Human factors aspects in effective communication

Effective communication is achieved when our mental process is able to accommodate and to interpret the information contained in a message.

This mental process can be summarized as:

§ How do we perceive the message?

§ How do we reconstruct the information contained in the message?

§ How do we link this information to an objective or to an expectation?

§ What bias or error is introduced in this process?

Workload, fatigue, distractions, interruptions and pressure are among the factors that may affect adversely pilot-controller communications and result in:

§ Incomplete communication

§ Omission of call sign or use of an incorrect call sign

§ Use of nonstandard phraseology

§ Failure to listen or respond

§ Failure to effectively implement the confirmation-correction loop

6.2 Language and communications

In response to a series of accidents involving language skills as a causal factor, an effort has been initiated to improve the English-language skills of pilots and controllers worldwide.

Nevertheless, even pilots and controllers for whom English is the native language may not understand all communications spoken in English because of regional accents, dialects or different word usage.

Language differences generate significant communications difficulties worldwide.

The practice of controllers who use English for international flights and the country’s native language for domestic flights prevents pilots from achieving the desired level of situational awareness due to loss of “party-line” communicatons.

6.3 Communication techniques

The first priority of any communication is to establish an operational context by using markers and modifiers to define the following elements:

§ Purpose — clearance, instruction, conditional statement or proposal, question or request, confirmation

§ When — immediately, anticipated or expected

§ What and how — altitude (climb, descend, maintain), heading (left or right), airspeed

§ Where — (i.e., before or at a waypoint)

The structure and construction of the initial and subsequent messages should support this context by:

§ Following the chronological order of the sequence of actions

§ Grouping instructions and numbers related to each action

§ Limiting the number of instructions in the transmission

The intonation, speech rate and placement and duration of pauses may positively or adversely affect the correct understanding of a communication.

International Civil Aviation Organization (ICAO) Annex 10, Volume II, and PANS ATM (Doc. 4444) provides rules and procedures for pilot-controller communications.

ICAO guidelines and techniques for radio transmission highlight the following objectives:

§ Transmissions shall be conducted concisely in a normal conversational tone

§ Full use shall be made of standard phraseologies whenever prescribed in ICAO documents and procedures

§ Speech-transmitting techniques shall be such that the highest possible intelligibility is incorporated in each transmission.

To reach these objectives, pilots and controllers should:

§ Enunciate each word clearly and distinctly

§ Maintain an even rate of speech (not exceeding — typically — 100 words per minute)

§ Make a slight pause preceding and following numerals; this makes them easier to understand

§ Maintain the speaking volume at a constant level

§ Be familiar with microphone-operating techniques (particularly in maintaining a constant distance from the microphone if the aircraft does not have a constant-level modulator)

§ Suspend speech temporarily if it becomes necessary to turn the head away from the microphone

6.4 Use of nonstandard phraseology

Use of nonstandard phraseology is a major obstacle to voice communications.

Standard phraseology is intended to be easily and quickly recognized.

Pilots and controllers expect each other to use standard phraseology.

Standard phraseology helps lessen the ambiguities of spoken language and thus guarantees a common understanding among speakers

§ of different native languages, or

§ of the same native language but who use or understand words differently (e.g., regional accents or dialects).

Nonstandard phraseology or the omission of key words may change completely the meaning of the intended message, resulting in potential conflicts.

For example, any message containing a number should indicate whether the number refers to an altitude, a heading or an airspeed. Including such key words prevents an erroneous interpretation and allows an effective readback and hearback.

Pilots and controllers might use nonstandard phraseology with good intentions; however standard ICAO phraseology always minimizes the potential for misunderstanding.

Use of nonstandard phraseology may result from national practice.

The most significant example is the North American phrase “Taxi into position and hold.” It has the same meaning as the ICAO phrase “Line up and wait,” whereas the ICAO phrase “Taxi to holding position” is a clearance to taxi to and hold at a point clear of the runway (e.g., the CAT I or CAT II/III holding point or line).

6.5 Building situational awareness

Radio communications (including party-line communications) contribute to building the pilot’s and the controller’s situational awareness.

Flight crew and controllers may prevent misunderstandings by providing each other with timely information, for better anticipation.

