By Joe Reynolds

July 2022

Experience has shown that non-standard testing can be transformative to the outcome of aviation litigation matters for several reasons, when it is utilized in the forensic engineering investigation of an aircraft accident.  As the term implies, these tests are not published by ASTM or SAE, but are uniquely designed to address important unanswered questions for which no standard tests exist.  This work can be best described as “Forensic Research.”  The need for non-standard testing arises when there is a need to verify proposed scenarios and confirm questionable recorded data.  Although very helpful, the fact is that the amount of information obtained from evidence inspections and reviewing data recordings often has limited direct value.  Questions remain, particularly in aviation, when a system, equipment, or component becomes suspect, but its role in the accident sequence of failure is not known.  When this is the case, the solution may be to conduct a non-standard test with exemplar equipment.  Exemplar test systems are set up in a dedicated laboratory, under controlled conditions, to determine what causes the system to fail or malfunction, while applying a non-standard test protocol to reconstruct the accident sequence.  Forensic research must be planned and conducted to the same standard as work that will be subjected to professional peer review with the intention of publishing in a recognized technical journal.  


Lithium battery testing of emergency location transmitter
Testing thermal runaway conditions in lithium battery packs


In aircraft accidents, we are interested in considering all equipment and systems related to the known sequence of events.  It could involve a power plant, the avionics, the flight control systems, or electric power distribution systems that early analysis shows to be most suspect of causing or contributing to the accident.  Once identified, a unique protocol is created to determine what information is required to answer the remaining questions.  The recorded results of these non-standard tests provide additional data about the accident to define and demonstrate what occurred in the initial failure sequence, back to the root cause.  

The additional data obtained from non-standard testing can benefit the accident investigation in many ways.  The test report, showing methodology and results, will greatly aid in reaching objective and supportable opinions, along with the satisfaction that the accident scenario has been accurately reconstructed.  

As an additional benefit, the test results can provide substantial digital data and information to create visuals and illustrations that could be used as demonstrative evidence.  A portion of the test documentation could be used as a tutorial to show how the system, equipment, or device functions normally, and then how it failed.  Therefore, new evidence is generated to support opinions and to clearly demonstrate those opinions to best resolve the litigation.

Non-standard testing can involve very challenging procedures.  In some cases, the non-standard testing is best conducted in conjunction with the OEM or equipment operator.  However, the majority of this research is carried out confidentially in proper laboratory facilities, exclusive of any manufacturer.  

The need for non-standard testing is best determined by regular discussions between counsel and an expert consultant, who is experienced in such matters.  When the first sign or indication arises that testing would be useful, such as when it is apparent that the basis for opinions is not going to be completely supportable from what is available, then non-standard testing should be included in the discussions.  In reality, there may not be sufficient information to make the decision until well into discovery and non-standard testing can be considered objectively.  However, planning early on ensures that the required foundational data is collected as soon as available, which will be needed to design and conduct any tests.  It may be the case that the available data is limited, or perhaps there is no reliable data, or the black box has not been recovered, or that evidence inspections reveal unexplained damages.  When faced with these conditions, forensic research and non-standard testing should be seriously considered.

There have been many cases that benefitted from the outcome of non-standard testing covering a wide range of aircraft and their various systems.  Many of these non-standard testing protocols begin with benchtop tests, where a device or equipment is examined in the laboratory to understand how it performs normally and responds to its potential failure modes.  Benchtop tests have typically involved avionics, batteries, relays and control systems, alarms and annunciator components, hydraulics, instruments, and windshields.  Beyond the benchtop, non-standard testing has included reconstructing wiring arcing failures and even aircraft flight testing.  An exemplar aircraft was flown at a safe altitude to determine what the recovery profile would be for a pinned flight control on takeoff.  Additionally, icing accidents have presented a transient evidence issue where non-standard tests have been conducted in sub-freezing wind tunnel research facilities, coupled with computer models to reconstruct icing on airspeed sensors.  See Figure 1. Airspeed Sensor X-ray of Anti-Ice Protection.  Also see companion Figure 2. Airspeed Sensor Frame of Reconstructed Icing Sequence.


Figure 1 Airspeed Sensor X-Ray
Figure 1 Airspeed Sensor X-Ray



Figure 2. Airspeed Sensor Frame of Reconstructed Icing Sequence.


There has been an amazing variety of non-standard testing, but most recently much has contributed to the knowledge of primary lithium-ion battery failures.  The cascading failure effect of lithium-ion batteries in aircraft equipment was one of the most productive and interesting reconstructive series of tests conducted to completely understand the unique failure mode in a laboratory setting and in a collaborative effort with a major research university.  See Figure 3. Lithium-ion Battery Pack Cascade Failure Non-standard Test and Results Display from Demonstrative Evidence.  Non-standard testing requires time and patience but can successfully reconstruct aircraft equipment failures by using research-level practices and good science techniques.

Non-standard testing has definitely contributed greatly to the successful outcome of aviation litigation.  The most immediate benefit of this testing is to provide additional “powder” to use at settlement.  When the compelling forensic research results are presented, the discussion usually moves to settlement.  As a counterpoint, there are situations when the task is presented to critique the opposition's theory and to challenge the results of their non-standard testing and research.  

When the non-standard testing being proposed involves the actual evidence in the case, a joint inspection and testing should be outlined in an agreed protocol.  It is critical that the draft protocol be carefully reviewed by all parties to ensure that it is presented in the proper sequence and that all non-standard test methods are productive and relevant.  Active participation in the joint inspection and testing is essential to validate the test results that will be shared by all present.  

To summarize, the value of conducting forensic research and non-standard testing is discovering all you can know about the incident under investigation, and certainly more than the other parties involved.  Without that goal, there is either some doubt about the conclusions, the assumptions that have been made, or the ability to conduct a strong cross-examination of the opposition.  With the technology evolving in aircraft today, the opportunity to conduct non-standard testing should be carefully reviewed every step of the way during the investigation of an accident to make sure it is not overlooked or delayed to a point when it may be too late to accomplish.  Non-standard testing is as important to an expert as doing proper calculations.  It is best practice to strive for as much supporting evidence behind opinions as reasonable.  The single objective in the end is to confidently and effectively explain how and why an aircraft accident occurred to a non-technical audience.  Forensic research using non-standard testing is the expert’s capstone evidence in aviation investigations.  

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