Miscommunication

Miscommunication In ATC

Rakesh Bhatnagar

"Many incidents and accidents in civil aviation have been attributed to human factors and the most prominent of these factors is miscommunication. While working in ATC units and also while imparting training as OJT instructor and later as CATC instructor; I, personally also have come across many such instances. It is difficult to quote and discuss all of them in detail here. But, in retrospect it was found that there are many reasons for such miscommunication. Majority of times it is because of the language problem as English is not our mother tongue but sometimes it is due to complacency, overconfidence of person and other factors such as poor knowledge of procedures and phraseology etc. Honestly speaking, such examples of miscommunication are evident not only in trainees but also in many working and experienced controllers. I recently came across a useful document, which is a research paper by a Sydney based Air Traffic controller, that deals with this aspect of human factor. I have taken out only a small and relevant portion out of that document and I hope it will enlighten all of us."

Introduction

The collision between the Pan Am and KLM Boeing 747's at Tenerife in March 1977, which killed 583 people, was a defining event in aviation safety. While there were many predisposing human factors involved, the accident was a tragic lesson in miscommunications. The accident demonstrated that, in the aviation industry, "information transmitted by radio communication can be understood in a different way to that intended, as a result of ambiguous terminology and/or the obliteration of key words or phrases" and that "the oral transmission of essential information, via single and vulnerable radio contacts, carries with it great potential dangers" .

Amongst controllers there is insufficient awareness of the pervasiveness of the miscommunication problem and its various manifestations. The insidiousness of some of these requires that controllers be provided with a deeper insight into the structures of language and the way which phrases and words can be misinterpreted.

Types of Miscommunication

Absent-mindedness and Slips

Ambiguity

Callsign Confusion

Code Switching

Different Voices

Emergencies

Enunciation

Expectation

Headsets

Homonyms and Homophony

Noise

Not Hearing

Number Problems

Open microphones

Readback Error

Similarity of SIDs, STARs and Waypoints

Speech Acts

Speed of Delivery and Pauses

Vigilance

1. Absent-mindedness and Slips

Absent-mindedness is a form of miscommunication which controllers and pilots will make occasionally. For instance, a controller may routinely assign the same level for descent to arriving aircraft. But on one occasion that conflicting traffic at that level has been noted, the controller may still absent-mindedly assign that level to an inbound aircraft instead of providing level separation. Such slips are usually associated with some degree of attentional 'capture' such as an internal preoccupation or external distraction. The crucial point about absentminded errors is that they are a characteristic of highly skilled or habitual activities (National Research Council, 1997; Reason, 1984). They are not signs of incompetence but of misapplied competence. They are a problem of experts, not of beginners. Thus the probability of making an absent-minded slip actually increases with task proficiency because, as we become more skilled at an activity, the less demands it makes upon our working memory. We perform at an automatic, subconscious level. Reason (1984) uses this example: should we inadvertently turn on the toaster instead of the coffee pot, the result is inconvenient. Should we make precisely the same mistake in the control room, the result may be catastrophic. The circumstances will determine the extent of the penalty. In such cases, the standard response of additional training would appear to be counter-intuitive. Spoonerisms and verbal blends are other forms of slips. Named after the Reverend W.A. Spooner (1844-1930), who said such things as "queer old Dean" when he meant "dear old Queen", they are most likely to occur when a controller is busy as, too, are verbal blends such as 'Tangee Yankee Delta' instead of 'Tango Yankee Delta'.

2. Ambiguity

As this paper has revealed, ambiguity can arise from many aspects of verbal communications. It has been implicated in many aviation accidents such as the 1992 Air Inter Flight 148 crash on Mont Sainte- Odile in France which killed 87 people where, because of the use of "less-than-optimum phraseology by both the flight crew and the controller, their respective intentions and expectations were ambiguous". This led to a sudden workload peak for the crew just prior to the crash.

