Black box and flight recorder explained: What investigators look for after an aircraft crashes

When Eurocopter EC130 B4 5Y-GYM crashed near Mt Ololokwe in Samburu County on August 19, killing all seven people aboard, investigators initially searched for the aircraft’s flight recorder.

There was an important complication: officials later said 5Y-GYM was not fitted with a black box, meaning investigators must reconstruct the final flight using wreckage and other evidence.

That makes the Samburu crash a useful example of what flight recorders are, and why investigators look for them after an aircraft accident.

It's not really a 'black box'

The name has stuck, but flight recorders are generally housed in bright orange or yellow protective cases, rather than black ones.

The colour and reflective markings are intended to make them easier to find in wreckage.

There are two main types:

The Flight Data Recorder (FDR) and the Cockpit Voice Recorder (CVR).

Some aircraft carry separate units, while others use combined recording systems.

What does a 'flight recorder' record?

The FDR records technical information about an aircraft's operation.

Depending on the aircraft and system, this can include altitude, airspeed, heading, attitude, engine parameters, fuel information and other system data.

Kenya's aviation regulations provide for helicopter recorders capable of capturing multiple flight and system parameters, with higher-capacity systems able to record substantially more information.

This allows investigators to reconstruct the aircraft's movements and performance, including what happened during the final stages of a flight.

What does the 'cockpit voice recorder' do?

The CVR records the cockpit audio environment.

That can include pilot conversations, radio transmissions, alarms, navigation signals and other sounds in the flight deck.

Kenyan regulations require the CVR, where fitted, to record radio communications, cockpit sounds and crew communications.

Together, the two systems can provide a much clearer picture:

The FDR shows what the aircraft was doing, while the CVR can help establish what the crew heard, said and responded to.

Why doesn't the recorder get destroyed?

Flight recorders are built to protect their stored information during severe accidents.

Kenya's regulations require them to be installed for maximum practical protection and to meet prescribed crashworthiness and fire-protection standards.

That is why an aircraft can be badly destroyed while its recording unit remains recoverable.

Even so, a crash involving intense fire, severe impact or difficult terrain can make recovery and data extraction harder.

Does every plane or helicopter have one?

Recorder requirements depend on the aircraft, its certification, weight, seating and type of operation.

Kenya has specific requirements for flight recorders on helicopters, meaning not every rotorcraft is necessarily required to carry the same equipment.

The Samburu crash illustrates that point.

With no black box installed on 5Y-GYM, investigators have to rely on other evidence.

What happens in the absence of a black box?

An investigation does not stop.

Investigators can examine the wreckage, engine and components, maintenance records, pilot qualifications, weather, communications, flight-path information and eyewitness accounts.

The aircraft itself can provide evidence of what happened before impact.

A black box is therefore not a verdict in a container.

It is one source of evidence - often an exceptionally valuable one - that investigators combine with everything else to establish the sequence and, ultimately, the cause of an accident.