1. Home
  2. PILOT TECHNIQUE
  3. Knowing when to do a go-around

Knowing when to do a go-around

0

Identifying unstable approaches early on and normalizing go-arounds helps prevent accidents.


By Shannon Forrest
President, Turbine Mentor
ATP/CFII. Challenger 604/605, Gulfstream IV, MU2B

When an approach does not meet your flight department’s safety criteria, it’s best to inform your passengers and execute a go-around.

Pilots don’t go around when they know they should. Ironically, in nearly all instances of unstable approaches culminating in incidents or accidents, foreboding clues were there. Sometimes the automation noted it first.

For example, the computer recognized that pre-programmed safety parameters were being exceeded and delivered a verbal caution, such as “Sink rate,” “Bank angle,” or “Caution – terrain.”

In a 2-pilot crew, the pilot monitoring is the most likely harbinger of an undesired outcome. Phrases similar to “You’re pretty high” or “We’re coming in fast” appear often in accident report transcripts.

Even the pilot’s own psyche can provide clues that something is amiss. An uneasy feeling in the gut or the inner voice that says, “You probably shouldn’t be doing this” usually comes before a bad outcome.

However, despite all these tools to avert catastrophe, pilots are still not abandoning an unstable approach and performing a go-around. The data is clear. In 2000, the Flight Safety Foundation (FSF) published a report that analyzed aviation accidents that occurred between 1984 and 1997. The FSF document noted that, in the 76 accidents that underwent review, an unstable approach was a salient factor 66% of the time. Although the FSF report is more than 20 years old, it remains one of the most comprehensive studies to date on reducing approach and landing accidents.

Given the passage of time, it’s a natural inclination to think the industry has improved. To a degree, yes, it has, but runway excursions and controlled flight into terrain (CFIT) continue to be annotated as contributing or causal factors in accidents. The question is why?

Defining unstable approaches

FAA defines an unstable approach as one that does not meet the criteria established by the operator. This interpretation provides wide scope for variance in technique. However, the consensus is that an aircraft should be in a landing configuration (gear and flaps extended), and briefings and checklists complete by 1000 ft AGL in instrument meteorological conditions (IMC), and 500 ft AGL in visual meteorological conditions (VMC). Upon reaching those altitudes during the descent to the runway, the aircraft must remain within a defined speed window (typically Vref plus 20 kts and minus zero kts).

Throughout the approach, the aircraft must not deviate from lateral and vertical boundaries of the approach corridor. Side-to-side and glidepath excursion parameters are most often described as “remaining within one dot,” but such terminology may not be clear to everyone. The term “dot” originated when all aircraft were equipped with round mechanical gauges and course deviation indicator (CDI) needles. The face of a navigational instrument was marked by dots to the left and right of center. When conducting an instrument approach, if the CDI moved off center toward a dot, the aircraft was off course. Exactly how far off course was a function of the number of dots of deflection and the remaining distance to the runway.

When glass cockpits became commonplace, so did proprietary displays. A dot (which implies a perfect circle) appears more frequently. However, it’s not uncommon to see other symbols depicted on a deviation scale, like dashes, lines, diamonds, or spheroids. To avoid confusion, it’s a better practice to eschew the anachronistic term “dot” and just refer to a variance as a “unit of deviation.”

No matter how it’s depicted, most operators agree that a stable approach is defined as no more than 1 unit of deviation vertically or laterally from the published approach course.

Descent rate must also be considered when defining a stable approach. Most experts agree that a descent rate of 1000–1200 ft per minute should be the standard from the final approach course inbound. Some operators have added a caveat to this parameter, with the phrase “unless briefed.”

Early in training, pilots learn the “3:1” ratio that defines the standard descent profile. To illustrate the 3:1 ratio in practice, if an aircraft is 30 miles from the airport, being at an altitude of 10,000 ft or lower is a good rule of thumb for being positioned correctly for the approach. At 60 and 90 miles from the airport, the altitudes are 20,000 and 30,000 ft, respectively. The same technique can be applied in close. The aircraft should be 300 ft high for each mile of distance from the runway. Operating under this technique, a pilot who is 3 miles from touchdown should aim for an altitude of 900 ft AGL.

FAA operates a system called Aviation Safety Information Analysis and Sharing (ASIAS), which is a collaborative effort between the government and industry to share safety data and make improvements. ASIAS analysts looked at the rate of unstable approaches by business aircraft operators, and concluded that, “even at 20 nm from touchdown, when a flight is above the optimum 3:1 descent ratio, the approach is more at risk of being unstable when closer to the runway.” Furthermore, the flight is 2.3 times more likely to become unstable below the 1000 ft threshold when flying a 50% steeper descent ratio than normal when measured at a point 5 nm from the runway.

The role of automation

chart

Always remember the 3:1 descent profile ratio – your aircraft should be 300 ft high for each mile of distance from the runway.


Reliance on automation has turned pilots into weak mathematicians. Modern aircraft with vertical navigation (VNAV) capability have symbology that indicates where the aircraft will end up once a descent is initiated. There’s lots of slang for the graphic (banana bar, Custer’s arrow, the down line, etc), but the result is the same – it depicts at what geographic point the descent terminates and the aircraft arrives at the new altitude.

This is a wonderful tool for situational awareness, but, unfortunately, it could also have the opposite effect. Pilots who fail to back up the automation with the 3:1 rule can find themselves unnecessarily high. Being high promotes higher descent rates closer to the runway environment, thus increasing the chances of being unstable. The gist of the phrase “unless briefed” is that a higher-than-standard descent rate should be planned, and thus known and expected, rather than forced and rushed.

