Structural and Fire Field Investigations
This is Aviation accident investigation class
The purpose of this week is to provide an understanding of structural investigation techniques and structural failure causes and evidence. Investigative techniques used to differentiate post-crash, inflight fires, and explosions; to determine the sources of fuel and ignition; and to determine if explosives were involved, are also explored. Finally, this section analyzes investigative techniques specific to mid-air collisions.
In an accident investigation, the Structures Working Group generally analyzes failure modes of any of five types of materials-metals, composites, ceramics, polymers, and semi-conductors, all of which have different properties. For example, metals respond differently to loads (tension, compression, shear, bending, and torsion) and stress than composite materials. Structures investigations, in general terms, address two primary types of material failure accidents:
1. Major component failure, which, although rare, is the separation or failure in-flight of a major component such as a wing or aileron, which generally indicates (1) inadequate design strength, or (2) excessive loads, or (3) deterioration of static strength through fatigue or corrosion.
2. Partial failure or malfunction of a major component generally results in altered flight characteristics. According to the ICAO,
Some of the general causes of accidents in this category are jammed controls, improper distribution of load on board, control surface not rigged properly, incorrect installation of parts, hard-over signals from auto-pilots, etc. Accidents of this type are frequently associated with recent repair or alteration work; therefore, the investigator can often discover valuable clues by studying the aircraftâ€™s history as reflected by maintenance entries, pilot reports and by other sources.
Your text, the NTSB Major Accident Investigation Manual, and the ICAO Manual of Aircraft Accident and Incident Investigation Part III â€” Investigation, Chapter 9, provide excellent detail on materials characteristics, failure types and causes.
An example of an investigation addressing structural failure is the 2005 Chalk’s Ocean Airways Flight 101, a Grumman Turbo Mallard, which suffered in-flight wing separation. The aircraft crashed into a shipping channel adjacent to the Port of Miami Florida, killing all 20 occupants, destroying the aircraft on impact. The National Transportation Safety Board determined that the probable cause of the wing separation to be the failure of the Chalkâ€™s Ocean Airways maintenance program to identify and properly repair fatigue cracks, and failure of the Federal Aviation Administration (FAA) to detect and correct deficiencies in the companyâ€™s maintenance program.
Fire investigation can pose a daunting task in complex accidents, but generally, sufficient evidence exists to support whether the fire occurred in-flight or post-crash and where the seat of the fire and ignition and fuel sources were. Also imperative is to address whether the fire was associated with explosive forces, as was the case with Trans World Airlines Flight 800. Because of the catastrophic and predominant non-survivable nature of in-flight fires, this is a particularly high focus area for investigators. It is important to note that in the United States, any evidence of terrorist activity would change the controlling agency from the NTSB to the Federal Bureau of Investigation (FBI), as was the case with the terrorist events of 9/11 (NTSB, 2007).
An example of in-flight fire is ValuJet Airlines, Inc. Flight 592, a DC-9 that crashed into the Florida Everglades, killing five crew and 105 passengers. The crash resulted from an in-flight fire in the airplane’s class D cargo compartment, which initiated by the actuation of one or more oxygen generators carried as cargo. The NTSB attributed the fire to the failure of SabreTech to properly package and identify chemical oxygen generators, ValuJet’s lack of oversight of contract maintenance and hazardous materials requirements and practices, and the failure of the Federal Aviation Administration (FAA) to require smoke detection and fire suppression systems in class D cargo compartments (NTSB, 1997).
ICAO. (n.d.). Manual of Aircraft Accident and Incident Investigation Part III. Retrieved from https://skybrary.aero/bookshelf/books/3708.pdf (Links to an external site.)
National Transportation Safety Board. (2007). In-flight separation of right wing, Flying Boat, Inc. (doing business as Chalkâ€™s Ocean Airways) flight 101 Grumman Turbo Mallard (G-73T), N2969 Port of Miami, Florida December 19, 2005. Retrieved from https://www.ntsb.gov/investigations/AccidentReports/Reports/AAR0704.pdf (Links to an external site.).
National Transportation Safety Board. (1997). In-flight fire and impact with terrain Valujet Airlines flight 592 DC-9-32, N904VJ Everglades, near Miami, Florida May 11, 19996. Retrieved from https://www.ntsb.gov/investigations/AccidentReports/Reports/AAR9706.pdf
In this discussion activity, discuss the type of artifact(s) you feel will best demonstrate achievement of the Aircraft Systems field investigations objectives. In addition to your discussion points, feel free to post a sample, outline, diagram, video clip, etc., of your artifact.
- Analyze accident investigation techniques associated with aircraft systems.
- Support the importance of cockpit instrument analytic techniques for accident investigation.
- Demonstrate the time influence of structural accident findings and recommendations to aviation safety.