Sagetech MXS - Cooling Requirements; Figure 4-3 Pressure Altitude Encoder Port to Static Pressure; Figure 4-4 Cooling Methods Vs. Device Temperature

To Next Page

To Previous Page

MXS System Description and Installation Manual UM06945

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:

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%.