The Earth Is Not Flat, and Stabilized Approaches Are Good for the Mobility Air Force
By JAMES BUSBEA, C-5 MFOQA FLIGHT DATA ANALYST
There is a never-ending supply of misinformation available on nearly every imaginable subject, including stabilized approaches. Even rational and logical individuals, as aviators are known to be, can be misled if they are not receiving information from a credible source. Let us take a few minutes to set the record straight and clear up some common misconceptions about stabilized approaches and the associated Military Flight Operations Quality Assurance (MFOQA) analysis.
The USAF modeled its stabilized approach program on the commercial airline industry’s best practice. The Flight Safety Foundation (FSF) Approach-and-Landing Accident Reduction Task Force (ALARTF) is considered to be the genesis of the stabilized approach concept that was adopted by the airlines in the late 1990s. In March 1998, A Study of Fatal Approach-and-Landing Accidents Worldwide, 1980-1996, commissioned by the United Kingdom Civil Aviation Authority in support of the FSF ALARTF, indicated that 46 percent of the fatal accidents involving commercial airlines between 1980 and 1996 occurred in the approach-and-landing phase. Unstable approaches contributed to many of those accidents and, therefore, garnered significant focus in the FSF ALARTF report. The USAF recognized that many of its mishaps were also associated with the approach-and-landing phase and implemented stabilized approach guidance that closely aligns with the recommendations of the FSF ALARTF report.
As MFOQA capability developed, the USAF began tracking unstable approach trends in each of its MFOQA-capable Mobility Air Force (MAF) airplanes around 2008. The USAF uses approach stability analysis as a tool to identify hazards in order to mitigate risk and reduce the frequency of events—not as a scorecard of compliance with stabilized approach guidance. Approach stability analysis has many practical uses, such as identifying seasonal, historical, and location-specific trends.
Seasonal trends show when the highest rates for unstable approaches are likely. Table 1 illustrates seasonal unstable approach trends for a typical MAF airplane averaged across 12 years. The seasonal trends of this Mission Design Series (MDS) are indicative of the MAF fleet. MFOQA analysis shows that the by-month unstable approach rate for nearly every MAF airplane peaks in April. It follows that these spring unstable approach trends closely correlate with a seasonal increase in gusty winds. Therefore, it is a good idea to brush up on procedures, limits, and techniques for dealing with winds before spring arrives.
Historical trends not only show progress toward reducing unstable approach hazards but also identify areas in which to concentrate our efforts. Several MAF platforms have reduced their unstable approach rates by more than one-half since MFOQA analysis has been tracking them. However, analysis shows certain facets of approach stability (speed, descent rate, bank, etc.) remain persistent drivers of unstable approaches by MDS despite lower overall rates. For example, Figure 1 illustrates historical trends for another MDS, indicating a plateau in the leading unstable approach event rate since 2014. Do you know the leading driver of unstable approaches in your airplane, what causes it, and how to avoid it?
Location-specific trends can draw attention to challenges with local approach procedures, Air Traffic Control, terrain, and weather phenomena. Pilots can study location-specific approach stability trends during mission planning while decisionmakers can use these trends to improve conditions. MFOQA provides a monthly by-airport breakout of unstable approach rates and triggers for each MAF airplane. Before you fly your first approach into an unfamiliar airport, it would be wise to educate yourself about the unstable approach trends for that location.
Despite the MAF making remarkable strides toward improving approach stability and a nearly universal recognition across the commercial industry that stabilized approaches reduce mishaps and save lives, many USAF pilots remain skeptical. A common contention is that the stabilized approach criteria are arbitrary and overly conservative. The premise of these criteria is not to identify when an approach is unsalvageable but to define acceptable deviations from target parameters. Unless you are the parent of a teenager, you probably have not thought much about road signs recently. Yellow “advisory†signs suggest a speed that engineers have determined will allow you to safely traverse a particular section of roadway. Like yellow speed limit signs, USAF subject matter experts and airplane manufacturers (of newer airplanes) establish stabilized approach criteria that represent the boundaries of how pilots should be flying during the final approach segment, thus discouraging operation in a flight envelope where any pilot’s ability to safely land the airplane might be uncertain.
