Home' RTCA Documents for Review : DO-204B, MOPS Aircraft ELT 406MHZ Contents © EUROCAE, 2018
If designed to be user-replaceable, the power source shall not require any special
tools, fixtures or soldering for installation in the field. Any interface connections shall
be accomplished in a manner to ensure maximum reliability and preclude reversed
polarity or incorrect installation. Provision shall be made to ensure the waterproofness
of the ELT unit upon replacement of the power source.
Aircraft Electrical Power
The ELT(DT) may use aircraft electrical power source when available. The ELT
system minimum duration of continuous operation shall however be demonstrated
with the ELT(DT)’s own internal/integral power source. The ELT(DT) performance for
triggered transmission shall not be affected when the aircraft electrical power source is
The ELT manufacturer shall establish a useful life and an expiration date for batteries.
The useful life is defined as the period of time after the battery manufacture date that
the battery will continue to meet the battery requirements as defined in C/S T.001 or
T.018 as applicable.
The ELT battery useful life shall be specified by the ELT manufacturer to meet the
requirement of § 3.5 and shall be compliant with the C/S T.007 and C/S T.021 as
applicable for the pre-test battery discharge calculations except that the useful life
(battery replacement date) shall be no more than one half of the shelf life of the
battery. The discharge calculation shall cover all the expected life cycle of the ELT unit
and include margin on the whole period. The expiry date shall be clearly and
conspicuously marked on an external label and calculated from cell date of
manufacture to end of battery replacement period.
The ELT manufacturer should justify the specified shelf life with
supporting data supplied by the battery manufacturer.
Non-rechargable Lithium Batteries
Non-rechargeable Lithium batteries shall meet the applicable requirements of RTCA
The use of rechargeable batteries are not addressed in this standard and, if used,
introduce additional implementation issues such as performance and operational
requirements related to battery charging and safety that would be necessary to ensure
the ELT meets it performance requirements. Manufacturers wishing to propose their
use should refer to the appropriate approval authority. Relevant standards may
include the following:
a. For nickel-cadmium or lead acid batteries refer to RTCA DO-293().
b. For rechargeable lithium batteries refer to RTCA DO-311().
All Lithium Batteries
For all Lithium batteries, the composition, quantities and potential toxicity of gases
produced by a full thermal runaway failure of the battery should be understood and
considered in the battery selection and ELT design.
The manufacturer may provide for the use of the aircraft power or any other
supplemental power supply for remote control and/or monitor functions provided that
other specifications of this document are not compromised. The transition from
external power to autonomous power shall not affect the performance of the ELT, in
particular, transmission or detection of crash conditions.
Selt-test Battery Life
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