Understanding Procedural Safety Barriers
Part 1: Standardized Callouts

Have you ever stopped and wondered about the reasoning behind some of our procedures? Going through initial qualification training as a new student, our mentality is like a Nike commercial: “Just Do It.” We read the procedures, our instructor demonstrates how to perform those procedures, and we spend hours in training devices learning those procedures through memorization and repetition. Over time, we begin to understand some of those procedures, like checklists and critical action items/ boldface, but we sometimes overlook the safety aspect of those procedures. Those procedures are there to ensure we properly operate the aircraft. They become our safety barriers. There are many procedures that we utilize while operating an aircraft, but briefings, checklists, cross-verification, and callouts represent some important procedural safety barriers.

As highlighted by Dr. James Reason’s “Swiss Cheese” Model, these procedures provide an opportunity to detect and correct errors that we might make while flying. If we omit those procedures or we do not properly utilize those procedures, then those procedures could become “holes” in the Swiss cheese that allow an error chain to continue. In other words, those procedural barriers become procedural errors in the error chain.

One procedural barrier that we tend to loathe is standardized callouts (Air Mobility Command [AMC] refers to them as Advisory Calls). Callouts are often dismissed as something we give the Pilot Monitoring (PM) to do while they are not flying, something we do if we have time, or something we simply ignore altogether out of complacency. In actuality, callouts play a major role in the safe operation of the aircraft.

CHARACTERISTICS OF A CALLOUT

Verbal Cue: Obviously, as the name implies, callouts are normally standardized communications that provide a cue. The callout is intended to be a short, concise, and unambiguous verbal communication between the crew.

Verbal Cue for Action: In some cases, the callout might be the initiation of a required action or procedure. For example, passing through FL180/18,000 (Transition), the PM gives the verbal cue to set the proper altimeter. The PF, or Pilot Flying, responds accordingly.

TABLE 29.1. (AMC) CLIMB OUT ADVISORY CALLS

Verbal Cue for Situational Awareness: A callout is frequently used as a cue to help maintain situational awareness, most often using altitude as our situational awareness cue. At the same time, the callout might be prompting a decision for action, depending on the situation. This occurrence is often seen in our instrument approach callouts:

TABLE 29.4. (AMC) PRECISION APPROACH ADVISORY CALLS

Verbal Cue for Aircraft Deviation: This cue is very similar to the situational awareness cue mentioned previously. It deserves its own category because it is a critical alert to the PF of deviations from flight path, such as heading, altitude, and airspeed. This callout is intended to use Crew Resource Management/ Threat and Error Management (CRM/ TEM) to detect an aircraft deviation quickly in order to prevent an Undesired Aircraft State (UAS), which is a reduction in safety margins.

29.6.4 (AMC) Deviation Advisories. In accordance with sound CRM/TEM practices, aircrew members will inform the PF when flight path deviations exceed (or will exceed) MDS tolerances and no attempt is being made to correct the deviation. (T-2). Any crewmember noticing a potential terrain and/or obstruction issue will immediately notify the PF. (T-2). The PF will take immediate corrective action. (T-2). This is especially important during critical phases of flight, nighttime, NVG ops, and/or instrument conditions.

29.6.4.1. (AMC) Under normal flight conditions, deviations observed in excess of heading (+/-5 degrees), airspeed (+10/-5 knots), or altitude (+/- 100 feet) will be announced by any aircrew member using clear and concise terminology (example: “XX knots fast. (T-2). When conducting planned maneuvers with tolerances different than those listed above, comply with AFTTP 3-3 guidance for “Terminate criteria.” (T-2).

AFMAN 11-202V3 AMC SUP, 29.6.4

TIMELY CALLOUT = TIMELY RESPONSE

Finally, another critical characteristic of a successful callout is the callout being made at the appropriate time. A callout made early, late, or omitted may be an ineffective safety barrier.

THE “SO WHAT?”

You may not recognize the importance of callouts in your everyday flying, especially if everything is going smoothly. However, callouts matter greatly when things are not going smoothly. As mentioned previously, callouts help us maintain situational awareness, ensure that the aircraft is maintaining the proper flight path, and in some cases, both. Let us look at an Aviation Safety Action Program (ASAP) example that highlights the importance of timely callouts.

ASAP #18177 SUMMARY [KC-135 AIRCRAFT], SUBMITTED ANONYMOUSLY

Getting vectored to visual on 34R at OTBH [Al Udeid Air Base, QA], [KC-135] [Aircraft Commander] AC was pilot hand flying approach. The weather was hazy. On base leg, we thought we had adequate visual references to complete the approach. We descended and configured gear and flaps 50, turned to dogleg, and began to slow to final approach speed. We overshot final, notified tower, and began a turn back to lineup with runway. AC was looking outside through the haze to aquiare [acquire] the appropriate runway. The power was not up enough to maintain final speed, and the airspeed began to slow. Copilot noticed the slow airspeed and called out “airspeed.” Pilot immediately added power to get back to appropriate speed and line up on final. We were approximately 15-20 knots below [Reference Airspeed] REF speed when airspeed was noticed as slow. No stall indications were noticed. We intercepted final, got on the appropriate glide path, and completed the landing without incident.

