French delegates will tell an ICAO conference on aircraft tracking that constant real-time downloading of flight data is too complex to implement in the near future.
The delegation will instead state, in a working paper, that triggered transmission is a “more realistic” option for increasing the chances of recovering flight recorders.
ICAO is hosting the event in Montreal to discuss technological strategies in the wake of the disappearance of Malaysia Airlines flight MH370.
The French delegation will encourage the adoption of short-term improvements to tracking and possible accident location.
"There are just too many aircraft operating at a given time for a system to be able to handle constant downloading of the flight data. Transmitting data will not replace...flight recorders in the near future," its paper states. "Triggered transmission is therefore a more realistic solution in terms of cost and manageable quantity of data."
It points out that, after the earlier loss of Air France flight AF447, the carrier modified its ACARS position reporting on long-haul aircraft, reducing the interval from 10min to just 1min if the aircraft is below 15,000ft – a form of triggered enhancement.
“Other French airlines also have systems in place that localise the aircraft continuously,” it adds.
But the response to MH370 raises not just the matter of robust tracking, and its potential costs, but various security aspects which were not an issue with AF447.
ICAO will hear from a European Union delegation which will expand on the options for tracking and localisation.
These include the use of two sets of flight recorders, one of which is deployable from the aft fuselage and fitted with an integrated emergency locator transmitter.
The option of an emergency locator activated in flight by a triggering event is also “technically feasible”, it adds, and could “also address the concerns of intentional disconnections”. Detection of 406MHz locators is already carried out by the COSPAS-SARSAT infrastructure.
Members of a working group set up to examine triggered flight-data transmission have identified several possible triggers, including deliberate deactivation.
But the European Union paper states that such a mechanism requires a rapid detection and transmission, possible only once a new MEOSAR medium earth orbit search and rescue satellite system is operational.
MEOSAR, which will be part of the European Galileo satellite constellation, will potentially offer a return link service designed to trigger an emergency locator transmitter from the ground, in the case of an unresponsive aircraft.
Although the paper acknowledges the benefits of improved position reporting via ACARS or automatic dependent surveillance – including triggered enhancement – it points out that both can be “disconnected easily”, via the power bus. “Making them robust to power outage and malevolent act would require costly retrofit,” it adds.