Home' RTCA Documents for Review : DO-204B, MOPS Aircraft ELT 406MHZ Contents © EUROCAE, 2018
These shall be plotted as shown in FIGURE 5-3.
Plot the data determined from the two preceding paragraphs in the format of
FIGURE 5-4. A study of the data will bracket the velocity change at the
specified g levels, (§ 126.96.36.199.4 d., above), and dictate any additional test which
may be necessary to refine the data to show compliance with FIGURE 5-4.
188.8.131.52.5 Cross-axis Inputs (Optional)
This test is optional provided that crash safety (§ 184.108.40.206) testing is performed with 100
g loading applied at ±45° with respect to each orthogonal axis of the ELT unit, while in
the operational mode, and crash sensor performance is confirmed during each test.
The sensor shall be shown to operate in the longitudinal axis, as specified above,
when a 30 g cross-axis pulse, of at least equal duration to the longitudinal pulse, is
applied. The cross-axis pulse shall be applied in the direction most likely to cause
interference with sensing. The following are suggested methods for performing this
A single pulse can be applied at an angle to the crash acceleration sensor such
that it is resolved into the appropriate longitudinal and cross-axis values.
b. A test device can be mounted on a centrifuge.
A multi-axis shock table can be used.
d. This test can be performed at any one of the following points on the curve of
FIGURE 5-4 (Test points 3, 6, 9 or 12 Gs. +/- 1G).
220.127.116.11.6 Data Interpretation
The procedure of § 18.104.22.168.3.3 determines the threshold acceleration level for
activation of the sensor. The procedure of § 22.214.171.124.4 determines the minimum
velocity change at which the sensor will activate.
b. The minimum velocity change data determined above can be put into the form
of average pulse acceleration level, g., and pulse duration, (TP). The procedure
for this determination is provided in FIGURE 4-1.
126.96.36.199.7 Procedure – Airframe directions other than forward
188.8.131.52.7.1 The following procedure uses any pulse form (half-sine, trapezoidal, square, triangular,
etc.) that contains the time duration and acceleration levels shown in TABLE 5-3.
The ELT unit in the “ARMED” mode shall be secured to a vibration table, by the
normal installation means specified by the vibration equipment manufacturer, so
that vibratory motion is exerted parallel orthogonal to the ELT direction of the
main crash sensor.
b. Pulse 1 shown in TABLE 5-3 shall be input to the ELT and the activation status
of the crash sensor recorded.
The ELT shall be RESET and the test repeated for pulses 2-5 of TABLE 5-3.
d. The procedure of steps a-c above shall be repeated along the remaining ELT
axis orthogonal to the direction of the main crash sensor.
Crash sensor activation status (YES or NO) shall be shown to agree with TABLE 5-3
for each test (10 total) in order to establish a successful test.
184.108.40.206 Shock robustness
The ELT system components shall be secured to a shock tester by the
mounting means or packaging techniques intended for use in equipment
b. The mounting of the ELT system components shall include those non-structural
connections which are a normal part of the installation.
One of the three major orthogonal axes of the equipment shall be aligned with
the direction of the shock.
d. The ELT unit shall be switched to ARMED, (OFF in the case of an ELT(S)
without water sensor, or “ON” for an ELT(DT) with crash survivability).
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