In the wake of recent major air accidents — Lion Air Flight 610, Ethiopian Airlines Flight 302, and the tragic downing of Ukraine International Airlines Flight 752 — professional investigators from around the world are dispatched to try to discover what went wrong. Their findings are intended to avert future disasters.
Professor Craig Steeves (UTIAS), who oversees a graduate course on air-accident investigations, explains the sequence of events in the immediate aftermath of a plane crash, and what happens after an investigation is complete.
How are air-accident investigations governed?
All air-accident investigations are governed by the International Civil Aviation Organization (ICAO) and its set of treaties. Based in Montreal, the ICAO is an agency of the United Nations.
Whether it’s a small plane or a large commercial passenger airliner, the fundamental principles of accident investigations are the same: an accident investigation is intended to improve safety for the future. It’s not intended to assign blame for something that has already happened.
Usually, air accidents are a consequence of complicated sequences of events.
Can you give an example?
About 70 years ago, there was a series of aircraft accidents in the same type of plane because pilots weren’t wearing their seatbelts. During turbulence they would get thrown forward onto the controls, which caused them to lose control of the aircraft.
You’d initially think that would be the fault of the pilots, but it turns out that the seatbelts were designed in such a way that made them incredibly uncomfortable to wear, so the pilots took them off, which was a completely reasonable thing to do. If you were to assign blame simplistically, these pilots would have been singled out — but really, there was a series of events that led to these accidents and included many other people, such as engineers and designers.
This often leads to people being disappointed by the result of an aircraft-accident investigation, because fault isn’t assigned. What happens is that an investigation leads to recommendations to the regulators and manufacturers.
In Canada, who’s responsible for investigating, and who’s responsible for changes in regulations?
The Transportation Safety Board of Canada (TSB) does the investigation. It is a completely independent body from Transport Canada, which is the body that would be responsible for changes in regulations.
How does an investigation work when there’s a major crash involving different countries?
The body responsible for the investigation is the government organization in the country where the accident happened. This country could ask additional countries for help if they don’t feel like they can carry out the investigation themselves.
The country where the aircraft is registered and where it operated would take part, as well as the country of the manufacturer of the aircraft. And then other countries with a special interest, such as the number of casualties associated with the country, have the right to appoint an expert to observe the investigation.
Historically, air-accident investigations have been fairly collegial, and generally everybody involved wants to understand what happened and make changes to make flying safer.
In the past few years, there have been several accidents that have been more political, and in some cases this collegiality has not been as strong as one might hope.
In the case of this recent crash in Iran, it’s very complicated and it’s hard to tell what’s going to happen. You hope that everybody abides by the agreed rules that are set out by the treaties and that everybody is honest about what information they have.
What is the black box and its importance to an investigation?
The black box, which is actually orange, is comprised of a flight data recorder and a cockpit voice recorder.
The former provides data on a large number of the aircraft systems: air speed, altitude, angle of attack, as well as more complicated data from the sensors on the engines and other sensors in the aircraft. Based on the information from this recorder, you can basically simulate the flight of the aircraft and know what all the systems were doing.
The cockpit voice recorder is exactly as it sounds. It picks up sounds heard in the cockpit, from conversations between the pilots, to conversation with air traffic control, and any other noises that may be audible within the cockpit.
Can you take us through what happens in the first 72 hours after a plane crash?
In Canada, any time there’s an accident, somebody involved is required to alert the TSB. If it’s a minor incident, it might be the pilot. If it’s something more significant, it might be air traffic control, or the police.
The TSB is statutorily empowered to take control of the investigation immediately. They can cordon off a site and interview anyone they want, as well as get warrants to enter premises, search and seize things.
The investigators would take possession of anything deemed necessary for the investigation, and at the same time, everything would be heavily documented and photographed before any pieces are touched or moved.
They would collect as much relevant information as possible: radar tracks and voice recordings from air traffic control, and of course physical evidence. If there was a mechanical problem with an aircraft, it might be possible to find the actual piece that malfunctioned. If the aircraft is in many pieces, it might be necessary to take everything and try to reconstruct the aircraft to see if some physical evidence of problems can be found.
The initial investigation at the site is usually finished within a few days.
What happens next?
After that, it’s a long process of decoding the flight data recordings, analyzing the cockpit voice recordings, and examining all the physical evidence.
Eye-witness accounts are also examined carefully. It’s hard to know what’s true and what’s misinterpreted. For example, what does a plane in distress sound like to an average person? Some people think they know exactly how it sounds, but that’s unlikely.
It’s often the case that reports don’t appear for many months, or up to a year or more, after the air accident occurred.
Once an investigation is concluded and a report is released, how are changes implemented?
It depends on what the report has to say. In some instances, the report just might state the facts of an accident or incident, and that might be the end of it — a plane crashed because the pilot forgot to put fuel in — that’s pretty cut and dried, there’s not much you can do.
For more significant accidents, involving commercial planes, usually a complicated chain of events leads to an accident. So then the question becomes, how do we change our rules and regulations in order to prevent this from happening again?
For example, the pilots losing control of the aircraft because they weren’t wearing seatbelts, the recommendation wouldn’t just be ‘pilots should wear seatbelts.’ That’s obviously clear. Recommendations would have to reach the level of making a difference, so in that case, the recommendation was to change the seatbelt design.
Now, in Canada, the TSB will make some recommendations to Transport Canada to change regulations. Transport Canada has a lot of responsibilities apart from safety, like making sure that the transportation industry is financially viable, so it may or may not implement recommendations that TSB makes.
Even if safety is at stake?
Transport Canada is compelled to make judgements on what level of risk is acceptable. The level of acceptable risk with commercial aviation is very low, so most recommendations made for major accidents are implemented at least in some ways, but that’s not always the case.
Given our current situation, I want to transmit the idea that these investigations are fairly slow, that it’s complicated to have a lot of countries involved in an investigation, and that even when the investigation is complete, it’s not going to be a fault-finding exercise, it’s going to be an exercise looking at how we can make aviation safer in the future.