Workload may increase vagueness and imprecision. Vague vernacular, such as jargon and acronyms, may confuse pilots or controllers. Vagueness is also a social affectation, considered polite when addressing superiors, but it may also restrict the flow of information between ATC team members, reducing situational awareness. Vagueness is often associated with trainee controllers and disappears with experience. Words with uncertain reference, such as the pronouns 'him' or 'it' or indefinite nouns such as 'things', may be ambiguous and can cause confusion, as we saw in the Florida Everglades crash in 1972.

A lack of definition can also be included here when controllers and pilots have differing understandings of words and procedures. In 1974 a Boeing 727 approaching Dulles Airport, Washington, was "cleared for a VOR/DME approach" which the pilot understood to mean he was

cleared to the final approach altitude of 1800 feet and that there was no other terrain above that level on his route. The controller understood it to mean that the aircraft could descend without conflicting with other traffic and that the pilot was responsible for terrain avoidance. The aircraft crashed into a mountain. The subsequent inquiry found that there was confusion by both pilots and controllers regarding each other's responsibilities; everyone simply made their own interpretation.

It found that pilots were often unsure of the type of radar service they were receiving. Twenty-five years later Airservices Australia is still encountering the problem. Pilots must be aware that the responsibility has shifted from the controller to them and is therefore incumbent on the controller to use standard phraseologies to ensure that pilots are in no doubt.

3. Callsign Confusion

Aircraft callsign confusion is a vexation throughout the world. It hampered ATC assistance to the charter DC-8 with an in-flight fire at Jeddah in 1991 which killed 261 people, was implicated in the Boeing B737 and Metroliner collision in Los Angeles in 1991, and has caused numerous other incidents when pilots have accepted clearances meant for others. There have been calls in the UK and North America for a central system for controlling the allocation of callsigns. One recent Confidential Aviation Incident Report (CAIR) complained that the following aircraft were on the same frequency: New Zealand 88, Qantas 28, Qantas 88, Qantas 188, Air Nippon 828 and Air Nippon 888. The writer complained of several mistakes on the radio.

(Apparently the number '8' has significance in the Asian market-another example of how culture may impinge on aviation safety). There has been a continuing trial of flight number callsigns in Australia. Job (1997) has argued against its acceptance due to the potential for confusion. Registration callsigns have 26 possible last letters whereas

numbers have only 10. Also, he writes, crews become familiar with their registration callsign during a flight, but a flight number changes every leg. Following feedback from the industry, the flight number element of the callsign has recently been reduced from 4 digits to 2 for domestic flights. In my experience, registration callsigns play a significant role in situational awareness because pilots and controllers quickly learn to recognise aircraft-type/callsign associations (i.e. Foxtrot Kilo Golf is a Fokker F28, Romeo Mike Foxtrot is a B767).

4. Code Switching

Code switching refers to the habitual switching back and forth from one language to another of bilingual and multilingual speakers during the course of a conversation. This is due to inherent social and cognitive features of how language works that are still poorly understood.

Perhaps the most well known example of this occurred at Tenerife . The problem can also arise between speakers of the same language when different dialects are in use. Most importantly, it can arise when pilots or controllers switch between the common usage of a word and

its more defined aviation equivalent. Cushing (1995) provides the communications transcript of the 1981 John Wayne Orange County Boeing 737 crash where the controller and pilots used the word 'hold' to mean 'stop' (its aviation meaning) and 'to continue' (as in 'hold your course' in ordinary English). Just what 'hold' meant in each transmission in which it was used led to confusion, wheels up landing,

34 injuries, and an aircraft destroyed by post-impact fire.

5. Different Voices

Voices become familiar, and it can confuse the pilot if a different controller from the one expected replies, and confuse the controller if parts of a single dialogue with the crew of an aircraft are with different crew members.

A controller may be unsure that the correct aircraft has received the instructions, especially since pilots sometimes mix up their callsigns if they have flown several different aircraft recently.

6. Emergencies

Language skills diminish as tension rises during in-flight emergencies. Tasks take priority which means that controllers may have to concentrate in order to deliver slow, clear speech, especially those for whom English is not their first language. Distraction with an emergency may cause slips with communications with other aircraft.

