MXS System Description and Installation Manual
UM06945
© Sagetech Avionics 2022 Proprietary Confidential
Page 24 of 56
Figure 4-3 Pressure Altitude Encoder Port to Static Pressure
4.6
Cooling Requirements
The MXS is designed such that its case conducts thermal load to the aircraft frame through the bottom
(Non-Labeled) side. The transponder can be firmly mounted directly to the aircraft, or to other
components within the aircraft.
•
The transponder should be mounted away from sources of excess heat to better guarantee an
operating environment within its designed temperature range.
•
To meet the required Mean Time Between Failures (MTBF), the Internal Circuitry shall not exceed
85°C.
•
The MXS can still operate above this temperature up to the temperature protection limit of 110°C,
however, above 85°C the MTBF will degrade. For example, if the ambient temperature is 55°C and
the temperature rise of the MXS is 35°C (see plots below) then the MXS internal junction
temperature would be 85°C and the MTBF will have degraded performance.
•
If the temperature protection limit is hit the MXS will cease transmissions until the device has
cooled down to a safe operating temperature. Once below the safe temperature threshold, the
transponder will automatically continue transmitting without any required actions of the operator
or host computer.
•
Internal temperature can be monitored by requesting the Health Monitor Response Message (see
ICD02373)
•
The plots below characterize the thermal performance of the MXS in 2 different scenarios and at
various transmit duty cycles.
Figure 4-4 Cooling Methods vs. Device Temperature
shows average internal device temperature and
self-reported temperature of the SoC under the following conditions:
3
Cooling method testing was performed with a SQUAWK code of 7777, with Emergency mode and X Bit off. One Mode A
reply equates to 0.00063%.