At all times, pilots should build and update a mental picture of the other traffic in the vicinity of their intended flight or ground path.

6.6 Frequency congestion

Frequency congestion significantly affects the correct flow of communications during critical phases such as takeoff and departure, and approach and landing, particularly at high-density airports. congestion requires enhanced vigilance by pilots and controllers.

6.7 Omission of call sign

Omitting the call sign or using an incorrect call sign jeopardizes an effective readback and hearback process.

6.8 Lack of readback or incomplete readback (readback errors)

ICAO Annex 11 requires that the safety-related part(s) of any clearance or instruction be read back by the pilot to the controller.

The following parts of a clearance shall always be read back:

§ ATC route clearances

§ Clearances and instructions to enter, land, take off, hold short of, cross or backtrack on a runway

§ Runway in use

§ Altimeter setting

§ ATC transponder code

§ Altitude or flight level instructions

§ Heading and speed instructions

§ Transition levels (whether issued by the controller or broadcast by the automatic terminal information system [ATIS])

The pilot’s readback must be complete and clear to ensure a complete and correct understanding by the controller.

The readback message shall always include the flight call sign.

Readback of a hold short, crossing, takeoff or landing instruction shall always include the runway designator.

The use of the term “roger” is not an acceptable readback as it does not allow the controller to confirm or correct the clearance or instruction, thus decreasing the pilot’s and the controller’s situational awareness.

§ A pilot may use “roger” to acknowledge a message containing numbers (instead of a normal readback), thus preventing effective hearback and correction by the controller, or

§ A controller may use “roger” to acknowledge a message requiring a specific answer (e.g., a positive confirmation or correction, such as acknowledging a pilot’s statement that an altitude or a speed restriction cannot be met).

6.9 Failure to correct an erroneous readback (hearback errors)

Any readback by the pilot requires a hearback by the controller in order to close the communications loop.

Most pilots perceive the absence of an acknowledgement or correction following a clearance readback as an implicit confirmation of the readback.

The absence of acknowledgement by the controller is usually the result of radio frequency congestion that requires the controller to issue clearances and instructions to several aircraft.

The controller’s failure to correct an erroneous readback (a hearback error) may cause deviations from the assigned altitude or noncompliance with altitude restrictions or radar vectors.

A deviation from a clearance or instruction may not be detected until the controller observes the deviation on the radar display.

Less-than-required vertical or horizontal separation, near midair collisions and runway incursions are usually the result of hearback errors. Perceiving what was expected or wanted (not what was actually said)

The bias of expectation can affect the correct understanding of communications by pilots and controllers.

It involves perceiving what was expected or wanted and not what was actually said.

The bias of expectation can lead to:

§ Transposing the numbers contained in a clearance (e.g., an altitude or flight level) to what was expected, based on experience or routine, or

§ Shifting a clearance or instruction from one parameter to another (e.g., perceiving a clearance to maintain a 280-degree heading as a clearance to climb or descend to and maintain FL 280).

6.10 Failure to seek confirmation when a message is not understood

Misunderstandings may include half-heard words or guessed-at numbers.

The potential for misunderstanding numbers increases when a given ATC clearance contains more than two instructions.

Videos

“Please, where is ahhty-ahm?” he asked. At least, that’s what I heard, even when he slowly repeated the question. I was flummoxed until he took a bank card out of his wallet and made the motion of inserting it into an imaginary slot.

“Oh, A.T.M.!” I said, and pointed the way to the nearest one.

As he thanked me, the man seemed to speak English well enough. But his question had been incomprehensible to me because of his pronunciation — a short rather than long A, an accent on the first rather than last syllable of “A.T.M.”

The exchange was inconsequential. But consider similar misunderstandings involving greater complexity in exchanges that are crucial indeed, like those, say, between airline pilots and air traffic controllers who do not share the same native language.

Confusion often occurs. Sometimes it’s just amusing, like a 2006 recording of exchanges between an Air China pilot and an air traffic controller at Kennedy Airport in New York. The controller becomes increasingly exasperated by the pilot’s hapless English, to the point where you can almost hear the steam coming out of his ears. That recording, on YouTube as Air China 981, is a favorite among air traffic controllers and pilots who have their own stories of language misunderstanding in global aviation.

Read the rest here on the New York Times

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