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Regarding the Mode S EHS MMEL / MEL, how does the pilot know if one or more DAP parameters is not functioning properly?

April 26, 2017dap functioning MeL mmel mode parameters pilot

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Regarding the Mode S EHS MMEL / MEL, how does the pilot know if one or more DAP parameters is not functioning properly?

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There are no flight deck indications to inform the pilot that the transponder is not sending one or more DAP’s, or the accuracy of the downlinked information. The pilot may be aware, indirectly, due to the failure of sensors which provide information to the transponder, such as the Flight Management System or Air Data System. The Air Traffic Controller may also report lost, missing or incorrect DAP’s, which should be recorded in the aircraft’s techical fault log – to be corrected within the time stated in the MMEL. Alternatively, lost or missing DAP’s may be discovered during the periodic maintenance check (see JAA NPA 20-12a para 12 and JAA Temporay Guidance Leaflet No. 13 para 12).