Some pilots are only onboard with certain aspects of approach stability because they assign a personal level of importance to individual stabilized approach criteria. For example, speed slow (five knots below target) is widely perceived to be the most important of the stabilized approach criteria. The minimum target airspeed is a function of stall speed (VSTALL) and is typically 20–30 percent above VSTALL. Flying five knots below the target airspeed is far from falling out of the sky. That is not to suggest that you should not care about flying below the minimum target airspeed, rather to illustrate how we can be biased to recognize speed slow as an unintentional pilot error and view deviation from other stabilized approach criteria less critically. Instead, we should view anything more than a momentary or minor deviation beyond any of the stabilized approach criteria as an “undesired state.†AFMAN 11-290, Cockpit/Crew Resource Management (CRM) and Threat & Error Management (TEM) Program, defines an undesired state as Operational conditions where an unintended situation results in a reduction in margins of safety. Undesired states are a result of ineffective CRM/TEM practices and may lead to an incident, accident, mishap, or mission failure.
On every approach, there are numerous tasks, distractions, and threats competing for a pilot’s attention. The objective of every approach is to orchestrate a cacophony of information and pilot workload into a symphony that culminates in a safe landing and rollout. Stabilized approach strategies simply place the airplane in the optimal position, configuration, and energy state for the pilot to achieve this goal. A stable final approach segment reduces the pilot’s workload, where the margin for error is thinnest and requires only minor adjustments instead of significant corrections.
Pilots do not intentionally set out to fly and land from unstable approaches. However, good intentions are sometimes counteracted by ineffective risk management and decision making. Ineffective risk management stems from an impulsive methodology devoid of prior evaluation or mitigation strategy for approach stability threats. Ineffective risk management compels reactionary corrections and dependence on undesirable remedies or compromises such as prolonged use of idle power, late/unbriefed configuration changes, overreliance on additional drag devices (if applicable), or simply tolerating the unstable approach attribute(s) until conditions improve. The burden of fixing an unstable approach close to the ground is the penalty of poor risk management and can diminish a pilot’s bandwidth to cope with emerging threats and tasks. Effective risk management involves a deliberate assessment of threats to approach stability so hazards can be anticipated and preempted. As a bonus, effective risk management increases the pilot’s capacity to recognize and mitigate additional, unforeseen threats during the approach.
Lapses in risk management are compounded by indecision. Fortunately, the stabilized approach philosophy transforms an otherwise complex and subjective issue—the right time to abandon an approach—into a straightforward no-brainer. Predefined criteria draw an objective and tangible line in the sand to facilitate recognition of the undesired state.
When grappling with the logic of approach stability, many pilots seek causality. If I am required to fly a stable approach or go around, then adverse consequences must follow each unstable approach that does not go around, right? False. A stable approach does not guarantee a stable touchdown and an unstable approach does not guarantee an unstable touchdown. To the casual observer, this apparent contradiction seems to undermine the premise of approach stability. However, this notion is easily refuted. Can a fast-steep approach contribute to a long-fast touchdown? Absolutely. But a perfectly stable, partial flap approach with a late power pull can also produce a long-fast touchdown. The fact is, approach and touchdown stability usually have a distant relationship because skilled pilots and forgiving conditions (long-dry runways, low aircraft gross weights, conservative landing performance calculations, etc.) often prevail and keep them separated. Stable approaches set the stage for stable touchdowns but do not provide a guarantee.
Finally, I would be remiss if I did not address the camo-face-painted elephant in the room—tactical approaches. Commercially derived stabilized approaches and the military purpose of our weapon systems seem to be at odds. However, each time we take an airplane out of the fight with a preventable mishap, we are doing our adversaries’ job for them.
“Tactical†does not equate to recklessness and “deliberate†does not equate to limiting combat capability.
Air Force Tactics, Techniques, and Procedures (AFTTP) 3-3.C-17 drives home the point perfectly with this statement: “Safe and successful arrival execution depends on proper energy management, regardless of the type of arrival and approach to be flown. Any approach type, when planned and managed properly, can be executed as a stable approach.†Professional military aviators are up to the task of flying tactically sound and stable approaches at the same time.
The stabilized approach philosophy has been around for a long time and is not going away. Do not think of it as an arbitrary requirement that has been unfairly levied upon USAF pilots. The stabilized approach is a proven and effective tool for managing risk and reducing the likelihood of mishaps. Moreover, the principles of this philosophy are applicable to every type of approach and can actually make the pilot’s job easier. Therefore, filter out all the misinformation and embrace the truth: stabilized approaches are good for the MAF.