warning system is provided with "attention getting" characteristics
(e.g. a flashing light). For the purpose of calculations it shall be assumed that the
electrical load conditions at the time of failure warning are those appropriate to
normal cruising flight at night (see paragraph 3).
2.4. Where all gyroscopic attitude reference instruments, i.e. bank and pitch indicator(s)
and turn and slip indicator(s), are dependent on electrical power for their operation, at
least one of these instruments shall continue to operate without crew action for the
prescribed 30 minute period.
Notes:(1) For certain aircraft types a turn and slip indicator may not be acceptable as
the sole remaining attitude reference instrument.
(2) Certain aircraft are equipped with both electrically operated and air driven
attitude reference instruments. In such cases the air driven instruments will
be accepted as providing the emergency attitude information provided that
the requirements of paragraph 2.4.1 are met.
2.4.1. The instrument(s) with which the requirement of paragraph 2.4 will be met
shall be clearly designated, and
(a) shall be so located on the instrument panel that it will be visible to, and
usable by, the pilot from his normal position;
(b) shall be provided with means of indicating that the power supply to the
instrument is operating correctly.
2.5. Precise drills covering crew action in the event of electrical general system failures
and malfunctions shall be included in the appropriate aircraft manual(s), together with
a statement of battery endurance under specified load conditions.
3. Additional Information
3.1. When ascertaining that the installed aircraft battery capacity is adequate for
compliance with paragraph 2.3, the following loads should be taken into account:
(a) Attitude information (where applicable in accordance with paragraph 2.4).
(b) Essential Radio Communication.
Note: For the purpose of calculations it will normally be accepted that
intermittent use of single VHF communication equipment satisfies this
requirement. Utilisation on the basis of a total 15 minutes reception
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DEPARTMENT OF CIVIL AVIATION
Airworthiness Notices
T/14
plus 3 minutes transmission in the 30 minute period would be an
acceptable interpretation.
(c) Essential cockpit lighting.
(d) Pitot Head Heater (applicable only to those aircraft certificated for flight in
icing conditions).
(e) Any other services essential for the continued safe flight and landing of the
particular aircraft.
(f) Those services which cannot readily be shed when carrying out the drills
required under paragraph 2.5.
3.1.1. In order to ensure that the essential services, taken into account in accordance
with paragraph 3.1, will function adequately for the prescribed period, the
calculation of the duration of battery supply should normally be based on the
following assumptions:
(a) Only 75% of the "name plate" rating of the battery is available (this is to
take into consideration loss of capacity with age, and a realistic state of
charge).
(b) The voltage/time discharge characteristic of the battery, appropriate to the
load of the listed services, is not extended beyond a battery terminal voltage
of 21.5 volts on a 24 volt system, pro rata for 12 volt systems, (this is to
ensure that the voltage available throughout the prescribed period is
adequate for satisfactory operation of the services).
Note: Only where compliance with this Notice cannot be shown within
the criteria of paragraphs 3.1 and 3.1.1, will consideration have to
be given to the fitment of additional, or larger capacity, batteries to
particular aircraft.
3.2. Guidance information for achieving compliance with this notice can be seen CAAIP
Leaflet 24-30. Applications for the approval of modifications necessary to ensure
compliance with the requirements of this Notice should be made in the manner
specified in the Myanmar Airworthiness Notice A/4. Owners and operators are
recommended to contact the constructor concerned or the main agent for information
regarding suitable modifications.
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