7. Enunciation

Poor enunciation by a sender leads to doubt by the receiver as to what has been heard. Many controllers are not aware that they have inadequate enunciation and that it is the reason for unacknowledged instructions or requests for message repeats. Some people find certain

words innately difficult to enunciate, particularly when they are busy, so, for example, 'Juliet Juliet Tango' becomes 'Jew Jew Tango' and a 'Bulls 2 arrival' becomes 'Buws 2 arrival'.

8. Expectation

We have discussed how we use expectation and context to hear and understand what has been said. Messages are misunderstood because the listener incorrectly infers the intended message. Expectation errors are a particularly insidious form of miscommunication because readbacks may indicate that the message has been received correctly when, in fact, it has not. Byron (1997) cites an example where an aircraft was cleared to climb to FL310 and at FL260 the controller asked about the aircraft's speed. The pilot answered "315 knots". The controller said "maintain 280", to which the pilot responded "280 knots".

The pilot slowed the aircraft to 280 knots and continued climbing. As it climbed through FL295, the controller said that the aircraft was cleared only to FL280. In this case, the controller had set a context of airspeed and failed to indicate, due to his poor phraseologies (i.e. not saying "maintain flight level 280"), that the subject had changed to altitude, nor did he vigilantly monitor the readback and detect the pilot say "knots".

9. Headsets

III-fitting headsets cause many miscommunications problems because the microphones tend to drop away from the mouth. Microphone clipping occurs when a controller (or pilot) fails to ensure that the microphone switch is activated prior to speaking, or deselects it prior to finishing speaking. Since the aircraft's callsign is the first part of a control message, dropping the first letter from the callsign may mean, for example, 'Echo Alpha Kilo' accepts a message meant for 'Tango

Alpha Kilo'. In order to detect this, recent changes require pilots to place their callsign last when acknowledging an instruction (i.e. "six thousand, Tango Alpha Kilo"). Problems with clipping of 'affirmative' and 'negative' led to the former being changed to 'affirm'. Microphone clipping is most likely to occur when controllers and pilots are busy or training.

10. Homonyms and Homophony

The Flying Tigers Boeing B747 crash at Kuala Lumpur in 1989 demonstrates the misinterpretation which may occur with the homonyms 'to, too and two'. Visibility was only two miles in fog as the

aircraft was issued the clearance, "Descend to two seven zero zero" (two thousand seven hundred feet) to which the pilot responded, "Roger, cleared to two thousand seven hundred. We're out of fortyfive".

The next clearance was, "Descend two four zero zero" (two thousand four hundred feet) to which the pilot replied, "OK, four zero zero" (four hundred feet). The four crew, who did not heed the ground proximity warning alarm, were killed when the freighter crashed 8 miles from the runway (Waldock, 1994). Had the controller not dropped the

'to' in the second instruction and instructed "descend to two four zero zero", or detected the incorrect readback, the accident would have been avoided. Controllers often encounter this problem with these homonyms and appear to use two different techniques to overcome it.

One is to pronounce 'to' as 'tah'; the other is to emphasise 'to' as in "descend to two seven zero zero". Homophony is a "confusion-inducing phenomena" due to different words or phrases sounding exactly or nearly alike (Cushing, 1994:12).

Examples are 'left' and 'west', and aerodromes such as 'Morawa' and 'Moora', 'Cowra' and 'Corowa". We saw earlier that in the Canadian Pacific accident in Sydney, 'take taxiway right' was heard as 'you can backtrack if you like'.

11. Noise

Noise causes message distortion and may be due to cockpit or ATC centre background noise, equipment noise, environmental noise (atmospheric static), substandard headsets or poor microphone technique.

12. Not Hearing

The problem of visual dominance phenomenon was discussed earlier. Not hearing important information is a clear sign that the controller involved is overtaxed. Such strain affects the hearing first before affecting the ability to think clearly and motor/manual dexterity.

13. Number Problems

Errors with numbers are ubiquitous, whether it be with callsigns, levels, heading, speeds, tracks, winds, latitudes and longitudes, and so on. It seems to occur most often when controllers give headings and distances in conjunction with altitudes. Numbers are likely to be transposed and the error may not be picked up in the pilot readback.

