PPRuNe Forums - View Single Post - EgyptAir 804 disappears from radar Paris-Cairo
Old 2nd Jun 2016, 17:11
  #972 (permalink)  
Ian W
Join Date: Dec 2006
Location: Florida and wherever my laptop is
Posts: 1,348
Originally Posted by vapilot2004 View Post
Short answer, No Rat 5.

Accurate answer - satellites have virtually no storage compared to the data they relay. Storage typically occurs at ground stations or data banks networked to the downlink site. On a SATCOM equipped aircraft, the prime limitation is bandwidth which in satellite terms equals dramatically greater cost.

The space bird companies would surely build to accommodate any rea$onable demand.
Answering the wrong question.
As you say, the Satellites have no storage they are part of the virtual 'electric string' from the aircraft to a receiving system. The receiver systems have close to limitless storage in terms of DFDR/CVR. There would be no problem in saving several hours of data for every aircraft in the world. However, that is not the issue. The issue is available bandwidth for the transmissions through the satellites and who would pay for the usage of that bandwidth.

This is where schemes are developed for sending only when the aircraft knows it has a problem. However, that may mean not getting anything as the problem may kill the satellite link especially if the link requires a satellite tracking antenna. So a better scheme may be to record the data onto ejectable ELTs that would be able to transmit their location and also when they are found they contain the DFDR/CVR data that is required - solid state storage being close to indestructible and of significant capacity.
Ian W is offline