Anatomy Of An Aircraft Accident Investigation

Flying Safety, Jan, 2001 by Kurt J. Saladana

Investigating the Accident

The SIB has no preconceptions; therefore, the investigation is thorough in determining what actually happened. In this scenario, the pilot didn't survive the crash, so there is no first-hand account of what happened. The next best source of information is the Crash Survivable Flight Data Recorder (CSFDR) (or cockpit voice recorder, flight data recorder, or similar device) which the news media often refers to as the "black box." However, not all aircraft are equipped with crash-survivable recording devices, they don't always work and, in spite of their name, they don't always survive a crash.

In addition to CSFDR data, the SIB will also obtain recorded data from various sources in the aircraft, which may contain non-volatile memory-- electronic data that's kept after the loss of electrical power. Even if this information is available, it provides only certain, limited types of data. Other sources of information could include HUD or on-board radar videotapes (if they survived the crash), recorded communications between the mishap aircraft and Air Traffic Control or other aircraft, and eyewitness testimony. All of this information can help the SIB corroborate and explain what its examination of the wreckage revealed.

Even with good testimony and data, the SIB will still examine the wreckage to determine what happened and, more importantly, why it happened. A typical crash site is one with an impact point and wreckage strewn out in a "V" pattern in the direction that the aircraft was traveling. The width and length of the "V" depend upon the aircraft's velocity and angle of impact. Usually, unless the aircraft was out of fuel, the site will be heavily scorched and, depending on the crash site, will usually include damage from ground fires. Apart from items that fell off, were intentionally jettisoned or broke off due to a midair collision, all the pieces from the aircraft will be in, or very close to the "V." Few of these pieces will be easily recognizable. They'll be shattered, melted, scorched and in some cases, completely destroyed. That said, even the destroyed pieces will leave some residue. It isn't uncommon for maintainers to be recruited by the SIB to assist with identification of individual pieces of wreckage.

The SIB will examine all the pieces that could have possibly been involved in the sequence of events that led to the crash. Although SIB members have a high degree of expertise in how the aircraft are maintained and operated, and how pilots and maintainers are trained and employed, they are, in reality, "generalists." That's why an SIB often enlists the aid of numerous specialists. Experts from both the USAF and the manufacturers examine the engine, flight controls and airframe. Egress system specialists will scrutinize the ejection seat, parachute and associated components to ensure they operated as designed. Engine mechanics and life support technicians from the mishap wing routinely assist the SIB with teardown of those components. Cockpit instruments and indicators, circuit breakers, wiring, actuators, control rods, structural members and engine pieces go to laboratories for detailed analysis.