Indeed, the pilot may read it back correctly but enter the transposed sequence into the aircraft's flight management system.

14. Open microphones

Stuck microphones tend to occur in aircraft when handset switches unknowingly get jammed. This blankets out transmissions by other aircraft and the controller. The controller relies on other pilots recognising the situation and returning to their previous or another frequency for instructions. This situation is obviously dangerous if aircraft are in conflict with each other and require separation, but it also adds workload to adjacent controllers relaying instructions for the affected sector.

15. Readback Error

Readback of pertinent parts of a controller's instructions does not guarantee that the readback message has been accurately received. Too often, confirmation is given of an incorrect readback. The Aviation Safety Reporting System (USA) has labelled this phenomenon hearback and cited four major causes. similar aircraft callsigns resulting in confusion in transmission or reception; only one pilot on board working and monitoring the frequency; numerical errors, such as confusing 'one zero thousand' with 'one one thousand'; expectancy-hearing what one expects to hear.

16. Similarity of SIDs, STARs and Waypoints

The similarity of names for standard instrument departures or arrivals may cause confusion and mistakes. Morrow (1997) cites two transitions 'Wave 1' and Wave 2' and two SIDs 'Dorval 5' and 'Dorval 6'-these are neither unambiguous nor error-tolerant because they are too similar. A

pilot may mistakenly fly the wrong one. Waypoint similarity can cause confusion. ROTAP and RONSA are similar distances from Perth to the north-east and -west respectively, as are POKIP and POMOT. A busy controller can mentally reverse the position of the two and develop a separation plan based on the incorrect route.

17. Speech Acts

Complexity is introduced into language resulting from the variety of functions-speech acts-that any sentence can represent, such as statement, question, request, and so on. As we discussed earlier, subtle differences in intonation and placement of pauses affects the way we interpret words. But when we are distracted, stressed or careless, these verbal 'keys' may be omitted or displaced, resulting in miscommunications. Hawkins (1993:169) provides an example of a near-miss at Stuttgart in 1977 when a query of "flight level 80 clear?"

was interpreted as a statement "flight level 80 clear". In the resulting confusion, two aircraft passed within 400m of each other at the same level.

I have had the good fortune to hear a colleague prod a pilot for a readback of an assigned altitude by requesting, with voice intonation, "and level?", to which the pilot replied "affirm", meaning he was flying level!

18. Speed of Delivery and Pauses

During peak traffic periods, controllers in some positions may be talking constantly. Difficult as it may be, if controllers pause between transmissions to different aircraft, the amount of irrelevant information received by pilots is reduced. This increases the pilot's chance of remembering and reduces requests for reiteration. Cushing (1994) refers to the danger of the 'delayed dangling phrase', an add-on during a transmission to a sentence that sounds, tonally and in contents, to have already terminated. Such afterthoughts risk being over transmitted and important information missed, as was the case in the Boeing 707 crash in the Azores in 1989.

The rapid speed at which controllers deliver instructions is probably the most common miscommunication complaint received from pilots.

19. Vigilance

Maintaining vigilance for critical but infrequent events, such as a pilot reading back an incorrect level, is an important part of air traffic control. Traditionally, maintaining vigilance has been thought of as undemanding and boring but recent research shows that it imposes considerable mental effort and that this does not simply arise from the controller's efforts to overcome tedium (National Research Council, 1997). Issues of vigilance involve many types of human attributes such as boredom, stress, tiredness, personal problems and so on.

Note:- The above list and short discussions of common forms of miscommunication are by no means comprehensive but it does give an indication of the scope of the problem. There is a great deal of overlapping, so the investigation of any incident is likely to provide examples at several levels, as with the much studied Tenerife accident.

Miscommunication also involves such complex human attributes as complacency, fatigue, professionalism, personal problems, and so on.

Shri Rakesh Bhatnagar is Asst. GM(ATC) with Airports Authority of India and presently posted as Instructor in Civil Aviation Training College, Allahabad, India.