Flight data recorders capture hundreds of parameters during aircraft operation—airspeed, altitude, heading, control positions, engine performance, and dozens of other variables recorded multiple times per second. When crashes occur, this data provides an objective record of what the aircraft was doing in the moments before impact. For aviation litigation, FDR evidence often proves the most definitive proof available of how accidents unfolded and who bears responsibility.

Understanding how flight data recorders work, what they capture, and how to use their data effectively helps accident victims build the strongest possible cases. This evidence can prove pilot error, mechanical failure, design defects, or combinations of factors with a precision impossible through other means. When FDR data is available, it typically becomes the centerpiece of accident reconstruction.

What Flight Data Recorders Capture

Modern flight data recorders capture far more information than early generation devices. Regulatory requirements specify minimum parameters that must be recorded, but many aircraft record substantially more. Large commercial aircraft may record over a thousand parameters; smaller aircraft record fewer but still capture essential flight information.

Required parameters include basic flight information—airspeed, altitude, heading, vertical acceleration, and time. Control inputs are recorded, showing what pilots commanded and how flight controls responded. Engine parameters reveal power settings, temperatures, and performance. Autopilot and flight management system status show what automated systems were doing. This comprehensive data set documents aircraft state throughout recorded flight.

Recording duration varies by aircraft type and regulatory requirements. Large transport aircraft must record at least 25 hours of data, ensuring that even long flights are fully captured. Older or smaller aircraft may have shorter recording durations. The continuous recording overwrites oldest data as new data is recorded, so the recorder contains the most recent flight hours when recovered.

The Physics of FDR Evidence

Flight data recorders measure physical parameters directly—pressure altitude from static ports, airspeed from pitot tubes, attitude from gyroscopes or accelerometers. This direct measurement makes FDR data uniquely reliable. The recorder captures what actually happened to the aircraft, not what anyone remembers or claims happened.

The data allows precise reconstruction of the flight path. Analysts can calculate exactly where the aircraft was at any moment, what trajectory it followed, and how that trajectory changed in response to control inputs, atmospheric conditions, and system status. This reconstruction reveals whether the aircraft behaved as commanded, whether pilots responded appropriately to conditions, and where the sequence went wrong.

Modern analytical tools create visualizations from FDR data. Animations show the aircraft maneuvering through reconstructed environments. Graphs display parameter trends over time. These presentations make technical data accessible to juries who might not understand raw numerical readouts. Seeing the aircraft fly into danger based on actual recorded data creates compelling evidence.

Obtaining FDR Data

The NTSB typically takes custody of flight recorders from major accidents. The agency downloads and analyzes recorder data as part of its safety investigation. This data eventually becomes part of the public docket, available to civil litigants after appropriate processing and release procedures.

For accidents the NTSB doesn't investigate—or for data beyond what the agency processes—civil litigants may need to arrange independent downloads. This requires specialized equipment and expertise; not all laboratories can read all recorder types. The chain of custody must be maintained to ensure data integrity and admissibility. Early coordination ensures proper handling of this critical evidence.

Preservation of recorder hardware matters even when data has been downloaded. Defense experts may want to verify download accuracy. Questions about recorder function may require physical examination. Spoliation demands should specifically require preservation of the physical recorder and any backups, not just downloaded data.

Interpreting FDR Evidence

Raw FDR data requires expert interpretation to become meaningful evidence. The data comes in engineering units that must be converted to understandable terms. Sensor characteristics affect accuracy in ways experts must account for. Synchronization with other data sources—radar tracks, communications, witness observations—creates complete pictures from multiple evidence streams.

Expert analysis identifies critical moments in the accident sequence. When did the problem begin? What indications did pilots have? How did they respond? Did the aircraft behave as expected given pilot inputs? Were there anomalies suggesting system malfunctions? These analytical conclusions form the basis for liability arguments.

Different experts may interpret the same data differently. Plaintiffs' experts may emphasize pilot errors or delayed responses visible in the data. Defense experts may argue that responses were reasonable given available information or that system anomalies contributed. Cross-examination of experts on their data interpretation often determines what conclusions juries accept.

Proving Pilot Error

FDR data is particularly powerful for proving pilot error. The data shows exactly what control inputs pilots made and when. It reveals whether pilots responded to warnings, whether they followed proper procedures, and whether their actions matched the situation's demands. This objective record is far more reliable than memories or self-serving accounts.

Failure to respond to conditions visible in the data establishes pilot negligence. If FDR data shows decreasing airspeed before a stall, why didn't the pilot add power or lower the nose? If the data shows descent toward terrain, why weren't procedures followed to arrest the descent? The data eliminates excuses by showing exactly what information was available and how pilots responded.

Control inputs inconsistent with proper technique similarly establish negligence. Abrupt control movements when smooth inputs were needed, failure to apply required corrections, or inputs that worsened rather than improved the situation all appear in FDR data. Expert testimony explains what the data shows about pilot performance and why it fell below acceptable standards.

Proving Mechanical Failure

FDR data also proves mechanical failures when aircraft don't respond normally to pilot inputs. If the data shows proper control inputs but improper aircraft response, something in the control system failed. If engine parameters show anomalies before power loss, the data supports mechanical failure claims. The recorder captures the aircraft's response to commands, revealing when that response was abnormal.

Correlating FDR data with physical evidence strengthens mechanical failure claims. If the data suggests a control system malfunction and wreckage examination reveals a failed component in that system, the combined evidence is compelling. The FDR data shows when and how the failure manifested; the physical evidence shows what component failed. Together they establish both that failure occurred and what caused it.

Limitations and Challenges

Not all aircraft have flight data recorders. While required on large transport aircraft, many general aviation aircraft lack FDR equipment. Some have basic engine monitoring or GPS track logs that provide limited data, but nothing approaching comprehensive FDR coverage. When recorders don't exist, other evidence must establish what happened.

Recorder damage can render data unrecoverable. Despite protective housings, some crashes destroy recording media. Fire, impact, and immersion can all damage recorders beyond recovery. When data is lost, its absence creates evidentiary gaps that other evidence must fill.

Defense attorneys will challenge FDR evidence where possible. They may question sensor accuracy, download integrity, or expert interpretation. They may argue that data showing pilot error actually shows appropriate responses to unrevealed system problems. Anticipating these challenges and preparing thorough responses ensures FDR evidence achieves maximum impact.