Why Are Black Boxes So Crucial in Air-Crash Investigations?

Here’s a crash course on what they are and how they work.

With the recent crash of an Ethiopian Airlines Boeing 737 Max 8 plane, the term ‘black box’ has been making headlines again as investigators try to decode what caused the plane to crash shortly after takeoff. This incident comes not long after a Lion Air plane of the same make crashed in a similar fashion in October. The why’s and how’s of the crash are usually contained in what are commonly called ‘black boxes’.

This ‘black box’ contains data crucial to piecing together what happened on the plane before and during a crash.

Early designs of the black box or the Flight Data Recorder included copper foils on which instruments indented the recordings. This design, which could withstand extreme heat and pressure, was built by Len Harrison and Vic Husband. Magnetic tape voice recorders date back to the World War II era.  Modern-day black boxes, however, are solid-state drives which store all the flight data.

Are Black Boxes Really Black?

What is commonly called the ‘black box’ is in fact two orange-coloured boxes, one is the Flight Data Recorder (FDR), the other is the Cockpit Voice Recorder (CVR). As the names suggest, CVR stores the last two hours of voice recording from the cockpit and the pilots’ headset microphones on four channels. The CVR also records ambient noises such as the turning on and off of switches, thuds and other noises.

Modern-day FDRs record the operating data from the plane’s systems. Sensors placed in different parts of the plane are connected to the Flight Data Acquisition Unit, which sends the data to the FDR. Hence, any change in the plane, any switch turning on or off of a switch, all the data is recorded. The FDR captures 88 different types of data, for the last 25 hours till the recorder loses power.

Parameters recorded commonly include:

• Time
• Pressure altitude
• Airspeed
• Vertical acceleration
• Magnetic heading
• Control-column position
• Rudder-pedal position
• Control-wheel position
• Horizontal stabiliser
• Fuel flow

Data from both the components are stored in memory boards inside a Crash Survivable Memory Unit.

Survival of the Sturdiest?

In the event of an air crash, it is highly unlikely that anything survives intact, sinceplane crashes are usually on a massive scale. However, it is usually the Crash Survivable Memory Units that make it, because they are designed to survive such an event. The CSMU is a large cylinder bolted to the floor of the recorder. The casing is made out of stainless steel or titanium, while the memory stacks are layered with thin aluminium and a dry-silica compound that protects it from extreme heat and pressure.

The black boxes are housed towards the rear end of the plane, just before the rudder, where the impact is lessened during the event of a crash.

Fun fact: In the event of a crash, black boxes have an underwater locator beacon that sends a stress signal, which can travel a distance of 14,000 feet for over 30 days. The beacon activates as soon as the sensor comes in contact with water.

You Ask The Questions, The Black Box Has The Answers

After the boxes have been recovered, they are sent to a lab where a team of experts use the data to try and recreate the events of the crash. The data in black boxes can be downloaded via USB. Usually, representatives of the airline and airline manufacturer are called in to analyse the data on the CVR.

The data found on the FDR and CVR provide insights into whether the crash was caused due to technical failure, pilot error or external causes.

Air Asia Flight QZ8501 from Surabaya to Singapore crashed into the Java Sea on 28 December 2018 with no survivors. Initial reports had suggested that bad weather may have caused the crash, but after analysing the data from the black box, it was determined that it was a faulty plane rudder that had caused the autopilot to disengage, and it was the actions of the crew that had a big hand in the crash.

A more recent instance is the Lion Air flight JT610 crash, where according to a Reuters report, the CVR showed that the three people in the cockpit were frantically leafing through a handbook minutes before the plane nosedived into the Java Sea. The recorder also suggested that the pilots had issued a warning signal to the air control tower two minutes into takeoff.

In the ongoing investigation of the two Boeing 737 Max 8 planes in question, initial black box data have shown similarities in the behaviour of both planes before the crash. This could hint to a problem with the model itself, and has led several countries to ban this model from flight.

Not All Black Boxes Are Found

When it comes to the limitations of black boxes, most critics point towards one infamous incident – the mysterious disappearance of the Malaysian Airlines flight MH370. Flight MH370 had seemingly disappeared into thin air in 2014 with 239 passengers on board – no answers have been found till date. Investigators who were hoping the black box would provide them were left disappointed, unable to locate it.

To solve this problem, scientists and aeronautic experts have suggested various alternative designs for black boxes that can record a plane’s data from a remote location, like from a satellite, for example.

But that improvement remains a way off. For now, investigators will have to rely on the physical black boxes.