With the analysis of data from the black boxes of the doomed Air India Boeing 787-8 aircraft underway at the Aircraft Accident Investigation Bureau’s (AAIB) laboratory in Delhi, there are expectations that the investigators would soon be able to piece together the causes behind the deadliest crash involving an Indian airline in at least four decades, and the first-ever fatal accident of the Boeing 787 Dreamliner.
The black boxes, which are actually bright orange in colour, are critical in aircraft accident investigations as they provide data on numerous parameters and aircraft systems, helping the investigators identify the most likely causes of an accident. According to the government, the analysis of the data from the Enhanced Airborne Flight Recorder (EAFR) is underway and will help reconstruct the sequence of events leading to the accident and identify contributing factors.
Unlike older aircraft models that had separate cockpit voice recorder (CVR) and flight data recorder (FDR), modern jets like the Boeing 787 aircraft have two combined black box sets, each with the joint functions of CVR and FDR, and a few other capabilities. The combined unit is called EAFR, and regulations require two units to be located in the aircraft—one at the front and one at the aft, or rear section—for redundancy, in case of unit is significantly damaged or is never recovered. The first EAFR were recovered on June 13 from a building rooftop at the crash site in Ahmedabad, while the second was recovered on June 16 from the aircraft debris.
The purpose of the FDR is to record flight data on numerous parameters of aircraft operations, while the CVR records the flight crew’s voices, as well as other sounds inside the cockpit. Communications with air traffic control, automated radio weather briefings, and conversation between the pilots and ground or cabin crew are also recorded.
Next steps in black box analysis
Apart from a few visual cues that suggest lack of thrust and insufficient lift beyond a point, there aren’t any tell-tale signs of what might have gone wrong with the Air India aircraft. In such instances, the black boxes become all the more crucial for the investigation. The data is expected to give insights into pilot action, functioning of aircraft systems and components, and identification of any system malfunction or failure, among others.
The FDR records many different operating conditions of the flight. By regulation, newly manufactured aircraft must monitor at least 88 key parameters like time, altitude, airspeed, heading, and aircraft attitude. The EAFRs installed on the Boeing 787 aircraft have the capability of recording around 2,000 parameters and in-flight characteristics that can aid in the investigation. According to experts, the modern black boxes can generate highly specific and minute data on scores of parameters, allowing investigators to go deeper into the analysis of the probable causes of the accident. Current regulations mandate that FDR should have data for at least 25 hours.
With the data retrieved from the FDR, investigators should be able to generate a computer animated video reconstruction of the flight. The investigators can then visualise the aircraft’s attitude, instrument readings, power settings, and other characteristics of the flight. This animation enables the investigating team to visualise the last moments of the flight before the accident, along with exhaustive flight data.
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Coming to the CVR, in addition to the pilots’ conversation with each other and the ATC, investigators would be highly interested in sounds pertaining to engine noise, any warnings that may have been sounded in the cockpit, sounds related to landing gear, among other clicks and pops. Regulations require CVR to store at least two hours of data.
Notably, at least one of the EAFRs on Boeing 787 aircraft are equipped with its own independent emergency battery, which keeps it running for around 10 minutes in the case of the plane suffering a total electrical failure. Given that the ill-fated aircraft was not airborne for even a minute before crashing, the emergency battery is expected to have helped record all flight data, if the plane indeed suffered total electrical failure.
“Both the Flight Data Recorder and the Cockpit Voice Recorder have proven to be valuable tools in the accident investigation process. They (FDR and CVR) can provide information that may be difficult or impossible to obtain by other means. When used in conjunction with other information gained in the investigation, the recorders are playing an ever-increasing role in determining the Probable Cause of an aircraft accident,” the US National Transportation Safety Board (NTSB) says on its website. The NTSB is among external organisations assisting India’s Aircraft Accident Investigation Bureau (AAIB) in the probe.
The timeline
Just the availability of extensive flight data does not mean that the investigation will be swift. And that is because that data needs to be carefully analysed, interpreted, and made sense of before zeroing in—as accurately as possible—on the most probable causes of the accident.
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Once the data is successfully retrieved, the interpretation process begins, which itself could be time consuming due to various factors, including multi-agency involvement, requirement of deep analysis of the FDR and CVR data, and likelihood of simultaneous system failures in a short span of time, among others. It could take anywhere between a few days to a few weeks to effectively analyse the black box data.
Aircraft are highly sophisticated and complex machines and air crash investigations, too, are extremely complex. Often, aircraft accidents are caused by multiple things going wrong almost simultaneously, or one thing leading to the other in quick succession. Data interpretation in crashes involving modern jetliners, in turn, can also be significantly complicated. Investigators need to be extremely meticulous in analyzing the data in order to identify the series of events that led to the catastrophic crash, and pinpoint the exact causes behind those events .
