Unmanned Aircraft Systems Safety — The Human Factor
CHIEF WARRANT OFFICER 3 NATHAN KOCH
Directorate of Assessments and Prevention
U.S. Army Combat Readiness Center
Fort Rucker, Alabama
As unmanned aircraft systems (UAS) continue to rapidly evolve to meet the needs of our Army, so has their evolution into our aviation formations. Our combat aviation brigades saw exponential growth over the last five years with the addition of the RQ-7B Shadow and MQ-1C Gray Eagle. Yet, this rapid and somewhat unfettered demand and growth has come at a price, particularly with safety. In fiscals 2019-2021, UAS mishap rates for the Army’s most popular systems — Shadow and Gray Eagle — have increased. As a result, the U.S. Army Combat Readiness Center heightened efforts to bring awareness to the safety issues currently affecting UAS.
Aviation mishaps fall into three causal categories: materiel, environmental and human. As in years past, materiel failures cause the majority of UAS mishaps; however, mishaps related to human error have increased significantly. The following paragraphs highlight the increase in human error mishaps, identify trends and attempt to raise awareness. How a human error mishap occurs
Human factors are broken down into five categories of what is known as “system inadequacies” — Leader Failure, Support Failure, Training Failure, Standards Failure and Individual Failure — and represent a significant portion of our UAS mishaps (see Figure 1 below). Mishaps are rarely simple and seldom result from just one cause or action of a single individual. Rather, mishaps are caused by a series of events resulting from multiple latent (hidden or concealed) failures or hazardous conditions that result in an individual’s active failure. UAS leaders and safety personnel must recognize that these latent failures and active failures are interrelated. Once understood, we can then successfully identify the obscured causes that lead to active failures in an effort to develop more effective risk control measures to mitigate or eliminate potentially hazardous conditions. RQ-7B Shadow by the numbers
Since fiscal 2017, Shadow flying hours have declined steadily. In fiscal 2017, the fleet’s total cumulative flight hours peaked at 77,286. By the end of fiscal 2021, it had flown approximately 30,700 flight hours. During that five-year period, Shadow experienced an average of a 21% reduction in flying hours annually. Inversely, the Class B-C mishap rates nearly doubled. The alarming statistic was the increase in human error mishaps. From fiscals 2019-2021, 40% of all Shadow mishaps were attributed to human error, compared to the previous three years where human error accounted for 17% of mishaps. In Figure 2 below, you can visualize the decline in hours and increase in mishap rates. MQ-1C Gray Eagle by the numbers
Prior to fiscal 2021, Gray Eagle experienced a steady rise over the previous five years’ in-flight hours with a steadier Class A-C mishap rate that saw increases and decreases revolving around new version/upgraded aircraft. However, there was a 30% reduction in flight hours with no corresponding reduction in the mishap rate. The human error attribution also remained unchanged. Over the last five years, an average of 41% of all Gray Eagle Class A-C mishaps were attributed to human error. UAS human error trends
The top three trends attributed to human error are all preventable. With most UAS mishaps, there has almost always been some form of standards or leader failure. The following are examples of recent mishaps due to human error.
Preventing human error mishaps
- Failing to ensure the digital terrain elevation data was loaded on the control station, resulting in controlled flight into terrain
- Disregarding an ice/frost warning and failing to apply deice, resulting in the inability to achieve lift on takeoff
- Failing to correctly upload the tactical common data link lost link settings according to the checklist and failing to point the modem assembly lower antenna toward the universal ground data terminal, resulting in the aircraft ditching due to fuel exhaustion
- Failing to correctly follow launch procedure in accordance with the checklist and launching in knobs flight mode, resulting in the aircraft pitching down immediately following takeoff due to the rudder in the pitch down position
The examples above demonstrate multiple failures ranging from performance-based to inadequate supervision. As Soldiers execute their military occupational specialty tasks, by-the-book maintenance and checklist use are a must. As we decipher these mishaps, a lack of oversight stands out clearly. When commanders review these mishaps, they should become directly involved in ensuring their subordinate leaders take actions to intensely supervise those operational tasks where human failures are occurring.
Commander spot checks are good ways to ensure the right things are being done. Asking questions and verifying subordinate leaders are more involved with Soldiers conducting the work assists in reducing these mishaps. Poor training and a lack of maintaining a standard for acceptable performance will lead to poor operational performance. A successful training program, enforced through command supervision and implementation of risk mitigation controls, sets high standards and produces high-quality task completion. There is no place for shortcuts in Army aviation maintenance and operations.
Human error failures can be corrected by leadership action, primarily analyzing mishap details and taking supervisory action to correct the deficiencies. From the top down to the immediate supervisor, maintaining high standards, instituting them within the training program and reporting all mishaps will lead to reduced failures and mishaps. Following training, applying direct supervision and spot checks on how the unit personnel are conducting flight operations and aircraft maintenance reinforces the commander’s intent to have a safe, high-performing unit capable of executing its combat mission successfully. Leader emphasis can and will reduce human error failures.