Steve Landells
Flight Safety Specialist
Two significant events in recent years have shaped how we view the nature of remote operations: AF447 and MH370. These incidents have led to a wider discussion about not only how acceptable it is to ‘lose’ an aircraft in this day and age but also why it can take so long to recover vital information about a doomed flight.

In the case of the Air France A330 that crashed into the Atlantic Ocean while en route from Rio to Paris in June 2009, investigators knew roughly where the aircraft crashed, but it took two years to recover the vital black boxes. MH370 simply disappeared and, despite wreckage now turning up on beaches thousands of miles away, we are still no closer to understanding what happened.

Improving handshakes

Inmarsat was crucial in determining the possible search area for MH370. While GPS usually requires four satellites to get a fix, on this occasion there was only one satellite receiving information from MH370 – the so-called ‘handshakes’. Every hour the satellite would contact the aircraft and the aircraft would normally respond with basic information and its status.

In the case of MH370, all that came back from the aircraft was a simple ping of recognition. I don’t want to get into the speculation game as to how or why the aircraft systems didn’t respond in the usual manner, but it is worth noting that it was fortunate that we were able to receive any useful information from these handshakes at all. It was only as a result of the issues surrounding the recovery of AF447 that Inmarsat had decided to embed a time signature into the handshakes and, by using a combination of Doppler calculations and dead reckoning, was able to suggest the most likely final routing of the 777.

While this was useful in suggesting an arc on which the search could be based, the time between pings still meant that the predicted search area was massive and has, at the time of writing, proved fruitless. Inmarsat has now reduced the time between handshakes to 15 minutes.

ICAO has, through its IATA Aircraft Tracking Task Force, developed the Global Aeronautical Distress and Safety System (GADSS). The stated areas of interest that need to be addressed are:

  • Aircraft tracking under normal and abnormal conditions
  • Autonomous distress tracking
  • Flight data recovery
  • GADSS procedures and information management
This proposes that aircraft should transmit their position every 15 minutes under normal circumstances, but this time would be reduced to every minute when the aircraft is in distress. The aircraft tracking Standards and Recommended Practices (SARPs) state that the time interval applies as a recommendation to all operations of aircraft with a take-off mass of 27,000kg, and as a requirement of all operations of aircraft with a take-off mass of 45,500kg when flying over oceanic areas. These will be applicable from November 2018.

What does distress look like?

The SARPs relating to the location of an aeroplane in distress establish the requirement for an aeroplane to transmit information autonomously from which a position can be determined at least once every minute. The SARP states: “An aircraft is in a distress condition when it is in a state that, if the aircraft behaviour event is left uncorrected, could result in an accident. The SARPs are applicable to new aeroplanes with take-off mass greater than 27,000kg from 1st January 2021. The requirement also recommends that it applies to new aeroplanes with take-off mass greater than 5,700kg from the same date.”

While ICAO does not wish to be prescriptive as to how the regulations are met, the distress aspect of this may depend on ‘triggered transmission’. This would involve the aircraft broadcasting a predetermined amount of information if it detects that it is out of control. The parameters of what ‘out of control’ looks like are being worked on as we speak.

The broadcast could also be triggered manually from the cockpit at any time in the event of a more controlled crash. This transmission could include basic position, data but it could also involve transmitting as much data as possible in order to give the accident investigators a useful amount of data to start their work. There are some issues about the security and ownership of any data that is transmitted, so robust regulations would be needed.

Changes to black boxes

Another possibility being looked at is that of deployable black boxes. One of the problems that accident investigators have at the moment is the fact that the most valuable tools in determining what occurred to a stricken aircraft – the flight data and cockpit voice recorders – end up wherever the aircraft does. This can be useful in landbased accidents as, if you can locate the wreckage, there is a good chance you can find the boxes.

However, when the aircraft ends up at the bottom of the sea, recovery can be problematical. If the black boxes were to be physically ejected immediately before impact, and they were equipped with flotation devices, their recovery after a water-based accident would be easier. Even over land the ejection may aid the survival of the boxes if the flotation devices are sufficiently robust to afford some protection to them from ground impact and, by removing them from the actual crash scene, we may see a lower rate of data degradation due to post-crash fire.

There are some obvious drawbacks with this method, including the fact that the boxes will inevitably float away from the crash site and there is a possibility of unauthorised recovery, but these problems are not insurmountable. The question of accidental deployment will also need to be thoroughly investigated but the system has been in operation with the US military for a number of years now, so there is a ready source of safety and reliability data.

How the tracking will take place is still being worked on, and any changes need to be proportionate and relevant to the operation. Obviously the tracking of aircraft in areas that have complete ATC coverage is going to be a lot simpler than for those operations in remote areas. If an operator works solely in Europe servicing major conurbations, then major changes should not be required, but the question of what facilities to use for remote operations is being discussed in many forums.

Automatic Dependant Surveillance (ADS) broadcast and contract data are obvious contenders for communications and it has been suggested that basic GPS position data is automatically included in every transmission. Interestingly, avionics and IT systems company Rockwell Collins is proposing a solution that would, in most cases, require no additional aircraft equipment. While it might sound a bit odd to be talking about high frequency (HF) as a modern solution, it claims that HF datalink is a robust system that requires no satellites and new aircraft are still being produced with HF boxes. There would need to be 15 HF datalink antenna installed around the world, but once that is done this may prove to be a very cost-effective way of meeting the new requirements.

Other issues that are being looked at as a result of these recent accidents are:
  • Extending the battery life of the underwatar locating beacons (ULBs) attached to data recorders from 30 days to 90-day minimum. The frequency on which ULBs currently operate should be altered to increase the transmission range.
  • Cockpit voice recorders should be increased to 25-hour duration

Making things safer

While these proposed changes are to be welcomed, none of them will stop an aircraft crashing. We still need to ensure that our priority is preventing accidents and that we do not introduce new hazards while trying to prevent others. For example, there is a lot of talk about making these selections ‘tamperproof’. Is having electrical equipment on board – that the pilots cannot isolate – sensible? And perhaps we have to ask ourselves if any solution that involves introducing a whole bunch of extra lithium batteries is really such a good idea.

Also, why do ULBs ping? Surely it would be more appropriate for them to send data bursts, or emit a sound that is completely different to other sea dwellers to avoid the confusion we have seen in recent years. We are moving in the right direction, but we still have a long way to go.
This article first appeared in The Log, Summer 2016 edition.

Posted on 15 July 2016

Comments 0
Blog post currently doesn't have any comments.