First, let us analyze this ASAP event using Threat and Error Management (TEM). The first aspect we notice in this narrative is the hazy weather, which is a threat. Of course, low ceiling or visibility during the approach can increase the mission complexity, especially if the conditions are not forecasted or noted in the current observation. As a result, the narrative suggests the hazy conditions led to an overshoot of the final approach, and the Aircraft Commander, as the PF, was trying to visually acquire the runway environment. Although not directly stated in the narrative, the crew is most likely fixated on finding the runway. Due to this fixation, the hazy conditions led to a chain of crew errors.

The first error that is described in the narrative is the incorrect power setting, leading to an airspeed error, in which the airspeed starts to decay.

The next error may not be quite as obvious. The second error is the late airspeed deviation callout. You might be saying, “Hey, wait a second, the PM did make an airspeed deviation callout!” The PM did make a callout: “Copilot noticed the slow airspeed and called out ‘airspeed.’” Pilot immediately added power to get back to appropriate speed and line up on final. We were approximately 15-20 knots below REF speed when airspeed was noticed as slow.” The AFMAN 11-202V3 AMC SUP helps us see the callout error.

29.6.4 (AMC) Deviation Advisories. In accordance with sound CRM/TEM practices, aircrew members will inform the PF when flight path deviations exceed (or will exceed) MDS tolerances and no attempt is being made to correct the deviation. (T-2). Any crewmember noticing a potential terrain and/or obstruction issue will immediately notify the PF. (T-2). The PF will take immediate corrective action. (T-2). This is especially important during critical phases of flight, nighttime, NVG ops, and/or instrument conditions.

29.6.4.1. (AMC) Under normal flight conditions, deviations observed in excess of heading (+/-5 degrees), airspeed (+10/-5 knots), or altitude (+/- 100 feet) will be announced by any aircrew member using clear and concise terminology (example: “XX knots fast. (T-2). When conducting planned maneuvers with tolerances different than those listed above, comply with AFTTP 3-3 guidance for “Terminate criteria.” (T-2).

AFMAN 11-202V3 AMC SUP, 29.6.4

The guidance states that an airspeed callout should be made when a deviation of 5 knots slow occurs. According to the ASAP narrative, the aircraft was approximately 15-20 knots below REF speed when airspeed was noticed as slow. Thus, the airspeed deviation callout was not timely. Analysis of this ASAP event showed that the aircraft was in an undesired state when the callout was made.

Analysis of this ASAP event revealed the reference airspeed for this approach was 150 knots. Based upon this reference speed, the speed slow deviation callout should have been made at 145 knots to comply with the AFMAN 11-202V3 AMC SUP. Furthermore, the analysis showed the lowest airspeed encountered during the event was 114 knots. The analysis showed that 22 seconds elapsed between 145 knots (when the callout should have been made) and throttle increase, which signified recovery from the undesired state. Thus, recognition of the slow airspeed probably occurred around 20 seconds after the airspeed decayed below 145 knots, which is a long time without recognizing the decaying airspeed.

We now see how crucial a timely aircraft deviation callout is. In this ASAP event, the crew was fixated on finding the runway due to the hazy conditions. While this situation was occurring, the airspeed was decaying along with the crew’s situational awareness of the aircraft’s state. Although an airspeed callout was made, it was not a timely callout (20 seconds late).

So how do we classify the airspeed callout? Recognition of the undesired state. AFMAN 11-290, 3.5.3 states: Undesired State (US) is a safety- or mission-compromised aircraft state (position, altitude, condition, configuration, or mission crew events/ performance) resulting from ineffective CRM/TEM. The appropriate response to a US is: Identify and Recover. Once the US has been identified, aircrews must take immediate corrective action—this action will likely include a combination of CRM, TEM, and technical skills. A US from which a crew does not immediately recover may lead to an incident, accident, mishap, or mission failure. Although the airspeed deviation callout was late, it was an important recognition of the Undesired State, which prompted the immediate recovery by the PF. The callout broke the error chain, which resulted in a positive outcome.

WRAPPING IT UP

Although callouts might feel like a mundane and useless task in our everyday flying, this task is a vital procedural safety barrier. Callouts are a verbal cue for initiating procedures, maintaining situational awareness, and announcing deviations from the desired flight path. In order for these callouts to be an effective safety barrier, we have to practice them in our everyday flying. If we do not practice them in our everyday flying, the callouts will not be a part of our habit pattern when we need them most … like when we lose situational awareness or become fixated on a task other than flying the aircraft. We need to treat callouts like a safety barrier; otherwise, the procedural safety barrier becomes a procedural error in the error chain on our way to a mishap.