A flight recorder is an electronic recording device placed in an aircraft for the purpose of facilitating the investigation of aviation accidents and incidents.
One of the earliest and proven attempts was made by François Hussenot and Paul Beaudouin in 1939.

How to investigate an air crash – according to the NTSB
and the International Civil Aviation Organization

https://flightrecorder.com/
https://en.wikipedia.org/wiki/Flight_recorder

When an aviation accident occurs, a meticulous process is set in motion to determine what happened, how it happened, and most importantly how similar incidents can be prevented in the future. The U.S. National Transportation Safety Board (NTSB) is tasked with investigating every commercial aviation accident in the US and is often called upon by international agencies to lend its expertise. The investigators at the NTSB play a crucial role in ensuring the safety of flight, with specialists working behind the scenes to retrieve and analyze flight data captured on various recorders, including the Flight Data Recorder and Cockpit Voice Recorder, commonly known as the aircraft’s “black boxes.”.

Aviation accidents come in all shapes and sizes, from a tailstrike to a complete hull loss. The NTSB’s response to an accident begins with its Response Operations Center (ROC), which monitors various information sources—including traditional media and social media—for reports of incidents. Once an accident is confirmed, the ROC notifies investigators via a text alert, and a go team is assembled to travel to the crash site.

At the crash site, investigators prioritize securing the flight recorders. If the aircraft had an FDR and CVR, the team works to retrieve them as quickly and securely as possible. “The immediate need is to get it back to headquarters in a secure method and as fast as possible,” said Payne. In the best-case scenario, the NTSB can transport the recorders on an FAA jet. More often, commercial flights are used, with assistance from the Federal Air Marshal Service to ensure safe delivery.

Water recoveries present additional challenges. If a recorder is found submerged, it is kept in water to prevent corrosion. “The enemy of electronics is corrosion,” Payne noted, explaining that keeping the recorder in deionized water minimizes damage until it reaches the lab.

Flight recorder analysis
Once at the NTSB’s Washington, D.C., lab, the flight recorders are examined to determine their condition and whether the data can be extracted. An undamaged recorder can often be downloaded normally, but damaged recorders require more effort.

The crash-survivable memory unit (CSMU) is the most critical component, as it stores the valuable flight data. If necessary, specialists transfer data chips into a golden chassis, a specialized device that prevents further data loss while allowing a safe download. “We have in the laboratory every western-made flight recorder, ordered from the manufacturers with one simple modification: a modification that turns off any further writing of data.

In some cases, the NTSB must rely on older magnetic tape recorders, which are still in use on some aircraft, particularly older business jets. Extracting data from these can be significantly more difficult, especially if the tape is damaged or tangled.

Flight data recorders contain hundreds of parameters that must be analyzed to reconstruct the sequence of events leading up to the crash. Meanwhile, the CVR holds crucial audio recordings from the cockpit, including pilot conversations and ambient sounds.

One of the most delicate aspects of the investigation is reviewing the cockpit voice recorder. A CVR audition is conducted by Payne and other specialists, along with the Director of Aviation Safety and the Director of Research and Engineering. Their primary goal is to verify whether the accident was recorded and to determine what insights can be gained. Importantly, CVR audio is legally protected, meaning that the NTSB cannot release actual cockpit recordings, only transcripts.

The transcription process is painstaking, often requiring a full week for a 30-minute recording. A group of accredited representatives—including airframe manufacturers, pilot unions, and engine manufacturers—collaborates to ensure accuracy. “NTSB don’t rely on speech-to-text AI, because it could introduce bias or errors”. “Instead, trained specialists listen and transcribe manually to ensure the highest level of accuracy.”

Once all data has been analyzed, the NTSB compiles its findings into a final report, which is presented at a public board meeting. The report includes:

A factual summary of the accident
Analysis of flight data and cockpit audio
Probable cause
Safety recommendations to prevent similar incidents

Unlike regulatory agencies like the FAA, the NTSB does not enforce safety regulations, but its recommendations often lead to important changes in aviation safety.

The importance of thorough investigation
Air crash investigations are complex, time-sensitive, and driven by a commitment to factual accuracy. Every step, from securing recorders to analyzing flight data, plays a role in ensuring that lessons are learned and aviation safety continues to improve.

Thanks to the work of specialists at NTSB, each accident is an opportunity to understand what went wrong and make flying even safer for the future.