Some approaches have a glidepath steeper than 3 degrees, which necessitates a greater descent rate. Circling approaches might position the aircraft at a point where the pilot needs to maneuver more intensely than in a typical ILS straight-in approach. Incorporating this information into the planning phase makes pilot actions proactive rather than reactive. Reactive responses in the moment are rarely as successful as those thought out in advance. Poor fuel planning that puts the aircraft in a low fuel state near the destination induces reactive behavior that can initiate an unstable approach.

Other factors leading to unstable approaches

Remaining unnecessarily high during the arrival phase can be induced by the pilot or air traffic control. Certain airports have reputations for “slam dunk” operations – a reference to the high-intensity, high-speed shot conducted by a basketball player from above the net, not below it, as usual. As defined by pilots, a slam dunk means the aircraft will be kept high and fast, which forces the pilot to initiate high rates of descent and late configuration changes to get established for landing.

Other ways in which ATC can contribute to an unstable approach are by conducting approaches to runways with tailwinds, giving pilots last-minute runway changes, and employing close-in side steps to parallel runways without adjacent runway thresholds.

How an approach becomes unstable is noteworthy, but the bigger story is how it ends. In 2017, FSF published the Go-Around Decision-Making and Execution Project, which identified that only 3% of unstable approaches end with a go-around. Continuation bias is a psychological tendency to follow a course of action to completion despite environmental cues that indicate the decision is not optimum. In common parlance, it’s digging a hole and then continuing to dig, even when sinking deeper and deeper.

There’s no doubt that pilots are mission oriented and want to see the flight completed successfully. When pilots were queried as to why they didn’t initiate a go-around from an unstable approach, some stated that the stigma of the go-around played a role. Going around is rare. So much so that, when it happens, passengers view it as abnormal. A few pilots felt that a go-around would draw a punitive response from their employer. But safety-driven flight departments would argue the complete opposite. The go-around is a tool that should be employed to increase safety margins. Improving go-around rates requires a change in perception. Another way to think of the go-around is that’s it’s abandoning an unstable approach.

Sim training

Unstable approaches don’t always end well. In September 2018, this Falcon 50 overshot the runway at GMU (Downtown, Greenville SC).

Every simulator-based aircraft qualification course contains a low-level windshear-on-landing scenario. Two situations are taught – a windshear caution (increasing performance), and a windshear warning (decreasing performance).

When the caution is initiated, the pilot has the option to continue or discontinue the approach. There’s a period of consideration in which the pilot is assessing airspeed fluctuations, sink rate, and other performance issues. From the perspective of the instructor, it’s always interesting to see what the student will do. Some go around immediately when they hear the windshear caution alert. Others wait a few seconds before deciding.

The windshear warning is another issue entirely. The aural alert is accompanied by a “windshear” message displayed in red on the primary flight display (PFD). The standard for a windshear warning is an immediate go-around.

In the simulator, the go-around happens every single time. The success of the go-around depends on the severity of the windshear and how quick the response is, but that’s not the point. The go-around happens every single time. In the windshear scenario, pilots have been trained to execute an action based on conditions. Windshear training transfers well to line operations. A pilot who fails to execute a go-around when faced with a windshear warning in the actual aircraft is rare indeed.

The need for a go-around has the same philosophical underpinning as a windshear scenario. Parameters are exceeded and action is required. If scenario X happens, then action Y should come automatically. Unfortunately, it doesn’t. Perhaps framing is to blame. The framing effect states that how something is framed (or promoted) affects perception and, consequently, behavior.

Imagine that you need to have an operation and the surgeon informs you that the procedure has a 90% success rate. Now imagine the same surgeon expressing it a different way, saying, “I’m going to kill 10% of the patients I perform this procedure on.” These are the exact same numbers phrased 2 different ways. Which sounds better and which is more likely to influence the decision to have the procedure?

Normalizing go-arounds

As an industry, we need to influence discontinuing unstable approaches. Perhaps the key is reframing the go-around as normal and the landing as abnormal. A typical briefing on a VMC day might go like this: “This will be an approach to landing to Runway 34, backed up by the ILS. The inbound course is 341. The altitude is 2200 ft to the final approach fix, and then we’re down to 220 ft. Missed approach is climb to 1000 ft, then a left turn to join the 060 degree radial to the ABCDE intersection, and hold…” Notice that the go-around is discussed last in the briefing? The nuances get lost and the procedure is an afterthought.

An alternative brief might go like this: “This will be a visual approach to Runway 34, with a go-around initiated at 1000 ft AGL unless the speed is within 10 kts of Vref, we’re within 1 unit of lateral and vertical deflection, and the aircraft is in the landing configuration. At that point, we will climb to 1000 ft, turn left to join the 060 radial, and go into holding at ABDCE. In the event of a landing, it’s a right turn off to the FBO.” Subtle, yes, but each briefing is geared toward a specific objective. In the first, the objective is landing. In the second, we’re going around unless the parameters are met.

Framing matters, and normalizing the go-around, is key. If all else fails, listen to that inner voice. In his book The Gift of Fear, author Gavin de Becker states, “You have the gift of a brilliant internal guardian that stands ready to warn you of hazards and guide you through risky situations.”

One question we should ask ourselves as pilots is how many times we’ve gone around. The follow-up question is how many times we should have.


ForrestShannon Forrest is a current line pilot, CRM facilitator, and aviation safety consultant. He has more than 10,000 hrs TT and holds a degree in behavioral psychology.